Alzheimer's Disease
Neuronix CEO Eyal Baror poses for a photo next to a newly-developed device to treat Alzheimer's disease at Assaf Harofeh Medical Center near Tel Aviv October 24, 2012. Reuters/Nir Elias

Scientists at Brigham and Women's Hospital (BWH) and Massachusetts General Hospital (MGH) have found a link between lower weight and Alzheimer’s disease risk. They have associated lower body mass index (BMI) with greater deposits of Alzheimer's-associated amyloid plaques in the brains of older individuals.

The study, published in the Journal of Alzheimer’s Disease, revealed that the association was most-pronounced in individuals carrying the APOE4 gene variant, which is known to increase the risk of Alzheimer's.

The study analysed 280 healthy subjects between the ages of 62 and 90. Being underweight as a person grows older may not be a good thing for brain health. The researchers believe that it is about frailty. Reduced weight, slower mobility and loss of strength are associated with Alzheimer’s disease.

“One way to get closer to determining any cause and effect relationship will be following these individuals over time to see whether their baseline BMI does predict the development of symptoms, which we are doing in Harvard Aging Brain Study (HABS), and eventually investigating whether maintaining or even increasing BMI in late life has an effect on outcomes,” MD of the MGH and BWH Departments of Neurology and senior author of the report, Gad Marshall, said in a statement.

The researchers are also studying if BMI is associated with any other clinical and imaging markers of Alzheimer's disease. The participants in the study were in good health and cognitively normal.

After adjusting for factors such as education, sex, age and APOE4 status, the scientists found that lower BMI was associated with greater retention of Pittsburgh compound B (PiB) that indicated more amyloid deposits in the brain.

This association was not much pronounced in normal-weight participants. Association between lower BMI and greater PiB retention was particularly significant for individuals with the APOE4 gene variant, which is associated with increased Alzheimer's disease risk.

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