February 18, 2010
Is middle aged spread increasing your risk for Alzheimer's? It may be, according to a new study from Sweden that found that women who store fat on their waist in their 40s and 50s are more than twice as likely to develop Alzheimer's disease in old age than their thin-waisted peers. The findings add to a growing body of evidence that belly fat, in particular, may be bad not just for the heart but also for the brain.
"Anyone carrying a lot of fat around the middle is at greater risk of dying prematurely due to a heart attack or stroke," said study leader Deborah Gustafson of the Sahlgrenska Academy in Sweden, where the research was carried out. "If they nevertheless manage to live beyond 70, they run a greater risk of dementia."
The research, published in the medical journal Neurology, is based on the Prospective Population Study of Women in Gothenburg. Researchers looked at some 1,500 Swedish women beginning in the late 1960s, when they ranged in age from 38 to 60. All were given comprehensive medical examinations and answered questions about their health and lifestyle.
A follow-up 32 years later showed that 161 women had developed Alzheimer's or other forms of dementia; their average age was 75. The investigators found that women who tended to be broad around the waist and hips at midlife were more than twice as likely to develop dementia as they aged. The researchers, however, did not find a link between being overweight in middle age, as determined by the body mass index or BMI, and an increased Alzheimer's risk.
"Other studies have shown that a high BMI is also linked to dementia, but this was not the case in ours," Dr. Gustafson said. "This may be because obesity and overweight were relatively unusual among the women who took part in the Prospective Population Study."
The findings may be particularly significant for the United States, since Americans have much higher rates of obesity than Swedes. Half of Americans have an unhealthy amount of abdominal fat, and as the population ages, Alzheimer's rates are expected to soar in the coming decades.
A large study from California last year found that men and women with thick middles at midlife were nearly three times more likely to suffer from Alzheimer's decades later than their slender peers. In that study, too, the risk of dementia increased regardless of whether someone was of normal weight, overweight or obese.
As with all observational studies, it is possible that belly fat is not a cause of dementia but a sign of an unhealthy lifestyle or some other metabolic illness. But ongoing research continues to suggest that belly fat, and the body changes that go with it, may be bad for the brain over the long term.
Carrying excess weight has been closely linked with diseases that affect the blood vessels, including diabetes, heart disease and high blood pressure. And being apple-shaped, with excess belly fat, as opposed to pear-shaped, with large hips and thighs, has particularly been linked with an increased risk of heart attacks, strokes and diabetes. Such vascular ailments are known to be important risk factors for Alzheimer's as well.
Fat in the midsection is thought to have particularly strong effects on the rest of the body. It is a common occurrence as people age, and studies show it is often associated with problems with fat or sugar metabolism, including high cholesterol 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 good fats, such as those found in fish, and to get less exercise than those who are of normal weight.
Age remains the most important risk factor for Alzheimer's: The older you are, the more likely you are to develop the disease. Smoking, high blood pressure, years of schooling, and genetic factors may also contribute to risk, other research has shown.
D. R. Gustafson, K. Bäckman, M. Waern, et al: "Adiposity indicators and dementia over 32 years in Sweden."Neurology. Volume 73, Nov. 10, 2009; pages 1559-1566.