Factors attributed to the higher in-hospital mortality of ST elevation myocardial infarction patients admitted during off-hour in comparison with those during regular hour

BACKGROUND: In-hospital mortality of patients with ST elevation myocardial infarction (STEMI) admitted during off-hour was reported higher than those admitted during regular hour, but which factors cause the difference remains largely unknown though the difference in medical resources was often accused. METHODS AND RESULTS: This registry-based study recruited 7456 STEMI patients prospectively from 99 level two hospitals across China. Generalized linear mixed models were applied to quantify the risk of in-hospital death attributed to admission time and the explainers of its change, accounting for the clustering of patients within hospitals. There were 45.2% patients admitted during regular hour and 54.8% during off-hour. In-hospital mortality was 7.0% for patients admitted during regular hour and 8.3% for those during off-hour (p<0.05). Generalized linear mixed models adjusting for age, gender and education showed that patients’ disease severity at admission and medical treatments received after admission could explain the risk difference attributed to admission time by 55% and 20%, respectively. After all factors accounted, the residual relative risk difference left only 6% (adjusted OR = 0.94) and became no longer significant. CONCLUSIONS: The regular-and-off-hour mortality difference exists among STEMI patients in Chinese level two hospitals, which could be attributed primarily to disease severity at admission and secondly to the poorer medical treatments. These results call for public attention to the more severity of STEMI patients admitted during off-hour in addition to improving medical resources for STEMI at off-hour.