COVID-19: Another Reason to Support Smoking Cessation

By Laurie Gelb, MPH, BCPA

Studies of a potential link between smoking status and the clinical course of COVID-19 infection have yielded contradictory results. A recent meta-analysis [3] sought to address the question more completely.

COVID-19 targets lung epithelial cells, causing, in part, viral pneumonia and atypical acute respiratory distress syndrome (ARDS). The CDC has reported pre-existing respiratory disease as 9.2% in patients diagnosed with a severe COVID-19 course [2], likely an underestimation.

The researchers scanned Embase, Google Scholar, PubMed, Scopus and Web of Science databases to identify appropriate clinical studies [3]. Studies that included smoking status and characterized disease severity were included, though nomenclature varied. “Nonsevere” cases were described as mild, common type, not requiring ICU treatment or as survivors, depending on the study. In turn, “severe cases” were characterized across studies as critical, requiring ICU stays, refractory, or fatal.

A total of 16 studies detailing 11,322 COVID-19 patients were analyzed. Subsequently, 525 patients whose hospitalization status was reported as “unknown” were excluded from the final analysis, yielding a final 10,797 patients. The researchers also examined previous meta-analyses and found them limited in terms of the number and heterogeneity of studies.

In the presentation of data that might be most meaningful to patients, in 10.7% (978/9067) of nonsmokers, COVID-19 disease was severe, while in active smokers, it was severe in 21.2% (65/305) of cases. Physicians can also explain the crosscorrelation with COPD, described in more detail below.

This meta-analysis found a significant relationship between a history of smoking and severe COVID-19 cases (OR = 2.17; 95% CI: 1.37–3.46; P < .001). In addition, researchers demonstrated a correlation between current smoking status and severe COVID-19 (OR = 1.51; 95% CI: 1.12–2.05; P < .008).

Power was limited in that not all studies differentiated past and current smokers. And, of course, a potential confound is that “quitting” can be a fluid rather than binary construct; in addition, self-reported smoking status is not always an accurate one.

Current smoking prevalence in patients with mild to moderate COVID-19 was 229/7850 (2.9%). In severe or critical cases, it was 66/1134 (5.8%). Study heterogeneity was low to moderate, and after sensitivity adjustments, the prevalence of a smoking history was 5.2% in nonsevere COVID-19 cases and 12.5% in severe ones.

A recent rapid nonsystematic meta-analysis [1] observed serious COVID complications in 48% of former smokers and 24% of current smokers. It is hypothesized that former smokers have had longer tobacco exposure times, which increase the probability of developing sequelae of smoking such as COPD. In turn, a COPD diagnosis may serve as a catalyst for smoking cessation, leading to classification as a former smoker. This hypothesis was supported by another analysis [4], in which COPD patients were 4.38x more likely to develop severe COVID-19.

Though smokers sometimes express fatalism relative to their health, physicians can point out that this pandemic is ongoing, and any reduction in tobacco use can potentially mediate future risk. Moreover, the associations among smoking, cancer, heart disease, stroke, lung diseases, diabetes, and other potentially fatal disorders are well-established.

Given bar/restaurant closures and smaller social gatherings, in some contexts, the pandemic may offer a unique opportunity for patients who use tobacco or marijuana, and/or vape, to reconsider these choices.

References

1. Alqahtani, JS, Oyelade, T, Aldhahir M, et al. (2020) Prevalence, severity and mortality associated with COPD and smoking inpatients with COVID-19: a rapid systematic review and meta-analysis. PLOS ONE, vol. 15, no. 5, article e0233147.
2. CDC COVID-19 Response Team, N. Chow et al. (2020). Preliminary estimates of the prevalence of selected underlying health conditions among patients with coronavirus disease 2019- United States, February 12-March 28, 2020,” Morbidity and Mortality Weekly Report, vol. 69, no. 13, pp. 382–386.
3. Gülsen, A., Yigitbas, B. A., Uslu, B., Drömann, D., & Kilinc, O. (2020). The effect of smoking on COVID-19 symptom severity: systematic review and meta-analysis. Pulmonary Medicine, 7590207. https://doi.org/10.1155/2020/7590207
4. Guo, F. R. (2020). Active smoking is associated with severity of coronavirus disease 2019 (COVID-19): An update of a meta-analysis. Tobacco Induced Diseases, 18, 37. https://doi.org/10.18332/tid/121915