Smoking Predictor for Covid-19 Severity and Mortality- A Systematic Review Based on Evidence for Clinical Practice

Abstract Background The objective of the study is to review the available data and investigate whether smoking is a risk factor for severe Covid-19, ICU admission, and mortality. Studies have shown conflicting data linking smoking to serious Covid-19 outcomes, necessitating updating knowledge. Methods A systematic review was conducted using PubMed, Cochrane, Scopus, and Web of Science databases until June 8, 2022. All original articles described the risk of smoking as a predictor for hospitalization and ICU admission among Covid-19 patients, and studies that assessed the association between smoking and Covid-19 severity and/or mortality in a multivariable analysis in a cohort study design were eligible. Outcomes were severity and mortality from Covid-19 infection. Results A total of 3085 articles were identified through the systematic search, and 34 deemed eligible were included after consensus. The selected articles were all published between 2020 and 2022. The majority of the studies originated in Asia and the United States. Most of patients were non-smokers. 12 articles were developed for predicting severe Covid-19 infection among tobacco users. However, the results did not examine depending on the smoking classification in most studies, despite the fact that the majority of the studies (n = 22) showed a substantial link between smoking and Covid-19 severity/mortality. Mortality (n = 32), ICU admission (n = 17), severe or hospitalization (n = 11), and mechanical ventilation (n = 10) studies were the outcomes presented. The nomogram study including smoking predictors may be useful for the early detection of Covid-19 patients who will be admitted to the ICU. Conclusions Smoking history significantly increased the probability of Covid-19 hospitalization, ICU admission, and mortality in patients. Healthcare professionals must assist smokers in giving up and changing their attitude toward smoking.