Design
This was a descriptive cross- sectional correlation study using secondary data. The independent variable of interest was level of global cognitive function. Ethical approval for this study was granted by SJH/AMNCH Research Ethics committee REC Ref 2015/09/04/ 2017- 05 List 17 (2), date granted 18/05/17. Data collection began on 21/06/17. The variables of age, gender and years of education ( demographic), number of medications & handgrip strength (physical health), depression, and quality of life ( psychosocial health) were treated as covariates in this analysis. The dependent variable was PA engagement in minutes per week, measured using the LAPAQ physical activity questionnaire and an Actigraph triaxial accelerometer device.
Participants & sampling
Sixty – two participants were recruited the community (n=26) and from memory clinics (n= 38) in Dublin, Ireland. Inclusion criteria were: i) a diagnosis of amnestic MCI due to AD based on the National Institute on Ageing and Alzheimer`s Association criteria, ii) a Montreal Cognitive Assessment (MoCA) score of 18- 26, and iii) age of 50 years +. Participants were excluded if they had i) received a diagnosis of severe chronic disease, ii) dementia, or iii) history of major psychiatric disorder. Purposive and convenience sampling was used. Memory clinic participants were approached by the study PI at St. James`s Hospital, Dublin, or by their primary physician at presentation to other community memory clinics. Community recruitment took place via newspaper advertisement and community group newsletters. Ethical approval for this study was granted by SJH/AMNCH Research Ethics committee REC Ref 2015/09/04/ 2017- 05 List 17 (2), date granted 18/05/17, and was carried out in accordance with institution guidelines and regulations. Participants were presented with a participant information leaflet for the NeuroExercise study and written informed consent was obtained. The participant information leaflet and consent form are presented in Appendix 2.
Measures
Physical activity engagement
Physical activity was measured using the self- report LASA Physical Activity Questionnaire (LAPAQ) (see Appendix 3.) and the Actigraph triaxial accelerometer device.
The LAPAQ is a researcher administered recall survey which records moderate to vigorous PA (MVPA) for the previous 14 days. Scoring is calculated by totalling minutes spent in each activity. Weekly totals were calculated to achieve minutes per seven days. The LAPAQ was designed for use in older populations and is valid and reliable in non – impaired older adults (Harris et al., 2009; Stel et al., 2004). In this sample Cronbach’s alpha coefficient was .44.
The Actigraph GT3X (Actigraph, Pensacola, Fl, USA), is a medical - grade triaxial accelerometer worn on the hip for seven consecutive days. It is valid and reliable for measuring PA in non – impaired adults (Aadland & Ylvisaker, 2015(Barrett, Dominick, & Winfree, 2017; Ozemek, Kirschner, Wilkerson, Byun, & Kaminsky, 2014). Freedson bouts (periods of MVPA for 10 minutes or longer) were taken as the objective measure of MVPA and are a valid, reliable method for estimating PA engagement (Leinonen et al., 2016). Data was extracted and analysed using Actilife software Version 6.13.3.
Cognitive Function
Cognitive function was measured using the Montreal Cognitive Assessment (MoCA, Appendix 4.) for global cognitive function and working memory, covering the domains of visuospatial and executive function, naming, verbal memory registration and learning, attention, abstraction, delayed verbal memory, and orientation. It is a 30- item researcher administered test, with scores ranging from 0 to 30. A score of 26 or higher is considered to show normal cognitive functioning. It has been validated for use in the detection of MCI (Freitas, 2012; Nasreddine, Phillips, Bedirian, Charbonneau, Whitehead, Collin, Cummings & Chertow, 2005) in MCI and dementia in elderly populations (Abd Razak et al., 2019).
Psychological health
Quality of life
The Quality of life for Dementia questionnaire (DemQoL) version 4 has been validity, acceptability, and reliability in individuals with dementia ( Smith, Lamping, Banerjee, Harwood, Foley, Smith, Cook, Murray, Prince & Levin, 2005) and MCI (Mhaolain, Gallagher, Crosby, Ryan, Lacey, Coen, Coakley, Walsh, Cunningham & Lawlor, 2012). It is a 28 – item, researcher administered questionnaire. In the current study, the Cronbach alpha coefficient was .89. Questions are scored on a 4 – point Likert scale. Higher scores indicating better health related quality of life (See Appendix 5).
Depression
Depression was measured using the Centre for Epidemiologic Studies Depression scales ( CES- D, Appendix 6), a 20 - item researcher administered questionnaire measuring symptomatic depression (Radloff, 1977). It has been validated as a screening instrument in older adults (Irwin, Artin & Oxman, 1999) and is scored on a 4 – point Likert scale, with a score of 16 or over indicating presence of depression. In this current study, the Cronbach alpha coefficient was .79.
Physical health
Number of medications
Number of medications was used as a proxy measure of chronic illness. In the current study, all medications taken regularly were recorded by researchers and medication counts performed, excluding vitamin supplements, over the counter eye and nasal drops and herbal treatments as per previous studies (Agostini, Han, & Tinetti, 2004). This method has been previously used in adults with MCI to measure presence of chronic illness (Rovner et al., 2016).
Physical frailty
Measurement of handgrip strength is a reliable proxy measure for overall muscle strength (Bohannon, Magasi, Bubela, Wang, & Gershon, 2012). It has been shown to have predictive value as a measure of all – cause and disease specific mortality and future function and has utility as a means of identifying older adults at risk of poor health status (Bohannon, 2019). It was used here to indicate frailty status using a Jamar Digital Dynamometer and measured in kilograms.
Missing Data
Missing data was identified using the Frequencies option in SPSS. Missingness was low: Little’s (1998) test of Missingness Completely at Random was not significant (x2 = 105.82 , DF = 101 , p = .352). Two participants failed to complete the CES- D, one was unable to complete the handgrip left measure, two were unable to complete the handgrip right measure and ten participants failed to supply Actigraph data. Table 1 provides an overview of all missing data.
Table 1.
Overview of Missing Data
Missing Data
(Total number of cases: 62)
|
n (%)
|
%
|
CES- D
|
3
|
4.8
|
DemQol
|
0
|
0
|
MoCA
|
0
|
0
|
Age at screening
|
0
|
0
|
LAPAQ
|
0
|
0
|
Actigraph
|
10
|
16.1
|
Years of education
|
0
|
0
|
Handgrip
|
2
|
3.2
|
Number of medications
|
2
|
3.2
|
Statistical Analysis
Baseline participant data was analysed using Spss V.25. Descriptive statistics were used to describe the distribution of the data. Kolmogorov – Smirnov values were inspected to assess normality of the distribution of scores ( Appendix 7, Table A1). Inspection of outliers showed some outliers which were not determined to be significant. The relevant boxplots for age, years of education, number of medications and the LAPAQ are presented in Appendices 8 - 11 (Figures A1 – A4). Scatterplot matrices were created to explore the linearity between each DV (LAPAQ (Appendix 12, Figure A5) and Actigraph (Appendix 13, Figure A6)) and the independent variables. Bar charts were used to inspect potential patterns in each IV across the categorical IVs (gender, recruitment source). Visual inspection of bar charts showed scores were similar when stratified (Appendix 14, Figure A7 and Appendix 15, Figure A8).
Hierarchical linear regression analyses were used to explore associations between the independent and dependent variables of the LAPAQ and the Actigraph data, controlling for covariates, to assess the individual contributions of these variables and the contributions of these variables as domain constructs. A one-sample t test was used to assess differences in means of PA minutes per week compared to recommended physical activity guidelines. A Bland -Altman plot was used to analyse level of agreement between objective and subjective measures of PA engagement. Alpha level was set at .005 following Bonferroni adjustment for multiple comparisons.