Women who suffer heart attacks may face a 12 percent greater risk of dying if their care is entrusted to a male doctor, according to a new study reported by Scientific American.

Researchers think one factor in this disparity is the shortage of female physicians, who make up only a quarter of emergency room doctors in the U.S. For the study, published in the journal PNAS, the researchers analyzed a Florida Agency for Health Care Administration database that contained 19 years of records on heart attack cases from nearly every emergency room in the state.

They analyzed the statistical relationship between rates of death and four different physician-patient combinations: male doctors treating men or women, and female doctors treating men or women. The statistics were “indistinguishable except for male doctor–female patient,” the study’s co-author, Brad Greenwood, tells Scientific American.

They found that one out of every 66 women who has a heart attack will die in the emergency room if she is treated by a male doctor instead of a female one.

Although heart disease is the main cause of death in both men and women in the U.S., it’s often wrongly perceived as being a male disease, as well as an ailment that only affects the elderly. However, the disease kills about 15,000 women under the age of 55 each year.

Men are also more likely to recover from it. According to American Heart Association statistics from 2016, 36 percent of men die within five years of a heart attack, compared to 47 percent of women.

Other research has yielded similar findings. A study published in February found that doctors are more likely to ignore signs of a heart attack when they’re reported by young female patients as opposed to young male patients. This could be because the symptoms tend to manifest differently in women than they do in men, with female heart attack patients sometimes complaining of neck and back pains, fatigue, and nausea; because most studies have focused on men, their symptoms are seen as the standard ones.

As a result, many women wait before seeking help. “I can’t tell you how many women I’ve seen who say they felt something and wondered if it was a heart attack,” Harmony Reynolds, a cardiologist who specializes in women’s heart health, told the New York Post in February. “That inkling is there, but for some reason it doesn’t convert into action.”

For more information about the symptoms of heart attacks in women, visit the Go Red for Women website.

[h/t Scientific American]