KANSAS CITY—Lean body mass appears to decline among patients with Alzheimer’s disease, possibly as a consequence of disease progression or through shared mechanisms associated to both Alzheimer’s and sarcopenia, and are associated with declines in brain volume and function, according to a new study in the Archives of Neurology (Apr 2010;67(4):428-33). Unintended weight loss is common in Alzheimer’s patients and has been associated with rate and severity of disease progression.
Jeffrey M. Burns, M.D., M.S., of the University of Kansas School of Medicine, Kansas City, and colleagues used dual-energy x-ray absorptiometry (DEXA) to assess body composition in 70 individuals age 60 and older without dementia and 70 with early-stage Alzheimer’s disease. Participants were also evaluated with brain magnetic resonance imaging (MRI) and neuropsychological testing.
The researchers found lean mass was reduced in the Alzheimer’s patients compared to controls. There were also significant associations between loss of lean mass and decreases in the volume of the brain and its white matter, as well as declines in cognitive performance. There was no relation between total body fat or body fat percentage and cognitive ability or brain volume.
“We observed a direct correlation between whole-brain volume (an estimate of brain atrophy) and lean mass, suggesting that brain atrophy and loss of muscle mass may co-occur,” the authors noted. “Brain atrophy is considered a neuroimaging measure reflective of Alzheimer’s disease pathology. Thus, our data are consistent with other studies suggesting that brain pathology may contribute to decline in body composition, perhaps by disrupting central nervous system regulation of energy metabolism and food intake.”
Of further interest was the fact that the Alzheimer’s patients in the study also had lower levels of physical activity compared to controls, and low levels of physical activity are strongly associated with sarcopenia, a loss of muscle mass typically associated with aging. The researchers noted there may be an association between the behavioral changes associated with dementia, or an underlying mechanism such as inflammation or tissue development that is common to both sarcopenia and Alzheimer’s disease.
