Body Mass and Physical Activity Uniquely Predict Change in Cognition for Aging Adults

Background: Physical activity and body mass predict cognition in the elderly. However, mixed evidence suggests that obesity is associated with poorer cognition, while also protecting against cognitive decline in older age. Purpose: We investigated whether body mass independently predicted cognition in older age and whether these associations changed over time. Methods: A latent curve structural equation modeling approach was used to analyze data from a sample of aging adults (N = 8442) split into two independent subsamples, collected over 6 years. Results: Lower baseline Body Mass Index (BMI) and higher physical activity independently predicted greater baseline cognition (p < 0.001). Decreases in BMI and physical activity independently predicted greater decline in the slope of cognition (p < 0.001). Conclusions: Our results support the obesity paradox in cognitive aging, with lower baseline body mass predicting better cognition, but less decline over time protecting against cognitive decline. We discuss how weight loss in the elderly may serve as a useful indicator of co-occurring cognitive decline, and we discuss implications for health care professionals.