Background and purpose: Little is known about gender differences in the temporal trend of mortality related to acute myocardial infarction (AMI) over the last decades. To that purpose, we retrospectively analysed prospective data collected over a 20-year span within the Swiss nationwide acute myocardial infarction registry AMIS Plus.
Methods: All AMI patients enrolled from January 1997 through December 2016 were included in the analysis. Patients were categorized as ST-elevation myocardial infarction (STEMI) or non-STEMI (NSTEMI) as well as according to gender. Adjusted in-hospital mortality rate were calculated logistic regression analyses.
Results: Among 51,725 patients, 30,398 (59%) had STEMI and 21,327 (41%) NSTEMI; 73% were males (mean age 63.9±12.8 years) and 27% were females (71.7±12.5 years). Women were older than men both in STEMI group (71.3y ±12.7y vs. 62.8y ±12.8y; p<0.001) and in the NSTEMI group (72.2y ±12.2y vs. 65.6y ±12.6y; p<0.001).
From 1997 to 2016, crude in-hospital mortality decreased from 9.8% to 5.5% in STEMI men and from 18.3% to 6.9% in STEMI women (p trend <0.001 for both). In NSTEMI men it decreased from 7.1% to 2.1% and in NSTEMI women from 11.0% to 3.6% (p trend <0.001 for both). The quadratic model of logistic regression for mortality of STEMI and NSTEMI patients demonstrated a significance for non-linearity of age of p<0.001 and p=0.001, respectively.
After adjustment for gender and age, early mortality reduction was 4% per additional admission year for STEMI (OR 0.96, 95% CI 0.95–0.97; p<0.001) and 6% per additional admission year for NSTEMI patients (OR 0.94, 95% CI 0.93–0.96; p<0.001). A borderline interaction between admission year and gender was observed in STEMI patients (p=0.019), but not in NSTEMI patients (p=0.75).
Age-adjusted mortality decreased per additional admission year in men with STEMI at a rate of 3% (OR 0.97, 95% CI 0.96 -0.98; p<0.001), in STEMI women 5% (OR 0.95, 95% CI 0.93–0.96; p<0.001), in NSTEMI men 6% (OR 0.94, 95% CI 0.93 -0.96; p<0.001) and in NSTEMI women 5% (OR 0.95, 95% CI 0.93–0.97; p<0.001).
In patients aged below 60 years a decrease in early mortality per year of STEMI was seen in women (OR 0.94, 95% CI 0.90–0.99; p=0.025) but not in men (OR 1.01, 95% CI 0.98–1.04; p=0.46) (interaction between sex and admission year p=0.019). Even greater differences were seen in NSTEMI patients. Mortality per year dramatically decreased in NSTEMI women (OR 0.87, 95% CI 0.80–0.94; p<0.001) but was not significant in men (OR 0.98, 95% CI 0.94–1.03; p=0.41) (interaction between sex and admission year; p=0.006).
Conclusions: During the last 20 years, in-hospital mortality of AMI patients in Switzerland has halved and the gender gap has been reduced. The reduction was more prominent in women, particularly in the population below 60 years of age.