The Impact of Tobacco Use on COVID-19 Outcomes: A Systematic Review

Abstract

Introduction. Tobacco use increases risks for numerous diseases, including respiratory illnesses. We examined the literature to determine whether a history of tobacco use increases risks for adverse outcomes among COVID-19 patients. Methods. We conducted a systematic search of PubMed, LitCovid, Scopus, and Europe PMC (for preprints) using COVID-19 and tobacco-related terms. We included studies of human subjects with lab-confirmed COVID-19 infections that examined tobacco use history as an exposure and used multivariable analyses. The data was collected between March 31st, 2020, and February 20th, 2021. Outcomes included mortality, hospitalization, ICU admission, mechanical ventilation, and illness severity. Results. Among the 39 studies (33 peer-reviewed, 6 preprints) included, the most common outcome assessed was mortality ( $n=32$ ). The majority of these studies (17/32) found that tobacco use increased risk, one found decreased risk, and 14 found no association. Tobacco use was associated with increased risk of hospitalization in 7 of 10 studies, ICU admission in 6 of 9 studies, mechanical ventilation in 2 of 6 studies, and illness severity in 3 of 9 studies. One study found that tobacco use history increased risk of pulmonary embolism in COVID-19 patients. Tobacco use was found to compound risks associated with diabetes ( $n=1$ ), cancer ( $n=2$ ), and chronic liver disease ( $n=1$ ). Conclusion. There is strong evidence that tobacco use increases risks of mortality and disease severity/progression among COVID-19 patients. Public health efforts during the pandemic should encourage tobacco users to quit use and seek care early and promote vaccination and other preventive behaviors among those with a history of tobacco use.