Propensity score-matched analysis of effects of clinical characteristics and treatment on gender difference in outcomes after acute myocardial infarction.

The greater mortality observed in women compared to men after acute myocardial infarction remains unexplained. Using an analysis of pairs, matched on a conditional probability of being male (propensity score), we assessed the effect of the baseline characteristics and management on 30-day mortality. Consecutive patients were included from January 2006 to December 2007. Two propensity scores (for being male) were calculated, 1 from the baseline characteristics and 1 from both the baseline characteristics and treatment. Two matched cohorts were composed using 1:1 matching and computed using the best 8 digits of the propensity score. Paired analyses were performed using conditional regression analysis. During the study period, 3,510 patients were included in the registry; 1,119 (32%) were women. Compared to the men, the women were 10 years older, had more co-morbidities, less often underwent angiography and reperfusion, and received less medical treatment. The 30-day mortality rate was 12.3% (130 of 1,060) for the women and 7.2% (167 of 2,324) for the men (p <0.001). The 2 matched populations represented 1,298 and 1,168 patients. After matching using the baseline characteristics, the only difference in treatment was a lower rate of angiography and reperfusion, with a trend toward greater 30-day mortality in women. After matching using both baseline characteristics and treatment, the 30-day mortality was similar for the men and women, suggesting that the increased use of invasive procedures in women could potentially be beneficial. In conclusion, compared to men, the 30-day mortality is greater in women and explained primarily by differences in baseline characteristics and to a lesser degree by differences in management. The difference in the use of invasive procedures persisted after matching by characteristics. In contrast, after matching using the baseline characteristics and treatment, the 30-day mortality was comparable across the genders.