Smoking and risk of COVID-19 hospitalization

Rationale: The association between smoking status and severe Coronavirus Disease 2019 (COVID-19) remains controversial. Objective: To assess the risk of hospitalization (as a marker of severe COVID-19) in patients by smoking status: former, current and never smokers, who tested positive for the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-COV2) at an academic medical center in the United States. Methods: We conducted a retrospective cohort study in patients with SARS-COV2 between March-1-2020 and January-31-2021 to identify the risk of hospitalization due to COVID-19 by smoking status. Results: We identified 10216 SARS-COV2-positive patients with complete documentation of smoking habits. Within 14 days of a SARS-COV2 positive test, 1150 (11.2%) patients were admitted and 188 (1.8%) died. Significantly more former smokers were hospitalized from COVID-19 than current or never smokers (21.2% former smokers; 7.3% current smokers; 10.4% never smokers, p<0.0001). In univariable analysis, former smokers had higher odds of hospitalization from COVID-19 than never smokers (OR 2.31; 95% CI 1.94-2.74). This association remained significant when analysis was adjusted for age, race and gender (OR 1.28; 95% CI 1.06-1.55), but became non-significant when analysis included Body Mass Index, previous hospitalization and number of comorbidities (OR 1.05; 95% CI 0.86-1.29). In contrast, current smokers were less likely than never smokers to be hospitalized due to COVID-19. Conclusions: Significantly more former smokers were hospitalized and died from COVID-19 than current or never smokers. This effect is mediated via age and comorbidities in former smokers.