How Does BMI Affect Alzheimer’s Risk?

Those with lower BMI showed higher levels of beta-amyloid, closely tied to the onset of Alzheimer's disease.

Elderly individuals with a lower body mass index (BMI) may have elevated levels of protein beta-amyloid, believed to be the first stage of the preclinical form of Alzheimer’s disease. The finding comes in a new report published in the Journal of Alzheimer’s Disease.

The link was particularly evident among individuals carrying the apolipoprotein gene (ApoE4), an indicator known to increase the risk of late-onset Alzheimer’s disease.

The study – part of the wider Harvard Aging Brain Study (HABS) – examined BMI and beta amyloid levels in 280 patients aged between 62 and 90 years old. All participants were in good overall health and with normal cognition. PET imaging was conducted with Pittsburgh compound B (PiB), which visualizes amyloid plaques in the brain.

Lower BMI results correlated with greater retention of PiB after adjusting for age, sex, education, and APoE4 status, suggesting a higher level of amyloid deposits in the brain. Furthermore, this link was most significant in normal-weight patients, who comprised the group with the lowest BMi in the study. Moreover, the link between lower BMi and greater PiB retention was especially significant for those with the APoE4 gene variant.

“A likely explanation for the association is that low BMI is an indicator for frailty,” said Gad Marshall, MD, senior author of the report. HABS is following these patients in order to monitor possible cause and effects of low BMI and Alzheimer’s onset. “Right now,” said Marshall, “we’re also studying whether BMI is associated with any other clinical and imaging markers of Alzheimer’s disease.”


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; doi:10.3233/JAD-150987.

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This article originally appeared on MPR