Impact of Snowfall on Ambulance Response Times to Out-of-Hospital Cardiac Arrest ― Nationally-Representative Population-Based Registry Analysis, 2009–2019 ―

Background: Because snowfall may affect the acute outcomes of severe cardiovascular diseases by prolonging emergency medical service (EMS) response times, we investigated the association between snowfall and EMS response times for out-of-hospital cardiac arrests (OHCAs) in the regions of Japan. Methods and Results: We used the Utstein database, a nationwide population-based registry that collects data on all OHCA patients in Japan, during winter from 2009 to 2019. A prefecture-specific logistic regression model was applied to estimate odds ratios (ORs) of prolongation of EMS response time (≥7 min), which was associated with poorer neurological outcomes, on days with moderate/heavy snowfall compared to no-snowfall days. A random-effects meta-analysis model was applied to obtain pooled ORs in both overall and subgroup analyses ("heavy snowfall prefectures" and "non-heavy snowfall prefectures"). Among 94,428 bystander-witnessed cardiogenic OHCA patients, the ORs of prolonged EMS response time were 1.05 (95% confidence interval (CI): 0.96, 1.14) on moderate snowfall days and 1.22 (95% CI: 1.07, 1.40) on heavy snowfall days, compared to no-snowfall days. Subgroup analysis revealed no statistical difference between heavy snowfall prefectures and non-heavy snowfall prefectures, although ORs were higher for heavy snowfall prefectures. Conclusions: Snowfall prolongs EMS response time to cardiogenic OHCA in both areas with heavy snowfall and those with less snowfall, which may also impact survival and neurological outcomes.