Physical activity in late middle- to older-aged people and dementia, cognitive, and physical function two decades later

Introduction: Low physical activity (PA) is a potential risk factor for dementia and cognitive impairment. However, few studies have focused on very old people (aged ≥80 years), the age group with highest prevalence of dementia. The aim was to investigate if PA associated with subsequent dementia, cognitive function, and gait speed (GS), in very old people. Methods: A population-based survey was conducted in 1999 and followed-up between 2016 and 2019 in participants ≥80 years. Altogether 541 individuals (56.2% women), 64.9 ± 4.2 years of age at baseline participated. Self-rated baseline PA was categorized into low, medium, or high. Cognitive function was assessed with the Mini-Mental State Examination (MMSE), executive function with the Frontal Assessment Battery (FAB), and GS (in meters/second) was measured over 2.4 m at follow-up. Results: During a mean of 19.0 ± 1.1 years, 175 (32.3%) developed dementia. Low or medium PA compared to high PA did not associate with subsequent dementia, and PA did not associate with future cognitive function (MMSE). PA associated with executive function (FAB) (unstandardized beta [95% confidence interval]) (0.67 [0.07–1.27]), but not after adjustments. PA associated with subsequent GS in the unadjusted model and after adjustment for age, sex, smoking, and education (0.06 [0.02–0.09], and 0.04 [0.01–0.08], respectively), but not after adding adjustment for hypertension, obesity, and glucose intolerance. Conclusion: No support was found for the hypothesis that low PA is a potential risk factor for dementia in very high age. However, PA and executive function were associated in unadjusted analyses which indicate that PA may be important for at least one aspect of cognitive function. The association between PA and GS around 2 decades later seems attenuated by cardiometabolic risk factors. Future investigations regarding PA, dementia, and cognitive decline may consider cardiometabolic risk factors such as hypertension, obesity, and glucose intolerance, and include repeated measures of PA over the life course.Originally included in thesis in manuscript form.