Mid- to Late- Life Body Mass Index and Dementia Risk: 38 Years of Follow-up of the Framingham Study.

Growing evidence relates Body Mass index (BMI) to poorer health outcomes; however, results across studies associating BMI and dementia are conflicting. A total of 3632 Framingham Offspring participants aged 20 to 60 years at their second health exam (1979-1982) were included in this study with 190 cases of incident dementia identified by 2017. Cox proportional hazards regression models were performed to investigate the association of BMI at each of their 8 exams as a baseline for dementia risk, and the associations between obesity and dementia across age groups. Spline models were fitted to investigate non-linear associations between BMI and dementia. Each 1 kg/m2 increase in BMI at 40-49 years was associated with higher risk of dementia, but lower risk after 70 years. Obesity at 40-49 years was associated with higher risk of dementia. Overall, the relationship between BMI and dementia risk was heterogeneous across the adult age range. Monitoring BMI at different age may mediate risk for dementia across an individual's lifetime.