While chest pain may be the hallmark symptom of heart disease, doctors should tune in to the possibility of heart disease even without it. That’s because heart attacks may go unrecognized in people with high pain tolerance, according to new research in the Journal of the American Heart Association.

Often a “silent” heart attack is discovered after the fact at the doctor’s office or the hospital, by coincidence, if an ECG is recorded, researchers said. Other typical symptoms like shortness of breath and cold sweats don’t always occur.

“It is unknown why some people experience heart attacks without symptoms. One possible explanation for the absence of chest pain is high pain tolerance,” said Andrea Ohrn, M.D., lead author of the study and a Ph.D. fellow at University of Tromsø in Norway.

Researchers studied about 5,000 adults who underwent tests to measure their pain tolerance and determine if they’d had a heart attack that was recognized or unrecognized, or if they hadn’t had a heart attack. Eight percent of participants were identified as having an unrecognized or silent heart attack, while 4.7 percent had recognized heart attacks.

Women had fewer heart attacks than men, but more heart attacks that were silent, and the association between silent heart attack and lower pain tolerance was stronger in women. The larger difference may be because women recognized with a heart attack might be those women most sensitive to pain, presenting with the most severe symptoms, Ohrn said.

A silent heart attack can put survivors at an increased risk for poor recoveries, researchers said.

“Asking patients about their pain sensitivity might provide a clearer picture about their probability of presenting with heart specific symptoms in the case of a heart attack,” Ohrn said.