BackgroundRising Alzheimer's disease (AD) incidence underscores the need to identify modifiable risk factors. The "obesity paradox" suggests higher late-life body mass index (BMI) may reduce AD risk. Because BMI does not distinguish between fat and lean mass, investigating body composition and brain amyloid accumulation may clarify this relationship.ObjectiveThis study tested whether baseline body stature predicts one-year change in brain amyloid.MethodsUsing data from the Alzheimer's Prevention through Exercise trial, we examined whether baseline body stature and composition (BMI, fat mass index FMI, lean mass index LMI, and total fat and lean mass) predicted one-year change in brain amyloid among 106 cognitively healthy older adults enriched with elevated amyloid status.ResultsHigher baseline BMI predicted less one-year amyloid accumulation globally (β = -0.33, p = 0.001) and in five of six brain regions (p = 0.001-0.05). Higher FMI predicted less amyloid accumulation globally (β = -0.35, p < 0.001) and in all six regions (p < 0.001-0.02), while higher LMI predicted less accumulation globally and in four regions (p < 0.001-0.02). Higher total fat mass was associated with less amyloid globally and regionally (p < 0.001-0.02), whereas higher total lean mass predicted reduced accumulation only in the lateral temporal lobe (p = 0.01).ConclusionsLarger body mass predicted less amyloid accumulation in cognitively healthy older adults over one year. More research is needed to investigate whether larger body stature protects against amyloid accumulation and explore underlying mechanisms.Clinical Trial RegistrationClinicalTrials.gov, Identifier (NCT02000583).
Smith et al. (Thu,) studied this question.