Forty-eight cohort studies were included (1,896,859 patients). Thirty studies were judged to be of low to moderate risk of bias.
Off-hour presentation was associated with higher in-hospital mortality (OR 1.05, 95% CI 1.03 to 1.08; 35 studies; Ι²=55%) and 30-day mortality (OR 1.05, 95% CI 1.02 to 1.09; 18 studies; Ι²=83%). Studies in Europe (OR 1.08, 95% CI 1.02 to 1.15; 18 studies; Ι²=49%) and other regions (OR 1.25, 95% CI 1.15 to 1.36; eight studies; Ι²=15%) seemed to be associated with a larger increase in mortality than North American studies (OR 1.03, 95% CI 1.01 to 1.04; 15 studies; Ι²=48%).
Patients presenting with ST elevation myocardial infarction during off-hours were less likely to receive percutaneous coronary intervention within 90 minutes than those presenting during regular hours (OR 0.40, 95% CI 0.35 to 0.45; seven studies; Ι²=41%). Door-to-balloon time was longer in patients presenting during off-hours than in those presenting during regular hours (14.8 minutes longer, 95% CI 10.7 to 19.0 minutes; 29 studies; Ι²=99%).