Smoking history and clinical outcomes in COVID-19 hospitalized patients.

Dear Editor,

In their paper Navas Alcantara et al. described a large group of patients hospitalized for COVID-19 in Spain focusing on the effects of cigarette smoking history on patients clinical outcomes concluding that an history of cigarette smoking (past or active) is an independent factor for negative prognosis in COVID-19 patients.

The unhealthy effects of cigarette smoking are well known and have not to be questioned and thus the observations of the Authors are probably expected also in COVID-19 patients. To this respect, at now, it is still debated a possible ‘protective’ effect of active cigarette smoking on the risk of hospitalization for COVID-19 and in particular for interstitial lung pneumonia due to SARS-CoV-2 infection.2, 3, 4

These hypothesized protective effect of active smoking on the risk of hospitalization for COVID-19 seems confirmed also by the data reported by the Authors even if they have not highlightened nor discuss them in their paper. Infact as detailed in Table 1 of Navas Alcantara et al. paper, among patients with a history of smoking (previous or active), only 733 were active smokers, i.e. 5% of all considered patients hospitalized for COVID-19. This means that among all hospitalized patients for COVID-19 considered by the Authors, 95% were no-active smokers.

Cigarette smoking has to be discouraged for its well known unhealthy effects. Nonetheless, although well far to suggest a ‘protective’ effect of active cigarette smoking on the risk of hospitalization for COVID-19, we have to push research to investigate what are the possible mechanisms leading to this quite low prevalence of active smokers among hospitalized patients for COVID-19 observed also in Spain, a country with about 25% of active smokers.