Study Title:

Body Weight and Risk for Cognitive Impairment

Study Abstract

Objective: The relation of overweight to dementia is controversial. We aimed to examine the association of midlife overweight and obesity with dementia, Alzheimer disease (AD), and vascular dementia (VaD) in late life, and to verify the hypothesis that genetic and early-life environmental factors contribute to the observed association.

Methods: From the Swedish Twin Registry, 8,534 twin individuals aged ≥65 (mean age 74.4) were assessed to detect dementia cases (DSM-IV criteria). Height and weight at midlife (mean age 43.4) were available in the Registry. Data were analyzed as follows: 1) unmatched case-control analysis for all twins using generalized estimating equation (GEE) models and 2) cotwin matched case-control approach for dementia-discordant twin pairs by conditional logistic regression taking into account lifespan vascular disorders and diabetes.

Results: Among all participants, dementia was diagnosed in 350 subjects, and 114 persons had questionable dementia. Overweight (body mass index [BMI] >25–30) and obesity (BMI >30) at midlife were present in 2,541 (29.8%) individuals. In fully adjusted GEE models, compared with normal BMI (20–25), overweight and obesity at midlife were related to dementia with odds ratios (ORs) (95% CIs) of 1.71 (1.30–2.25) and 3.88 (2.12–7.11), respectively. Conditional logistic regression analysis in 137 dementia-discordant twin pairs led to an attenuated midlife BMI-dementia association. The difference in ORs from the GEE and the matched case-control analysis was statistically significant (p = 0.019).

Conclusions: Both overweight and obesity at midlife independently increase the risk of dementia, AD, and VaD. Genetic and early-life environmental factors may contribute to the midlife high adiposity–dementia association.

From press release:

According to a new study, being overweight or obese during middle age may increase the risk of certain dementias. The research is published in the May 3, 2011, print issue of 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," said study author Weili Xu, MD, PhD, with the Karolinska Institutet in Stockholm, Sweden. "Our results contribute to the growing evidence that controlling body weight or losing weight in middle age could reduce your risk of dementia."

Researchers studied information from the Swedish Twin Registry on 8,534 twins age 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 body mass index (BMI), a measure of total body fat: underweight, normal weight, overweight and obese. Being overweight was defined as having a body mass index 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 found that people who were overweight or obese at midlife had an 80 percent higher risk of developing dementia, Alzheimer's disease or vascular dementia in late life 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 had been overweight in midlife, compared to 36 percent of those with questionable dementia and 39 percent of those with diagnosed dementia. Three percent of those with no dementia had been obese in midlife, 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 in midlife. "This suggests that early life environmental factors and genetic factors may contribute to the link between midlife overweight and dementia," Xu said.

Study Information

W.L. Xu, A.R. Atti, M. Gatz, N.L. Pedersen, B. Johansson, and L. Fratiglioni.
Midlife overweight and obesity increase late-life dementia risk: A population-based twin study
Neurology
2011 May
Aging Research Center, Karolinska Institutet, Gävlegatan 16, S-113 30 Stockholm, Sweden.

Full Study