Is There a Link Between Obesity and Alzheimer's Disease?
(HealthDay News) – There is still no definable cause of Alzheimer’s disease.
Scientists can identify the lesions in the brain that are Alzheimer’s indicators, and they can track the sometimes slow, sometimes rapid cognitive decline that Alzheimer’s causes, especially in the elderly.
But what makes it occur remains a mystery.
Two studies, one about three years old and one done in 2006, seem to indicate that there may be a relationship between Alzheimer’s and physical fitness.
The 2003 study was confined to elderly women, and it suggested an association between body weight and the onset of Alzheimer’s disease.
The conclusion: 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.
The finding was published in the July 15 2003 issue of the Archives of Internal Medicine. It pointed only to an association and not to a cause-and-effect relationship.
But in January 2006, another research paper indicated that adding exercise to diet also might prevent the onset of Alzheimer’s.
"Regular exercise at least three times a week could delay the onset and reduce the risk of developing Alzheimer's, and the more frail a person is, the more he or she is gong to benefit from exercise," said lead author Dr. Eric B. Larson, director of the Group Health Cooperative's Center for Health Studies in Seattle. The results of the study were published in the Jan. 17, 2006 Annals of Internal Medicine.
"So use it even after you start to lose it -- that's the banner headline," he added. "There's a tendency to sit down and do nothing when you start to lose function, but the opposite is probably exactly what's in order if you want to stave off Alzheimer's disease."
Between 1994 and 2003, Larson and his team assessed the health, physical and mental function, and lifestyle characteristics of 1,740 men and women over the age of 65.
All the patients were members of a Seattle-based health-maintenance organization. None had been diagnosed with dementia or were living in a nursing home at the start of the study.
Every two years, the researchers used examinations and in-person interviews to evaluate participants' weekly exercise routines; physical abilities such as walking, standing, balancing, and gripping; memory, attentiveness, and concentration skills; and smoking, drinking and dietary supplement habits.
They noted that 107 participants went on to develop Alzheimer's within six years of the study. Another 51 patients developed other forms of dementia, while 276 participants died during the course of the study.
Those who had been engaging in regular exercise when the study began -- defined as 15 minutes of physical activity at least three days a week -- had a 32 percent lower risk of developing dementia than those exercising less than three days a week.
Both the 2003 obesity study and the 2006 exercise research give important clues into possible ways to prevent Alzheimer’s.
"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 2003 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.
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 Deborah Gustafson, lead author of the 2003 study while she was 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," says Gustafson, who is now an epidemiologist at the Medical College of Wisconsin in Milwaukee. "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."
On the Web
For more information the latest research into Alzheimer’s disease, visit the National Institute of Neurological Disorders and Stroke.
SOURCES: Deborah Gustafson, Ph.D., epidemiologist, the Medical College of Wisconsin, Milwaukee; William Thies, vice president, medical and scientific affairs, the Alzheimer's Association, Chicago; Eric B. Larson, M.D., director, Center for Health Studies, Group Health Cooperative, Seattle; July 15, 2003, Archives of Internal Medicine
Publication date: January 2007
Author: Amanda Gardner, HealthDay Reporter
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