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MONDAY, July 14, 2003 (HealthDayNews) -- Women who are overweight or obese when they are 70 appear to have a greater risk of developing Alzheimer's disease over the next 10 to 18 years of their life.
While the finding, published in the July 15 issue of the Archives of Internal Medicine, points only to an association and not to a cause-and-effect relationship, it nevertheless represents a potential milestone in Alzheimer's research.
"It continues to reinforce the idea that there's some relationship between traditional vascular risk factors and Alzheimer's disease," says Bill Thies, vice president for medical and scientific affairs at the Alzheimer's Association, which partially funded the study. "It pulls stuff together in a way that continues to move us in the direction of being able to say there actually may be some modifiable risk factors for Alzheimer's."
Right now, there are no known risk factors for Alzheimer's other than age and, to a certain degree, genetics. And there are no effective treatments for the devastating disease that gradually robs people of their ability to remember, think and take care of themselves.
A number of other studies have pointed to vascular diseases such as hypertension, diabetes, atherosclerosis and heart disease as risk factors for Alzheimer's. Obesity is a risk factor for all of these conditions, and obesity, too, is on the rise in Western societies. More than 50 percent of adults in the United States and Europe are either overweight or obese.
Until now, however, no one had looked at a possible link between obesity and Alzheimer's.
The problem with conducting such a study is that many people with extremely early stages of dementia, including Alzheimer's, lose weight.
"Even before a person is clinically diagnosed, they're already losing weight," says Deb Gustafson, lead author of the study, which she completed while an assistant professor of nutrition and food sciences at Utah State University and a guest researcher at Goteberg University in Sweden. "To be able to look at the effect of overweight and obesity on dementia, you have to be able to follow people for a very long period of time."
That is what these researchers did, patiently following 382 white adults, all residents of the Swedish city of Goteberg, for 18 years. All the participants were 70 years old at the beginning of the study and none had dementia. Body Mass Index (BMI) was calculated at set points over the course of the study.
As it turned out, the women who developed dementia between the ages of 79 and 88 were overweight and had a higher average BMI when they were 70 than the women who were not diagnosed with dementia. The women with dementia had an average BMI of 27.7 (versus 25.7 in the other group) when they were 70, an average BMI of 27.9 (versus 25) when they were 75 and an average BMI of 26.9 (versus 25.1) when they were 79.
The results were similar for women who specifically developed Alzheimer's. These women tended to have a BMI of 29.3 at the age of 70, 29.6 at the age of 75 years and 28.2 at 79 years. For every additional 1.0 in BMI at age 70, the risk for Alzheimer's increased by 36 percent.
A BMI between 18.5 and 24.9 is considered normal, over 25 is considered overweight and 30 or greater is defined as obese. According to the study, a BMI of 29 corresponds to a woman who is 5-foot-4 and weighs about 170 pounds. The average BMI for women who did not develop Alzheimer's was 25, which is at the cusp of healthy and overweight. They were not unnaturally thin.
For men, however, there were no significant differences in BMI at age 70 between those who became demented between 79 and 88 years of age and those who did not.
In this case, the finding among males probably had more to do with the sample size.
"We didn't have enough men who survived long enough, and there were a small number of men to begin with," Gustafson says. "But in addition to that, there are potential sex differences when it comes to Alzheimer's disease. Women are more likely to become demented than men." Some experts have hypothesized that this difference can be traced to hormones such as estrogen.
The real importance of the study is that it highlights something people can actually do that might stave off Alzheimer's.
"This study shows that it's important to be concerned about overweight and obesity even to the oldest ages," Gustafson says. "In terms of preventive health measures, we need to be concerned about that even when people are 70 or 80 or 90."
"There are lots of good reasons for trying to remain as functional as possible as you age, and there are relatively simple sets of rules for healthy aging," Thies says. "They may not eliminate the possibility of your developing Alzheimer's, but they are going to make you as functional as possible for as long as possible."
He adds, "You are still going to be blessed with a certain genetic background, you are going to be blessed with a certain impact of your environment and, by the time you're 80, you can't get out from under your 80 years of history. [But] if you paid attention to these rules, they give you the best possible chance."
More information
For more information, visit the Alzheimers Association or the National Institute of Neurological Disorders and Stroke. To calculate your BMI, visit the U.S. Centers for Disease Control and Prevention.
