Sex differences in the impact of day/night distribution of ST-segment elevation myocardial infarction onset on in-hospital outcomes: findings from the Improving Care for Cardiovascular Disease in China-Acute Coronary Syndrome Project.

<bold>Background: </bold>Circadian system plays an important role in cardiovascular health. Experimental studies have also identified sex differences in circadian system. We aim to explore the impact of sex on the association between symptom-onset pattern of STEMI and in-hospital adverse outcomes in Chinese population.<bold>Methods: </bold>Data were used from the Improving Care for Cardiovascular Disease in China-Acute Coronary Syndrome Project. 18271 STEMI patients undergoing primary percutaneous coronary intervention entered the study, including 14785 (80.9%) men and 3486 (19.1%) women. The outcomes included all-cause mortality and a composite of major adverse cardiovascular and cerebrovascular events (MACCE) during hospitalization.<bold>Results: </bold>Most participants experienced STEMI onset during 06:00 h to noon, and there was no difference in onset pattern between men and women (p = 0.582). Logistic regression showed that, after adjustment for cardiovascular risk factors, symptom onset time was significantly associated with in-hospital mortality in men, but not in women or the total population. The odds ratios (ORs) for male patients were 1.86 (95% CI 1.05 to 3.27) for midnight to 06:00 h, 1.58 (95% CI 0.95 to 2.64) for 06:00 h to noon, and 0.80 (95% CI 0.49 to 1.73) for 18:00 h to midnight as compared with STEMI presenting during noon to 18:00 h. But symptom onset time was not associated with MACCE in both sexes or the entire cohort.<bold>Conclusions: </bold>These findings show that STEMI onset time was independently associated with in-hospital mortality in male Chinese patients, indicating that sex should be taken into account in studying impact of circadian system on myocardial infarction. [ABSTRACT FROM AUTHOR]