Obesity after 70 Increases Risk for Alzheimer's Disease

Alzheimer's Association
Monday, 14 July 2003

There was a striking association between women overweight at 70 and their risk of developing Alzheimer's disease ten to 18 years later, according to a Swedish study appearing in the July 14 issue of the Archives of Internal Medicine. In the study, sponsored in part by a grant from the Alzheimer's Association, 392 adults were followed for 18 years, from the age of 70 until they were 88, to determine whether being overweight put them at increased risk for dementia and Alzheimer's disease.

It has been difficult to determine how obesity and being overweight affect risk of Alzheimer's disease because weight loss frequently occurs before clinical symptoms of dementia appear, according to first author of the study, Deborah Gustafson, Ph.D., who conducted the research while at Gothenburg University in Gothenburg, Sweden.

"Overweight and obesity are very closely associated with vascular diseases, such as diabetes, coronary heart disease and hypertension, and there is more and more evidence that vascular risk factors may be important in Alzheimer's disease," said Gustafson. "But because of the weight loss associated with pre-clinical dementia, it took an extended study to uncover the dangers that overweight may pose to a very elderly population."

"Obesity increases multiple vascular risk factors like high blood pressure, high cholesterol and high blood sugar," said Bill Thies, Ph.D., vice president of medical and scientific affairs at the Alzheimer's Association. "All of these have been implicated as risk factors in Alzheimer's disease."

Women in the study who developed Alzheimer's disease between the ages of 79 and 88 were significantly more likely to have been overweight at age 70, as well as at 75 and 79. The women who developed Alzheimer's disease were much heavier, with a body mass index (BMI) averaging 3.6 units higher than that of women who did not become demented. For every unit increase in BMI at age 70, the risk of developing Alzheimer's disease increased by 36 percent.

BMI is a measure of body fat in both men and women based on height and weight. BMI is calculated as kilograms per meter squared. A BMI between 18.5 and 24.9 is considered normal weight. A BMI over 25 is defined as overweight and 30 or greater as obese. According to the study, women who had a BMI greater than 29 when they were 70 years old were more likely to have Alzheimer's disease in their 80s. A BMI of 29 corresponds to a woman who is 5 feet 4 inches tall and weighs about 170 pounds. "A moderate, healthy weight seems to be best."

"It's important to note that the ideal weight is not super-skinny," said Gustafson. "The average BMI for women who did not develop Alzheimer's disease was 25, the border between healthy and overweight. A moderate, healthy weight seems to be best."

The study is part of a larger population-based longitudinal health study that enrolled a representative group of 70-year-old residents of Gothenburg, Sweden in 1970. One hundred and sixty-six men and 226 women who had no symptoms of dementia, based on psychiatric evaluations, were enrolled.

Body mass index (BMI) for subjects in the study was recorded at age 70, 75, and 79. Neuropsychiatric evaluations for dementia were performed approximately every 5 years until age 81 and then every other year thereafter.

There was no association in women who were overweight or obese at 70 and 75 and the development of Alzheimer's disease at ages 70-79. This may be the result of weight decline in pre-clinical dementia. "It's possible that overweight at ages 50 or 60 affected risk of dementia in these women," said Gustafson. "But we don't have that data for this group of women."

In the study, it was not possible to establish a relationship between overweight and obesity and risk of dementia in the men in the study because of the small number of men reaching very old age. Age remains the greatest risk factor for Alzheimer's disease.

Obesity and overweight are epidemic in the US and Europe with the highest prevalence among adults fifty and older. These findings have important public health implications, according to the authors. The prevention of overweight and obesity, even in old age, might help to prevent dementia, the fastest growing disease of late life, the authors conclude.

"People are living longer," said Gustafson. "It's important that they be able to enjoy those extra years. Enjoying those extra years may mean maintaining a healthy weight."

This work was supported by grants from the Alzheimer's Association Zenith Award (supporting the work of Ingmar Skoog, principal investigator, and Gustafson), the Swedish Research Council and other sources of funding. The Alzheimer's Association is the premier source of information and support for the millions of Americans with Alzheimer's. The largest private funder of Alzheimer research in the United States, the Association has committed $138 million toward research into the disease.

For more information, or to contact Alzheimer's Association, see their website at: www.alz.org