Women Younger than Age 75 Twice as Likely to Die as Men After Heart Attack, According to Yale School of Medicine Study

Among heart attack patients younger than age 75, women were almost twice as likely to die in the hospital following a heart attack as men, according to a Yale study published in the Oct 12 issue of the AMA’s Archives of Internal Medicine. Conversely, women in the age group 75 years old or older had a significantly lower risk of death than men that age.

The researchers studied data from the medical records of 1,025 patients who met accepted criteria for myocardial infarction. “When examining sex differences in outcomes from heart attacks, findings have been conflicting,” said Viola Vaccarino, assistant professor of epidemiology and public health, Yale School of Medicine, who led the study. “Averaging the risks over a broad age range may have obscured the higher risk for women in the younger age group.”

She added that further investigations are needed to confirm the findings in larger populations, and to look at the reasons for the relatively poor prognosis after heart attacks for younger female patients.

The study was based on the Myocardial Infarction Project II (MIP II), a database developed for quality improvement purposes by the Connecticut Peer Review Organization and 15 Connecticut hospitals. Included in the study were 1,025 patients with a confirmed acute myocardial infarction who were hospitalized in those hospitals in 1992 and 1993. Trained nurses and medical record technicians abstracted the medical records of these patients to obtain information on demographics, medical history, clinical characteristics on admission, treatments and hospital mortality.

“We found that, overall, women of all ages had a 40 percent higher hospital mortality than men, but that simple age adjustment eliminated the sex differences in mortality rate, as previous studies have shown,” said Vaccarino, who collaborated on the study with Ralph I. Horwitz, M.D.; M.P.H.; and Harlan M. Krumholz, M.D., of the Yale School of Medicine; and Thomas P. Meehan, M.D; Marcia K. Petrillo, M.A.; and Martha J. Radford, M.D. of the Connecticut Peer Review Organization. “However, when the sample was subdivided into two age groups, women younger than 75 years old showed twice as high mortality as men of the same age, while older women showed no difference in mortality.

The researchers then took the study a step further. After taking into account sex differences in coexisting illness, clinical severity of the heart attack, and hospital treatments, they found the higher mortality persisted for women under age 75 (although somewhat less dramatically at only 49 percent higher). while women 75 or older actually showed a 46 percent lower mortality rate than men. In addition, the study found that there is no “threshold effect,” which means that higher risk did not occur suddenly at age 65 or 70. Instead, they found that the younger the woman, the higher her risk of death after a heart attack compared with men.

Because of the protective effect of estrogen in premenopausal women, myocardial infarction is much less common than in men up to about age 75, Vaccarino said. Women who have a heart attack before then may be genetically predisposed to early onset or more severe heart disease, and may represent “a distinct group in terms of risk factors and pathophysiology, with a particularly aggressive course for the disease,” she said. Another explanation could be a delay in detection of coronary heart disease in younger women and less frequent referrals for treatment.

“When examining sex differences in outcomes of myocardial infarction, it may not be sufficient to adjust for age alone, but future studies should also consider the interaction between sex and age,” she added.

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