Prognostic impact of bystander-patient relationship and age in patients with out-of-hospital cardiac arrest.

AIM OF THE STUDY: Bystander presence improves outcomes after out-of-hospital cardiac arrest (OHCA). Although bystander type is reportedly associated with neurological outcomes, the potential modifying effect of age on this association remains uncertain. METHODS: Using the All-Japan Utstein Registry, we included adults with witnessed OHCA between 2005 and 2023. Patients were categorized into 3 groups according to the bystander-patient relationship (family members, friends and colleagues, and passersby) and further divided into 4 age categories (18-69, 70-79, 80-89, and ≥90 years). The primary endpoint was 1-month neurologically favorable survival. RESULTS: Of the 554,923 patients included, 459,841 (82.9%) were witnessed by family members, 55,112 (9.9%) were witnessed by friends or colleagues, and 39,970 (7.2%) were witnessed by passersby. With advancing age, the proportion of patients witnessed by family members increased (P<0.001). The probability of neurologically favorable survival at 1 month was lowest in the family members group, followed by the passersby and the friends and colleagues group (4.2% vs. 10.1% vs. 15.3%, P<0.001). This trend overall remained consistent across age groups. Multivariable analysis showed that OHCA witnessed by family members was associated with poorer neurological outcomes. Among younger patients (aged 20-40 years), however, OHCA witnessed by family members was related to better neurological outcomes. CONCLUSIONS: Patients with OHCA witnessed by family members had worse neurological outcomes than those witnessed by friends, colleagues, and passersby. This association differed by patient age, with family-member-witnessed OHCA associated with more favorable outcomes in younger patients but poorer outcomes in the elderly.