Mid-Life Physical Activity and Late-Life Cognitive Performance among American Indians.

Introduction: Research on factors associated with late-life cognitive performance in diverse racial/ethnic groups is increasingly important due to the growing size and racial diversity of the elder population.

Methods: Using data on American Indians (AIs) from the Strong Heart Study, we measured associations between mid-life physical activity (PA), assessed by a questionnaire or pedometer, and performance on tests of general cognitive function, phonemic fluency, verbal learning and memory, and processing speed. Cognitive tests were administered 7-21 years after PA measurements. To estimate associations, we used regression models with and without inverse-probability weights to account for potential attrition bias in the cohort.

Results: Questionnaire and pedometer measures of PA were positively associated with cognitive function. Participants in the top quartile of questionnaire-based PA had Modified Mini-Mental State examination scores 3.2 (95% CI: 1.5-4.9) points higher than participants in the lowest quartile. Phonemic fluency scores also trended higher for participants in the top compared to the bottom categories for both PA measures: top questionnaire quartile = 2.7 (95% CI: 0.6-4.8) points higher and top pedometry tertile = 6.7 (95% CI: 2.7-10.7) points higher. We observed no associations between PA and tests assessing verbal learning and memory, or processing speed. Weighted model results were similar, but less precise.

Conclusions: In this cohort of AIs with relatively low levels of PA, positive associations between mid-life PA and late-life cognitive performance were dose-dependent and of modest clinical significance.