Association between Handgrip Strength and Depression in Older Adults - A Systematic Review and a Meta-Analysis

Background: Depression remains an important health problem among older adults. Disorders in older age result from the accumulation of various factors, chief among them somatic diseases, stressful life events, social isolation, unfavorable social attitudes towards older people, declined cognitive function, malnutrition, polypharmacy. Depression may be associated with the deterioration of physical tness, whose chief indicator is hand grip strength (HGS). The aim of the study was to investigate the relationship between depression and HGS among older populations using the available literature. Methods: PubMed, Web of Science and Science Direct databases were searched. The inclusion criteria were as follows: written in English and published after 2009, subject age: ³60 years, HGS measured using a hand dynamometer, assessment of the depressive symptoms using a validated tool. The following articles were excluded: studies conducted among institutionalized subjects and/or populations with a specic disease. Results: The total combined effect of 33 results presented in 16 studies included in the meta-analysis, converted to the correlation coecient, was OEr =-.148(SE = .030, 95%CI:-.206 – -.091), indicating a weak, negative correlation between HGS and depressive symptoms. Conclusion: The review of the literature and the meta-analysis demonstrated a relationship between low muscle strength measured with the HGS test and intensied depressive symptoms in older populations. Bearing in mind that depression is often unrecognized or underdiagnosed among older patients, lowered muscle strength in older subjects, should be an important sign for physicians and physiotherapists and an incentive to screen them for depression.


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The inclusion criteria for the reports were as follows: (a) written in English and published after 2009, (b) subject age: ≥60 years, (c) HGS measured using a hand dynamometer, (d) assessment of the depressive symptoms using a validated tool.
The following articles were excluded: studies conducted among (a) institutionalized subjects and/or (b) populations with a speci c disease, e.g. malignancy or carpal tunnel syndrome.

Data collection and analysis
All articles were independently analyzed by two authors (EZ and TT) to remove duplicates. The results were reviewed, and full versions were checked for compliance with the inclusion and exclusion criteria. The following data were extracted from each study: rst author, year of publication, study population characteristics, study design, inclusion/exclusion criteria, method of assessing HGS and depressive symptoms, assessment of the outcome, and results. Next, methodological quality standards and risk of bias (using the Newcastle -Ottawa Scale (NOS) adapted for cross sectional studies were investigated.
[16] NOS assesses three parameters (selection, comparability, and outcome) on eight items, with the maximum score of 10 points. Studies with the score of < 5 points (< 5NOS) are considered to have high risk of bias. The questionnaire was adapted for the present study in the following way: (a) in the Selection section (Ascertainment of exposure), 1 point was awarded if the measuring tool was presented but the method was either not described or not compliant with the American Society of Hand Therapists (ASHT) guidelines, [17] and 2 points were awarded if the tool was presented and the method was compliant with the ASHT guidelines; (b) in the Outcome section (Assessment of outcome), 2 points were awarded if HGS and depressive symptoms were assessed by two independent blind assessors. Methodological quality assessment was conducted independently by two authors (EZ and TT). All con icts were discussed and if consensus could not be reached, the third author (AP) had the deciding vote.

Measures of effect sizes
The collected results had been presented in various ways and had to be converted to the correlation coe cients. The highest number of relationships between depressive symptoms and HGS was expressed as beta coe cients, obtained by the linear regression analysis (n = 12). The linear regression method allowed to control for the effects of mediator variables such as age, sex, education, and others, and that is why these values represent a partial effect of HGS on the level of depression. Odds ratio (OR) calculated for cross tables was the next most frequent (n = 9) measure. The tables were prepared based on the threshold values for the number of depressive symptoms and according to the generally accepted thresholds for HGS or the thresholds calculated using the Receiver Operating Curve (ROC). Other indices of the effect size expressed as requivalent were calculated using mean values in the study and control groups (n = 4), correlation (n = 2), contingency coe cient (n = 2), standardized beta value (n = 1) and d Cohen (n = 1). In two cases, the identi ed texts did not report the effect size but only the p-values. Given the sample size and assuming test power of the analyzed studies (1-β = .80), the minimal effect was calculated. The total effect for the relationship between depressive symptoms and HGS was not described in six studies -the results were presented for groups with varying levels of depression and different sex groups, but it did not differentiate the total effect (Z = 0.715, p = .475).
Most studies did not present sex-strati ed data as they used statistical measures which allowed to control for sex, but also other variables. Nevertheless, nine results were related to male subjects only, also nine to female subjects only, and eleven to male and female participants. No statistically signi cant differences in the effect size were found between these groups (F(2, 15.6) = .741, p = .493).
Statistical analysis was conducted using the Jamovi software (2020), with the Viechtbauer metaphor package. [18] Publication bias was assessed visually by funnel plots and statistically by Egger's test. The τ index, calculated using the Maximum-Likelihood method, was τ = 0.147 and was statistically signi cantly different from zero (Q(32) = 280.4, p < .001) and revealed high heterogeneity of the results. The I² index was 92.3%, which justi es the use of the random effects model in the meta-analysis.

Sensitivity analysis
The Fail-Safe N coe cient, according to the Rosenberg algorithm, indicates that a 2932 of texts with null effect would need to be included in the selection for the total score to reach zero. Sequence analysis (Fig. 4) of the results included in the meta-analysis con rmed a statistically signi cant correlation between depression and HGS in the study population. Based on the data, the chance for the effect in the population is 81-fold higher that the chance for null effect.

Discussion
This systematic review and meta-analysis of 16 studies involving 19637 individuals aged ≥ 60 revealed a weak negative correlation between HGS and depression. The GDS-15 scale was the most commonly used tool for evaluating depression in the analyzed publications. According to Friedman et al. [35] GDS has robust internal reliability, construct validity, and operational characteristics for the screening of community-dwelling, cognitively intact older adults.
Its usefulness for the evaluation of depression in older subjects has been demonstrated by numerous reports. [36,37] HGS was most often measured using the Takei or Jamar hand dynamometers. Studies show that both measuring devices are successfully used to assess HGS, [38,39] but the scores may differ due to different shapes of the handles. The devices and the methods of measuring HGS should be made uniform. The use of standardized measuring tools for assessing HGS and depressive symptoms, in well-matched groups of older people, will allow to achieve reliable results. [40] In recent years, HGS has been perceived as a reliable indicator of the whole-body muscle strength, physical function, and health status, as well as a predictor of the length of hospitalization and even mortality for older populations, and has been investigated by a number of authors. [41][42][43] Also, HGS is a diagnostic criterion for sarcopenia. [11,12] Thus, as many as four publications on the matter were found during our search and included in the analysis [19,21,22,34]. Olgun Yazar & Yazar [34] and Wang et al. [19] concluded that sarcopenia was more common in older people with depression and depressive symptoms and that HGS was lower in those individuals. In turn, M. Hamer et al. [22] demonstrated that reduced grip strength was associated with higher risk of depressive symptoms in obese participants only. The possible link between weight status and HGS was investigated by Smith et al., [30] who found that obese subjects with moderate to severe depressive symptoms had lower HGS. Brown et al. [21] who analyzed frailty and depression in older adults, demonstrated that older people with symptoms of depression had lower HGS.
HGS test is also used to assess physical and functional tness in older people. Vasconcelos et al. [32] investigated the cut-off points of HGS to identify mobility limitation and calculated the following values: ≤17.4 kg for women and ≤25.8 kg for men in community-dwelling settings. HGS below these values was characteristic for the group with muscles weakness, who presented with depressive symptoms signi cantly more often.
Chen et al. [26] investigated the relationship between HGS and duration of sleep in older people, with depressive symptoms as an additional variable. These authors found lower HGS in subjects with depressive symptoms. Laredo-Aguilera et al. [27] also analyzed the link between HGS and quality of sleep in older populations, considering their mood and psychical functioning. They found a correlation between HGS and vigor, depression, insomnia, and sleep quality.
Pearson correlation analysis adjusted for age showed signi cant correlations between HGS and depression (r = 0.379, p = 0.021).
HGS allows to predict mortality among older populations, especially the 'oldest' old [25,31]. Also, late-life depression could be associated with high risk mortality, as reported by Hamer et al.. [23] These authors suggest that the relationship may be the result of lack of physical activity and poor physical function, measured with HDS. Depressed patients had lower HGS scores as compared to non-depressed individuals.
Depression in older people is associated with more functional and cognitive impairment than in younger adults [44]. Holmquist et al. [33] investigated the risk factors for depression in the context of functional performance. They concluded that high risk for depressive symptoms in older people was associated with low levels of functional performance (including HGS) combined with low physical activity.
Depression is one of the multiple geriatric syndromes [29,45]. Seino et al. [29] analyzed different measures of physical performance in order to determine the indicators of geriatric syndromes. They demonstrated that lower HGS was found in all geriatric syndromes (including depression) apart from urinary incontinence and malnourishment.
In our meta-analysis, we also took into consideration research of Korean authors, who studied a relationship between blood cadmium levels and HGS and depressive symptoms. Higher HGS values were associated with a lower number of depressive symptoms, assessed with the Korean Version of the GDS-short form. [28] Out of the 16 texts which were deemed eligible for the meta-analysis, only two aimed to establish the relationship between HGS and depression. [20,24] Han et al. [24] investigated that link in the context of socioeconomic status of the older subjects. These authors demonstrated a strong relationship between low HGS and intensi ed depression in socioeconomically deprived older people. Brooks et al. [20] concluded that reduced levels of combined HGS are independently associated with depression among U.S. adults aged 60 years and older.
To sum up, the review of the literature and the meta-analysis demonstrated a relationship between low muscle strength measured with the HGS test and intensi ed depressive symptoms in older population, even though they were merely the additionally analyzed variables in the vast majority of the included texts. The fact that the modi ed NOS scale was used to analyze the quality of the studies, due to the lack of a more adequate tool to evaluate cross-studies, was a certain limitation of our study.
Bearing in mind that depression is unrecognized or underdiagnosed in approximately 16% of the older patients, [46] lowered muscle strength reported or found in older subjects should be an important sign for physicians and physiotherapists who work with older people and an incentive to screen them for depression, especially among older adults.
The mechanism linking HGS with depressive syndromes remain to be fully investigated. Their interdependence is a complex matter, indicating a strong twoway interconnection and the need for further studies to elucidate the matter.

Availability of data and materials
The data analyzed during the study are available from the authors on reasonable request.

Competing interests
The authors declared no potential con icts of interest with respect to the research, authorship, and/or publication of this article.

Funding
The authors received no nancial support for the research, authorship, and/or publication of this article.
Authors' contributions EZ substantial contributions to the conception, analysis and interpretation of data, drafted the work, approved the submitted version, agreed both to be personally accountable for the author's own contributions and to ensure that questions related to the accuracy or integrity of any part of the work, even ones in which the author was not personally involved, are appropriately investigated, resolved, and the resolution documented in the literature.
AP analysis and interpretation of data, drafted the work, approved the submitted version, agreed both to be personally accountable for the author's own contributions and to ensure that questions related to the accuracy or integrity of any part of the work, even ones in which the author was not personally involved, are appropriately investigated, resolved, and the resolution documented in the literature.
TT analysis and interpretation of data, drafted the work, approved the submitted version, agreed both to be personally accountable for the author's own contributions and to ensure that questions related to the accuracy or integrity of any part of the work, even ones in which the author was not personally involved, are appropriately investigated, resolved, and the resolution documented in the literature.
PK analysis and interpretation of data, drafted the work, approved the submitted version, agreed both to be personally accountable for the author's own contributions and to ensure that questions related to the accuracy or integrity of any part of the work, even ones in which the author was not personally involved, are appropriately investigated, resolved, and the resolution documented in the literature.
MP substantial contributions to the conception, substantively revised, approved the submitted version, agreed both to be personally accountable for the author's own contributions and to ensure that questions related to the accuracy or integrity of any part of the work, even ones in which the author was not personally involved, are appropriately investigated, resolved, and the resolution documented in the literature.
All authors have read and approved the manuscript.