Exercise and physical activity are go-to recommendations from cardiologists hoping to reduce the risks of heart disease in their patients. Research shows that being generally fit makes someone less likely to have cardiac disease, and the benefits of exercise — like muscle strength, lower blood pressure, and improved cholesterol — are also linked to lower risk of disease.
However, the research to date hadn’t established if exercise could reduce the rates of disease for those who are already at a high genetic risk for cardiovascular problems. A new study, which analyzed genetic risk factors, level of physical fitness, and rates of cardiovascular events for nearly a half a million people in the United Kingdom, aimed to close that gap. The study, published this month in the journal Circulation, found that physical fitness lowers rates of cardiac disease about the same amount for everyone, regardless of their degree of genetic risk.
“It wasn’t totally surprising,” says Erik Ingelsson, professor of medicine at the Stanford University School of Medicine in California and an author on the study. “But that said, no one had ever shown it before.”
The relationship between exercise and lowered risk of cardiac diseases has been established in studies in the past, Inglesson says. But that research was often done only in small groups and struggled with accurately and consistently tracking fitness levels, he says.
“This is the largest study that has been done looking at different disease endpoints and looking at aspects of activity and fitness,” he says.
The team used data from the United Kingdom Biobank, a longitudinal study that started in 2006. The fitness and activity levels of the participants were measured with grip strength, which serves as a proxy for overall body strength; a self report of physical activity, collected on questionnaires; cardiorespiratory fitness, measured by oxygen consumption during a workout on a stationary bike; and a seven-day period with a wrist-worn activity monitor.
Then, they analyzed the data to look for associations between fitness levels and instances of cardiac diseases in the participants and stratified results by level of genetic risk. The risk profiles were based on genetic markers pulled from large, genome-wide meta-analyses.
For participants with the highest genetic risk for coronary heart disease, a condition that causes plaque to build up in the arteries, having a high level of cardiorespiratory fitness was associated with a 49 percent reduction in the risk of developing the disease. High cardiorespiratory fitness was also linked to a 60 percent reduction in risk of atrial fibrillation, an irregular heartbeat, among participants with a high genetic risk.
“The very low risk is going to be if you have both a low genetic risk, and you’re physically active,” Ingelsson says. “The highest risk is going to be if you have a high genetic risk and are not physically active.” But being physically active, or having a high cardiorespiratory fitness, can help reduce the likelihood of coronary heart disease, for example, for someone with a high genetic risk — and put their risk of developing the disease more in line with someone who has a medium genetic risk and has poor fitness. “It’s additive,” Ingelsson says.
For Ingelsson, the key takeaway from the study is that, regardless of genetic risk, it’s still beneficial to be physically fit. “So if parents or a sibling have cardiac disease, and if you know at a higher genetic risk, you still can benefit,” he says. “It’s less deterministic, and you can still do something.”
Continuing to study the relationship between genetic risk and physical activity might, at some point, allow for clinicians to personalize exercise recommendations, Ingelsson says.
However, the results from this particular research aren’t enough to start down that path, says Aaron Folsom, a cardiovascular epidemiologist and professor at the University of Minnesota school of public health. Although this study is a useful and comprehensive look at genetics risks and lifestyle factors, it doesn’t show that genetics can identify the people who might benefit the most from exercise, he says.
“This shows that everyone kind of gets the same benefit from lifestyle changes,” Folsom says. “If you’re at a higher genetic risk, you might be more likely to benefit personally, but the relative magnitude that your risk goes down is the same as everyone else.”
For Folsom, the results indicates that clinicians should simply be encouraging everyone, across the board, to exercise. “We need to figure out ways to get everyone more active.”
Participants in this study were 54 percent female and 46 percent male, but the team did not analyze the role that sex and gender might play in risk factors and response to exercise. Ingelsson says he hopes to scrutinize that piece more closely going forward. And although ethnicity might be another interesting variable to consider, he says, the U.K. BioBank is 94 percent white, vastly limiting the power of any attempted analysis. “If we want to look at ethnicity, it would have to be with another dataset,” Ingelsson says.