NEW YORK - Women, especially younger women, are more likely than men to show up at the hospital with no chest pain or discomfort after having a heart attack, a new study suggests.

Those symptoms, or lack of symptoms, can result in delayed medical care and differences in treatment that might in turn help explain why women in the study were also more likely to die of their heart attacks, according to researchers.

“They might not even know they’re having a heart attack,” said Dr. John Canto, from the Watson Clinic in Lakeland, Florida, who worked on the report.

According to the Centres for Disease Control and Prevention, close to 800,000 Americans have their first heart attack every year, and heart disease is the leading cause of death for both men and women.

Although the results are based on a study of more than a million heart attack patients, Canto cautioned, they are still preliminary. But, he added, they do challenge the notion that chest pain and discomfort should be considered “the hallmark symptom” for all heart attack patients.

“If our results are in fact true, I would argue that rather than the one-size-fits-all symptom message, we also have to tailor that message to say that women less than 55 are also at higher risk for atypical presentation,” which includes jaw or arm pain, Canto told Reuters Health.

He and his colleagues analyzed medical records in a national database of heart attack patients from 1994 to 2006, including about 1.1 million people treated at close to 2,000 hospitals.

They found that 31 percent of male patients didn’t have any chest pain or discomfort, compared to 42 percent of women.

The likelihood of having such an “atypical presentation” differed most between younger women and younger men, the researchers reported Tuesday in the Journal of the American Medical Association.

Women under 45 were 30 percent more likely than men in their age group to present without chest pain; between ages 45 and 65 the difference dropped to around 25 percent, and after 75, it all but disappeared.

A similar pattern, with smaller differences between sexes, was seen in the likelihood of death. Almost 15 percent of women died in the hospital after their heart attack, compared to about 10 percent of men. Younger women with no chest pain were almost 20 percent more likely to die than male counterparts. But after age 65, the women’s risk fell below that of men.

Dr. Patrick O’Malley, an internist at the Uniformed Services University of the Health Sciences in Bethesda, Maryland, said at least part of that difference could be due to lack of action by patients and doctors when symptoms are unusual.