Low incidence of daily active tobacco smoking in patients with symptomatic COVID-19

Importance: As the pandemic of COVID-19 is still under progression, identification of prognostic factors remains a global challenge. The role of cigarette smoking has been suggested among the disease’s epidemiological risk factors, although it is highly controversial. Objective: To evaluate the correlation of daily smoking with the susceptibility to develop SARS-CoV-2 infection. Participants: We estimated the rates of daily current smokers in COVID-19-infected patients in a large French university hospital between February 28th , 2020 and March 30th , 2020 for outpatients and from March 23rd , till April 9th , 2020 for inpatients. Design: The rates from both groups were compared to those of daily current smokers in the 2018 French general population, established in 2018, after standardization of the data for sex and age. Results: The inpatient group was composed of 343 patients, median age 65 yr: 206 men (601%, median age 66 years) and 137 women (39.9%, median age 65 years) with a rate of daily smokers of 4.4% (5.4% of men and 2.9% of women).The outpatient group was composed of 139 patients, median age 44 years: 62 men (44.6 %, median age 43 years, and 77 women (55.4 %, median age 44 years). The daily smokers rate was 5.3% (5.1% of men and 5.5 % of women). In the French population, the daily smokers rate was 25.4% (28.2% of men and 22.9% of women). The rate of current daily smokers was significantly lower in COVID-19 outpatients and inpatients (80.3% and 75.4%, respectively), as compared to that in the French general population with standardized incidence ratios according to sex and age of 0.197 [0.094 - 0.41] and 0.246 [0.148 - 0.408]. These ratios did not significantly differ between the two groups (P=0.63). Conclusions and relevance: Our cross sectional study in both COVID-19 out- and inpatients strongly suggests that daily smokers have a very much lower probability of developing symptomatic or severe SARS-CoV-2 infection as compared to the general population.