Women aged 55 years and younger have nearly twice the risk of rehospitalization in the year immediately following a heart attack compared to men of similar age, according to a new study supported by the National Institutes of Health (NIH).  The study, funded by the NIH’s National Heart, Lung, and Blood Institute (NHLBI), was recently published in the Journal of the American College of Cardiology.

Longstanding research has demonstrated that women aged 55 years and younger have approximately twice the risk of in-hospital death from a heart attack than similarly aged men.  However, prior to this research, it had been unclear whether women also experience a higher risk of cardiovascular and non-cardiovascular complications a year after leaving the hospital following treatment for a heart attack.

Gender’s role in heart attack recovery

The objective of the study was to determine sex differences in causes and timing of 1-year outcomes following acute myocardial infarction (AMI) in individuals aged 18 to 55 years.  In order to arrive at their findings, the research team analyzed data from NHLBI’s VIRGO (Variation in Recovery: Role of Gender on Outcomes of Young AMI Patients) study.  VIRGO explores a broad range of risk factors related to outcomes among women and men who have experienced heart attacks.  The study enrolled 2,979 patients—2,007 women and 972 men—at 103 US hospitals.  The participants had an average age of 48 years and were from racially and ethnically diverse populations.

Sex differences in all-cause and cause-specific hospitalizations were compared by calculating incidence rates ([IRs] per 1,000 person-years) and IR ratios with 95% CIs.  The study authors then performed sequential modeling to evaluate the sex difference by calculating subdistribution hazard ratios (SHRs) accounting for deaths.

The analysis showed that nearly 30% of these patients were rehospitalized in the year after first leaving the hospital following a heart attack.  Most of those re-visits peaked within the first month of a patient’s discharge, then slowly declined in subsequent months.  The researchers found that women had nearly twice the risk (1.65 times higher risk) of rehospitalization than men.

Women with a myocardial infarction with nonobstructive coronary arteries (MINOCA) had lower rates of rehospitalization than women who experienced myocardial infarction with obstructive coronary artery disease (MI-CAD).

Same causes, worse outcomes

The leading cause of rehospitalization for both men and women was determined to be coronary-related complications—those such as heart attacks and angina related to blood vessel blockage.  Yet, the rate of coronary-related complications for women was nearly 1.5 times higher than for men—differences driven in large part by risk factors such as obesity and diabetes.

Notably, the most significant gender disparities were found to be in non-cardiac rehospitalizations.  These, defined as hospitalizations caused by events not related to heart disease or stroke such as digestive problems, depression, bleeding, and pneumonia, were more than twice as high (or 2.10 times higher) in women than in men.

The findings suggest a need for closer health monitoring of the approximately 40,000 American women aged 18 to 55 years who suffer heart attacks each year following hospital discharge, and a better understanding of the reasons behind the different outcomes.

Theories on why

The factors driving women’s higher non-cardiac rates are murky, but the research team did find that a higher percentage of the female study participants tended to identify as low income than men (48% vs 31%).  More women also more frequently registered a history of depression than their male counterparts (49% vs 24%).

The team hypothesized that, while low income in itself is not a medical parameter, data shows that it is frequently associated with limited access to healthcare often resulting in poor health status.  Further, the risk for depression is known to rise post-heart attack and may be a component in the higher hospitalization rates due in part to the documented undertreatment of the condition in women.  However, the authors note, further studies are necessary to ascertain how these factors impact disparate hospitalizations after a heart attack.

Narrowing the ‘equity gap’

“We have shown for the first time that rehospitalizations following heart attacks in women aged 55 and younger are accompanied by certain non-cardiac factors, such as depression and low-income, that appear more common in women than men and are associated with more adverse outcomes,” noted corresponding author Harlan M. Krumholz, MD, a cardiologist and professor of medicine at the Yale School of Medicine, New Haven, Connecticut, and director of the school’s Center for Outcomes Research and Evaluation (CORE).

The study points to a need for more focus on risk factors in women 18 to 55 to create better treatment and recovery after discharge, Krumholz contends.

“Future research on non-cardiac risk factors after hospital discharge following heart attack could lead to the development of targeted strategies that can narrow this equity gap,” stated Gina S. Wei, MD, MPH, associate director of NHLBI’s Division of Cardiovascular Sciences and NHLBI’s senior scientific advisor on women’s health.  “We look forward to more studies in this area.”

 Access to the complete study findings in the full paper, “Sex Difference in Outcomes of Acute Myocardial Infarction in Young Patients,” is available at this link.

The contents of this feature are not provided or reviewed by NPWH.