Impact of Extreme Temperature and Particulate Matter 2.5 on Outcomes of Out-of-Hospital Cardiac Arrest

Extreme temperature and particulate matter-2.5 (PM_2.5) are known to affect the outcomes of out-of-hospital cardiac arrest (OHCA). However, studies that examine their effects at the exact time of OHCA occurrence are limited.

This study aimed to investigate the impact of extreme cold, extreme heat, and PM_2.5 on OHCA outcomes at the time of occurrence.

We analyzed data from 82,497 OHCAs (aged > 18 years) in South Korea between January 2016 and December 2021. Extreme temperatures were defined as extreme cold (≤5th percentile) and extreme heat (≥95th percentile). PM_2.5 refers to particulate matter ≤ 2.5 micrometers, with extreme PM_2.5 defined as ≥95th percentile. The outcomes were survival to discharge and good neurological outcome, defined as a cerebral performance category of 1 or 2 at hospital discharge. We performed a multivariable logistic regression analysis to assess the impact of extreme temperature and PM_2.5 on OHCA outcomes.

Extreme cold (-4.2°C to -20.2°C) showed no association with OHCA outcomes when compared to normal conditions (-0.9°C to 26.6°C). However, OHCAs during extreme heat (28.7°C to 39.3°C) showed a 15% significantly lower probability of survival to discharge (adjusted odds ratio [aOR]: 0.85, 95% confidence interval (CI): 0.74-0.98) compared to normal conditions. OHCAs during extreme PM_2.5 (56 to 218 µg/m³) were associated with 14% lower probability of survival to discharge (aOR: 0.86, 95% CI: 0.75-0.99) compared to normal PM_2.5 (0 to 43 µg/m³).

Extreme heat and PM_2.5 were significantly associated with a decreased probability of survival to discharge in OHCA patients.