Stability in BMI over time is associated with a better cognitive trajectory in older adults

OBJECTIVE: Evidence on simultaneous changes in body mass index (BMI) and cognitive decline, which better reflect the natural course of both health phenomena, is limited. METHODS: We capitalized on longitudinal data from 15,977 initially non‐demented elderly from the Alzheimer's Disease Centers followed for 5 years on average. Changes in BMI were defined as (1) last minus first BMI, (2) mean of all follow‐up BMIs minus first BMI, and (3) standard deviation of BMI change from baseline and all follow‐up visits (representing variability). RESULTS: Participants with significant changes in BMI (increase or decrease of ≥5%), or who had greater variability in BMI, had faster cognitive decline. This pattern was consistent irrespective of normal (BMI < 25; N = 5747), overweight (25 ≤ BMI < 30; N = 6302), or obese (BMI ≥ 30; N = 3928) BMI at baseline. CONCLUSIONS: Stability in BMI predicts better cognitive trajectories suggesting clinical value in tracking BMI change, which is simple to measure, and may point to individuals whose cognition is declining.