Kelly C Young-Wolff1,2, Natalie Slama1, Stacey E Alexeeff1, Lori C Sakoda1, Renee Fogelberg3, Laura C Myers1, Cynthia I Campbell1,2, Alyce S Adams4, Judith J Prochaska5. 1. Division of Research, Kaiser Permanente Northern California, Oakland CA. 2. Department of Psychiatry and Behavioral Sciences, University of California, San Francisco, CA. 3. Richmond Medical Center, Kaiser Permanente Northern California, Richmond, CA. 4. Stanford Cancer Institute, Stanford University, Stanford, CA. 5. Stanford Prevention Research Center, Stanford University, Stanford, CA.
Abstract
INTRODUCTION: The relationship between cigarette smoking status and SARS-CoV-2 infection and coronavirus disease 2019 (COVID-19) severity is highly debated. We conducted a retrospective cohort study of >2.4 million adults in a large healthcare system to evaluate whether smoking is associated with SARS-CoV-2 infection and disease severity. METHODS: This retrospective cohort study of 2,427,293 adults in KPNC from 3/5/2020 (baseline) to 12/31/2020 (pre-vaccine) included smoking status (current, former, never), socio-demographics, and comorbidities from the electronic health record. SARS-CoV-2 infection (identified by a positive PCR test) and COVID-19 severity (hospitalization, ICU admission or death ≤30 days of COVID-19 diagnosis) were estimated in time-to-event analyses using Cox proportional hazard regression models adjusting for covariates. Secondary analyses examined COVID-19 severity among patients with COVID-19 using logistic regression. RESULTS: During the study, 44,270 patients had SARS-CoV-2 infection. Current smoking was associated with lower adjusted rates of SARS-CoV-2 infection (aHR=0.64 95%CI:0.61-0.67), COVID-19-related hospitalization (aHR=0.48 95%CI:0.40-0.58), ICU admission (aHR=0.62 95%CI:0.42-0.87), and death (aHR=0.52 95%CI:0.27-0.89) than never-smoking. Former smoking was associated with a lower adjusted rate of SARS-CoV-2 infection (aHR=0.96 95%CI:0.94-0.99) and higher rates of hospitalization (aHR=1.10 95%CI:1.03-1.08) and death (aHR=1.32 95%CI:1.11-1.56) than never-smoking. Logistic regression analyses among patients with COVID-19 found lower odds of hospitalization for current versus never-smoking and higher odds of hospitalization and death for former versus never-smoking. CONCLUSIONS: In the largest US study to date on smoking and COVID-19, current and former smoking showed lower risk of SARS-CoV-2 infection than never-smoking, while a history of smoking was associated with higher risk of severe COVID-19. IMPLICATIONS: In this cohort study of 2.4 million adults, adjusting for socio-demographics and medical comorbidities, current cigarette smoking was associated with a lower risk of both COVID-19 infection and severe COVID-19 illness compared to never-smoking. A history of smoking was associated with a slightly lower risk of COVID-19 infection and a modestly higher risk of severe COVID-19 illness compared to never-smoking. The lower observed COVID-19 risk for current versus never-smoking deserves further investigation. Results support prioritizing individuals with smoking-related comorbidities for vaccine outreach and treatments as they become available.
INTRODUCTION: The relationship between cigarette smoking status and SARS-CoV-2 infection and coronavirus disease 2019 (COVID-19) severity is highly debated. We conducted a retrospective cohort study of >2.4 million adults in a large healthcare system to evaluate whether smoking is associated with SARS-CoV-2 infection and disease severity. METHODS: This retrospective cohort study of 2,427,293 adults in KPNC from 3/5/2020 (baseline) to 12/31/2020 (pre-vaccine) included smoking status (current, former, never), socio-demographics, and comorbidities from the electronic health record. SARS-CoV-2 infection (identified by a positive PCR test) and COVID-19 severity (hospitalization, ICU admission or death ≤30 days of COVID-19 diagnosis) were estimated in time-to-event analyses using Cox proportional hazard regression models adjusting for covariates. Secondary analyses examined COVID-19 severity among patients with COVID-19 using logistic regression. RESULTS: During the study, 44,270 patients had SARS-CoV-2 infection. Current smoking was associated with lower adjusted rates of SARS-CoV-2 infection (aHR=0.64 95%CI:0.61-0.67), COVID-19-related hospitalization (aHR=0.48 95%CI:0.40-0.58), ICU admission (aHR=0.62 95%CI:0.42-0.87), and death (aHR=0.52 95%CI:0.27-0.89) than never-smoking. Former smoking was associated with a lower adjusted rate of SARS-CoV-2 infection (aHR=0.96 95%CI:0.94-0.99) and higher rates of hospitalization (aHR=1.10 95%CI:1.03-1.08) and death (aHR=1.32 95%CI:1.11-1.56) than never-smoking. Logistic regression analyses among patients with COVID-19 found lower odds of hospitalization for current versus never-smoking and higher odds of hospitalization and death for former versus never-smoking. CONCLUSIONS: In the largest US study to date on smoking and COVID-19, current and former smoking showed lower risk of SARS-CoV-2 infection than never-smoking, while a history of smoking was associated with higher risk of severe COVID-19. IMPLICATIONS: In this cohort study of 2.4 million adults, adjusting for socio-demographics and medical comorbidities, current cigarette smoking was associated with a lower risk of both COVID-19 infection and severe COVID-19 illness compared to never-smoking. A history of smoking was associated with a slightly lower risk of COVID-19 infection and a modestly higher risk of severe COVID-19 illness compared to never-smoking. The lower observed COVID-19 risk for current versus never-smoking deserves further investigation. Results support prioritizing individuals with smoking-related comorbidities for vaccine outreach and treatments as they become available.
Authors: Pietro Ferrara; Domenico Ponticelli; Roberto Magliuolo; Mario Borrelli; Beniamino Schiavone; Lorenzo Giovanni Mantovani Journal: Vaccines (Basel) Date: 2022-08-19