Presence and type of bystanders on delay time in acute myocardial infarction: a transcultural cross-sectional clinical study with 907 patients in Shanghai and Munich

Background Bystanders may critically influence prehospital delay during acute myocardial infarction (AMI), but existing evidence is limited and largely outdated. This study aimed to examine the association between bystander presence and type on prehospital delay in AMI across two culturally distinct cities with attention to gender differences. Methods This cross-sectional observational study included 907 patients with confirmed AMI from the Munich Examination of Delay in Patients Experiencing AMI (MEDEA) study (n=614) and the multicentre MEDEA FAR-EAST study in Shanghai (n=293). The primary outcome was prehospital delay time, analysed by bystander presence and type. Multivariable logistic regression identified independent predictors of prehospital delay related to bystander type. Results Overall, 216 (24%) patients were women (median age 62 (IQR 54–72) years) and 636 (70%) patients experienced AMI with bystanders, resulting in shorter delays than those without (180 min vs 213 min; p=0.023). Non-family bystanders consistently facilitated the most rapid responses (128 min). Women suffering from AMI all alone delayed by 254 min (IQR 130–725) compared with 166 min (IQR 67–979) in women living alone but being supported by a bystander. Patients in Shanghai experienced shorter delays than those in Munich (150 min vs 203 min; p<0.001). Conclusions Non-family bystanders were associated with markedly shorter prehospital delay but their effectiveness differed by sex and cultural context. These findings support a paradigm shift in public health strategies: alongside patient education, community-wide first-aid training and targeted interventions that enable non-family bystanders to act promptly are critical to improving outcomes.