Body mass index and 2‐year change of in vivo Alzheimer's disease pathologies in cognitively normal older adults

Abstract Background Multiple studies supported that low body mass index (BMI) or underweight status in late‐life was associated with increased risk of dementia. We tried to test the hypothesis that lower late‐life BMI is related with greater increase of in vivo AD pathology including Aβ and tau deposition for two years in cognitively healthy individuals. Additionally, we explored the same relationship in each sex separately, considering previous reports that showed prominent sex differences for the relationship between BMI and AD dementia risk. Method Total 194 cognitive normal older adults from the Korean Brain Aging Study for Early Diagnosis and Prediction of Alzheimer’s Disease (KBASE) were included. All participants underwent comprehensive clinical assessment including BMI measurement, [ 11 C] Pittsburg compound B and [ 18 F] AV‐1451 PET at baseline. The same brain imaging scans were repeated at a year follow‐up assessment. The association of baseline BMI with longitudinal changes of AD biomarkers were analyzed using linear mixed effect models. Result Lower BMI at baseline was significantly associated with greater increase of tau deposition in AD‐signature region for 2 years. In contrast, BMI was not related with 2‐year change of global Aβ deposition. In additional exploratory analysis for each sex, lower baseline BMI was associated with greater increase of both Aβ and tau deposition in male, whereas neither Aβ nor tau change was not related with baseline BMI in female. Conclusion The present study suggest that lower late‐life BMI may accelerate the accumulation of AD pathology in the brain, especially in male. To prevent AD, more attention is needed to be paid to avoiding underweight in old age and maintaining an appropriate BMI status.