Feb. 5, 2025 – Staying fit is one of the best ways to lower the risk of dementia — even for those with a genetic predisposition to the condition.
A new study in the British Journal of Sports Medicine calculated a 35% decrease in the odds of developing dementia among those with a genetic risk but who have a high level of cardiorespiratory fitness, or CRF. CRF refers to how well the heart, lungs, and muscles work together to supply oxygen during sustained physical activity. It’s a measure of overall cardiovascular and respiratory efficiency and is often assessed through activities like running, cycling, or brisk walking. In general, higher cardiorespiratory fitness is linked to better heart health, lower disease risk, and improved endurance.
Overall, high CRF cut the risk by 40%, according to the new evidence.
The researchers discovered that CRF was related to dementia risk in a linear, “dose-dependent” manner. The higher fitness that a person had at baseline, the lower their risk of developing dementia.
This confirms years of previous research linking a lack of fitness with a higher risk of dementia. But the finding that people at genetic risk can lower that risk if they’re fit is a new piece of evidence, according to Kerem Shuval, PhD, MPH, a research professor at the Texas Tech Health Sciences Center in Lubbock, Texas, who was not involved in the new study.
Lead study author Qing Zeng, PhD, said the research “strongly suggests that physical exercise is an important component of comprehensive prevention strategies against dementia.” Zeng is professor of clinical research and leadership at George Washington University’s medical school in Washington, D.C.
The new study analyzed data from more than 61,000 British people over 12 years, ranging in age from 37 to 70 at the start of the study. Their fitness was gauged by a 6-minute test on an exercise bike. CRF refers to how well the body delivers oxygen to muscles.
People in the new study also had their genetic risk for Alzheimer’s disease assessed when they enrolled in the UK Biobank program. Neuropsychological tests assessed their cognitive function. Higher CRF was associated with higher cognitive function at baseline. (The study was observational and didn’t address cause and effect.)
The study arrives at a time when cases of Alzheimer’s, vascular dementia, and other forms of dementia are rapidly rising. According to another recent paper, the lifetime risk of dementia after age 55 is now estimated at 42%. The number of U.S. adults who develop this incurable disease is expected to jump from 514,000 per year in 2020 to 1 million per year in 2060.
Some of Shuval’s colleagues published a paper in 2013 that showed that among a large group of nonelderly people, a high level of fitness was correlated with a 36% lower risk of dementia than for the least fit people. The new study was an effort to look at the effects of exercise in older people.
The Role of Genetics in Fitness and Dementia
The relationship between cardiorespiratory fitness and physical exercise, however, is not as clear-cut. “Generally, fitness is an indicator of physical activity, but there’s also a genetic component of fitness; between 20% and 50% of fitness is genetics,” Shuval said. “Based on the evidence we have right now, fitness — not physical activity itself — is an independent risk factor for dementia.”
About half of dementia risk is said to be preventable. According to a major report on dementia by the Lancet Commission, preventive measures include controlling blood pressure, obesity, diabetes, and smoking, getting plenty of exercise and sleep, avoiding social isolation, and fighting depression. Together, modifying a dozen risk factors could avert 40% of all dementias, the report said.
A paper on “international exercise recommendations in older adults” says there is robust evidence that physical exercise can help prevent or treat many chronic diseases, including dementia. “Declines in muscle function and cardiorespiratory fitness with aging … are also associated with cognitive decline,” the report said.
In general, it’s recommended that older adults get at least 150 minutes of moderate aerobic activity per week. But Shuval said that more exercise is better, not only for your overall health, but also for preserving cognitive function. “It’s not just walking briskly with your friend,” he said. “You need to start running and exercising vigorously.”
Staying fit can also slow the decline of CRF, which accelerates as you grow older, Shuval noted. The new study did not look at fitness changes over time, as CRF in the UK Biobank was measured only at baseline. But Zeng cited another study that shows that while a drop in CRF over time increases the risk of dementia, starting at a higher CRF level confers protection against dementia, even after a decline.
Various studies have looked at the association between fitness and dementia in different ways. For example, another paper from the Cooper Institute examined the relationship between both CRF and body mass index (BMI) and dementia. It found that participants who were unfit and overweight or had obesity had the highest dementia risk compared with their fit and healthy-weight counterparts. Lower midlife fitness is a risk marker for dementia irrespective of weight status, the study concluded. But being unfit and overweight might increase dementia risk further.
Genetic Risk Factor vs. Lifestyle
The new study’s genetic component is based on a “polygenic risk score” that looks at multiple markers to estimate a person’s genetic risk of dementia. This is not trivial: If your father or mother or sibling had or has Alzheimer’s, for example, you’re more likely to develop it, as well, according to the Alzheimer’s Association.
Courtney Kloske, PhD, director of scientific engagement for the Alzheimer’s Association, highlights the study’s findings that high CRF can help reduce the risk of Alzheimer’s and other types of dementia, even in those with a genetic predisposition. But she wishes that the researchers had separated out the people who had the APOE4 protein, which she said is a strong marker for Alzheimer’s disease.
Kloske looks at the correlation between CRF and dementia risk within the larger context of how healthy habits can help everyone lower their risk. She recommends reading the Alzheimer’s Association’s “10 healthy habits guide” to get some tips on how to do that.
“It all comes back to the idea that a healthy lifestyle is going to be beneficial across the board,” Kloske said. “If you have a genetic predisposition, you should be thinking about what that healthy lifestyle is, and that’s going to be different for everyone. But eating right, exercising, doing all the things your doctor tells you to do — those are things you can be considering, regardless of your risk of developing Alzheimer’s.”
