Abdominal Fat Boosts Later Dementia Risk

Research has shown that people who accumulate abdominal fat as they age — making them "apple shaped" rather than "pear shaped" — are at higher risk of developing cardiovascular disease and type 2 diabetes than people whose weight gain is more evenly distributed. Now a study published online in March 2008 in Neurology suggests that abdominal fat may also increase people's risk of developing Alzheimer's disease or another type of dementia.

Researchers analyzed data collected from 6,583 male and female members of Kaiser Permanente of Northern California, a health maintenance organization. The patients had their upper abdomens measured when they were middle-aged (ranging from 40 to 45), as part of routine office visits between 1964 and 1973. The researchers then examined medical records for the same patients starting three decades later, when they were ages 73 to 87, to determine how many had developed dementia.

Between 1994 and 2006, 1,049 of the original patients were diagnosed with dementia. The greater the abdominal measurements in middle age, the greater the risk of dementia in old age. When compared with patients whose abdominal measurements placed them in the lowest quintile, those in the second quintile were 20% more likely to develop dementia, those in the third quintile 49% more likely, those in the fourth quintile 67% more likely, and those in the top quintile 272% more likely.

The waist-to-hip ratio (WHR) is one way to estimate how much weight a person is carrying around the abdomen versus around the hips. People with a higher WHR (resembling an apple shape) have a higher risk for dementia than people with a lower WHR (resembling a pear shape).

These risks held even after adjusting for body mass index (BMI), a measure of overall height and weight. The people most at risk of developing dementia, however, were those with the largest abdominal measurements and whose BMI indicated they were obese at midlife: they were 360% more likely to develop dementia than those with the lowest abdominal measurements and normal BMI.

Although previous research has shown that obesity increases the chances of developing Alzheimer's disease and other dementia, this is the first study to show that the distribution of excess weight to the abdomen is particularly risky. It's not clear why abdominal fat increases dementia risk, but it may do so indirectly, by increasing risk of diabetes and cardiovascular disease.

Regardless of the mechanism, this study does indicate that a large abdomen may threaten the mind as well as the body — one more reason to eat better and exercise more.

Whitmer RA, et al. "Central Obesity and Increased Risk of Dementia More Than Three Decades Later," Neurology (March 26, 2008): Electronic publication.