Being overweight has long been linked to increasing the odds of getting dementia. But does it affect the age when it starts?

To learn more, researchers at the National Institute on Aging, part of the NIH, further explored the relationship between weight at midlife and Alzheimer’s among volunteers participating in the Baltimore Longitudinal Study of Aging (BLSA). BLSA is one of the longest running studies of human aging in North America. (Continued below video…)

They found that being obese or overweight at midlife—as measured by body mass index (BMI) at age 50—may predict earlier age of onset of the devastating neurodegenerative disorder. The study, led by Madhav Thambisetty, M.D., Ph.D., will appear online Sept. 1, 2015, in Molecular Psychiatry.

Testing Cognitively Healthy People

Cognitively healthy at the start of the nearly 14-year study, each of the 1,394 BLSA participants received cognitive testing every one to two years; 142 volunteers eventually developed Alzheimer’s disease. The investigators found:

• Each unit increase in BMI at age 50 accelerated onset by nearly 7 months in those who developed Alzheimer’s disease.
• Higher midlife BMI was associated with greater levels of neurofibrillary tangles—a hallmark of the disease—in the brains of 191 volunteers, including those who did not develop Alzheimer’s.
• Among 75 cognitively healthy volunteers who had brain imaging to detect amyloid, a protein whose fragments make up the brain plaques that are a hallmark of Alzheimer’s, those with higher midlife BMI had more amyloid deposits in the precuneus, a brain region that often shows the earliest signs of Alzheimer’s-related changes.

More Study on Weight and Alzheimer’s

More study is needed to determine the relationship behind BMI at midlife and Alzheimer’s onset. The findings suggest, however, that maintaining a healthy BMI at midlife might be considered as one way to delay the onset of Alzheimer’s.