People in their forties with large bellies are at an increased risk of developing dementia, finds a new study.
And, this risk doubles or triples in people who are overweight and obese.
The study, which is the first to look at the longitudinal association between midlife belly fat and the risk of dementia, was conducted by researchers at Kaiser Permanente.
As a part of the study, the boffins analysed 6,583 people age 40 to 45 in northern California.
The volunteers had their belly fat measured using a caliper to determine the distance from the back to the upper abdomen, midway between the top of the pelvis and the bottom of the ribs.
An average of 36 years later, the researchers found that 16 percent of the participants had been diagnosed with dementia.
According to them, people who are overweight and have a large belly are 2.3 times more likely to develop dementia than people with a normal weight and belly size.
The risk is further increased to 3.6 times for people who are both obese and had a large belly.
"It is well known that being overweight in midlife and beyond increases risk factors for disease. However, where one carries the weight -especially in midlife -- appears to be an important predictor for dementia risk," said Rachel Whitmer, PhD, a research scientist at the Kaiser Permanente Division of Research in Oakland, CA, and lead author of the study.
Based on the results the researchers also concluded that people who are overweight or obese but do not have a large abdomen have an 80-percent increased risk of dementia.
Belly fat was found to be higher for non-whites, smokers, people with high blood pressure, high cholesterol or diabetes, and those with less than a high school level of education.
"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. These findings imply that the dangerous effects of abdominal obesity on the brain may start long before the signs of dementia appear," she added.
She added that further research needs to be completed to determine the underlying mechanisms that link abdominal obesity in midlife to dementia risk.
The study appears in the online issue of Neurology, the medical journal of the American Academy of Neurology.