Lower BMI May Raise Risk of Alzheimer Disease in Elderly

Older adults with a low body mass index (BMI) have more accumulation of β-amyloid, a protein associated with Alzheimer disease, according to a new study.

Those carrying the apolipoprotein E ɛ4 (APOE4) gene variant had an even higher risk of accumulation of β-amyloid.
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Because previous studies had found associations between lower weight and increased risk of dementia, the researchers aimed to examine the association between BMI and β-amyloid accumulation on Alzheimer disease risk.

To conduct their study, the researchers performed a cross-sectional analysis of 280 community-dwelling, clinically normal adults aged 62 to 90 years who participated in the Harvard Aging Brain Study.

The researchers examined participants’ medical histories and physical examination findings, used positron emission tomography with Pittsburgh compound B (PiB), which can visualize amyloid plaques in the brain, and tested for APOE4.

After adjusting for age, sex, education, and APOE4 status, they found that participants with a lower BMI had greater PiB retention, indicating greater amyloid deposits in the brain and greater risk of Alzheimer disease.

A secondary analysis showed that participants who carried the APOE4 gene and had lower BMI also had significantly greater accumulation of β-amyloid.

“This finding offers new insight into the role of BMI at the preclinical stage of [Alzheimer disease], wherein lower BMI late in life is associated with greater cortical amyloid burden,” the researchers concluded. “Future studies are needed to elucidate the mechanism behind this association, especially in those with lower BMI who are APOE4 carriers.”

—Amanda Balbi

Reference:

Hsu DC, Mormino EC, Schultz AP, et al. Lower late-life body-mass index is associated with higher cortical amyloid burden in clinically normal elderly. J Alzheimers Dis. 2016;53(3). http://www.ncbi.nlm.nih.gov/pubmed/27340843?dopt=Abstract.