Regular exercise is considered one of the most cost-effective ways of preventing heart disease. Evidence also suggests it may help extend the lives of people already diagnosed with the disease.

Little has been known, however, about whether exercise can also help people with a genetic predisposition for heart disease. That situation changed Monday with the publication of a study in Circulation, a journal of the American Heart Association. The study found that being physically fit may protect your heart — even if you have a strong family history of the disease.

This finding has “important public health impact,” the authors of the study write. “The knowledge that lifestyle choices have substantial effects on disease risk could encourage individuals to initiate a healthier lifestyle to reduce that overall risk.”

Each year, about 610,000 people die of heart disease in the United States, making it the leading cause of death among both men and women. Many types of heart disease can be passed down genetically through families, and researchers have linked more than five dozen gene variants to an increased risk of developing the disease.

Source of the data

For the current study, researchers at Stanford University in the United States and Uppsala University in Sweden used data collected from more than 500,000 men and women, aged 49 to 60, who were participating in UK Biobank, an ongoing study aimed at finding better ways to prevent, diagnose and treat a wide range of serious and life-threatening illnesses, including heart disease.

When they entered the study, none of the participants had any evidence of heart disease. Their genetic predisposition to the disease was assessed with blood tests (with the participants’ consent). Other health information was also gathered, including measurements of physical activity, cardiovascular fitness and grip strength (an indicator of overall muscle strength).

The participants were followed for an average of six years. During that time, almost 21,000 of them experienced a cardiovascular “event,” such as a heart attack, stroke, heart failure, or a diagnosis of atrial fibrillation (an irregular heartbeat that increases risk of stroke, heart failure, and other complications).

When the researchers analyzed all that data, they found that having more physical activity, better cardiovascular fitness and greater grip strength were associated with a lower risk of heart disease and atrial fibrillation, even among people with an elevated genetic risk for heart disease. 

For example, people with an intermediate genetic risk for heart disease who were in the group with the strongest grips were 36 percent less likely to develop heart disease and 46 percent less likely to develop atrial fibrillation than participants with the same genetic risk who had the weakest grips.

Among people in the study with the highest genetic risk for cardiovascular disease, those whose cardiovascular systems were the most fit were 49 percent less likely to develop heart disease and 60 percent likely to develop atrial fibrillation than participants with the lowest level of fitness.

Interestingly (and surprisingly), grip strength and cardiorespiratory fitness were more closely associated with a lower risk for heart disease than self-reported physical activity. The researchers say that may be because the participants inaccurately reported their level of physical activity. For when the physical activity of the participants was measured by an objective tool — a wrist-worn accelerometer — the association between physical activity and a decreased risk of heart disease became stronger.

Limitations and implications

The study comes with several important caveats. Most notably, it is an observational study and therefore can’t prove a causal connection between exercise and a lower risk of heart disease for genetically at-risk people. The researchers adjusted their results for a long list of confounding factors (ones known to be associated with an increased risk of heart disease), including age, gender, ethnicity, socioeconomic status, body mass index, diabetes and smoking. But factors not included in that adjustment might also explain the study’s results.

Still, the findings are supported by another recent study that found a similar association between healthy lifestyle factors — including physical activity — and a lower risk of heart disease among genetically at-risk people. 

“The main message of this study is that being physically active is associated with a lower risk of heart disease, even if you have a high genetic risk,” said Dr. Erik Ingelsson, the study’s lead author and a professor of medicine at Stanford University, in a released statement.

People with such a risk should “discuss a physical activity plan with a physician,” he added.

FMI: The study can be read in full on Circulation’s website.