Heart disease is the leading cause of death in the U.S., yet one in eight Americans who suffer from the condition can't afford to take the medication they need to stay alive, according to a new study from the American Heart Association.

To save money, many patients either skip doses, take a lower dose than what is prescribed or delay filling a medication, the study found.

"In recent years, insurance has been shifting the cost of health care to patients via higher deductibles, co-pays and co-insurance," said Dr. Khurram Nasir, one of the authors of the study, as well as a cardiologist at Houston Methodist hospital and a professor at the Yale School of Medicine. "In our practice, we can see that our patients are feeling the pinch."

Researchers used National Health Interview Survey data from 2013 through 2017 to determine what percentage of people with heart disease isn't following doctors' orders specifically because of medication costs.

For patients, deviating from a treatment regimen poses health risks, medical experts say. It also raises overall health care costs when someone's condition worsens and they require emergency room visits or hospitalization.