Comparison of the survival and neurological outcomes in OHCA based on smoking status: investigation of the existence of the smoker's paradox

The smoker’s paradox has been reported to reduce mortality following out-of-hospital cardiac arrest (OHCA). However, recent studies on this paradox have reported contradictory findings, with some indicating that it does not exist. Therefore, the purpose of this study was to evaluate the association between smoking status and OHCA outcomes. This retrospective observational study was conducted using multicenter registry data. The associations between smoking status and OHCA outcomes were assessed using multivariable logistic regression analyses and propensity score-adjusted methods. We compared outcomes among current, former, and never-smokers, as well as between current and non-smokers and between ever- and never-smokers. The primary outcome was survival to hospital discharge, and the secondary outcome was favourable neurological outcomes. Among 4443 patients with OHCA, 19.9% were current smokers, 15.2% were former smokers, and 64.9% were never-smokers. Current smokers had significantly better outcomes than former or never-smokers. However, the significant differences observed in univariable analysis or before propensity score matching were not observed after adjustments with multivariable logistic regression or after propensity score matching analysis in both current vs. non-smokers and ever- vs. never-smokers. Other propensity score adjusted models also did not show significant differences, except for the stratification method. This study suggests that smoking is not an independent prognostic factor for OHCA. The statistically significant better outcomes observed in current or ever-smokers were not maintained after adjusting for confounders. Therefore, the smoker’s paradox should be investigated in additional prospective studies.

Smokers; Ex-smokers; Non-smokers; Cardiac arrest; Propensity score

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