While there are some known risk factors for developing dementia, such as genetics, there’s a lot experts still don’t know about why some people develop the disease. Now, a new study has found a surprising link between height in young adulthood and the risk of dementia.
The study, which was published in the journal eLife, analyzed data on 666,333 Danish men born between 1939 and 1959 —including 70,608 brothers and 7,388 twins—from Danish national registries. Of those men, 10,599 developed dementia later in life.
The researchers looked at the men’s heights and found that there was about a 10 percent reduction in their risk of developing dementia for every six centimeters (about two inches) of height in men who were above the average height of five feet, nine inches. The relationship also existed when the researchers analyzed data for brothers who had different heights, which suggested genetics alone couldn’t explain why shorter men in the study had a larger risk of developing dementia. Researchers also adjusted for educational level and intelligence test scores.
Worth noting: The scientists aren’t sure how this applies to women, given that they only studied men. Previous studies also found that the link between height and dementia risk in women was inconclusive. “We cannot say for sure if our results apply to women,” senior author Merete Osler, a professor at the University of Copenhagen, tells Yahoo Lifestyle. “But we find it likely that the mechanism described above would be the same for women.”
This isn’t the first time height has been linked to dementia risk. One meta-analysis, published in 2014, analyzed height and deaths from dementia and found that taller people were less likely to die of the disease. A case-control study published in the Journal of Alzheimer’s Disease found that taller men (those who were five feet, nine inches or more) had a 59 percent lower risk of developing Alzheimer’s disease than men who were shorter than five feet, five inches.
Related: Eating More Fruits, Vegetables May Reduce Risk of Alzheimer’s Dementia
What’s going on here?
It’s important to stress that correlation doesn’t equal causation in this case. So, the researchers didn’t actually prove that height raised or lowered a person’s dementia risk—just that people who were taller tended to have a lowered risk of developing the disease.
But lead study author Terese Sara Høj Jørgensen, an assistant professor at the University of Copenhagen, says that there does seem to be some relationship here. “Height is an expression of growth early in life, and a taller body height may express that the body has had an optimal development,” she tells Yahoo Lifestyle. “At the same time, a shorter height may be an indicator of harmful exposures early in life. Thus, the association between body height and dementia may exist because body height expresses early life circumstances that are linked to later risk of dementia.”
Of course, height also has a strong genetic component, and it’s difficult to say that all shorter people have a higher risk of dementia, Douglas Scharre, MD, director of the Division of Cognitive Neurology Chief of Staff Elect at the Ohio State University Wexner Medical Center, tells Yahoo Lifestyle. While he agrees with Jørgensen’s theory that early development may play a role in height and brain development, he’s hesitant to say that height is a major risk factor for dementia. “I don’t think it’s all that important,” he says.
Clifford Segil, DO, a neurologist at Providence Saint John's Health Center in Santa Monica, Calif., agrees. He tells Yahoo Lifestyle that factors like genetics, age, cardiovascular health, diet and exercise, and alcohol use play more important roles in the development of dementia.
Regardless of your height and known dementia risk factors, Segil recommends following a healthy diet and all-around lifestyle to try to lower your dementia risk. Having an active social life and staying mentally sharp can also help, Scharre says, adding, “These are things you can do something about.” This particular study also found that having a good cognitive reserve—that is, the brain’s ability to improvise and solve problems that come up in everyday life—can help lower the risk of developing dementia.
Segil calls the study findings “interesting,” but stresses that people who are on the shorter side shouldn’t worry about their dementia risk based on their height alone. “In clinical practice, I have lots of patients above five foot nine inches with dementia and plenty below five foot nine inches,” he says.
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