Functional social support and cognitive function in middle- and older-aged adults: A systematic review of cross-sectional and cohort studies

doi:10.21203/rs.3.rs-2488817/v1

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Functional social support and cognitive function in middle- and older-aged adults: A systematic review of cross-sectional and cohort studies

https://doi.org/10.21203/rs.3.rs-2488817/v1

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Journal Publication

published 22 May, 2023

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Background

Intact cognitive function is crucial for healthy aging. Functional social support is thought to protect against cognitive decline. We conducted a systematic review to investigate the association between functional social support and cognitive function in middle- and older-aged adults.

Methods

Articles were obtained from PubMed, PsycINFO, Sociological Abstracts, CINAHL and Scopus. Eligible articles considered any form of functional social support and cognitive outcome. We narratively synthesized extracted data by following the Synthesis Without Meta-Analysis (SWiM) guidelines and assessed risk of bias using the Newcastle-Ottawa Scale (NOS).

Results

Eighty-five articles with mostly low risk-of-bias were included in the review. In general, functional social support—particularly overall and emotional support—was positively associated with cognitive function in middle- and older-aged adults. However, these associations were not all statistically significant. Substantial heterogeneity existed in the types of exposures and outcomes evaluated in the articles, as well as in the specific tools used to measure exposures and outcomes.

Conclusions

Our review highlights the role of functional social support in the preservation of healthy cognition in aging populations. This finding underscores the importance of maintaining substantive social connections in middle and later life.

Systematic review registration

Rutter EC, Tyas SL, Maxwell CJ, Law J, O'Connell ME, Konnert CA, Oremus M. Association between functional social support and cognitive function in middle-aged and older adults: a protocol for a systematic review. BMJ Open;10(4):e037301. doi: 10.1136/bmjopen-2020-037301

cognitive function

functional social support

systematic review

Maintaining cognitive function is crucial for healthy aging [1–3]. Therefore, identifying and exploring modifiable risk or protective factors for cognitive function are key foci of aging research [4]. Social support is an important modifiable protective factor for cognitive function [5–8].

Structural social support is a quantifiable measure of social relationships, such as the number of people in one’s social network or the degree of participation in social events. Functional social support is the extent to which an individual perceives their needs can be met by members of their social network, such as the availability of someone to drive them to the doctor or help with grocery shopping, if required [9, 10].

Multiple reviews reported that large social networks and frequent engagement with these networks promote cognitive stimulation and protect against cognitive decline [11–14]. However, the literature has devoted less attention to functional social support and cognitive function, even though functional support more accurately represents the depth and quality of social support experienced by individuals than structural support [9].

Kelly et al. reviewed the association between functional social support and cognitive function in nine longitudinal studies of healthy older adults [15]. They reported variability in the direction and magnitude of the association, depending on the measures of functional support and cognitive function. Since Kelly et al.’s review [15], additional literature [6, 7, 16, 17] has emerged on the topic, underlining the need for an updated review.

We conducted this systematic review to investigate the association between functional social support and cognitive function across multiple cognitive domains (i.e., memory, executive function) and cognitive disease states (i.e., mild neurocognitive disorder, major neurocognitive disorder) in middle-aged and older adults. Our review focused exclusively on functional social support, reflecting Menec et al.’s conceptual distinction between objective (structural) and subjective (functional) social relationships: one may report many social contacts yet believe most will not help in times of need, or vice versa [18]. This review differs from Costa-Cordella et al.’s recently published review [19], which included articles on structural and functional social support without age restrictions and excluded articles on neurological conditions characterized by cognitive deficits (e.g., mild or major neurocognitive disorder).

Our review followed the 2020 Preferred Reporting Items for Systematic Reviews and Meta Analyses (PRISMA) guidelines [20] (Additional file 1). We departed slightly from our published protocol [4] and did not conduct a meta-analysis or formally assess publication bias, nor did we narratively synthesize the extracted data by sex, setting, or risk of bias level. These proposed undertakings were precluded by heterogeneity in definitions and measures of functional social support and cognitive function, as well as by multiple different means of reporting quantitative results in the included articles.

Data Sources and Searches

We searched PubMed, PsycINFO, Sociological Abstracts, CINAHL and Scopus from inception to September 2021. Google Scholar was searched to retrieve grey literature. A medical librarian generated the syntax for PubMed (Additional file 2), which was adapted for the other databases.

Eligibility Criteria

The review included any study with a comparison group enrolling adults aged ≥ 40 years, regardless of residential setting (e.g., community, long-term care facility). Articles had to be published in English or French and report distinct results for persons in the age range of interest. The exposure was functional social support, sometimes called ‘perceived social support’ or ‘social support availability’, and the outcome was cognitive function. Included articles could assess global/overall functional social support or a subtype, such as emotional/informational support, tangible support, affectionate support, positive social interaction, using any tool or questionnaire. Similarly, the articles could measure cognitive function globally or by domain (e.g., memory, executive function) with any instrument or combination of tools (neuropsychological battery). We also included studies of neurological conditions characterized by cognitive deficits (e.g., mild or major neurocognitive disorder).

Study Selection, Data Extraction and Risk of Bias Assessment

Following removal of duplicates, two reviewers used the eligibility criteria and Covidence software (Veritas Health Innovation, Melbourne, Australia) to independently screen the titles/abstracts and full texts of identified citations. Two reviewers independently extracted the following data from included articles into a prepared Excel spreadsheet: first author, year of publication, country of data collection, proportion female, setting, length of follow-up, type and measure of social support, type and measure of cognitive function, and outcomes. Reviewers extracted outcome data in the form reported by authors. Where possible, extracted data came from fully adjusted regression models. Two independent reviewers assessed risk of bias using the Newcastle-Ottawa Scale (NOS) [21]. In all cases, discrepancies between reviewers were resolved by consensus or a third reviewer.

Synthesis Methods

The extracted data were narratively synthesized in groups based on cognitive outcome, study design, and functional social support subtype. Studies of visuospatial skills or reasoning were classified under executive function; those of verbal memory, non-verbal memory, working memory, or episodic memory were classified under memory; and those of attention or processing speed were placed in their own unique category. We followed the Synthesis Without Meta-Analysis (SWiM) guidelines to conduct a narrative synthesis [22] and reported the effect measures contained in the included articles.

Study Characteristics

Our search yielded 2,976 articles and 85 of these articles, published between 1986 and 2021, were included in the review (Fig. 1). Of these 85 articles, 44 were cross-sectional and 41 were cohort studies, with sample sizes ranging from 20 to 30,029 (Table 1). Most samples included community-dwelling persons, but four studies exclusively enrolled persons in institutionalized settings [23–26]. Nineteen articles examined dementia due to Alzheimer's disease (AD) or all-cause dementia, 38 examined global cognitive functioning or general cognitive impairment or decline, and 20 examined specific cognitive domains. Sixty-two articles reported multiple subtypes of functional social support. Common control variables were age, sex, race, education, income, social network, marital status, activities of daily living (ADLs), depression, and chronic conditions such as diabetes, cardiovascular disease, and hypertension. Most articles had low risk of bias (Table 2; Fig. 2). Overall, functional social support was protective against cognitive outcomes (Fig. 3).

Table 1

Study Characteristics
Author (Year)	Sample Size	Prop. Female	Age Range	Setting	Cognitive Outcome Measure	Analysis Method	Covariates
Cross-Sectional
Alpass et al., 2004	232	1.29 (3/232)	53.8 to 95.2	Community dwelling	MMSE	Hierarchical regression analysis	Age, education, income, social network, depression
Bourne et al., 2007	266	50 (134/266)	64	Community dwelling	MHT (in 1947); Raven’s standard progressive matrices (at age 64)	Bivariate correlation	Sex
Bourgeois et al., 2020	359	15%	> 50	Institutionalized (HIV Clinic)	MoCA	Poisson Regression Analysis	Age, sex, education, income, marital status, ethnicity, tobacco use, employment
Conroy et al., 2010	802	53% (423/802)	65 to 102	Community dwelling	AMT	Multinomial Odds Ratio	Education, social network, marital status, loneliness, depression
Deng & Liu, 2021	10,556	55.26%	≥ 65 years	Community dwelling and institutionalized	Chinese-MMSE	Multivariate logistic regression	Age, sex, education, income, marital status, area of residence
Ficker et al., 2002	194	71.60%	NR	Institutionalized	MDRS	Independent t-test	Race, education
Frith & Loprinzi, 2017	1874	59.10%	60 to 85	Community dwelling	WAIS: DSST	Weighted multivariable regression	Age, sex, race
Ge et al., 2017	3159	58.90%	60 to 105	Community dwelling	Chinese-MMSE, EBMT, SDMT, Digit Span Backwards Test	Linear regression analysis	Education, income, social network, marital status, ADLs, depression
Gow et al., 2007	488	58%	NR	Community dwelling	MHT - raw MHT scores converted into IQ scores	Regression analysis	Age, education, income, marital status, loneliness
Gow et al., 2013	1091	NR	NR (mean age 70)	Community dwelling	WAIS-III UK and WMS-III UK, tests of reaction and inspection time	ANCOVA	Social network, marital status, loneliness, depression
Hamalainen et al., 2019	30, 029	50.90%	45 to 85	Community dwelling	Mental Alternation Test, Animal Fluency test, Controlled Oral Word Association Test, Stroop test, RAVLT with immediate and 5-minute recall	Multiple regression analysis	Age, sex, race, education, income
Harling et al., 2020	5059	53.6%	≥ 40	Community dwelling	Battery from Health and Retirement study (orientation in time, episodic memory, number patterns)	Poisson regression; linear regression	Age, sex, education, income, marital status, country of origin, self-reported literacy, self-rated childhood health, father’s occupation, household size, employment status
Henderson et al., 1986	274	NR	70-79 80+	Community dwelling	GMS; MMSE	MANCOVA	Age, sex, marital status
Holtzman et al., 2004	354	68.60%	50 to 81	Community dwelling	MMSE	Simultaneous linear or logistic regression	Age, sex, race, education, depression
Jang et al., 2020	2061	66.8%	≥ 60	Community dwelling	Korean-MMSE; self-rated cognitive health	Bivariate regression; hierarchical linear regression	Age, sex, education, social network, marital status, depression, chronic conditions (functional disability, chronic disease), tobacco use, alcohol use
Keller-Cohen et al., 2006	20	15/20	85–93	Independent living in retirement community	composite cognistat; BNT	Hierarchical multiple regression; bivariate correlation	Education
Kim et al., 2019	410	252/410	60+	community dwelling	VMS; CERAD-TS; MMSE	One-way ANCOVA	Age, sex, education, depression
Kotwal et al., 2016	3310	52%	62 to 90	community dwelling	MoCA-SA	Multiple linear regression	Age, sex, race, education, marital status, depression
Krueger et al., 2009	838	75(NR/883)	NR	subsidized housing facilities and continuous care retirement communities	Episodic: Word List Memory, Recall, and Recognition; WMS; Semantic: BNT, National Adult Reading Test; Working: Digit Span Forward and Backward, Digit Ordering	Linear regression analysis	Age, sex, education, depression
La Fleur & Salthouse, 2017	2613	18–39: 66 40-59: 72 60-96: 63	NR	ND	Logical memory task; free recall task; paired associates’ task; Letter sets task; Shipley’s Abstraction; matrix reasoning	Multiple regression	Age, sex, education
Lee & Waite, 2018	2260	52.05	57–85	community-dwelling	MoCA-SA	multivariate regression	Age, sex, race, education
Mehrabi & Béland, 2021	1643	50.2%	≥ years	Community-dwelling	MoCA	Regression	Age, sex, education, income, smoking, alcohol consumption, sleeping disturbance
Millán-Calenti et al., 2013	579	57.2	≥ 65 years	Community-dwelling residents	MMSE; The Geriatric Depression Scale-Short Form	multinomial logistic regression	Age, sex, education, ADLs
Murayama et al., 2019	897	50 (450/897)	≥ 65 years	community residents	MMSE-J	multilevel logistic regression	Age, sex, education, income, social network, marital status
Nakamura et al., 2019	331	100 (331/331)	≥ 65 years	ND	BOMC	Unadjusted bivariate analysis	Age, education, ADLs, depression
Okabayashiet al., 2004	1976	NR	≥ 65 years	ND	Japanese-SPMSQ	regression (unspecified)	Age, sex, education, depression
Oremus et al., 2019	21,241	51%	45–85	ND	RAVLT, Animal Fluency Test, Mental Alternation Test	Rao-Scott chi square	Age, region of residence, urban / rural residence, education
Oremus et al., 2020	21,241	51.3 (10835/21241)	45–85	ND	RAVLT	multiple linear regression	Age, sex, education, income, marital status, ADLs, depression
Pillemer & Holtzer, 2016	355	55.2 (196/355)	65.00–95.00	Community dwelling	RBANS	Linear regression analysis	Age, sex, education, depression
Poey et al., 2017	779	58 (452/779)	70–110 years	ND	Diagnosis of normal cognition, CIND, AD, and non-AD dementia	multiple logistic regression	Age, sex, race, education, depression
Rashid et al., 2016	2005	68 (1363/2005)	60–99	Community dwelling	ECAG	Regression Analyses	Age, sex, race, education, social network, marital status
Saenz et al., 2020	4,017 (married dyads)	50% (4017/8034)	50+	Community dwelling	Cross-Cultural Cognitive Examination	Regression analysis	Age, sex, education, income, ADLs, depression
Sims et al., 2014	175	45%	54–83	Community dwelling	Stroop Color-Word Test, Judgment of Line Orientation; WAIS-R: The Block Design subscale, Digit Span Forward, Digit Span Backward; WMS: Logical Memory I and II Visual Reproductions I and II; The Grooved Pegboard, The Trailmaking Test,	Multiple Regression	Age, sex, race, education, depression
Weng et al., 2020	1706	53.01%	≥ 45 years	Community dwelling	Subjective cognitive decline	Univariate and multiple logistic regression	Age, sex, race, education, marital status, depression, chronic conditions (coronary heart disease, diabetes), exercise, employment status
Yang et al., 2020	470	52.6%	≥ 65 years	Community dwelling	CDR; MMSE	Multiple linear regression	Age, sex, education, income, ADLs, depression, functional assessment questionnaire, neuropsychiatric inventory questionnaire (nighttime behaviors, irritability, apathy, motor disturbances)
Yeh & Liu, 2003	4993	46.67% ( 2330/4989)	65+	Community dwelling	SPMSQ	Multiple regression analysis	Sex, education, marital status, loneliness, ADLs
Zahodne et al., 2014	482	54.1	55–85	Community dwelling	NIH Toolbox Cognition module: Dimensional Change Card Sort, Flanker, List Sorting, Pattern Comparison, Picture Sequence Memory	Regression analysis	Race, education, loneliness
Zahodne et al., 2018	548	62.6	ND	Community dwelling	NIH Toolbox Cognition module: Dimensional Change Card Sort, Flanker, List Sorting, Pattern Comparison, Picture Sequence Memory, Selective Reminding Test. Language scores, Benton Visual Retention Test, the Rosen Drawing Test, and the Identities and Oddities subtest of the DRW	Multiple Regression	Race, education, income
Zank & Leipold, 2001	63	76%	53–96	Geriatric day care units	MMSE	Hierarchical regression analysis	Education, marital status
Zhaoyang et al., 2021	311	67%	70–90	Community dwelling	5 cognitive domains (memory, executive function, attention, language, visual-spatial) with 10 neuropsychological instruments	Multilevel Poisson and logistic models	Age, sex, race, education, employment, marital status, living status
Zhu et al., 2012	120	37.50%	60–86	Community dwelling	MMSE	Multiple regression analysis	Age, sex, education, income, social network, marital status,
Zuelsdorff et al., 2013	623	71%	40–73	Community dwelling	RAVLT, Digits Forward, Digits Backward; WAIS-III: Letter-Number Sequence subtests; Trails A, Trails B, and Stroop Color-Word	Regression analysis	Age, sex, education, social network, marital status
Zuelsdorff et al., 2019	1052	69%	40–78	Community dwelling	RAVLT; BVMT-R; WAIS-R: Logical Memory immediate and delayed recall subtests; Trailmaking Test A & B, Stroop; Color-Word Interference condition; WAIS: Digit Span Forward, Digit Span Backward, and Letter-Number Sequencing	Regression analysis	Age, sex, race, education, social network, marital status, ADLs
Zullo et al., 2021	1567	58.65%	≥ 65 years	Community dwelling	Questionnaire de la Plaite Cognitive (QPC)	Binary logistic regression	Age, sex, depression, personality dimensions, quality of life, professional activity, interaction term between neuroticism and quality of life
Cohort
Amieva et al., 2010	Study sample size = 3777, Analytic/included sample: 2089	59.9% (1251/2089)	ND	Community dwelling	AD / Dementia diagnosis; MMSE; NINCDS-ADRDA criteria for AD.	Multivariate analysis	Sex, education, social network, ADLs, Diabetes, CVD
Andel et al., 2012	10,106	52%	ND	Community dwelling	Dementia diagnosis using DSM-4 criteria	Regression analysis	Age, sex, education, vascular disease
Bedard & Taler, 2020	11,152 (440 cases, 10712 controls)	Controls: 55.3% Cases: 42.1–44.9%	45–85	NR	Animal Fluency Test, controlled oral word association test, mental alternation test, and victoria Stroop test, Ray auditory verbal learning test, Miami prospective memory test	Binary logistic regression	Age, sex, education, marital status, depression, testing language
Bowling et al., 2016	9119	50.69% (4622/9119)	ND	Community dwelling	Reading and comprehension test, arithmetic test, copying design test, general ability test	Multiple linear regression	Sex, education, social network, marital status
Camozzato et al., 2015	220	70%	ND	Community dwelling	DSM5 and NINCDS-ADRDA criteria	Multivariate Cox Proportional- Hazards Moel	Age, sex, education, income, marital status, ADLs
Chen & Chang, 2016	2300	44.87%	65–93	Community dwelling	SPMSQ; Chinese-MMSE	Multinomial Logistic Regression	Age, sex, education, ADLs, hypertension, diabetes, heart disease, stroke
Chen & Zhou, 2020	16, 786	NR	≥ 65 years	Community dwelling	Chinese-MMSE	Generalized structural equation modelling (GSEM)	Age, sex, education, marital status, cardiometabolic diseases (diabetes, cardiovascular, stroke, heart disease), residence
Crooks et al., 2008	initial = 2249	100%	ND	Institutionalized	Telephone Interview for Cognitive Status; Telephone Dementia Questionnaire	Cox proportional hazards	Age, sex, education, social network, marital status, depression, stroke, myocardial infarction, diabetes, hypertension, PD
Dickinson et al., 2011	213	63.85%		Community dwelling	CERAD; WMS-R; Logical Memory subtest; Trail Making Test Parts A (TMT-A) and B (TMT-B), SDMT; WAIS-R: Digit Span Forward; ascending Digit Span task modeled after the Digit Ordering Test.	Linear regression models	Age, sex, education, social network
Eisele et al., 2012	2367 (1869 = analytic sample)	65.90%	79–95	Community dwelling	SIDAM	Multifactorial ANCOVA	Age, sex, education, marital status, ADLs, hypertension, CVD, coronary heart disease, alcohol use, BMI
Ellwardt et al., 2013	2255	54.00%	55–85	Community dwelling	MMSE; coding task, and Reven's Colored Progressive Matrices	Latent growth mediation model	Age, sex, education, loneliness, ADLs
Heser et al., 2014	2300	ND	ND	Community dwelling	SIDAM	proportional hazard models, cox regression analysis	Age, sex, education, ADLs
Holtzman et al., 2004	354	68.60%	50–81	Community-dwelling	MMSE	Simultaneous linear regression	Age, sex, race, education, social network
Howrey et al., 2015	2767	58.29%	ND	Community dwelling	MMSE	multivariate analyses by using simultaneous linear or logistic regression	Age, sex, education, income, marital status, ADLs, hypertension, heart attack, stroke, diabetes, vision, Nativity, BMI
Hudetz et al., 2007	80	0%	55–85	Institutionalized	RBANS: Story Memory and Word List Memory subtests; BVMT-R	Stepwise multiple regression analysis	Age, sex, education, hypertension, hypercholesterolemia, angina, myocardial infarction, type 2 diabetes
Hughes et al., 2008	at baseline = 417, analytic = 217	51.80%	ND	Community dwelling	MMSE; Stroop test, Trailmaking Test, Hopkins verbal learning tests	Random Effects Model	Age, sex, education, social network, marital status
Kats et al., 2016	13,782	ND	48–64	Community dwelling	DSST, DWRT, WFT	Generalized linear models	Age, sex, race, education, social network
Khondoker et al., 2017	10,055	46%	ND	Community dwelling	The short-form IQCODE questionnaire and physician	Proportional hazard regression models	Age, sex, education, income, diabetes, CVD, stroke, hypertension, cancer
Khoo & Yang, 2020	1735	NR	40–70	NR	Brief Test of Adult Cognition by Telephone (BTACT)	Structural equation modelling	Age, sex, education, income, general health
Liao et al., 2018	6,863	29.20%	ND	Community dwelling	Alice Heim 4-I test (AH4-I), an inductive reasoning test, and two tests of verbal fluency	Bivariate dual change score model; goodness of fit	Age, sex, race, education, income, marital status, coronary heart disease, stroke, diabetes, cancer, depressive symptoms
Liao & Scholes, 2017	10,241	53.30%	ND	Community dwelling	Verbal fluency and letter cancellation task.	Linear mixed model	Age, sex, education, income, ADLs
Liu et al., 2020	13, 636	55%	≥ 65 years	Community dwelling	Dementia Scale (Degree of Independence in Daily Living for Older Adults with Dementia)	Multivariate adjusted Cox proportional hazards model	Age, sex, education, history of disease (stroke, hypertension, myocardial infarction, diabetes, cancer), smoking, alcohol drinking, BMI, time spent walking per day, psychological distress score, motor function score, social participation
Luo et al., 2021	497	48%	64–68	NR	Subtest of verbal comprehension index in German WAIS-R; verbal fluency and vocabulary; subtest of perceptual reasoning index in WAIS-R	Mplus8	NR
Miyaguni et al., 2021	15, 313	51.80%	≥ 65 years	Community dwelling	I to IV and Medical, I (= 22 on MMSE), II (= 16), III (= 13), IV (= 6)	Multilevel survival analyses with sensitivity analyses model	Age, sex, education, marital status, depression, living conditions, present illness, smoking status, alcohol consumption, individual social support
Moreno et al., 2021	2242	100%	65–83	NR	Primary Mental Abilities Vocabulary Test; Category Fluency Test; Letter Fluency Test; Benton Visual Retention Test; California Verbal Learning Test; California Verbal Learning Test; Digit Span Test; Card Rotation Test	Linear mixed models with covariate adjustment	Age, race, education, income, region, job classification, major medical comorbidities
Murata et al., 2019	14,088	50.97%	65–99	Community dwelling	Incident dementia ascertained upon eligibility for Japan’s public LTCI system, Level II or higher, on the index for the evaluation of care needs for people with dementia.	Cox proportional hazard models	Age, sex, education, marital status, health behaviors (alcohol, smoking daily physical activity), cognitive complaints to predict dementia, depression
Noguchi et al., 2019	121 (analytic sample)	47.10%	ND	Community dwelling	Japanese MoCA	Multivariable linear regression analysis	Age, sex, income, ADLs, stroke, hypertension, dyslipidemia, diabetes, depression, living alone, BMI
Okely et al., 2021			70–84	Community dwelling	5 questions about current state of participants’ memory	Spearman’s Rho	Age, sex, education, depression, diabetes, cardiovascular disease, occupational social class, personality, living situation, anxiety, older age fluid cognitive ability
Pais et al., 2021	341	57.5%	60–85	Community Dwelling	MMSE	Multivariable Cox analysis of social support on cognitive impairment (hazard ratio)	Age, sex, social network, marital status,
Pillemer et al., 2019	493	57.20%	65–95	Community dwelling	RBANS	Cox proportional hazard ratio	Sex, race, education, diabetes, chronic heart failure, arthritis, hypertension, depression, stroke, Parkinson’s disease, chronic obstructive lung disease, angina, myocardial infarction, depressive symptoms
Riddle et al., 2015	299	normal = 59.43%, MCI = 57.89%, dementia = 70.83%	ND	Community-dwelling	The neuropsychological battery	χ2 for categorical variables and ANOVA, logistic regression models	Age, sex, race, education, ADLs, depression
Rote et al., 2021	2880	57.7%	≥ 65 years	Community dwelling	MMSE	Logistic regression	Age, sex, country of birth (Mexico or USA), Medicaid (yes or no)
Saito et al., 2018	13,984	50.90%	ND	Community dwelling	Long-term Care Insurance, The Degree of Autonomy in the Daily Lives of Elderly Individuals with Dementia Scale	Cox proportional hazard models	Age, sex, education, income, social network, marital status, ADLs, stroke, diabetes, depression, SCI, physical activity
Salinas et al., 2017	1834 (for dementia analysis)	44%		Community dwelling	DSM-IV	Cox proportional hazard models	Age, sex, education, social network, marital status, atrial fibrillation, diabetes, CVD, smoking status, depression, physical activity, antihypertensive treatment
Seeman et al., 2001	1189	55.20%	70–79	Community dwelling	BNT; WAIS-R	multivariate linear regression	Age, sex, race, education, income, social network, marital status, physical activity
Sörman et al., 2015	1715	No Dementia: 53.3% all cause dementia: 65.1% AD: 73.9%		Community Dwelling	DSM-IV	multivariate linear regression	Age, sex, education, CVD, stroke, HBP, diabetes, alcohol use, smoking status, obesity, stress, depression
Thomas & Umberson, 2018	2,788	64.70%	60–95	Community dwelling	SPMSQ	estimated growth curve models within a mixed-model framework Intercept (SE), Linear Slope	Age, sex, race, education, income, marital status, number of children, stressful life events
Wilson et al., 2015	529	78.90%		Institutionalized and Community dwelling	Clinical classification of MCI	Proportional hazards model	Age, sex, education, social network, loneliness, depression, negative life events
Yin et al., 2020	5897	51%	≥ 65 years	Community dwelling	MMSE	Multivariable Cox regression (hazard ratio)	Age, sex, education, income / occupation, ADLS, residence, participation in physical activity, smoking, drinking, negative well-being, baseline MMSE, leisure activities, physical diseases
Zahodne et al., 2019	8,538	56.24%	45–93	Community dwelling	Consortium to Establish a Registry for Alzheimer’s Disease Word List; Tests of semantic and letter fluency	Multivariate-adjusted standardized estimates	Age, sex, race, education, income, social network, heart disease, dyslipidemia, diabetes, nonlife threatening cancer, kidney failure, number of adults and children in childhood home, prenatal education, systolic BP, systemic inflammation, depression symptoms, perceived stress, BMI
Zahodne et al., 2021	578	663.5%	≥ 65 years	Community dwelling	WHICAP neuropsychological battery (episodic memory, language, visuospatial functioning); NIH Toolbox cognition module (executive function, working memory)	Longitudinal models	Age, sex, race, education, depression, presence / absence of 15 chronic conditions, baseline cognition
MMSE = Mini Mental State Examination, MHT = Moray House Test, AMT = Abbreviated Mental Test, BNT = Boston Naming Test, BOMC = Blessed Memory Orientation Concentration Test, BVMT-R = Brief Visuospatial Memory Test – Revised, CERAD = Consortium to Establish a Registry for Alzheimer's Disease, DRS = Dementia Rating Scale, DSST = Digit Symbol Substitution Test, DWRT = Delayed Word Recall Test, EBMT = East Boston Memory Test, ECAQ = Cognitive Assessment Questionnaire, GMS = Geriatric Mental State, MANCOVA = Multivariate analysis of Covariance, MDRS = Mattis Dementia Rating Scale, MoCA = Montreal Cognitive, RAVLT = Rey Auditory Verbal Learning Test, RBANS = Repeatable Battery for the Assessment of Neuropsychological Status, SCI = Subjective Cognitive Impairment, SCOPA-COG = Scales for Outcomes in Parkinson’s Disease – Cognition, SDMT = Symbol Digit Modalities Test, SIDAM = Structured Interview for the Diagnosis of Dementia of the Alzheimer type, Multi-infarct Dementia and Dementia of other Aetiology, SPMSQ = Short Portable Mental Status Questionnaire, VMS = Verbal Memory Score, WAIS = Wechsler Adult Intelligence Test, WFT = Word Fluency Test, WMS = Wechsler Memory Scale

Table 2

Overall Risk of Bias Ratings
Cross-Sectional Studies
Author, Year	Rating	Author, Year	Rating
Alpass et al., 2004	Medium	Millán-Calenti et al., 2013	Low
Bourgeois et al., 2020	Medium	Murayama et al., 2019	Low
Bourne et al., 2007	Medium	Nakamura et al., 2019	Low
Conroy et al., 2010	Medium	Okabayashi et al., 2004	Low
Deng & Liu, 2021	Medium	Oremus et al., 2019	Low
Ficker et al., 2002	Medium	Oremus et al., 2020	Low
Frith & Loprinzi, 2017	Low	Pillemer & Holtzer, 2016	Low
Ge et al., 2017	Low	Poey et al., 2017	Medium
Gow et al., 2007	Low	Rashid et al., 2016	Low
Gow et al., 2013	Low	Saenz et al., 2020	Low
Hamalainen et al., 2019	Low	Sims et al., 2014	Medium
Harling et al., 2020	Medium	Weng et al., 2020	Medium
Henderson et al., 1986	Medium	Yang et al., 2020	Low
Holtzman et al., 2004	Low	Yeh & Liu, 2003	Low
Jang et al., 2021	Low	Zahodne et al., 2014	Low
Keller-Cohen et al., 2006	Medium	Zahodne et al., 2018	Low
Kim et al., 2019	Low	Zank & Leipold, 2001	Low
Kotwal et al., 2016	Low	Zhaoyang et al., 2021	Low
Krueger et al., 2009	Medium	Zhu et al., 2012	Medium
La Fleur & Salthouse, 2017	Low	Zuelsdorff et al., 2013	Low
Lee & Waite, 2018	Low	Zuelsdorff et al., 2019	Low
Mehrabi & Béland, 2021	Low	Zullo et al., 2021	Medium
Cohort Studies
Author, Year	Rating	Author, Year	Rating
Amieva et al., 2010	Low	Liu et al., 2020	Low
Andel et al., 2012	Low	Luo et al., 2021	Low
Bedard & Taler, 2020	Medium	Miyaguni et al., 2021	High
Bowling et al., 2016	Low	Moreno et al., 2021	Medium
Camozzato et al., 2015	Low	Murata et al., 2019	Low
Chen & Chang, 2016	Medium	Noguchi et al., 2019	Low
Chen & Zhou, 2020	Low	Okely et al., 2021	Medium
Crooks et al., 2008	Low	Pais et al., 2021	Low
Dickinson et al., 2011	Medium	Pillemer et al., 2019	Low
Eisele et al., 2012	Low	Riddle et al., 2015	Medium
Ellwardt et al., 2013	Low	Rote et al., 2021	Medium
Heser et al., 2014	Low	Saito et al., 2018	Low
Holtzman et al., 2004	Low	Salinas et al., 2017	Low
Howrey et al., 2015	Medium	Seeman et al., 2001	Low
Hudetz et al., 2010	Medium	Sörman et al., 2015	Low
Hughes et al., 2008	Low	Thomas & Umberson, 2018	Medium
Kats et al., 2016	Low	Wilson et al., 2015	Low
Khondoker et al., 2017	Low	Yin et al., 2020	Low
Khoo & Yang, 2020	Medium	Zahodne et al., 2019	Low
Liao & Scholes, 2017	Low	Zahodne et al., 2021	Low
Liao et al., 2018	Medium

Narrative Synthesis

Alzheimer’s Disease or All-cause Dementia

Cross-Sectional Studies. Four of the five cross-sectional studies reported on dementia, while the remaining study reported results for AD and non-AD dementia (Table 3). Four studies focused on the ‘perceived support’ dimension of functional social support, two of which reported no association between perceived social support and dementia. One found greater perceived social support to be significantly associated with lower severity of dementia. One reported perceived support as being a moderate protective factor against AD, but a small risk factor for non-AD dementia. One study found that all-cause dementia was associated with lower satisfaction with diffuse social relationships, but not with close social relationships [27–31].

Table 3

Studies Reporting Outcome of Alzheimer’s Disease or Dementia
Study Design: Cross-Sectional
Author (year)	Dimension of FSS	Coefficient (CI or P-value)	Interpretation
Conroy et al., 2010	Perceived / Subjective	Dementia: OR = 1.0 (p = 0.934)	Perceived social support not associated with dementia.
Kotwal et al., 2016	Perceived / Subjective	Dementia: 0.00 (-0.45, 0.46)	Perceived social support not associated with dementia.
Poey et al., 2017	Perceived / Subjective	AD: RR = 0.567 (p = 0.174) Dementia: RR = 1.135 (p = 0.701)	Perceived social support has a protective effect against AD. Perceived support is associated with a small increased risk of non-AD dementia.
Yang et al., 2020	Perceived / Subjective	Severity of dementia: x² = 64.70 (p < 0.001)	Greater perceived social support significantly associated with lower severity of dementia.
Henderson et al., 1986	Satisfaction with FSS	Dementia: 0.06 (p = 0.002)	Participants with dementia reported significantly lower satisfaction with diffuse social relationships than non-demented participants (value for satisfaction with close relationships not reported).
Study Design: Cohort
Andel et al., 2012	Social Support at Work	AD: OR = 0.88 (0.76, 1.0) Dementia: OR = 0.87 (0.78, 0.97)	Greater overall social support at work has protective effect against AD and dementia. Significant in case of dementia.
Amieva et al., 2010	Satisfaction with FSS	AD: RR = 0.84 (0.3, 1.3) Dementia: RR = 0.77 (0.6, 0.9)	Satisfaction with social support has protective effect against dementia and AD; significant protective effect in case of dementia.
Crooks et al., 2008	Satisfaction with FSS	Dementia: HR = 0.74 (0.78, 1.23)	Satisfaction with social support reduces risk of dementia.
Camozzato et al., 2015	Perceived / Subjective	AD: HR = 0.19 (0.07, 0.52)^b	Perceived support based on presence of confidants associated with significantly decreased risk of developing AD.
Riddle et al., 2015	Perceived / Subjective	Dementia: x² = 0.29 (p = 0.59)	Perceived support did not predict conversion to dementia.
Heser et al., 2014	Emotional	AD: HR = 0.54 (0.19, 1.55) Dementia: HR = 1.02 (0.39, 2.66)	Small positive association between emotional support and all-cause dementia. Emotional support has protective effect against AD.
Liu et al., 2020	Emotional	Dementia: HR = 1.10 (0.88, 1.37)	Receiving emotional social support associated with small (non-significant) increased risk of dementia.
Miyaguni et al., 2020	Emotional	Dementia: 0.97 (0.94, 0.99)	Receiving emotional support significantly associated with decreased risk of dementia.
Murata et al., 2019	Emotional	Dementia – Males: HR = 0.95 (0.39, 2.66) ^a Dementia – Females: HR = 0.98 (0.82, 1.18) ^a	Emotional support has small protective effect against dementia in both males and females.
Rote et al., 2021	Emotional	Low Support Likely dementia: 40.6% Increasing dementia: 49.1% No impairment: 10.3% High Support Likely dementia: 43.6% Increasing dementia: 36.9% No dementia: 19.5%	Values reported are conditional probabilities. Higher conditional probability of increasing dementia risk group belonging to low emotional support group.
Saito et al., 2018	Emotional	Dementia: HR = 0.96 (0.89, 1.04) ^a	Emotional support from family has small protective effect against dementia; effect even smaller in case of emotional support from friends. Small positive association between emotional support from relatives and dementia.
Salinas et al., 2017	Emotional	Dementia: HR = 0.78 (0.56, 1.09)	Emotional support has protective effect against dementia.
Sörman et al., 2015	Emotional	Dementia: HR = 0.82 (0.60, 1.11) AD: HR = 0.72 (0.48, 1.07)	Emotional support has protective effect against dementia and AD.
Heser et al., 2014	Instrumental	Dementia: HR = 2.34 (0.91, 6.02) AD: HR = 3.57 (1.12, 11)	Large positive association between instrumental support and dementia and AD; association is significant in case of AD.
Murata et al., 2019	Instrumental	Dementia: Female: 0.98^a (0.88, 1.09) Dementia: Male: 0.95^a (0.83, 1.08)	Instrumental support has a small protective effect against dementia in both males and females.
Riddle et al., 2015	Instrumental	Dementia: x² = 1.99 (p = 0.16)	Instrumental support did not predict conversion to dementia.
Rote et al., 2021	Instrumental	Low Support Likely dementia: 40.0% Increasing dementia: 48.4% No impairment: 11.6% High Support Likely dementia: 43.7% Increasing dementia: 36.8% No dementia: 19.5%	Values reported are conditional probabilities. Higher conditional probability of increasing dementia risk group belonging to low instrumental support group.
Khondoker et al., 2017	Positive social support	Dementia: HR = 0.87 (0.72, 1.06)	Positive social support has a small protective effect against dementia.
AD = Alzheimer's Disease, CI = Confidence Interval, FSS = Functional Social Support, HR = Hazard Ratio, OR = Odds Ratio, RR = Relative Risk
^a Effects merged using Borenstein: Murata et al. (2019) and Saito et al. (2018) both reported specific sources of functional social support (co-residing family, relatives, or friends), which were merged using Borenstein’s equation for reporting in the data tables (Borenstein et al., 2009)
** Inverse of point estimate and confidence limits taken to convert outcome to yes versus no

Cohort Studies. Nine of 14 cohort studies reported an outcome of all-cause dementia, four studies reported outcomes of AD and non-AD dementia independently, and one study reported an outcome of only AD (Table 3). Eight studies explored the effects of emotional social support, six of which found small to moderate protective effects against dementia (one reached statistical significance). One observed a small protective effect in both male and female strata. Two studies reported small positive, but not statistically significant, associations between emotional support and all-cause dementia. Two of the eight studies found moderate protective effects for emotional social support against AD [16, 25, 32–40].

Four studies assessed instrumental social support, one of which reported a large positive association with both AD and non-AD dementia (statistically significant in the case of AD). Another study found small protective effects against dementia in both male and female participants. One study found that individuals identified as having increasing dementia were more likely to fall within the low instrumental support group. One study found no association [16, 34, 38, 39].

Two studies found satisfaction with social support to have moderate protective effects against dementia, with one being statistically significant. One of these also found satisfaction to have a moderate and nonsignificant protective effect against AD [25, 41]. Khondoker et al. reported positive social support had small protective effects against dementia [35]. Andel et al. showed workplace social support was protective against AD and non-AD dementia (statistically significant for non-AD) [42].

Global Cognitive Functioning

Cross-Sectional Studies. Three cross-sectional studies examined participant satisfaction with functional social support and global cognitive function (Table 4). Two reported positive yet statistically non-significant associations, and one found no association [43–45].

Table 4

Studies Reporting Outcome of Global Cognitive Functioning
Study Design: Cross-Sectional
Author (year)	Dimension of FSS	Coefficient (CI or P-value)	Interpretation
Alpass et al., 2004	Satisfaction with FSS	0.034 (p-value not reported)	Satisfaction with social support is positively but not significantly associated with cognitive function.
Gow et al., 2013)	Satisfaction with FSS	positive direction of association (p = 0.278)	Satisfaction with social support is positively but not significantly associated with cognitive function.
Keller-Cohen et al., 2006	Satisfaction with FSS	Quantitative data for this variable not reported	Satisfaction with social relationships did not predict performance on Composite Cognistat or BNT.
Bourgeois et al., 2020	Perceived / Subjective	1.72 (p = sig)	Perceived social support significantly positively associated with better outcome on MoCA.
Conroy et al., 2010	Perceived / Subjective	OR = 1.3 (p = 0.175)	Low perceived social support (+ widowed and lives alone) positively associated with possible cognitive impairment.
Ficker et al., 2002	Perceived / Subjective	3.589 (p < 0.001)	Cognitively impaired elders perceived their social support as significantly less adequate than did the cognitively intact participants.
Krueger et al., 2009	Perceived / Subjective	0.068 (p = 0.003)^a	Small significant positive association between perceived support and global cognitive function.
Lee & Waite, 2018	Perceived / Subjective	Female − 0.65 (p < 0.05) Male – no association	Significant positive effect of social support on cognition only in female participants. No association in male participants.
Mehrabi & Béland, 2021	Perceived / Subjective	Partner − 0.275 (0.028, 0.522) Children – no association Friends – no association Extended family – no association	Low perceived social support from partner significantly positively associated cognitive impairment. No association between perceived support from children, friends, or extended family and cognitive function.
Oremus et al., 2019	Perceived / Subjective		Proportion of participants with low cognitive function greater among persons who reported low perceived social support (and vice versa).
Saenz et al., 2020	Perceived / Subjective (from spouse)	Husbands: 0.02 (0.01,0.03) Wives: 0.00 (-0.01, 0.01)	Perceived social support from wife significantly positively associated with the husband’s cognitive ability.
Yeh & Liu, 2003	Perceived / Subjective (from friends)	0.11 (p = 0.005)	Perceived positive support from friends is significantly and positively associated with cognitive function.
Zank & Leipold, 2001	Perceived / Subjective	R²⁼0.085 (p < 0.05)	Perceived social support positively and significantly associated with cognitive function.
Zhu et al., 2012	Perceived / Subjective	0.020 (p < 0.05)	Total perceived support positively and significantly associated with cognitive function.
Zullo et al., 2021	Perceived / Subjective	OR = 0.93 (0.70, 1.24)	Individuals with subjective cognitive decline scored higher on the MSPSS indicating greater perceived social support.
Deng & Liu, 2021	Emotional	Relatives/friends/neighbors: OR = 0.219 (0.154, 0.311) Children: OR = 0.400 (0.293, 0.546) Spouse: OR = 0.242 (0.160, 0.366)	Emotional support from relatives / friends / neighbors, children, or spouse significantly associated with a reduced risk of cognitive impairment.
Harling et al., 2020	Emotional	0.72 (0.63, 0.82)	Emotional support significantly associated with decreased risk of cognitive impairment.
Kim et al., 2019	Emotional	4.160 (p = 0.002)	Emotional support significantly positively associated with cognitive function.
Murayama et al., 2019	Emotional	Male: OR = 0.46 (0.24, 0.86) Female: OR = 0.59 (0.35, 0.99)	Higher emotional support significantly associated with decreased risk of cognitive impairment.
Nakamura et al., 2019	Emotional	-0.02 (p = 0.04)	Higher emotional social support significantly associated with better cognitive scores.
Okabayashi et al., 2004	Emotional	Spouse: 0.02 (p < 0.05) Children: 0.05 (p < 0.05) Others: 0.01 (p < 0.05)	Emotional support from spouse, children, or others all significantly positively associated with cognitive function.
Pillemer & Holtzer, 2016	Emotional	1.620 (0.343, 2.897)	Emotional support positively associated with cognitive function.
Weng et al., 2020	Emotional	OR = 1.68 (1.37 to 2.06)	Insufficient emotional support significantly associated with increased reporting of subjective cognitive decline.
Deng & Liu, 2021	Instrumental	OR = 0.242 (0.630, 0.804)	Instrumental (financial) support significantly associated with decreased risk of cognitive impairment.
Harling et al., 2020	Instrumental	0.73 (0.64, 0.82)	Instrumental support significantly associated with decreased risk of cognitive impairment.
Millán-Calenti et al., 2013	Instrumental	OR = 1.04 (0.27, 4.0) ^b	Small positive association between instrumental support and cognitive function.
Murayama et al., 2019	Instrumental	Male: OR = 0.43 (0.22, 0.83) ^b Female: OR = 0.62 (0.30, 1.28) ^b	Higher instrumental support associated with decreased risk of cognitive impairment. Significant association in males.
Nakamura et al., 2019	Instrumental	0.00 (p = 0.97)	No association between instrumental support and cognitive function.
Pillemer & Holtzer, 2016	Instrumental	-0.235 (-1.535, 1.066)	Tangible support has a small negative association with cognitive function.
Ge et al., 2017	Emotional + Instrumental	R²⁼0.11 (p < 0.001)	Emotional and instrumental support significantly positively associated with cognitive function.
Gow et al., 2007	Emotional + Instrumental	0.14 (p < 0.01)	Emotional and instrumental support significantly positively associated with IQ.
Holtzman et al., 2004	Emotional + Instrumental	0.25 (p < 0.0005)	Emotional and instrumental support significantly positively associated with cognitive function
Pillemer & Holtzer. 2016	Positive Interaction	B = 1.8883 (0.595, 3.171)	Positive social interaction positively associated with cognitive function.
Pillemer & Holtzer, 2016	Affectionate	B = -0.093 (-1.369, 1.183)	Affectionate social interaction not associated with cognitive function.
Rashid et al., 2016	FSS	OR = 2.6 (1.2–5.4)	Increased risk of cognitive impairment among individuals with poor social support.
Jang et al., 2020	Family Solidarity	0.00	No association between family solidarity and cognitive function.
Study Design: Cohort
Hughes et al., 2008	Satisfaction with FSS	0.09 (p = 0.22)	Positive association between satisfaction with social support and cognitive function.
Bowling et al., 2016	Perceived / Subjective	Family: -0.01 (-0.30, 0.27) Friend: 0.02 (-0.29, 0.32)	Small negative association between perceived support from family and cognitive function. Small positive association between perceived support from friends and cognitive function.
Chen & Zhou, 2020	Perceived / Subjective	OR = 2.09 (p < 0.001)	Social isolation significantly associated with cognitive impairment.
Eisele et al., 2012	Perceived / Subjective	F-ratio = 2.114	Positive association between perceived support and cognitive function.
Howrey et al., 2015	Perceived / Subjective	Rapid decline: 1.89 (p < 0.001) Slow decline: 0.25 Stable: 0.35	In rapid decline group, social support significantly associated with increases in MMSE
Hudetz et al., 2007	Perceived / Subjective	0.01 (p = 0.64)	Small positive association between perceived support and cognitive function.
Kats et al., 2016	Perceived / Subjective	African Americans: -0.01 (-0.14, 0.12); Caucasians: 0.01 (-0.05, 0.05)	Small negative association between perceived support and cognitive function in African American population. Small positive association between perceived support and cognitive function in Caucasian population.
Luo et al., 2021	Perceived / Subjective	b = 1.90 (p = 0.050)	Quality of social relationships significantly predicts cognitive function.
Moreno (2021)	Perceived / Subjective	0.066 (p < 0.001)	Significant positive association between perceived social support and cognitive function.
Pais et al., 2021	Perceived / Subjective (from friends)	HR = 0.77 (0.635, 0.933)	Perceived social support from friends significantly associated with a reduced risk of cognitive impairment.
Bedard & Taler, 2020	Emotional	OR = 0.97 (0.95, 0.99)	Emotional support had a small but significant protective effect against cognitive decline.
Chen & Chang, 2016	Emotional	Starting high and declining: 0.87 (0.71, 1.07) Starting low and declining: 0.77 (0.60, 0.99)	Emotional social support had a significant protective effect in the starting low and declining group compared with the high-stable group. (Protective but not statistically significant effect in starting high and declining group).
Ellwardt et al., 2013	Emotional	0.03 (intercept), 0.40 (slope), p = 0.06	Emotional support positively associated with cognitive function.
Holtzman (2004)⁵⁶	Emotional	Continuous model: 0.15 (p < 0.005) Categorical model: 0.18 (p < 0.004)	Emotional support was a significant predictor of MMSE scores.
Hughes et al., 2008	Emotional	-0.05 (p = 0.45)	Small negative association between emotional support and cognitive function.
Noguchi et al., 2019	Emotional	-0.42 (p = 0.462)	Emotional support negatively associated with cognitive function.
Pillemer et al., 2019	Emotional	Incident cognitive decline: HR = 1.43 (0.94,2.18) Cognitive decline – males: HR = 1.62 (0.93,2.84) Cognitive decline – females: HR = 1.39 (0.68,2.84)	Emotional support positively associated with cognitive decline.
Seeman et al., 2001	Emotional	1.26 (p = 0.07)	Emotional support positively associated with cognitive function.
Thomas & Umberson, 2018	Emotional (from children)	-0.004, p < 0.05	Support from children related to fewer cognitive limitations
Bedard & Taler, 2020	Instrumental	OR = 0.98 (0.94, 1.02)	Instrumental support had a small protective effect against cognitive decline.
Dickinson et al., 2011	Instrumental	0.578 (p = 0.0333)	Instrumental support significantly positively associated with cognitive function.
Ellwardt et al., 2013	Instrumental	-0.01 (intercept), -0.02 (slope)	Small negative association between instrumental support and cognitive function.
Hughes et al., 2008	Instrumental	0.01 (p = 0.88)	Small positive association between instrumental support and cognitive function.
Noguchi et al., 2019	Instrumental	0.38 (p = 0.642)	Instrumental support positively associated with cognitive function.
Pillemer et al., 2019	Instrumental	Incident cognitive decline: HR = 1.75 (1.12,2.72) Cognitive decline – males: HR = 1.91 (1.00,3.62) Cognitive decline – females: HR = 1.78 (0.94,3.35)	Instrumental support positively associated with cognitive decline.
Seeman et al., 2001	Instrumental	-0.04 (p = 0.93)	Small negative association between instrumental support and cognitive function.
Yin et al., 2020	Instrumental (sick care)	HR = 0.795 (0.550, 1.148)	Instrumental support negatively associated with cognitive impairment.
Noguchi et al., 2019	Emotional + Instrumental	Co-residing family: 0.28, p = 0.813 Non-residing family and relatives: 0.51 (p = 0.283) Neighbours and friends: 1.23, p = 0.006	Significant positive association between emotional and instrumental social support from neighbours and friends and MoCA-J scores. Negative association between emotional and instrumental support from co-residing family or non-residing family and relatives and cognitive function.
CI = Confidence Interval, FSS = Functional Social Support, HR = Hazard Ratio, MoCA-J = Japanese version of the Montreal Cognitive Assessment, OR = Odds Ratio, RR = Relative Risk
^a Effects merged using Borenstein (Borenstein et al., 2009)
^b Inverse of point estimate and confidence limits taken to convert outcome to yes vs. no or high vs. low

Twelve cross-sectional studies explored the association between perceived or subjective functional social support and global cognitive function, with 11 reporting positive associations (10 statistically significant), and one reporting a negative association (Table 4). One study observed significant positive effects among females only. One reported that support from a wife was positively associated with a husband’s cognitive function, but not vice versa. One observed a positive association for spouse-provided support, but not support from children, friends, and extended family. One found links between greater subjective cognitive decline and greater levels of perceived social support [6, 23, 24, 27, 46–53].

Eight studies assessed the association between emotional social support and global cognitive function; authors reported positive associations in all eight, with seven reaching statistical significance. Six studies explored the effect of instrumental social support on cognitive function and two found statistically significant positive associations, one found a non-significant positive association, one found no association, one reported a small (non-significant) negative association, and one found positive associations in male (significant) and female (non-significant) strata. Three studies assessed the combined effects of emotional and instrumental social support on global cognitive function and found significant positive associations [54–65].

Rashid et al. assessed general functional social support and observed that individuals with lower reported levels of support were at an increased risk of cognitive impairment [66]. Jang et al. used family solidarity as a measure of functional social support and found no association between this variable and cognitive function [67].

Cohort Studies. One study found a positive association between functional social support and global cognitive function. Nine other studies assessed the association between perceived / subjective social support and global cognitive function, with six reporting positive associations, four of which were significant. One reported a negative association for Black people and a positive association for White people, though neither was significant. One showed a negative association for support from the family and a positive association for support from friends, with neither being statistically significant. One found perceived social support to be significant positively associated with cognitive function in persons whose cognition test scores were rapidly declining but found no association when scores were slowly declining or stable [26, 68–76].

Nine other cohort studies assessed the impact of emotional social support on global cognitive function. Three reported positive associations, one of which was significant. Two studies reported negative associations, neither of which was significant. In one study, emotional social support received from participants’ children was inversely associated with cognitive function. Similarly, inverse associations were found in male and female strata, though neither was statistically significant. One study identified significant protective effects for emotional support in persons whose baseline cognition was low and declining over time, and non-significant protective effects in those with high and declining cognition, compared to individuals with high and stable cognition

[17, 58, 72, 77–82].

Eight cohort studies explored instrumental social support and global cognitive function. Six studies reported positive associations, one of which was statistically significant. Three found non-significant negative associations. One study assessed the combined effects of emotional and instrumental social support, stratified by the source of support (co-residing family, non-residing family and relatives, neighbours and friends), and reported significant positive associations in the neighbours and friends stratum; the associations in the other two strata were inverse and non-significant [17, 72, 77, 79–81, 83, 84].

Studies Reporting Outcomes by Cognitive Domain

Twenty-seven studies examined the effects of functional social support on one or more specific cognitive domains (Table 5). Most studies assessed multiple domains, with 17 studies examining memory, 13 executive function, 3 attention and processing speed, 4 language ability, and 3 mild cognitive impairment (MCI).

Table 5

Studies Reporting Other Cognitive Outcomes
Study Design: Cross-Sectional, Outcome: Executive Function
Author (year)	Dimension of FSS	Coefficient (CI or P-value)	Interpretation
Gow et al., 201	Satisfaction with FSS	positive direction of association; p = 0.075	Satisfaction with social support is positively but not significantly associated with executive function.
Bourne et al., 2007)	Emotional	-0.14 (p < 0.05)	Emotional support significantly negatively associated with executive function.
Frith & Loprinzi, 2017	Emotional	Any support: B = 6.4 (2.9, 10)	Emotional functional social support significantly positively associated with executive function (of individual support types, only spousal support significantly associated with cognition).
La Fleur & Salthouse, 2017	Emotional	0.10 (p < 0.001)	Emotional support significantly positively associated with executive function.
Zahodne et al., 2014	Emotional	0.17 (0.06) 0.09 (0.06)	Emotional support positively associated with executive function.
Bourne et al., 2007	Instrumental	-0.13 (p < 0.05)	Satisfaction with instrumental support negatively associated with executive function.
La Fleur & Salthouse, 2017	Instrumental	0.02 (p > 0.01)	Small positive association between instrumental support and executive function.
Zahodne et al., 2014	Instrumental	DCCS: -0.04 (0.05) Flanker: 0.00 (0.05)	Instrumental support not associated with executive function.
Ge et al., 2017	Emotional + Instrumental	R^2 = 1.44 (p < 0.001)	Emotional and instrumental support significantly positively associated with executive function.
Hamalainen et al., 2019	Perceived / Subjective	B = 0.002 (p = 0.001)	Small positive association between perceived support and executive function.
Krueger et al., 2009	Perceived / Subjective	0.089 (p = 0.036) ^a	Perceived support significantly positively associated with executive function.
Study Design: Cohort, Outcome: Executive Function
Dickinson et al., 2011	Instrumental	0.284 (p = 0.0064) 0.578 (p = 0.0333)	Instrumental support significantly positively associated with executive function.
Liao & Scholes, 2017	Positive social support	0.017 (0.009, 0.026)	Positive social support significantly positively associated with executive function.
Liao et al., 2018	Confiding support	Y = − 0.05 (− 0.17, 0.07)	No association between confiding support and executive function.
Hudetz et al., 2007	Perceived / Subjective	z-score=-0.01, p = 0.33	Perceived social support does not significantly predict post-operative executive functioning
Zahodne et al., 2021	Emotional	0.11 (not significant)	Emotional social support positively associated with executive function.
Zahodne et al., 2021	Instrumental	-0.03 (not significant)	Instrumental social support negatively associated with executive function.
Study Design: Cross-Sectional, Outcome: Memory
Gow et al., 2013	Satisfaction with FSS	positive direction of association (p = 0.275)	Satisfaction with social support is positively but not significantly associated with memory.
Ge et al., 2017	Emotional + Instrumental	Working: R² = 0.18 (p < 0.05) Episodic: R² = 0.11 (p < 0.001)	Emotional and instrumental support significantly positively associated with both episodic and working memory.
Hamalainen et al., 2019	Perceived / Subjective	B = 0.002 (p < 0.001)	Small positive and significant association between perceived support and memory.
Krueger et al., 2009	Perceived / Subjective	Episodic: 0.023 (p = 0.444) Semantic: 0.055 (p = 0.056) Working: 1.07 (p = 0.003)	Small positive association between perceived support and episodic and semantic memory. Much larger and statistically significant positive association between perceived support and working memory.
Okely et al., 2021	Perceived / Subjective	− 0.169 (p < 0.05)	Lower perceived social support significantly associated with increased memory problems.
Zuelsdorff et al., 2013	Perceived / Subjective	Immediate: 0.006 (not significant) Verbal:0.037 (not significant) Working: -0.024 (not significant)	Small positive association between perceived support and immediate and verbal memory. Small negative association between perceived support and working memory.
Zuelsdorff et al., 2019	Perceived / Subjective	Immediate: 0.07 (p = 0.01) Verbal: 0.04 (not significant) Working: 0.04 (not significant) Visual: 0.09 (p < 0.001)	Perceived support significantly positively associated with immediate and visual memory. Perceived support positively associated with verbal and working memory.
Kim et al., 2019	Emotional	1.696 (p = 0.003)	Higher emotional support significantly associated with better verbal memory.
La Fleur & Salthouse, 2017	Emotional	0.11 (p < 0.001)	Emotional support significantly positively associated with memory.
Oremus et al., 2020	Emotional	Immediate: B = 0.06 (0.03, 0.09) Delayed: B = 0.05 (0.02, 0.08)	Emotional support significantly positively associated with both immediate and delayed memory.
Zahodne et al., 2014	Emotional	Working: 0.09 Episodic: 0.09	Emotional support positively associated with both working and episodic memory.
La Fleur & Salthouse, 2017	Instrumental	-0.01 (p > 0.01)	No association or small negative association between instrumental support and memory.
Sims et al., 2014	Instrumental	-0.17 (p < 0.05)	Significant negative association between instrumental support and nonverbal recall.
Zahodne et al., 2014	Instrumental	Working: 0.01 Episodic: -0.01	Small positive association between instrumental support and both working memory. Small negative association between instrumental suport and episodic memory.
Oremus et al., 2020	Positive	Immediate: B = 0.05 (0.02, 0.07) Delayed: B = 0.04 (0.01, 0.07)	Positive support significantly positively associated with both immediate and delayed recall.
Oremus et al., 2020	Affectionate	Immediate: B = 0.05 (0.02, 0.08) Delayed: B = 0.05 (0.02, 0.07)	Affectionate support significantly positively associated with both immediate and delayed recall.
Study Design: Cohort, Outcome: Memory
Hudetz et al., 2007	Perceived / Subjective	z-score=-0.02, p = 0.40	Perceived social support does not significantly predict post-operative verbal memory
Zahodne et al., 2018	Perceived / Subjective	Working: R^2 = 0.18 (p < 0.05) Episodic: R^2 = 0.11 (p < 0.001)	Significant positive association between perceived social support and both working and episodic memory.
Hughes et al., 2008	Emotional	-0.02 (p = 0.83)	Small negative association between emotional support and memory.
Zahodne et al., 2021	Emotional	Working: 0.04 (not significant) Episodic: -0.11 (not significant)	Small positive association between emotional support and working memory. Negative association between emotional spport and episodic memory.
Hughes et al., 2008	Instrumental	0.01 (p = 0.93)	Small positive association between instrumental support and memory.
Zahodne et al., 2021	Instrumental	Working: -0.03 (not significant) Episodic: 0.00 (not significant)	Small negative association between instrumental support and working memory. No association between instrumental support and episodic memory.
Hughes et al., 2008	Satisfaction with FSS	0.18 (p = 0.06)	Satisfaction with social support positively associated with memory.
Liao & Scholes, 2017	Positive social support	0.018 (0.003, 0.033)	Positive social support significantly positively associated with memory.
Study Design: Cross-Sectional, Outcome: Language
La Fleur (2017)⁸⁸	Emotional	0.13 (p < 0.001)	Emotional support significantly positively associated with language ability.
La Fleur (2017)⁸⁸	Instrumental	0.01 (p > 0.01)	No association or small positive association between instrumental support and language ability.
Study Design: Cohort, Outcome: Language
Hudetz et al., 2007	Perceived / Subjective	z-score = 0.01 (p = 0.69)	Perceived social support does not significantly predict verbal memory
Zahodne et al., 2018	Perceived / subjective	Initial cognitive level: 0.022 (-0.010, 0.054) Annual rate of cognitive change: 0.029 (-0.035, 0.092)	Reported childhood social support positively but not significantly associated with initial verbal fluency and rate of decline in verbal fluency
Zahodne et al., 2021	Emotional	-0.05 (not significant)	Negative association between emotional support and language ability.
Zahodne et al., 2021	Instrumental	-0.07 (not significant)	Negative association between instrumental support and language ability.
Study Design: Cross-Sectional, Outcome: MCI
Kotwal et al., 2016	Perceived / Subjective	0.02 (-0.33,0.37)	Perceived social support positively associated with better outcome on MoCA-SA.
Poey et al., 2017	Perceived / Subjective	RRR = 0.962 (p = 0.259) (reference group no social support available)	Social support has a slightly protective effect on the onset of MCI.
Zhaoyang et al., 2021	General social support	-0.13 (-0.34, 0.07)	Negative association between general social support and MCI.
Study Design: Cohort, Outcome: MCI
Wilson et al., 2015	Negative social interaction	HR = 1.09 (0.81, 1.495)^a	Negative social interaction positively associated with MCI.
Study Design: Cross-Sectional, Outcome: Attention / Processing Speed
Zuelsdorff et al., 2013	Perceived / Subjective	0.084 (p < 0.05)	Perceived social support significantly positively associated with processing speed.
Zuelsdorff et al., 2019	Perceived / Subjective	0.05 (not significant – specific p value not reported)	Perceived social support positively associated with processing speed.
Study Design: Cohort, Outcome: Attention / Processing Speed
Hughes et al., 2008	Emotional	0.07 (p = 0.95)	Small positive association between emotional support and attention / processing speed.
Hughes et al., 2008	Instrumental	-0.004 (p = 0.99)	Instrumental support not associated with attention / processing speed.
Hughes et al., 2008	Satisfaction with FSS	1.24 (p = 0.30)	Satisfaction with social support positively associated with attention / processing speed.
CI = Confidence Interval, FSS = Functional Social Support, HR = Hazard Ratio, MCI = Minor Neurocognitive Disorder, MoCA-SA = Montreal Cognitive Assessment Survey Adaptation, RR = Relative Risk
^a Effects merged using Borenstein (Borenstein et al., 2009)

Memory.Cross-Sectional Studies. Twelve cross-sectional studies explored the association between functional social support and memory. One found a positive non-significant association for relative satisfaction with available support. Two of five studies reported positive and statistically significant associations between perceived social support and memory. Two reported positive associations between perceived support and verbal memory, with the only statistically significant association involving memory measured longitudinally. They also found negative and non-significant associations between perceived support and working memory at both time periods, and a positive and significant association between perceived support and visual memory measured longitudinally. One found a significant association between lower perceived social support and greater problems with memory or forgetfulness [44, 46, 85–88].

Four studies examining emotional social support and memory reported positive associations, with results in three achieving statistical significance. One found the association between emotional support and verbal memory to be mediated by hippocampal volume, one reported similar strengths of association for immediate and delayed recall memory, and one found positive associations of the same magnitude for working and episodic memory [7, 59, 89, 90].

Three studies assessed the effects of instrumental social support on memory: one reported a statistically significant negative association with general memory [91]; one found a small and non-significant negative association with overall memory [89]; and one identified a small positive and non-significant association with working memory and a small negative and non-significant association with episodic memory [90]. Finally, Oremus et al. found positive social interactions and affectionate support to be independently and positively associated with immediate and delayed recall memory (statistically significant for affectionate support) [7].

Cohort Studies. Two studies of perceived support and memory found either no association [26] or statistically significant and positive associations with both working and episodic memory [92]. Liao and Scholes found a positive and statistically significant association between positive social support and global memory [93]. Hughes et al. found a negative association in the case of emotional support, and positive associations for instrumental support and satisfaction with social support [72]. Zahodne et al. found positive and negative associations, respectively, between emotional and instrumental support, and working memory; they also observed negative associations between emotional support and episodic memory, and no association between instrumental support and episodic memory [94].

Executive Function. Cross-Sectional Studies. Gow et al. reported a positive and non-statistically significant association between participant satisfaction with functional social support and executive function, although they did not provide any numerical findings [44]. Hamalainen et al. and Krueger et al. reported positive and statistically significant associations between perceived social support and executive function [46, 85].

Three of four cross-sectional studies found positive associations between emotional social support and executive function, two of which were statistically significant. One stratified by individual sources of emotional support and only spousal support remained statistically significantly associated with executive function. One study observed a statistically significant negative association [89, 90, 95, 96].

Three cross-sectional studies assessed the independent effect of instrumental social support on executive function: La Fleur and Salthouse found a small yet non-significant positive association, Zahodne et al. observed no association, and Bourne et al. reported a statistically significant negative association [89, 90, 95]. Ge et al. evaluated combined emotional and instrumental support on executive function and reported a statistically significant positive association [55].

Cohort Studies. Five cohort studies evaluated the effect of functional social support on executive function. Dickinson et al. and Liao & Scholes found positive and statistically significant associations for instrumental and positive support [83, 93]. Zahodne et al. showed a positive, but non-significant, association for emotional support and a negative, non-significant association for instrumental support [94]. Liao found no association for confiding support, and Hudetz et al. showed no significant association between perceived social support and post-operative executive function [26, 97].

Other Cognitive Domains. (Table 5). La Fleur and Salthouse’s cross-sectional study found a positive association between instrumental support and language ability, and a stronger and statistically significant association between emotional support and language ability [89]. Three cohort studies reported mixed results of no [26], positive [92], or negative associations (the latter being non-statistically significant) with language ability [94].

Two cross-sectional studies and one cohort study measured attention or processing speed. The cross-sectional studies reported positive associations for perceived social support [87, 88], with the former reporting a statistically significant result. The cohort study found no association for instrumental support, a positive association for emotional support, and a larger positive association with satisfaction with social support [72].

Three cross-sectional studies found slight protective effects between perceived/overall support and conversion to MCI [29, 30, 98]. One cohort study observed that negative social interaction was a risk for MCI [99].

Overall, functional social support was positively associated with cognitive function in middle- and older-aged adults (Fig. 3). However, the results were not uniform across the 85 included studies.

Perceived or Overall Functional Social Support

Individual perceptions of functional social support did not appear to be associated with a diagnosis of AD or all-cause dementia. Conversely, perceived support was most often positively associated with improved cognitive function, although these associations did not always reach statistical significance. Negative associations, or a lack of association, were sometimes observed in the context of male participants or family members as the only sources of perceived social support [47, 68]. The negative association observed for male participants could suggest that males and females experience social support differently and emphasizes distinct aspects of the quality of social relationships. Social support from family members may be inversely associated with cognition because tumultuous intra-family relations could lead to psychosocial stress.

Emotional Social Support

Most studies involving a clinical diagnosis of AD or all-cause dementia reported non-significant negative associations between emotional social support and these outcomes. Most of these studies also found significant and positive associations with both global and domain-specific cognitive function. However, negative associations or absence of any association were sometimes observed when considering emotional support provided by family members [72, 80]. Individuals in need of strong emotional support from their co-residing family members might concomitantly be experiencing some form of family-based physical or psychological stressors that negatively affect cognition.

Instrumental Social Support

In contrast to the findings with perceived or emotional support, an equal number of studies observed positive and negative associations between instrumental support and AD or all-cause dementia. Most studies reported non-significant positive associations between instrumental support and domain-specific cognitive outcomes, although several studies in this group found an inverse association. For global cognitive function, an approximately equal number of studies reported positive and negative associations. The number of studies with negative associations was larger in the case of instrumental support compared to perceived and emotional support. Perhaps these findings merely reflect the increased need for functional support in day-to-day life among people with dementia, which can be partially provided by instrumental social support.

Emotional-Instrumental Social Support, Satisfaction with Social Support

Most studies that assessed the combined effects of emotional and instrumental support reported positive associations with global and domain-specific cognitive function. All studies that assessed participant satisfaction with functional social support found protective effects against both AD or global dementia. All articles that measured domain-specific cognitive outcomes found satisfaction with social support to be non-significantly positively associated with cognition. Reported satisfaction with social support was also positively associated with global cognition in most cases.

Positive, Affectionate, Confiding Social Support

Five studies examined these types of support [7, 35, 64, 93, 97]. Receiving positive social support was associated with a decreased risk of dementia, as well as improved global cognition and memory. Similarly, affectionate social support was associated with decreased risk of dementia and improved memory. One study explored the effects of confiding support on executive function and reported no association between the two variables.

Domain-Specific Cognitive Outcomes

Memory was the most frequently assessed, domain-specific, cognitive outcome. In most cases, functional social support was positively associated with memory. The same results were found with executive function. Turning to the domains of language and attention/processing speed, all studies reported either no association or a positive association. Some studies used a clinical diagnosis of MCI as the cognitive outcome and found functional social support acted as a protective factor, whereas negative social interaction served as a risk factor.

Strengths and Limitations

A self-assessment with AMSTAR2 (Additional file 3) showed the quality of our systematic review was strong [100]. Our comprehensive search strategy captured many articles across a spectrum of functional social support exposures and cognitive outcomes. The nature of the exposure prevented us from looking at randomized controlled trials. One of the included articles was at high risk of bias and the narrative synthesis was facilitated by the similarity of covariate sets in the included articles.

Our review is unique from Kelly et al. [15] and Costa-Cordella et al. [19] because it focused exclusively on functional social support. Further, our review contained the most up-to-date synthesis of the literature on the topic. The adverse impact of the COVID-19 pandemic on social engagement, especially among older adults, provides a renewed impetus to understand how functional social support affects the cognitive health and well-being of aging populations.

The findings of this review show that functional social support may act as a protective factor against dementia and cognitive decline. This association appears to be stronger in the case of perceived (overall) and emotional support, relative to instrumental support. Policy makers may wish to allocate public funds for community-based programs centered on fostering quality social relationships high in emotional support among middle-aged and older adults.

Alzheimer’s disease

ADL

Activities of daily living

AMSTAR

A Measurement Tool to Assess Systematic Reviews

MCI

Mild cognitive impairment

NOS

Newcastle-Ottawa Scale

PRISMA

Preferred Reporting Items for Systematic Reviews and Meta Analyses

SWiM

Synthesis Without Meta-Analysis

Ethics approval and consent to participate

Not applicable

Consent for publication

Not applicable

Availability of data and materials

The raw data extraction and risk of bias tables used during the current study are available from the corresponding author on reasonable request.

Competing interests

The authors declare that they have no competing interests.

Funding

This work was supported by Velux Stiftung (No. 1190) the Canadian Institutes of Health Research (No. MM1 – 174917).

Authors’ contributions

Lana Mogic: Investigation, Data Curation, Writing – Original Draft, Visualization Emily Rutter: Conceptualization, Investigation, Data Curation, Writing – Review and Editing, Supervision Suzanne Tyas: Conceptualization, Methodology, Investigation, Writing – Review and Editing Colleen Maxwell: Conceptualization, Methodology, Investigation, Writing – Review and Editing Megan O’Connell: Investigation, Writing – Review and Editing, Mark Oremus: Conceptualization, Methodology, Investigation, Writing – Review and Editing, Visualization, Supervision, Project Administration, Funding Acquisition.

Acknowledgements

The authors thank the following persons for help with screening, data extraction, and risk of bias assessment: Shailesh Advani, Orna Awele Charles-Obazei, Arden Fenton, Bailey Grigg, Laura Jimeñez, Mahwish Khan, Safa Khurram-Hafeez, Peter Missiuna, Arsh Maira Muhammad Muhyiddin, Hamisha Ramesh, Michelle Vuong, and Camilla Zienkiewicz. We also thank Jackie Stapleton for devising the literature search strategy.

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Functional social support and cognitive function in middle- and older-aged adults: A systematic review of cross-sectional and cohort studies

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