Body Composition in Early Alzheimer's Disease

Abstract

Background: Alzheimer's disease (AD) is associated with unintended weight loss. We examined body composition in early AD and nondemented aging and its relation to brain volume and cognition. Methods: Brain magnetic resonance imaging (MRI) and neuropsychological testing were performed on nondemented (CDR 0, n=70) and early-stage AD (CDR 0.5 or 1, n=70) subjects. Dual energy x-ray absorptiometry (DEXA) determined whole-body fat mass and lean mass. Body mass index (BMI) was determined from height and weight. Linear regression analyses controlling for age and sex assessed the relationship between body composition, cognition, and brain volume. Results: Lean mass was reduced in early AD compared to nondemented controls (F=7.73, p=0.006) after controlling for sex. Lean mass was associated with whole-brain volume (beta=0.20, p<0.001) and white matter volume (beta=0.19, p<0.001) when controlling for age and sex. Lean mass was also associated with global cognitive performance (beta=0.12, p=0.007) when controlling for age and sex. Total body fat and percent body fat were not different across groups or related to cognition and brain volume. Conclusion: Loss of lean mass is accelerated in AD and associated with brain atrophy. AD and sarcopenia may share common underlying mechanisms or sarcopenia may be a direct or indirect consequence of AD pathophysiology.