Working Schedule, Sleep Quality, and Susceptibility to Coronavirus Disease 2019 in Healthcare Workers

To the Editor—We read with interest the recent article by Ran et al on predisposing factors for healthcare workers (HCWs) infection during the coronavirus disease 2019 (COVID-19) outbreak [1]. In particular, data collected by the authors evidenced that longer duty hours appeared to be a risk factor for COVID-19. The authors cited previous studies that sustained, prolonged work would possibly increase the risk of respiratory infections. They concluded that “duty hour restrictions (less than 10 hours/day) should be considered, depending on the medical staff’s specific role” [1]. We agree with the authors of this report that working schedule could be an important factor of susceptibility to COVID-19, but we would like to focus attention on shift work also. HCWs have an increased risk of contracting COVID-19 due to their close contact with patients affected by severe acute respiratory syndrome coronavirus 2. In our country, Italy, > 16 000 HCWs have tested positive for COVID-19 and at least 115 physicians and 30 nurses have died after contracting coronavirus, confirming the high risk of healthcare professionals [2, 3]. Further studies on this population should be conducted for understanding the reasons of increased susceptibility and high mortality in categories of HCWs. As is well known, HCWs often suffer from sleep disorders and low sleep quality due to work-related stress, sleep deprivation, and shift work [4]. Since circadian rhythm disruption may impair immune system function, some scholars have posited that it could enhance susceptibility to infection [5, 6]. A recent prospective cohort study showed that shift workers in healthcare had 20% more acute respiratory infections and influenza-like illnesses than non–shift workers [7]. These infections also appeared to be more severe. Perceived sleep quality seems to be an underlying mechanism in the relation between shift work and increased susceptibility to infection [8]. No studies have yet been conducted on the association between shift work, sleep quality, and COVID-19 infection, but it is presumed that the mechanisms are similar. Stress could also play a determinant role in worsening sleep quality, as already evidenced in previous studies [4]. Undoubtedly, during the COVID-19 outbreak, HCWs are exposed to an unprecedented stressful situation of unknown duration, with an important emotional involvement. For these reasons, recommendations to healthcare staff on working schedule—including the considerations of Ran et al on prolonged hours—should be widespread in hospitals and well known by hospital managers. Finally, we believe that future studies on susceptibility of HCWs to COVID-19 should not be limited to demographic characteristics of workers and the presence of personal protective equipment, but should also consider working conditions in the hospital, including an analysis of shift work and its effects on sleep quality. The study by Ran et al could be a starting point. Author contributions. M. B. and M. A. R. designed the study. M. A. R. drafted the manuscript. M. E. P. and M. B. critically revised the manuscript. Potential conflicts of interest. The authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest.