The Association Between Depressive Symptoms and Executive Function in the Canadian Longitudinal Study on Aging

Abstract

Populations around the world are aging at a rapid pace, presenting new challenges for health services. This is because older adults encounter a different set of challenges than younger age groups, such as an increase in the proportion of the population at risk for age-related cognitive decline. As cognitive function is one of the most commonly referenced indicators of health because it is necessary for everyday functioning and adaptation to change, and studying factors that influence cognitive function is important. To date, most of the factors associated with cognitive decline are determined in early life, or develop across the lifespan. However, there may be some factors that can be altered at any point of the lifespan, including later life. Depressive symptoms have been previously examined as a potential area of intervention because they have been shown to be positively associated with many health outcomes in later life, including cognitive function. While the relationship between major depression and cognitive function has been investigated, much of the research focuses on older adults and global cognitive impairment. As such, the relationship between depressive symptoms and specific domains of cognitive function, such as executive function, is not well understood. This study used baseline cross-sectional data from the Comprehensive cohort of the Canadian Longitudinal Study on Aging (CLSA). The CLSA is an ongoing prospective cohort study of community-dwelling adults who were between 45 to 85 years of age at recruitment. The 30,097 participants in the Comprehensive cohort lived within 25–50 km of 1 of 11 Data Collection Sites across seven provinces. Depressive symptoms were measured using the Center for Epidemiological Studies Short Depression Scale. A neuropsychological battery was used to assess executive function, a key domain of cognitive function required for purposeful decision making, planning, and behaviour. Bivariate and multivariable logistic regression were used to examine the association between depressive symptoms and executive function. This study builds on previous research that has largely focused on the association between major depression and global cognitive impairment. Specific aims of the current study were to examine whether the presence of depressive symptoms was associated with low executive function after stratifying by age group and sex, and adjusting for confounders (i.e., province, education, household income, urban/rural residence, self-rated general health, chronic conditions, medication for depression, marital status, social support availability, smoking status, and alcohol use). In descriptive analyses, the prevalence of depressive symptoms was found to be highest among those 45¬–54 years compared to other age groups, and higher in females compared to males. The prevalence of low executive function was highest among those 75 years and over compared to other age groups and was approximately equal among males and females. In multivariable analyses, depressive symptoms were associated with low executive function overall. As social support availability (SSA) was identified as an effect modifier, those with higher SSA who reported depressive symptoms had significantly greater odds of low executive function compared to those who did not report depressive symptoms. In contrast, those with low SSA who reported depressive symptoms had lower odds of low executive function, although this finding was not significant. When stratified by age group, those 45–54 years, 55–64 years, and 75 years and over with higher SSA had significantly greater odds of low executive function when reporting depressive symptoms compared to not. A positive association between depressive symptoms and low executive function was found in those 65–74 years, although this finding was not significant. The direction of the association in those 75 years and over with low SSA was reversed, where reporting depressive symptoms was associated with lower odds of low executive function compared to not reporting depressive symptoms. In males, both current and former/never drinkers had significantly greater odds of low executive function when reporting depressive symptoms compared to not. In females, those with higher SSA and depressive symptoms had significantly greater odds of low executive function, whereas those with low SSA and depressive symptoms had lower odds of low executive function, although this was not significant. Findings from this study add to existing evidence that psychosocial factors are important to the health of middle-aged and older adults, and that depressive symptoms are associated with specific domains of cognitive function. Overall, the presence of depressive symptoms appears to negatively affects cognitive function, and that the association differs by age group and sex. As well, SSA may be another important psychosocial factor closely linked with depressive symptoms and cognitive function. Future work should examine the longitudinal association between depressive symptoms and executive function, and investigate whether this longitudinal association differs by age, sex, and SSA.