Carrying around extra pounds during middle age was associated with a higher risk of dementia later in life in a new study that followed twins in Sweden for 30 years.
This wasn't a subtle effect either. Being overweight increased the likelihood of later life dementia by about 80%.
Dr. Weili Xu, the study's lead author from the Karolinksa Institutet in Stockholm, said that the evidence is pointing in that direction. The findings, published in the journal Neurology, suggest that "control of body fat as early as middle life is important to prevent dementia later in life," she told Reuters Health.
Get baseline data
Xu and her colleagues analyzed data from close to 9,000 Swedish twins. When the participants were an average age of 43, they gave researchers information about their height and weight.
Get the follow up data
Thirty years later, the researchers examined the same individuals for signs of declining thinking and memory skills, then diagnosed some of them with Alzheimer's disease and other types of dementia.
Close to one in three of the participants were overweight or obese in middle age. And those that were had about an 80 percent higher chance of getting any kind of dementia than people of normal weight.
The more participants weighed in mid-life, the higher their chance of getting dementia or "questionable dementia" - meaning they had signs of thinking and reasoning problems, but not enough to be diagnosed with dementia.
In total, about 4 percent of everyone in the study was diagnosed with dementia, and another 1 to 2 percent with questionable dementia.
Whether genes predispose a person to being overweight in adulthood, or it's just bad eating habits, the likely explanation for the link to dementia, researchers say, is that fat tissue in the body releases hormones and other signaling cells that may affect the brain's functioning.
In addition, Xu said, extra weight has been shown to increase a person's risk for diabetes and heart and blood vessel diseases - and those conditions are related to a higher dementia risk. However, the link between weight and dementia remained even after the researchers took other diseases into account.The findings are the latest evidence that preventing Alzheimer's disease and dementia starts long before their signs and symptoms typically show up, said Rachel Whitmer, an epidemiologist at Kaiser Permanente Division of Research in Oakland who was not involved in the study.