Young women hospitalized with acute myocardial infarction (MI) have greater in-hospital mortality than young men. However, the reasons for this difference have not been well characterized. We analyzed the data from 423,067 patients (247,701 men and 175,366 women) who were discharged with the diagnosis of MI from nonfederal hospitals in New Jersey and 355,569 coronary heart disease (CHD) deaths in New Jersey from 1990 to 2004 in 4 age strata: 35 to 54, 55 to 64, 65 to 74 and ≥75 years. Of the patients hospitalized for MI, young (35 to 54 years) women had greater in-hospital mortality than young men (5.2% vs 2.5%, adjusted odds ratio 1.64, 95% confidence interval 1.48 to 1.81, p <0.0001). However, in a community-wide analysis, when the total out-of-hospital CHD deaths in New Jersey were examined, young women had a lower out-of-hospital death rate than young men (11 vs 55/100,000). Statewide, young women were 4 times less likely to be hospitalized for MI (78 vs 297/100,000, relative risk 0.26), but they were only 1/2 as likely to die from MI in the hospital (7 vs 17/100,000, relative risk 0.41). Thus, women had a greater odds ratio for in-hospital mortality but a lower odds ratio for out-of-hospital CHD death than men. In conclusion, the greater in-hospital mortality of young women hospitalized for MI compared to young men could be explained in part by the finding that young men were more likely to have out-of-hospital CHD death.
Coronary heart disease (CHD) is a common cause of death of both women and men in the United States. Although women, on average, develop their first acute myocardial infarction (MI) about 10 years later than men and, overall, are less likely to develop MI than are men, several studies have shown that young women have greater in-hospital mortality than young men. The reasons for this difference are not well known. Women are more likely to have atypical symptoms, are more likely to wait longer than men before going to the hospital, and are less likely to be diagnosed with MI on admission. In addition, altered pain perceptions in women might result in improper management and a missed diagnosis. It has been speculated that the worse outcome of MI in young women could be explained, in part, by the death of more men than women before hospitalization and that the rate of death of young women during hospitalization is balanced by a greater rate of death before hospitalization among men. The present study examined, in a statewide database, whether the greater mortality of young women hospitalized for MI could be explained by more young men dying from CHD outside the hospital.
Methods
The present study was conducted using a statewide MI hospitalization database and CHD deaths in New Jersey from 1990 to 2004.
Hospitalization data were obtained from the Myocardial Infarction Data Acquisition System (MIDAS). MIDAS contains hospital discharge abstracts submitted by nonfederal acute care hospitals in New Jersey (n = 91) and includes all records with a primary diagnosis of MI ( International Classification of Diseases, Ninth Revision [ICD-9] codes 410.0 to 410.9). From 1990 to 2004, 423,067 patients (247,701 men and 175,366 women) were discharged with a primary diagnosis of MI. For these patients, information was obtained on the following variables: age, gender, race, co-morbidity (i.e., hypertension, renal disease, diabetes, chronic obstructive pulmonary disease, liver disease, anemia, cerebrovascular disease, and cancer), and complications (i.e., left ventricular dysfunction and arrhythmia), as described in a previous publication. MIDAS also includes all hospitalization records with any invasive cardiac procedure, including cardiac catheterization, percutaneous coronary intervention, and coronary artery bypass grafting. Patients who were <35 years old were excluded from the present study. The information from the database, including the diagnosis of MI, was validated using a random sample of the medical charts.
The vital status of the hospitalized patients with MI was determined by linkage of the MIDAS records with the New Jersey death registration, using the AutoMatch-Generalized Record Linkage System, version 3.0. The method of determining the sensitivity and specificity of this probabilistic record linkage procedure has been described in a previous report and was found to be 98% and 99%, respectively. The in-hospital and 28-day case-fatality after hospitalization for MI were computed separately for men and women.
Multivariate logistic regression analysis was used to estimate the odds ratios (ORs) for the association between gender and mortality in 4 age strata: 35 to 54, 55 to 64, 65 to 74, and ≥75 years. The association between gender and mortality was stratified by age and was adjusted within each age group for age, gender, race, diabetes, hypertension, renal disease, anemia, cancer, cerebrovascular disease, complications, year of admission, and site of MI, as coded at discharge (anterio r , ICD-9 code 410.0, 410.1; inferior, 410.2, 410.3, 410.4, 410.6; lateral, 410.5; subendocardial, 410.7; and other, 410.8, 410.9).
We used ICD-9 codes 410 to 414 and 429 and ICD-10 codes I20 to I25 to identify 355,569 CHD deaths, 173,671 in men and 181,898 in women, in New Jersey, from 1990 to 2004. We categorized a death as an out-of-hospital death using the variable location of death in the death registry. Trends in gender- and age-specific population CHD mortality were estimated. The age-specific population estimates by calendar year for men and women were obtained from the New Jersey Department of Health and Senior Services Vital Statistics.
Statistical analysis was performed using Statistical Analysis Systems, version 9.0 (SAS Institute, Cary, North Carolina). The State of New Jersey Department of Health and Senior Services and the Robert Wood Johnson Medical School institutional review boards approved the present study.
Results
In the 35 to 54-year age group, 21% of the patients hospitalized for MI were women compared to 45% of the patients in the ≥55-year age group. Young (age 35 to 54 years) women were more likely to have co-morbid conditions than were young men, including diabetes mellitus, hypertension, renal disease, anemia, and cerebrovascular disease during hospitalization ( Table 1 ). Also, young women were more likely to have left ventricular dysfunction, and young men were more likely to have arrhythmias associated with MI. The MI of young men was more likely to be coded at discharge as anterior, inferior or lateral. In young women, it was more likely to be coded as subendocardial. Young women were less likely to undergo invasive cardiovascular procedures, including cardiac catheterization, percutaneous coronary intervention, and coronary artery bypass grafting than young men.
Variable | Age Group (years) | |||
---|---|---|---|---|
35–54 | ≥55 | |||
Women (n = 14,510) | Men (n = 52,909) | Women (n = 160,856) | Men (n = 194,792) | |
Race | ||||
White | 70.3% | 78.2% | 83.8% | 84.9% |
Black | 18.9% | 8.7% | 8.2% | 6.1% |
Other | 10.8% | 13.1% | 8.0% | 9.0% |
Co-morbidity | ||||
Diabetes mellitus | 30.1% | 18.2% | 31.5% | 27.5% |
Hypertension | 44.3% | 38.9% | 51.6% | 45.2% |
Renal disease | 4.9% | 2.8% | 8.9% | 9.2% |
Anemia | 11.7% | 5.4% | 17.3% | 12.4% |
Cancer | 1.4% | 0.6% | 3.5% | 5.0% |
Cerebrovascular disease | 3% | 1.5% | 7.8% | 6.2% |
Complications | ||||
Arrhythmia | 13.4% | 15.6% | 16.7% | 19.9% |
Left ventricular dysfunction | 13.1% | 8.6% | 27% | 20.2% |
Arrhythmia and left ventricular dysfunction | 5.6% | 4.6% | 20.2% | 17.9% |
Procedure | ||||
Cardiac catheterization | 45.2% | 49.3% | 26.1% | 34.8% |
Percutaneous coronary intervention | 22.8% | 29.3% | 11.3% | 15.7% |
Coronary artery bypass grafting | 5.9% | 8.0% | 5.7% | 9.3% |
Site of myocardial infarction | ||||
Anterior, interior, lateral | 52.2% | 62.9% | 38.9% | 43.8% |
Subendocardial | 38.2% | 30.2% | 48.2% | 44.8% |
Other | 9.7% | 6.9% | 12.9% | 11.4% |
Table 2 lists the in-hospital and 28-day case-fatality of the men and women hospitalized for MI. In-hospital case-fatality increased with age in both genders, and women had greater in-hospital case-fatality than men in all age groups. The OR for in-hospital mortality for women versus men attenuated with age ( Table 2 ). The OR (women vs men) for in-hospital mortality, adjusted for age, co-morbidities, complications, year of diagnosis, and MI type, was 1.64 (95% confidence interval 1.48 to 1.81) in the young age group and decreased to 1.06 (95% confidence interval 1.04 to 1.09) for the oldest (≥75 years) age group. The adjusted OR (women vs men) for mortality at 28 days was 1.39 (95% confidence interval 1.26 to 1.54) for women aged 35 to 54 years compared to men in the same age group, decreased with increasing age, and was of borderline significance in the oldest age group ( Table 2 ).
Age Group (yrs) | Women | Men | Women Versus Men | |||
---|---|---|---|---|---|---|
Admissions (n) | Deaths (n) | Admissions (n) | Deaths | Adjusted OR* | 95% CI | |
In-hospital | ||||||
35–54 | 14,510 | 758 (5.2%) | 52,909 | 1,313 (2.5%) | 1.64 | 1.48–1.81 |
55–64 | 23,427 | 1,871 (8%) | 54,230 | 2,737 (5%) | 1.59 | 1.49–1.70 |
65–74 | 44,120 | 5,469 (12.4%) | 65,302 | 6,750 (10.3%) | 1.35 | 1.29–1.41 |
≥75 | 93,309 | 19,358 (20.7%) | 75,260 | 15,329 (20.4%) | 1.06 | 1.04–1.09 |
28 Days | ||||||
35–54 | 14,510 | 764 (5.3%) | 52,909 | 1,526 (2.9%) | 1.39 | 1.26–1.54 |
55–64 | 23,427 | 1,932 (8.2%) | 54,230 | 3,010 (5.6%) | 1.44 | 1.35–1.53 |
65–74 | 44,120 | 5,622 (12.7%) | 65,302 | 7,186 (11%) | 1.25 | 1.21–1.31 |
≥75 | 93,309 | 20,939 (22.4%) | 75,260 | 16,571 (22%) | 1.02 | 1.00–1.05 |
Considering the total population of New Jersey, rather than only those hospitalized for MI, women had lower population out-of-hospital CHD death rates ( Table 3 ). Similar effects were observed when MI hospitalizations and in-hospital deaths were examined in a community-wide analysis when the total out-of-hospital CHD deaths in New Jersey were examined. Young women had a lower out-of-hospital death rate than young men (11 vs 55/100,000). Although young women were 4 times less likely (78 vs 297) to be hospitalized for MI, they were only 1/2 as likely (7 vs 17) to die from MI in the hospital. Thus, women had greater adjusted ORs for in-hospital mortality but lower ORs for out-of-hospital CHD death than men.
Age (yrs) | Acute MI Hospitalization | In-Hospital Deaths | Out-of-hospital CHD deaths | ||||||
---|---|---|---|---|---|---|---|---|---|
Women | Men | Relative Risk | Women | Men | Relative Risk | Women | Men | Relative Risk | |
35–54 | 78 | 297 | 0.26 | 7 | 17 | 0.41 | 11 | 55 | 0.20 |
55–64 | 402 | 1,029 | 0.39 | 67 | 144 | 0.47 | 81 | 276 | 0.29 |
65–74 | 891 | 1,686 | 0.53 | 259 | 495 | 0.52 | 260 | 621 | 0.42 |
≥75 | 1,910 | 2,793 | 0.68 | 1,211 | 1,648 | 0.73 | 1,741 | 1,896 | 0.92 |
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