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

Obesity has been associated with increased risk of dementia with several studies reporting a reverse causality, with weight loss preceding the onset of dementia.

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.

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).

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.