Covid-19 and ex-smokers: an underestimated prognostic factor?

Abstract

Dear Editor,
 The recent and explosive worldwide outbreak of Covid-19 leads many scientists and clinicians to identify the most responsible triggering risk factors in individuals without comorbidities, as well as potential prognostic factors. A notable field of research has been conducted on the role of smoking, which has been initially hypothesized as being a protective factor for Covid-19....

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“…It is noted that the decay of the immunity is observed in ageing and, therefore, the SARS-CoV-2 virus may get an easier access on the respiratory tract in elder patients. Men are more affected than women (67%), as there are more smokers in the male population and the female immune system has a better antibody system lined to the X chromosome [ 7 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. The role of smoking has been initially hypothesized as risk factor for the COVID-19.…”

“…Indeed, smokers and patients affected by chronic obstructive pulmonary disease (COPD) have a higher quantity of ACE2 receptors, which also are the receptors of access for the COVID-19 virus. Moreover, the ex-smokers highlighted a peculiar genic expression included in non-smokers and active smokers [ 19 , 20 ]. A report analyzed 28 studies and reported that the smokers were more susceptible to contract COVID-19 compared to the non-smokers-population [ 19 , 28 ].…”

“…Moreover, the ex-smokers highlighted a peculiar genic expression included in non-smokers and active smokers [ 19 , 20 ]. A report analyzed 28 studies and reported that the smokers were more susceptible to contract COVID-19 compared to the non-smokers-population [ 19 , 28 ]. Another study reported a percentage of 12.4% of smokers hospitalized for COVID-19 in an intensive care unit with invasive/non-invasive assisted mechanical ventilation, while a percentage of 4.7% of the non-smokers needed of the intensive therapy [ 19 ].…”

“…A report analyzed 28 studies and reported that the smokers were more susceptible to contract COVID-19 compared to the non-smokers-population [ 19 , 28 ]. Another study reported a percentage of 12.4% of smokers hospitalized for COVID-19 in an intensive care unit with invasive/non-invasive assisted mechanical ventilation, while a percentage of 4.7% of the non-smokers needed of the intensive therapy [ 19 ]. A higher predisposition to COVID-19 has been reported for male subjects (67%) compared to the female patients (288 million men vs. 12.6 million of women), while a predominant smoking habit is present in the occidental male population [ 19 ].…”

“…Another study reported a percentage of 12.4% of smokers hospitalized for COVID-19 in an intensive care unit with invasive/non-invasive assisted mechanical ventilation, while a percentage of 4.7% of the non-smokers needed of the intensive therapy [ 19 ]. A higher predisposition to COVID-19 has been reported for male subjects (67%) compared to the female patients (288 million men vs. 12.6 million of women), while a predominant smoking habit is present in the occidental male population [ 19 ]. In another study that uses the sequencing of single cells, it has emerged that the expression of ACE2 was predominant in Asian men, which was significantly higher in the current smokers of Asian ethnicity than the non-Asian smokers [ 29 ].…”