To investigate, researchers 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.
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. Participants who were overweight or obese 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 signs of thinking and reasoning problems, but not enough to be diagnosed with dementia.
In total, about 4 percent of the study participants were diagnosed with dementia.
Researchers add that extra weight has been shown to increase a person's risk for diabetes and heart and blood vessel diseases - all of which are related to a higher dementia risk.
These findings highlight the fact that preventing Alzheimer's disease and dementia starts long before their signs and symptoms typically show up, and that what you do today can dramatically effect your health 30 or 40 years down the road.
The findings were published in the journal Neurology.
All research on this web site is the property of Leslie Beck Nutrition Consulting Inc. and is protected by copyright. Keep in mind that research on these matters continues daily and is subject to change. The information presented is not intended as a substitute for medical treatment. It is intended to provide ongoing support of your healthy lifestyle practices.