Obesity at Midlife May Speed Alzheimer’s Onset

November 2, 2015

Various studies suggest that being overweight at midlife increases your risk of developing Alzheimer’s in old age. Now, a new study found that people who are obese at age 50 may get Alzheimer’s at a younger age.

The study, from researchers at the National Institutes of Health, looked at 1,394 men and women who were part of the Baltimore Longitudinal Study of Aging, a large and ongoing study of Baltimore residents as they age. Their average age was around 60.

None had Alzheimer’s disease or other serious memory problems at the start of the study. They got regular checks of memory and thinking skills, for an average of about 14 years. During that time, 142 were diagnosed with Alzheimer’s disease.

The researchers found that people with the highest body mass index, or BMI, at age 50 were much more likely to develop Alzheimer’s disease. BMI is a formula doctors use that takes into account both height and weight to estimate body fat and the likelihood of developing health problems due to excess weight. People at a healthy weight generally have a BMI under 25. Those with a BMI of 25 to 30 are considered to be overweight, while those with a BMI over 30 are considered obese.

A man who is 5 foot 11 and weighs 180 pounds, for example, has a BMI just over 25, while a 5 foot 4 woman who weighs 145 would have a similar BMI on the healthy-overweight border. You can calculate your BMI at various online sites, including at NIH: http://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm

The researchers found that the higher someone’s BMI at midlife, the earlier they tended to get the disease. Each one-point increase in BMI was associated with getting Alzheimer’s six to seven months earlier. Someone with a BMI of 30, for example, might develop Alzheimer’s two-and-a-half years earlier than someone with a BMI of 25. Those with the highest BMIs also tended to have more brain changes typical of Alzheimer’s, even if they didn’t have symptoms of the disease.

Do those with higher BMI at midlife tend to stay that way? Or can the effects of BMI at midlife be changed for those who lower their BMI? These questions were not made clear by the current study, but answers to these questions could allow people to make more lifestyle changes that would reduce their risk of developing Alzheimer’s disease at an earlier age.  

“As we try to cure Alzheimer’s disease, we also want to delay the onset of symptoms,” said study author Dr. Madhav Thambisetty, a neurologist at the NIH’s National Institute on Aging. “Maintaining a healthy BMI at midlife is likely to have long-lasting protective effects.” The findings appeared in the journal Molecular Psychiatry.

Increasingly, doctors believe that what’s good for the heart is good for the brain. Carrying excess weight has been closely linked with a variety of diseases that affect the heart and blood vessels, including heart disease, high blood pressure and diabetes. Being “apple-shaped,” with excess belly fat, as opposed to “pear-shaped,” with large thighs, may be a particular risk factor for heart disease – as well as Alzheimer’s.

Scientists also speculate that fat cells may produce harmful chemicals that promote inflammation in blood vessels throughout the body, including in the brain. People who are overweight may also tend to have diets low in “good” fats, such as those found in fish, and to get less exercise than those who are of normal weight.

Additional study is needed to determine how weight and body fat might affect brain health. Many factors go into determining who ultimately gets Alzheimer’s disease, including what genes you inherit. But anything that delays the onset of Alzheimer’s could have significant impacts on the costs – both human and financial — of caring for the disease.

By www.ALZinfo.org, The Alzheimer’s Information Site. Reviewed by William J. Netzer, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.

Source: Y-F Chuang, Y An, M Bilgel, et al: “Midlife Adiposity Predicts Earlier Onset of Alzheimer’s Dementia, Neuropathology and Presymptomatic Cerebral Amyloid Accumulation.” Molecular Psychiatry, Sept. 1, 2015


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