A study published in the May 2008 issue of Obesity Reviews shows that weight matters when it comes to warding off dementia. Researchers with Johns Hopkins Bloomberg School of Public Health in Baltimore have found that obese people have an 80% increased risk for Alzheimer's disease compared to those with normal weight.
But being underweight makes you 36% more likely to develop such cognitive disorders.
Scientists have long debated the link between obesity and dementia. Previous findings have been "mixed and inconclusive," according to information in the journal report.
For the current study, Youfa Wang, MD, associate professor of International Health and Epidemiology, and colleagues reviewed and analyzed 10 international studies (U.S., Finland, Sweden, France, Japan) from 1995 to 2007 that included people with various forms of dementia. Each person was aged 40-80 when the studies started, and they were followed from three to 36 years.
The reviewed studies included all forms of dementia, including Alzheimer's disease and vascular dementia, which is associated with high blood pressure and high cholesterol and can result from strokes.
"Our meta-analysis showed that obesity increased the relative risk of dementia, for both sexes, by an average of 42 percent when compared with normal weight," Wang says in a news release.
The researchers noted that obesity seemed to have a particularly profound influence on Alzheimer's disease and vascular dementia risk in those who developed the cognitive decline before age 60, or in studies with follow-up periods of more than 10 years. Risk also seemed to vary slightly depending on one's gender.
"Obesity was more likely to be a risk factor for women when it came to developing Alzheimer's disease and for men when it came to vascular dementia," says Wang.
The analysis also revealed that central obesity appeared to increase the risk of vascular dementia but not Alzheimer's disease. Central obesity refers to a buildup of fat around the midsection. Such dangerous belly fat has been linked to high cholesterol and a greater risk of heart attack.