Overweight at mid life may raise dementia risk

A novel study from Karolinska Institutet shows that being overweight or obese during middle age may increase the risk of certain dementias. The research is based on data from the Swedish Twin registry and published in Neurology, the medical journal of the American Academy of Neurology.

Currently, 1.6 billion adults are overweight or obese worldwide, and over 50 percent of adults in the United States and Europe fit into this category. The recent study, which was lead by Dr Weili Xu at the Department of Neurobiology, Care Sciences and Society, contribute to the growing evidence that controlling body weight or losing weight in middle age could reduce your risk of dementia.

The researchers studied information from the Swedish Twin Registry on 8,534 twins aged 65 or older. Of those, 350 were diagnosed with dementia and 114 had possible dementia. Information on participant's height and weight had been taken 30 years earlier. Participants were grouped according to their BMI, a measure of total body fat: underweight, normal weight, overweight and obese. Being overweight was defined as having a BMI between 25 and 30 and obesity was defined as a body mass index of higher than 30. In the study, 2,541 twins, or nearly 30 percent, were either overweight or obese during middle age.

The study showed, that people who were overweight or obese at midlife had an 80 percent higher risk of developing dementia, Alzheimer's disease or vascular dementia compared to people with normal BMI. The results remained the same after considering other factors, such as education, diabetes and vascular disease. A total of 26 percent of those with no dementia were overweight, compared to 36 percent of those with questionable dementia and 39 percent of those with diagnosed dementia. Three percent of those with no dementia were obese, compared to five percent of those with questionable dementia and seven percent of those with diagnosed dementia.

The researchers also analyzed the data in twin pairs where one twin had dementia and one twin did not and found that there was no longer a significant relationship between overweight and obesity and dementia.

"This suggests that early life environmental factors and genetic factors may contribute to the link between midlife overweight and dementia", says Dr Weili Xu.

The study was supported by the National Institute on Aging, the Swedish Research Councils, the Swedish Brain Power, the Gamla Tjänarinnor Foundation, the Gun and Bertil Stohnes Foundation, the Swedish Dementia Fund, the Loo and Hans Ostermans Foundation for Geriatric Diseases. Weili Xu is also affiliated to the Aging Research Center in Stockholm, a co-operation between Karolinska Institutet and Stockholm University.