Functional social isolation mediates the association between depression and executive function in older women: findings from the Canadian Longitudinal Study on Aging Comprehensive cohort

ABSTRACT

Depression and social isolation increase risk for executive function declines and are among the top five modifiable risk factors for dementia. However, the interrelationships between depression, social isolation and executive function are not well established. Further evidence is needed to inform strategies to promote executive function and independence in older age. We examined whether social isolation mediated the association between depression and executive function in community-dwelling middle-aged and older adults and whether this association was modified by age and sex. Adults aged 45 to 85 years from the Canadian Longitudinal Study on Aging (CLSA) Comprehensive cohort were followed over three years (complete case analysis, n = 14,133). Baseline depressive symptoms, a history of clinical depression, and functional social isolation (perceived lack of social support) were self-reported. Executive function at follow-up was a composite measure of five cognitive tests. Conditional process analysis assessed the mediating effects of functional social isolation across age group and sex, adjusted for sociodemographic and health covariates. Functional social isolation significantly mediated the association of depressive symptoms (proportion mediated [P_M] = 8.0%) or clinical depression (P_M = 17.5%) with executive function only among women aged 75+ years. Functional social isolation explains a proportion of the total effect of depressive symptoms or clinical depression on executive function in women aged 75 and older. Although reverse causation cannot be ruled out, our findings suggest that interventions that reduce functional social isolation or depression in older women may promote executive function.

KEYWORDS:

• Depression
• cognition
• social factors
• CLSA
• risk factors

Acknowledgments

This research was made possible using the data/biospecimens collected by the Canadian Longitudinal Study on Aging (CLSA). Funding for the Canadian Longitudinal Study on Aging (CLSA) is provided by the Government of Canada through the Canadian Institutes of Health Research (CIHR) under grant reference: LSA 94473 and the Canada Foundation for Innovation, as well as the following provinces, Newfoundland, Nova Scotia, Quebec, Ontario, Manitoba, Alberta, and British Columbia. This research has been conducted using the CLSA datasets Baseline Comprehensive Dataset version 4.1 and Follow-up 1 Comprehensive Dataset version 3.0, under Application Number 1909020. The CLSA is led by Drs. Parminder Raina, Christina Wolfson and Susan Kirkland.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

AI and ST designed the study and analysis, with contributions from CM and MO. AI conducted the literature search and analyses and wrote the first draft of the manuscript. ST supervised and provided funding for the project. All authors critically reviewed the manuscript and have approved the final manuscript.

Data availability statement

Data are available from the Canadian Longitudinal Study on Aging (www.clsa-elcv.ca) for researchers who meet the criteria for access to de-identified CLSA data.

Disclaimer

The opinions expressed in this manuscript are the author’s own and do not reflect the views of the Canadian Longitudinal Study on Aging.

Ethics approval

The University of Waterloo’s Office of Research Ethics provided ethics clearance for this study (ORE # 41682).

Additional information

Funding

This work was supported by the Canadian Institutes of Health Research (grant reference number ACD 170315)