Does type or diversity of activities delay aging-related cognitive decline?

Background and Objectives: Research has shown a correlation between engagement in activities and late-life cognition, but cross-sectional associations are likely to be inflated by reverse causality. This study investigated the prospective effects of activity engagement-frequency of and diversity across activity types-on aging-related cognitive decline. Research Design and Methods: Using data from the Health and Retirement Study (HRS) and Midlife in the United States (MIDUS) study, we evaluated whether baseline measures of 4 activity types (cognitive, physical, contact with family/friends, and social group participation) predicted subsequent cognitive decline adjusted for potential confounders. We compared the effects of activity type frequency with the effect of activity diversity. Results: In HRS, activity diversity was associated with slower midlife (ages 55-65) cognitive decline, whereas more frequent cognitive activities yielded the largest reduction in late-life (ages 65-85) cognitive decline. Frequency of social contact was associated with slower midlife cognitive decline, whereas more frequent social group participation had a stronger association in later life. Physical activity did not significantly affect the cognitive decline trajectory. In MIDUS, neither the activity frequency nor diversity was associated with subsequent cognitive decline. Discussion and Implications: Our results underscore that both type and timing of activity matter: Efforts to promote activity diversity and social contact are likely to be most effective in midlife, whereas cognitive activities and social group participation may be more impactful in late life. Physical activity alone had little effect on mid-to-late-life cognition but may be valuable earlier in life and in the context of activity diversity.