THURSDAY, July 30, 2020 (HealthDay News) -- Need fresh motivation to lose some weight? New research suggests that young adults who are overweight or obese face a higher risk for dementia in their golden years.
For the study, the researchers looked at just over 5,100 older adults who were involved in two long-term studies. The investigators found that women who were overweight between 20 and 49 years of age had nearly twice the risk of dementia after age 70. And older men and women who were obese in those earlier years saw their risk jump 150%.
The finding builds on prior studies that have linked excess weight during middle age to an increased risk of dementia among seniors.
But the new research does not prove excess weight causes dementia, only that the two are linked, said lead author Adina Zeki Al Hazzouri. She's an assistant professor of epidemiology at Columbia University in New York City.
"However, our study does suggest that adult life obesity is an important risk factor for dementia," she added.
The participants were enrolled in two long-running studies of older people, one launched in 1988 to track heart disease and the other in 1997 to track declining function. Nearly one in five participants were Black and 56% were women.
Each study found cases of dementia. Hazzouri's team used a computer model to chart each participant's lifetime body mass index (BMI), a standard measure of body fat based on height and weight.
BMI status was broken down according to three stages of life: early adulthood (ages 20 to 49); middle age (ages 50 to 69); and late life (ages 70 to 89).
The relationship between BMI and dementia risk differed by gender and age, the analysis found.
For example, being overweight or obese in middle age did not appear to affect women's dementia risk.
But men who were overweight during midlife saw their dementia risk rise 50% after age 70. And middle-aged obesity among men doubled late-life dementia risk, the study found.
Gender differences were also seen when looking at BMI during early adulthood. For example, being overweight during that time did not appear to affect men's dementia risk. But women had no such luck. For those who were overweight between 20 and 49 years of age, dementia risk was 1.8 times higher after age 70.
In other respects, an expanding waistline had similar effects on dementia risk for both sexes. A higher BMI after age 70, for example, was linked to a lower risk for both sexes. And being obese during early adulthood caused dementia risk in old age to more than double for men and women alike.
Which raises the question: Does obesity in one's 30s mean a higher risk for dementia is inevitable, or can getting in shape lower it?
Hazzouri isn't sure. "Irrespective of a person's BMI in mid- or late life, being obese or sometimes overweight (while young) is associated with a higher dementia risk (after 70)," she noted.
But Keith Fargo, director of scientific programs and outreach for the Alzheimer's Association, said it's all speculation at this point.
"We just don't know exactly why being overweight or obese might raise dementia risk," he said, noting that excess weight can have negative impacts on heart health and inflammation that may ultimately affect brain health.
"Overall, I would put this issue in the category of modifiable risk factors," he said.
"Make healthier eating choices," Fargo suggested. "Exercise and get that heart pumping several times a week. The more you can do, the better. And the earlier, the better. Because what your doctor and your mom have been telling you for decades about eating well and getting exercise is right -- not just for your heart but also for your brain."
Hazzouri and her colleagues were scheduled to present their findings Thursday during an online meeting of the Alzheimer's Association. Findings presented at meetings are typically considered preliminary until published in a peer-reviewed journal.
Find out more about risk factors for dementia and Alzheimer's disease from the Alzheimer's Association.
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