Having an “apple-shaped,” rather than a “pear-shaped” body at middle-age appears to increase the later-life risk of dementia, California researchers report.

Moreover, the link between abdominal obesity and increased dementia risk appears to be independent of overall body weight and the presence of diabetes or cardiovascular disease, report Dr. Rachel A. Whitmer, from Kaiser Permanente Division of Research, in Oakland, and colleagues.

These findings, published in the medical journal Neurology, add to increasing evidence of the dangers of abdominal obesity. Previous research implicated large abdominal girth, as a risk factor for type 2 diabetes, heart disease, and stroke, Whitmer and colleagues note.

The investigators assessed weight, waist measurements, and other factors, in 6583 men and women, who were members of the Kaiser Permanente Medical Care Program of Northern California, who entered the study between 1964 and 1973.

Over 36 years of follow-up, 1049 men and women developed dementia.

The researchers found that, compared with subjects with the least amount of body fat, those with the highest levels of abdominal obesity had nearly a 3-fold increased risk of dementia in analyses that factored in the effect of age, gender, race, education, marital status, diabetes, high blood lipids (fats), high blood pressure, and cardiovascular disease.

Overweight and obesity combined with high levels of abdominal fat, increased risk of dementia by 2.3-fold and 3.6-fold, respectively, whereas overweight and obesity combined with low abdominal fat carried about a 1.8-fold increased risk of dementia - a risk level slightly lower than that identified among participants of normal weight and high abdominal fat.

These findings imply the harmful effects of central obesity impact both normal and overweight individuals, and if replicated, suggest that central obesity may contribute to cognitive aging, the investigators conclude.

SOURCE: Neurology, September 30, 2008.