Obesity at Midlife Tied to Increased Dementia Risk

Obesity may lead to Alzheimer's

January 21, 2020

Being obese in middle age may increase your risk of developing Alzheimer’s disease or other forms of dementia later in life. Those are the findings from a large analysis of more than a million women living in Britain.

For the study, researchers had health information, including height, weight, and diet and exercise habits, on one of every four women who were born in the United Kingdom between 1935 and 1950. Their average age was 56 at the start of the study, and all the women were free of dementia.

The women were followed for up to two decades. The researchers found that women who were obese at the start of the study had, over an average of 18 years a follow-up, a 21 percent greater risk of dementia compared to women with a healthy body mass index.

Researchers typically use body mass index, a measure of height and weight, to define obesity. You can calculate your BMI using online tools such as that found at the Centers for Disease Control and Prevention at https://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/english_bmi_calculator/bmi_calculator.html

A BMI between 18 and 25 is considered healthy; 25 to 30 is overweight; and over 30 is considered obese.

“Obesity in midlife was linked with dementia 15 or more years later,” said Sarah Floud, a study author, of the Nuffield Department of Population Health at the University of Oxford. The findings, which appeared in the medical journal Neurology, are consistent with earlier studies tying obesity at midlife to late-life dementia. This was one of the largest studies to date.

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 diseases, high blood pressure and diabetes.

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 “healthy” fats, such as those found in fish, and to get less exercise than those who are of normal weight.

This study, however, did not find a link between diet or inactivity and later risk of dementia. “Some previous studies have suggested poor diet or a lack of exercise may increase a person’s risk of dementia,” Dr. Floud said. “However, our study found these factors are not linked to the long-term risk of dementia.”

Additional study is needed to determine how weight and body fat, as well as diet and exercise, might affect brain health. Many factors go into determining who ultimately gets Alzheimer’s disease, including the genes you inherit. But anything that delays the onset of Alzheimer’s could have a significant impact on quality of life for both those with the disease and those caring for them.

By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Marc Flajolet, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.

Source: Sarah Floud, PhD, Rachel F. Simpson, MBBS, Angela Balkwill, MSc, et al: “Body mass index, diet, physical inactivity, and the incidence of dementia in 1 million UK women.” Neurology Dec. 18, 2019

May A. Beydoun, PhD, and Mika Kivimaki, FMedSci: “Midlife obesity, related behavioral factors, and the risk of dementia in later life.” Editorial, Neurology, Dec.  18, 2019


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