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Obesity Associated with Earlier Alzheimer’s Disease Onset

FILE - An obese person is seen reading a newspaper.

Gaining weight in midlife is unhealthy for a number of reasons, including increasing the risk of high blood pressure, diabetes and heart disease. A new study concludes that obesity in middle age may also cause people to develop Alzheimer’s disease symptoms at a younger age.

Alzheimer’s disease affects an estimated 35 million elderly people around the world, and that number is expected to jump to nearly double in 20 years.

The neurodegenerative disorder causes severe memory loss, disability and death. Previous studies have linked it to obesity, although the reasons are still unclear.

A new study has found that those who are obese in midlife are at greater risk of developing Alzheimer’s at a younger age than they would have otherwise. Researchers followed almost 1,400 cognitively normal individuals for about 14 years. Of these, 142 eventually developed Alzheimer’s disease.

U.S. Institute on Aging neurologist Madhav Thambisetty is lead author of the study, which used a calculation of obesity called the body mass index to compare with the age of onset of Alzheimer’s.

“We find that for every unit increase in body mass index at age 50 years, the age at which the symptoms of Alzheimer’s disease appear, appears to decrease by almost six-and-a-half months," said Thambisetty.

In the study, the average age of Alzheimer’s onset was 83. But symptoms began almost seven months earlier for each unit above a normal BMI of 25.

In other words, a person with a BMI of 27 was more likely to show symptoms of Alzheimer’s almost 14 months earlier, at the age of 82, while someone with a BMI of 32 might start to show signs at 79, four years younger than average.

Thambisetty and colleagues saw a trend in Alzheimer’s development among obese individuals. It is important to note that not all the overweight participants developed Alzheimer’s.

Researchers conducting autopsy and imaging studies on those who died of Alzheimer’s disease noted the higher the BMI, the more plaques and tangles they saw in their brains. Plaques and tangles are the hallmarks of the disease.

The study was published in the Nature journal Molecular Psychiatry.

Thambisetty says there is a take-home message.

“Maintaining a healthy body mass index even as early as in midlife may have long-lasting protective effects in delaying the onset of Alzheimer’s disease even decades later," he said.

The authors write that intervention, in the form of weight management, could potentially delay the worldwide prevalence of the disease by 22 million people by the year 2050.

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