Body mass change in Alzheimer's disease

Abstract

A high body mass index (BMI) at mid-age or a decrease in BMI at late-age has been considered as a predictor for the development of Alzheimer's disease (AD). However, little is known about the BMI change close to or after AD onset. BMI of participants from three cohorts -the Washington Heights / Inwood Columbia Aging Project (WHICAP; population-based), the Predictors Study (clinic-based), and the National Alzheimer's Coordinating Center (NACC; clinic-based)- were analyzed longitudinally. We separately examined change of BMI before AD diagnosis in incident AD patients and after AD diagnosis in incident and prevalent AD patients. We used generalized estimating equations to test whether there were significant changes of BMI over time, adjusting for age, sex, education, race, and research center (for NACC study and Predictors study). Stratification analyses were run to determine whether the BMI changes depended on baseline BMI status (underweight or normal <25 kg/m 2, overweight ≥25-<30 kg/m 2, and obese ≥30 kg/m 2). BMI declined over time up to AD clinical onset, with an annual decrease of 0.21 (p=0.02) and 0.19 (p=0.03) kg/m 2(in WHICAP and NACC, respectively). Following the clinical onset of AD, there was no longer a significant decrease of BMI. BMI even increased (b=0.10, p=0.01) in prevalent AD participants of NACC study. During the prodromal period BMI decreased significantly over time only in obese participants of the NACC study (β= -0.82, p<0.0001). During the period shortly after diagnosis of AD, BMI increased in underweight/normal weight subjects (β= 0.31, p<0.0001) and BMI decreased in obese subjects (β= -0.40, p=0.05) in NACC. Among prevalent AD participants, BMI increased in underweight/normal weight in Predictors study (β= 0.21, p=0.06) and NACC (β= 0.21, p<0.0001), and decreased in underweight/normal weight participants in NACC (β= -0.26, p=0.001). No significant change was observed for overweight subjects in any of the three cohorts. Our study suggests that while BMI declines before AD incidence, decline levels off after clinical AD onset and it might even increase. The pattern of BMI change may also depend on the initial BMI.