Current tobacco smoking and risk of SARS-CoV-2 infection and hospitalization: Evaluating the role of socio-demographic factors and comorbidities

Prev Med. 2023 Jul;172:107523. doi: 10.1016/j.ypmed.2023.107523. Epub 2023 Apr 26.


Our recently published study of >2.4 million adults in Northern California indicated that current versus never-tobacco smoking was associated with lower risk of SARS-CoV-2 infection and less severe coronavirus disease 2019 (COVID-19). We extended this research by evaluating whether these associations were moderated by socio-demographic factors and medical comorbidities. This retrospective cohort study of 1,885,826 adults with current or never-smoking status in Kaiser Permanente Northern California from 3/5/2020 (baseline) to 12/31/2020 (pre-vaccine) included electronic health record-based socio-demographics (sex, age, race/ethnicity, neighborhood deprivation index (NDI)) and medical comorbidities (obesity, cardiovascular conditions, diabetes, renal disease, respiratory conditions). We estimated the adjusted risk of SARS-CoV-2 infection and hospitalization (≤30 days of infection) associated with smoking status using Cox proportional hazard regression models. We estimated associations within subgroups of socio-demographics and comorbidities, and tested for effect modification using interaction terms. During the study, 35,627 patients had SARS-CoV-2 infection. Current versus never-smoking status was associated with lower adjusted rates of SARS-CoV-2 infection (aHR ranging from 0.51 to 0.89) and hospitalization (aHR ranging from 0.32 to 0.70) within nearly every socio-demographic and comorbidity subgroup. Statistically significant interactions showed that the magnitude of protection for SARS-CoV-2 infection varied by sex, age, race/ethnicity, NDI, cardiovascular conditions and diabetes, and for SARS-CoV-2 hospitalization by age and renal disease. Taken together, results indicated that while some socio-demographics and comorbidities moderated the associations, the lower risk of SARS-CoV-2 infection and hospitalization associated with current versus never-smoking status persisted among patients regardless of socio-demographics or comorbidities.

Keywords: Age; COVID-19; Comorbidities; Hospitalization; Nicotine; Race; SARS-CoV-2; Smoking; Tobacco.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • COVID-19* / epidemiology
  • Cardiovascular Diseases*
  • Comorbidity
  • Diabetes Mellitus* / epidemiology
  • Ethnicity
  • Hospitalization
  • Humans
  • Retrospective Studies
  • Risk Factors
  • SARS-CoV-2
  • Tobacco Smoking