The strong association between obesity and overweight in middle age and increased risk of dementia in old age is seen regardless of the presence of cardiovascular disease and diabetes in mid and late life.

The new study, conducted by the Kaiser Permanente Division of Research in Oakland, California, is the first to evaluate the effect of obesity in middle age on the subsequent risk of future dementia and the first to determine whether skin-fold thickness is associated with dementia, according to the article.

Modifiable Risk Factor

People who were obese in mid-life were 74 percent more likely to have dementia, while overweight people were 35 percent more likely to have dementia, compared to those with normal weight, said lead investigator Rachel A. Whitmer, PhD, a research scientist with the Kaiser Permanente Division of Research in Oakland, California.

The researchers determined that middle age, high body mass index and high skin-fold thickness in the upper back and upper arm are strongly associated with risk of dementia.

"This is important because obesity is a modifiable risk factor. Our findings imply that weight loss in middle age may have positive effects at the end of your life span, as well," said Whitmer.

No Heart Disease, Diabetes Connection

Dementia currently affects over 5 million adults in the United States. By 2020 the number is estimated to reach 10 to 15 million, according to the National Institutes of Health, which funded the Kaiser Permanente study.

The strong association between obesity and overweight in middle age and increased risk of dementia in old age is seen regardless of the presence of cardiovascular disease and diabetes in mid and late life, Whitmer said.

Researchers accounted for the effect of obesity on dementia as independent from cardiovascular disease and diabetes by adjusting for these conditions in both middle and late age.

Women at Greater Risk

Investigators analyzed data for 10,276 members of Kaiser Permanente medical care program in California who underwent detailed health checks from 1964 to 1973 when they were aged 40-45 and who were still members of the health plan in 1994.

In 1994, dementia was diagnosed in 713 (7 percent) participants. Obese people (body mass index 30 or above) were 74 percent more likely to have dementia, while overweight people (body mass index 25-29.9) were 35 percent more likely to have dementia compared with those of normal weight (body mass index 18.6-24.9).

Body mass index predicted dementia more strongly among women. For example, obese women were 200 percent more likely to have dementia than women of normal weight, while obese men had a non-significant 30 percent increase in risk.

Both men and women with the highest skin-fold measurements had a 60-70 percent greater risk of dementia compared to those with the lowest measurements.