Obesity linked to dementia and Alzheimer's disease

Individuals who were obese at midlife had an increased risk for dementia later in life compared to individuals of normal weight, according to an article in the October issue of Archives of Neurology.

Obesity is on the rise all over the world and is related to vascular diseases, which may be linked to dementia and Alzheimer's disease (AD), according to background information in the article. However, the link between obesity and dementia risk has not been extensively studied and long-term follow-up studies performed thus far have yielded somewhat conflicting results.

Miia Kivipelto, M.D., Ph.D., from the Karolinska Institutet, Stockholm, Sweden, and colleagues re-examined participants in the Cardiovascular Risk Factors, Aging, and Dementia (CAIDE) study to investigate the relationship between midlife body mass index (BMI; weight in kilograms divided by square of height in meters) and a group of vascular risk factors, and subsequent dementia and AD. Participants in the CAIDE study were derived from random, population- based samples previously studied in a survey carried out in 1972, 1977, 1982, or 1987. After an average follow-up of 21 years, 1,449 individuals aged 65 to 79 years participated in the 1998 reexamination.

The researchers discovered dementia and AD to be prevalent significantly more among those with a higher midlife BMI. One-third of the participants had a BMI lower than 25 (normal weight), half had a BMI from 25 to 30 (overweight), and the remaining 16 percent had a BMI higher than 30 (obese) at midlife. A history of heart attack and diabetes mellitus were more prevalent in those with the highest midlife BMI . Midlife obesity, high systolic blood pressure, and high total cholesterol level were all significant risk factors for late-life dementia. Being overweight in midlife was not significantly associated with dementia later in life.

"This study shows that obesity at midlife may increase the risk of dementia and AD later in life," the authors write. "… midlife obesity, high SBP, and high total cholesterol level were all significant risk factors for dementia, each of them increasing the risk around two times. Clustering of these vascular risk factors increased the risk of dementia and AD in an additive manner so that persons with all three risk factors had around a six times higher risk for dementia than persons having no risk factors."