Impact of EMS call timing on bystander CPR and survival after cardiac arrest in care facilities

The impact of pre- versus post-arrest emergency calls from care facilities on out-of-hospital cardiac arrest (OHCA) outcomes remains unclear. This study examined how call timing and time of day influence bystander cardiopulmonary resuscitation (BCPR) and 1-month survival. We conducted a nationwide retrospective cohort study from 2017 to 2022. We analyzed 27,222 witnessed OHCAs of presumed cardiac origin in adults aged ≥ 65 years in care facilities. Pre-arrest calls were defined as cases in which the witnessed time occurred after the EMS call time; post-arrest calls were those in which the witnessed time was the same as or earlier than the call time. The primary outcome was 1-month survival and the secondary was BCPR rate. Propensity score matching and logistic regression were used for survival analysis. Of all cases, 10,789 (39.6%) were preceded by pre-arrest calls. BCPR was less frequent in pre-arrest than post-arrest cases (43.3% vs. 84.4%; p < 0.01). Survival was highest during daytime (8.0%) and lowest at night (3.3%). Nighttime occurrence (adjusted odds ratio = 0.45, confidence interval = 0.40–0.51) and pre-arrest calls (0.78, 0.68–0.89) independently predicted lower survival. Early EMS activation alone is insufficient. Continuous dispatcher guidance and improved night-shift preparedness in care facilities may enhance OHCA outcomes.