Study Reveals Link between Obesity and Dementia

If your waistline is expanding, your brain could be shrinking - especially if you are a middle-aged woman. Results of a study conducted by researchers at the Medical College of Wisconsin and Göteborg University in Sweden reveal that women who are overweight throughout middle to later life are more likely to lose brain tissue, which is linked to dementia.

Researchers followed 290 Swedish women over a period of 24 years and then, when the women were between the ages of 70 and 84, performed CT (computed tomography - advanced x-ray technology) scans on their brains to measure for any loss of brain tissue. The study showed that as the women aged, their BMI (body mass index, a measure of body fat that shows weight adjusted for height) increased. The results also revealed that women with the highest BMI also were the most likely to have suffered cerebral deterioration.

"This study indicates that a high BMI is a risk factor for dementia in women," says Deborah Gustafson, PhD, of the Department of Family and Community Medicine at the Medical College of Wisconsin. A growing body of scientific evidence indicates obesity can be detrimental to overall health, but this is the first study to show a higher BMI is related to brain atrophy, particularly of the temporal lobe. The temporal lobe, which is often affected in Alzheimer's disease, plays a role in memory, verbal expression and language comprehension.

Long-Term Effects
"This is the first study to look at a measure of overweight and obesity over a lengthy period of time," Dr. Gustafson said. The study began in 1968 and four follow-up examinations were done on the women between 1968 and 1992.

"A long period of time for follow-up is important because we know that BMI declines during the preclinical stages of dementia (10-15 years before dementia onset), that low BMI is related to dementia, and that temporal lobe atrophy appears to precede and/or accompany dementia," Dr. Gustafson explained.

The researchers found that for every one-point rise in BMI, the risk of temporal lobe atrophy increased between 13% and 16%. "Women who were on average heavier were more likely to have any temporal lobe atrophy (presence versus absence).The severity of atrophy was not related to increasing levels of BMI. In other words, those women with more severe temporal lobe atrophy did not have a higher BMI compared to women with mild atrophy," according to Dr. Gustafson.

The statistical models that were used to examine this relationship included consideration for a variety of other factors, such as blood pressure, cigarette smoking, and socioeconomic status. Even then, BMI was the only factor related to brain atrophy. While these models explain a relatively small amount of total risk, they are similar to models identifying risk factors for other chronic diseases.

It is not surprising that a high BMI increases risk for temporal atrophy over time, according to the report. "This study was begun as a result of other data from our Swedish studies and now has been replicated by others, showing that a high BMI may be a risk factor for Alzheimer's disease when measured at least 10 years prior to the onset of dementia. That is why the role of BMI as a risk factor must be evaluated a significant time prior to the diagnosis of disease," Dr. Gustafson said.

What You Need to Know
What does this study mean to the average woman? "Women should know that vascular risk factors, such as overweight and obesity, are important not only for cardiovascular health during mid- and later life, but for the latest periods of life as well, and potentially for dementing disorders," Dr. Gustafson said. "We are too comfortable with being overweight in the US, eating too much food, and not getting enough exercise. We should all be able to improve our vascular risk profile to some extent, through better eating habits - better quality and reduced quantity - and more exercise," she said.

And there is definite cause for us to be concerned. The US Centers for Disease Control indicate that an estimated 65% of American adults aged 20 years old or older are either overweight or obese, defined as having a BMI of 25 or higher. Europeans are not far behind us, with more than 50% of European adults either overweight or obese.

Following Up
Scientists are continuing to follow the women who participated in this study. "In 2005-2006, we will take another look at these overweight and obesity relationships after 37 years of follow-up. We are hopeful that we will be able to evaluate more women with dementia and more women who have age-related brain changes, such as atrophy," Dr. Gustafson said.

The researchers did not pinpoint a reason why obesity leads to brain atrophy, but they say there are several possible ways. "Obesity is related to ischemia, hypertension, and cerebrovascular and cardiovascular diseases. These conditions contribute to an unhealthy vascular system, and therefore to a higher risk of dementia," Dr. Gustafson said.

Dr. Gustafson urges physicians to stress a healthy lifestyle to their patients. "Physicians should be aware of yet one more potential health outcome of excess weight, and should monitor BMI and vascular risk on a regular basis to adequately advise their patients of ways to reduce their risk for age-related heart and brain disease," Dr. Gustafson advised. If you have questions about this, be sure to ask your physician for guidance.

If the present epidemic of obesity continues, it might lead to a boom of dementia in the future. "It is clear that leading a healthy lifestyle could help to reduce the risks of dementia," Dr. Gustafson said.

JoAnn Petaschnick
HealthLink Contributing Writer

This article contains information from: Gustafson DR, Rothenberg, E, Blennow K, Steen B, Skoog I. An 18-year follow up of overweight and risk for Alzheimer's disease. Arch Intern Med. 203; 163: 1524-1528.

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.