OAKLAND, Calif., April 27, 2005 – Obesity has long been known to increase the risk of a number of diseases, including diabetes, stroke, insulin resistance and hypertension. This same obesity in mid life may also have damaging effects on the brain.
In a new study from the Kaiser Permanente Division of Research in Oakland, California, investigators are reporting that obesity in middle age increases the risk of dementia in later life. The study appears online in the British Medical Journal (BMJ.com).
The study 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.
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.
Dementia currently affects over 5 million adults in the United States. By 2020 the number is estimated to be between 10 and 15 million, according to the National Institutes of Health.
Obesity and overweight in middle age is strongly associated with an increased risk of dementia in old age, regardless of the presence of cardiovascular disease and diabetes, in mid and late life, she 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.
In the 27-year longitudinal study, 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 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.
Additional researchers include: Erica P. Gunderson, PhD, research scientist at the Kaiser Permanente Division of Research; Charles P. Quesenberry, PhD, biostatistician at the Kaiser Permanente Division of Research; Elizabeth Barrett-Connor, MD, professor, University of California, La Jolla; Kristine Yaffe, MD, associate professor, UCSF. The study was funded by the National Institutes of Health.