BMI decline patterns and relation to dementia risk across four decades of follow‐up in the Framingham Study

Abstract Background Obesity has been associated with increased risk of dementia with several studies reporting a reverse causality, with weight loss preceding the onset of dementia. Methods Two thousand forty‐five non‐demented Framingham Offspring participants, aged 30 to 50 years, were included to determine effect of body mass index (BMI) decline patterns from mid‐ to late life over a 39‐year follow‐up. Group‐based trajectory models were used to create BMI trajectories. Results Decreasing BMI trends were associated with higher risk of developing dementia in late life. Decliners with first early mid‐life increasing and then later mid‐life declining patterns of BMI were at greater increased risk of dementia compared to non‐decliners (hazard ratio 3.84, 95% confidence interval 1.39–10.60). Conclusion While patterns of decline in BMI were associated with dementia, a subgroup with a pattern of initial increasing BMI followed by declining BMI, both occurring within mid‐life, appeared to be central to declining BMI–dementia association. Further validations are needed to provide robust conclusions.