A new study conducted on 8,534 twin individuals in Sweden has found that those who were obese in midlife were 288% more likely to develop dementia in later life, and even those who were merely overweight in midlife were 71% more likely to develop dementia in their senior years.
The study, led by Dr. Weili Xu of the Karolinska Institutet in Stockholm and her colleagues, was reported in the May 3, 2011 issue of Neurology, the journal of the American Academy of Neurology.
The researchers studied 8,534 twin individuals aged over 65 years (mean age 74.4) from the Swedish Twin Registry. The twins were assessed to detect dementia cases in late life, diagnosed in accordance with the criteria of DSM-IV, an official diagnostic guide for dementia widely accepted by the medical profession. This definition of dementia includes both Alzheimer’s Disease and Vascular Dementia.
Dementia was diagnosed in 350 of the study subjects, and 114 individuals had questionable dementia.
Height and weight at midlife (mean age 43.4) of the study subjects were available in the Swedish official Twin Registry. A total of 2,541 (29.8%) of the individuals in the study were Overweight (having a body mass index (BMI) between 25 and 30, by the researchers’ definition) or Obese (with a BMI over 30, by their definition) at midlife.
Body Mass Index (BMI) is a measure of body fat based on height and weight scientifically used to measure whether one is Underweight, Normal weight, Overweight, or Obese.
In analyses of these data, the researchers found that the study subjects who were Obese (BMI over 30) at midlife were 288% more likely to have dementia in later life than those with a normal weight (BMI less than 25) at midlife. And, strikingly, those that were merely Overweight (BMI of 25-30) at midlife were 71% more likely than those with a normal weight at midlife to have dementia in later life.
Previous studies had found a correlation between Obesity and dementia, but the relation of mere Overweight to dementia had been controversial before this study, according to its authors.
The researchers concluded that, “Both overweight and obesity at midlife independently increase the risk of dementia, AD, and VaD [both Alzheimer's Disease and Vascular Dementia]” in later life.
“Our results contribute to the growing evidence that controlling body weight or losing weight in middle age could reduce your risk of dementia,” lead author Dr. Weili Xu of the Karolinska Institutet in Stockholm said in a statement.
This finding of a link between mere overweight and dementia “has public health importance because of the large number of people worldwide who are overweight,” Dr. Xu told the BBC. According to the study, 1.6 billion adults are overweight worldwide.
See also our previous reports on the growing epidemic of dementia in the U.S. and worldwide.
When the Swedish scientists examined pairs of twins in which only one had dementia, however, they found only an attenuated association between midlife weight and dementia. In other words, the twin who was overweight or obese in midlife was not significantly more likely to develop dementia in later life than the twin who had normal weight at midlife. Dr. Weili Xu said this may suggest that genetics and environmental factors in early life may also play a significant role in the relationship.
The researchers, thus, also concluded that, “Genetic and early-life environmental factors may contribute to the midlife high adiposity [high BMI]-dementia association.”
The causes of the relationship between midlife weight and later life dementia are not fully explained, and the scientists indicated that further research is needed. One possibility is that the inflammation associated with being overweight could damage brain cells, causing or contributing to dementia. A higher BMI is also associated with diabetes and vascular disease, both of which could also contribute to dementia.
See also scientific opinion quoted in our earlier article on Weight Loss and Walking Exercise Improve Memory, Studies Find.
For more information on dementia, see our resource pages on Alzheimer’s/ Dementia.
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