Does Late-Life Depression Counteract the Beneficial Effect of Physical Activity on Cognitive Decline? Results From the NESDO Study

Objectives: Depression both affects physical activity (PA) and cognition in older persons, yet its impact on the association between PA and cognitive decline is to be determined. We aimed to investigate the association between baseline PA and cognitive functioning over time, stratified for depression. Methods: We used data of the Netherlands Study of Depression in Older persons (NESDO), a multi-site cohort study with 6-years follow-up. Patients with complete data on PA and cognitive functioning at baseline were included, yielding 394 participants for the analyses of whom 297 were depressed and 97 non-depressed. PA (continuous) was measured with the International Physical Activity Questionnaire. Linear mixed models were used to determine differential effects of baseline PA on the rate of decline of 5 standardized outcomes of cognitive functioning over 6-year follow-up. For this purpose, we examined the significance of the interaction-term (PA*time) in both basic and adjusted models. We also assessed the association between time and cognitive functioning. All analyses were stratified for depression. Results: In both groups, no robust significant interactions of PA with time were found. Furthermore, only decline in working memory was significantly worse in the depressed compared to the non-depressed. Conclusion: At older age, the impact of a more inactive lifestyle on cognitive decline was shown to be limited, irrespective of depression that appeared to worsen age-related decline of working memory only. As a higher PA-level at older age has a positive effect on a multitude of other health outcomes, PA should still be encouraged in this population.