"Our results contribute to the growing evidence that controlling body weight or losing weight in middle age could reduce your risk of dementia," says study researcher Weili Xu, MD, PhD, of the Karolinska Institutet in Stockholm, Sweden.
In this new study, published in the May 3 issue of Neurology, researchers looked at 8,534 twins aged 65 and older who participated in the Swedish Twin Registry.
Thirty years earlier, the registry had collected self-reported heights and weights from each twin. Nearly 30% of them were overweight or obese in middle age.
Three decades later, scientists gathered data about each twin's current weight, height, health status and medical history, and educational background. They also did a telephone interview to rate their cognitive skills, asking 1,450 people to come in for a follow-up exam.
After receiving neurological tests, 350 participants, or about 4% of the twins, were diagnosed with dementia. This included 232 cases of Alzheimer's disease and 74 with vascular dementia, the most common type of dementia after Alzheimer's.
Another 114 people had possible dementia.
This study found that 39% of twins diagnosed with dementia had been overweight in midlife and 7% of them had been obese. Compared to twins who did not have dementia, people with memory problems were also older, had a lower level of education, and were more likely to have diabetes, stroke, and heart disease.
Scientists also looked at twosomes where one twin had dementia and the other did not. But they did not find a significant relationship between being overweight or obese at midlife and dementia when evaluating this group.
"This suggests that early life environmental factors and genetic factors may contribute to the link between overweight and dementia," says Xu. Twins also have similar childhood nutrition and socioeconomic situations.