Belly Fat May Pose Dementia Risk

By Charles Bankhead
OAKLAND, Calif., March 26 -- A middle-age paunch may heighten the risk of older-age dementia, according to an analysis of almost 6,600 patients followed for more than three decades.Those with the greatest central fat accumulation had almost a three-fold higher rate of dementia at follow-up compared with patients who had the least amount of central adiposity, Rachel Whitmer, Ph.D., of Kaiser Permanente of Northern California, and colleagues reported in the April issue of Neurology.Central adiposity posed a dementia threat even in patients who had a normal body mass index."These results contribute to a recent but growing body of evidence that a centralized distribution of adiposity is particularly dangerous, even for those who are not overweight, and that the brain may also be a target organ to the harmful effects of central obesity," the authors concluded. "If these results are replicated, our findings imply that central obesity may contribute to degree of cognitive aging."

Central obesity is an independent predictor of diabetes, insulin resistance, coronary heart disease, stroke, and mortality, and has a greater impact on morbidity and mortality compared with total body obesity, the authors pointed out. The increased risk conferred by central obesity may lie in the heightened metabolic activity of visceral fat, which appears to give rise to tissue-toxic adipocytokines and fuel insulin resistance.
Recent population-based studies have suggested that obesity is a risk for cognitive impairment. Whether the pattern of fat distribution influences dementia risk had not been examined.
Dr. Whitmer and colleagues analyzed data on 6,583 Kaiser-Permanente members whose sagittal abdominal diameter was measured during 1964 to 1973, when the patients were ages 40 to 45. Dementia diagnoses were abstracted from medical records an average of 36 years after the assessment of abdominal fat volume.
Medical records showed that 1,049 (15.9%) participants had dementia diagnoses. After stratification by sagittal abdominal diameter, those in the top quintile of visceral fat accumulation had a 2.72 relative risk of dementia compared with patients in the bottom quintile (95% CI 2.33 to 3.33).
There was a dose-dependent increase in the risk of dementia from visceral adiposity. Compared with those in the bottom quintile of sagittal abdominal diameter, the risk of dementia was 20% greater in the second quintile, 49% greater in the third, and 67% greater in the fourth.
After accounting for BMI in the statistical model, the authors found that people with the greatest sagittal abdominal diameter had a two-fold increased risk of dementia compared with those in the lowest quintile (HR 1.92, 95% CI 1.58 to 2.35).
People with sagittal abdominal diameter ≥25 cm and a normal BMI had double the dementia risk of those with less abdominal fat and normal BMI (HR 1.89, 95% CI 0.98 to 3.81). The combination of obesity (BMI>30) and sagittal abdominal diameter ≥25 cm had a dementia risk that was 3.6 times greater than that of individuals with neither anthropomorphic characteristic (95% CI 2.85 to 4.55).
The results were unchanged in separate analyses of different types of dementia.
The authors noted several limitations to the study.
"No information on dieting, nutrition, or cognitive function was collected although obese persons have different nutritional and exercise habits than non-obese persons."
"Due to body composition imaging technology (CT or MRI) not being available in the 1960s we were not able to directly distinguish the effects of visceral versus subcutaneous adiposity."
"Our study only included those who were still alive in 1994, the onset of dementia ascertainment, therefore we only could examine the association between central obesity and dementia among those who made it to old age."
The authors had no disclosures.
Primary source: NeurologySource reference:Whitmer RA, et al "Central obesity and increased risk of dementia more than three decades later" Neurology 2008; epub.