Can Intraindividual Variability in Cognitive Speed be Reduced by Physical Exercise? Results from the LIFE Study.

Objectives: Findings are mixed regarding the potential to improve older adults' cognitive ability via training and activity interventions. One novel sensitive outcome may be intraindividual variability (IIV) in cognitive speed, or moment-to-moment changes in a person's performance. The present paper evaluated if participants who participated in a moderate physical activity intervention showed a reduction in IIV, compared to a successful aging education control group.

Method: For approximately 2.6 years, sedentary adults aged 70-90 years participated in the Lifestyle Interventions and Independence for Elders (LIFE) Study (n = 1635), a multi-site Phase 3 randomized controlled trial to reduce major mobility disability. They completed four reaction-time tests at baseline and at approximately 24 months post-test.

Results: Analyses were conducted following both the intent-to-treat principle and complier average casual effect modeling. Results indicated that participants in the physical activity group did not show a reduction in their IIV.

Discussion: The lack of a significant reduction in IIV may be due to the mild nature of the physical activity program and the cognitively healthy sample. It is also possible that other types of lifestyle activity interventions (e.g., social and cognitive engagement) can elicit reductions in IIV for older adults.