As you get older, it's important to take care of your physical and cognitive health—but experts say that doing so starts long before you enter your golden years. A wide body of research now suggests that one common midlife occurrence can have a profound affect on your cognitive health down the line. The good news? There may still be something you can do about it, if you act fast. Read on to learn how your midlife years can make or break this one dementia risk factor, and why experts believe they're linked.
If this happens in midlife, it increases your dementia risk.
According to a 2011 study published in the journal Neurology, becoming severely overweight or obese during midlife significantly raises your risk of later developing dementia. Analyzing data from the Swedish Twin Registry, a databank of 8,534 twin individuals over the age of 65, the research team looked at possible risk factors related to dementia, including height, weight, health history, and more.
"In this nationwide Swedish twin study, overweight and obesity at midlife increase the risk of all dementia, AD [Alzheimer's disease], and VaD [vascular dementia], independently of lifespan diabetes and vascular diseases," the team wrote. They noted that familial factors including both genetics and early life environments seemed to contribute to the association between midlife high adiposity [severe obesity] and dementia in late life.
However, being obese later in life did not appear to have the same effect. The study authors concluded that the relationship between high body mass index (BMI) and dementia among people aged over 65 is "controversial," not conclusive.
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Here's how closely BMI and risk are linked.
The team also reviewed several existing studies and noted that their findings were consistent with the broader research. "A growing body of evidence suggests that a high level of adiposity is associated with cognitive decline and dementia," they explained.
But just how directly are these factors linked? "In this Swedish twin cohort, we found that having dementia or AD was associated with more than a 70 percent higher odds of being overweight at midlife, while the odds of being obese at midlife were higher for those with AD as well as those with VaD," the researchers said.
People in these other BMI ranges appear to be at risk, too.
The team determined that being overweight but not obese during midlife was still a dementia risk—albeit a lesser one. "Although the effect of midlife overweight on dementia is not as substantial as that of obesity, its impact on public health and clinical practice is significant due to the fact that there are 1.6 billion overweight adults worldwide," the team wrote.
A separate 2011 study published in the journal Obesity Reviews noted that people who are underweight in midlife are also at outsized risk of later developing dementia. They determined that all BMI ranges other than a "healthy" BMI range were considered an independent risk factor for cognitive decline.
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There are several reasons BMI and dementia risk could be linked.
The twin study researchers say there are several potential reasons that weight and dementia are linked. They note that having a high BMI is linked with diabetes and vascular diseases, both of which are known dementia risk factors. "Nonetheless, in our study, the association between midlife high BMI and dementia remained significant after controlling for lifespan vascular diseases, suggesting that nonvascular pathways might play an important role in the adiposity-dementia association," the study authors hedged.
Another possible reason has to do with inflammation: a higher weight in midlife may go hand in hand with a "lifetime exposure to an altered metabolic and inflammatory state," they write. Additionally, they note that fat tissue secretes inflammatory cytokines and growth hormones which may prompt cognitive decline.
If you suspect your BMI is in a risky range, speak with your doctor to discuss healthy ways to lower your weight for a lower dementia risk and better overall health.
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