The effect of atmosphere temperature on out-of-hospital cardiac arrest outcomes.

BACKGROUND: It is unclear whether the atmosphere temperature is associated with outcomes after out-of-hospital cardiac arrest (OHCA).

METHODS: This is a nationwide observational study using the national OHCA registry merged with a geographical and weather database. Adult patients with a cardiac etiology that occurred from 2006 to 2013 were included, excluding patients with unknown outcome or unknown weather information. The main exposure was the hourly measured temperature matched to the OHCA event time. The covariates were age, gender, metropolis, place, and weather factors (wind speed and humidity). The primary outcome was good cerebral performance scale (CPC) 1 or 2. Patients were classified with three temperature groups by quartile range: Cold (<4°C), Intermediate (4-21°C), and Hot (≥22°C). We tested the associations between the atmosphere temperature (by 1°C and by temperature group) and outcomes using multivariable logistic regression analysis.

RESULTS: Of 17,3051 OHCAs, a total of 115,578 cases were matched to weather database. A total of 78,717 OHCAs were analyzed. The proportion of good CPC 1 or 2 was 1.7% in the Cold group, 1.8% in the Intermediate group, and 2.3% in the Hot group. As the temperature at the event of OHCA increased by 1°C, AORs (95% CIs) were 1.006 (1.002-1.009) for good CPC. The AORs (95% CIs) for good CPC in Cold and Hot group comparing with Intermediate group for good CPC were 0.964 (0.845-1.100) and 1.246 (1.096-1.416), respectively.

CONCLUSION: The temperature at the time of the OHCA event was associated with outcomes after OHCA in a nationwide observational study in Korea.