ObjectivesTo evaluate emergency medical services (EMS) delays and their impact on time to treatment and mortality in patients with ST-elevation myocardial infarction (STEMI).MethodWe collected data on EMS time intervals from published studies across five electronic databases. The primary EMS interval was the time in minutes between first medical contact and arrival at hospital door (FMC-to-door time). Secondary intervals were other components of EMS delay. Weighted means were measured using random-effects models. Meta-regression was used to identify factors associated with EMS delays and to assess the impact of EMS delay on the proportion of patients treated within90 min and mortality.ResultsTwo independent reviewers included 100 studies (125 343 patients) conducted in 20 countries. The weighted mean FMC-to-door time was 41 min (n=101 646; 95% CI 39 to 43, range 21–88). However, substantial heterogeneity was observed with each interval, which could be explained by region and urban classification, distance to hospital and method of ECG interpretation. In a meta-regression adjusted for door-to-balloon time, a 10 min increase in FMC-to-door time was associated with a 10.6% (95% CI 7.6% to 13.5%; p<0.001) reduction in the proportion of patients treated within 90 min. Shorter EMS delay was significantly associated with lower short-term mortality in patients receiving prehospital thrombolysis (p=0.018).ConclusionEMS delays account for half of the total system delay in STEMI. There is a fourfold global variation in EMS delays, which are not completely explained by differences in system characteristics. Reducing unexplained variation could yield improvements in the time to treatment and outcome of STEMI patients.PROSPERO registration numberCRD42017074118.