The Role of Functional Social Isolation in Mediating the Association Between Baseline Depression and Subsequent Executive Function in the Canadian Longitudinal Study on Aging Comprehensive Cohort

Abstract

Background: Depression is a risk factor for decline in executive function. One mechanism that may link depression to executive function is functional social isolation, which pertains to the qualitative and behavioural aspects of social interactions. The extent to which functional social isolation mediates the association between depression and executive function over time is unknown.

Objective: To determine whether functional social isolation at follow-up (T2) mediates the association between depression (self-reported clinical depression or depressive symptoms) at baseline (T1) and executive function at T2 across age and sex.

Methods: Community-dwelling adults aged 45 to 85 from the Canadian Longitudinal Study on Aging (CLSA) Comprehensive Cohort were followed over three years (complete case analysis, n=14,133). Indirect (i.e., mediation) effects were assessed using percentile bootstrapping across moderators (age and sex) in conditional process analysis controlling for sociodemographic, physical health and health behaviour covariates.

Results: Functional social isolation was a significant mediator of the association between depressive symptoms (β = -0.0032, 95% CI: -0.0069, -0.0005; PM = 8.0%) or self-reported clinical depression (β = -0.0644, 95% CI: -0.1282, -0.0166; PM = 17.5%) and executive function only among women aged 75 and older, after controlling for T1 covariates.

Discussion: Functional social isolation may partially explain the association between depression and executive function in women aged 75 and older. Interventions that reduce either functional social isolation or depression in women aged 75 and older may promote executive function in this population.