Puzzling connection: Overweight people with large bellies were found to be 230 to 360 per cent more likely to develop dementia than people of normal weight.

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CHICAGO: Having a large belly in middle age nearly triples the risk of developing dementia in later life, according to a study in the journal Neurology.

"Considering that 50 per cent of adults [in the U.S.] have abdominal obesity, this is a disturbing finding," said study author Rachel Whitmer of the Kaiser Permanente Division of Research in Oakland, California.

Abdominal fat

Being overweight in midlife and beyond has long been linked to increased risk for disease such as stroke, diabetes and heart disease. But this is the first study to link excess fat to dementia and, interestingly, excess abdominal fat increased the risk even among those who were of normal weight overall.

Researchers measured the abdominal fat of 6,583 people age 40 to 45 in northern California and some 36 years later 16 per cent had developed dementia, the study found.

Those who were overweight or obese but did not have a pot belly had an 80 per cent increase in the risk of dementia compared to people with a normal body weight and abdominal fat level. The risk increase jumped to 230 per cent among overweight people with a large belly and 360 per cent among the obese with large abdomens.

"Where one carries the weight – especially in midlife – appears to be an important predictor for dementia risk," Whitmer said.

Complex behaviours

While more research is needed to understand why this link exists, it is possible that the abdominal obesity is part of a complex set of health-related behaviours that increase the risk of dementia.

"Autopsies have shown that changes in the brain associated with Alzheimer's disease may start in young to middle adulthood, and another study showed that high abdominal fat in elderly adults was tied to greater brain atrophy," she said. "These findings imply that the dangerous effects of abdominal obesity on the brain may start long before the signs of dementia appear."