New study findings published in the Journal of the American College of Cardiology link smoking to an increased risk of a serious type of heart attack known as acute ST segment elevation myocardial infarction (STEMI) among women under age 50, reports the American College of Cardiology.

For the study, researchers assessed smoking as an independent risk factor for STEMI and determined the differences in risk between age groups and genders. Scientists compiled the data of 3,343 patients in the South Yorkshire region of the United Kingdom who presented with acute STEMI from 2009 through 2014. A total of 46.8% of female patients and 47.6% of male patients were current smokers.

All patients—regardless of age or gender—experienced an increase in their risk of STEMI as a result of smoking. But researchers determined that the chance of the condition was much higher in females than males.

The greatest risk difference between men and women was in smokers between ages 50 and 64. However, scientists noted the greatest increased risk occurred among individuals in the 18-to-49 age group. Female smokers faced a greater than 13 times higher risk of STEMI compared with women who didn’t smoke. (Male smokers had an 8.6 times increased risk.)

Researchers proposed several theories for this increased STEMI risk among women. One possibility is that smoking may lower serum estrogen levels, which are known to protect against the buildup of fats, cholesterol and other substances in and on the artery walls. Another theory is that chronic inflammation from smoking causes more narrowing in women’s smaller coronary arteries.

In addition, several other vascular conditions are more prevalent in female STEMI patients. These include vasospasm, a sudden contraction of an artery’s muscular walls; vasculitis, or inflammation of blood vessels; and spontaneous coronary artery dissection, a rare condition triggered by a tear in one of the heart’s blood vessels.

“Patients who smoke merit encouragement to give up their habit, and this study adds quantitative evidence to the massive benefits of doing so,” said Ever Grech, MD, FACC, a consultant cardiologist and senior author of the study.

The biggest advantage for all smokers, researchers agreed, is that quitting could lower the risk of developing STEMI to that of a never smoker in as little as a month.

For more about the effects of smoking on health, read “Another Reason for African Americans to Quit Smoking Right Now” and “Can Smoking E-Cigarettes Damage Your DNA?”