Body mass index and cognitive decline among community-living older adults: the modifying effect of physical activity

OBJECTIVE: To examine the associations between BMI categories and subsequent 3-year cognitive decline among older adults, and to test whether physical activity modifies the associations. METHODS: Study sample included n = 1028 cognitively unimpaired older adults participating in the Étude sur la Santé des Aînés (ESA)-Services longitudinal study and followed 3 years later. Cognitive decline was defined as a decrease of > 3 points in MMSE scores between baseline and follow-up. BMI categories (normal weight (reference), underweight, overweight, obese) were derived from self-reported weight and height. Moderate to vigorous physical activity of ≥20 min (# of times per week) was self-reported. The presence of chronic disorders was ascertained from administrative and self-reported data. Logistic regression analyses were used to study the risk of cognitive decline associated with BMI categories stratified by weekly physical activity (≥140 min), the presence of metabolic, cardiovascular and anxio-depressive disorders. RESULTS: In the overall sample, there was no evidence that underweight, overweight, or obesity, as compared to normal weight, was associated with cognitive decline, after adjusting for sociodemographic, lifestyle factors, and comorbidities. Individuals with overweight reporting high physical activity had lower odds of cognitive decline (OR = 0.25, 95% CI = 0.07–0.89), whereas no association was observed in individuals with overweight reporting low physical activity (OR = 0.85, 95% CI = 0.41–1.75). Among participants with metabolic and cardiovascular disorders, individuals with overweight reporting high physical activity had lower odds of cognitive decline (OR = 0.09, 95% CI = 0.01–0.59 and OR = 0.03, 95% CI = 0.01–0.92 respectively), whereas no association was observed in those with low physical activity. CONCLUSION: Physical activity modifies the association between overweight and cognitive decline in older adults overall, as in those with metabolic and cardiovascular disorders. Results highlight the importance of promoting and encouraging regular physical activity in older adults with overweight as prevention against cognitive decline. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s11556-022-00284-2.