Are night shift workers at an increased risk for COVID-19?

Recent data has revealed an association between coronavirus disease-19 (COVID-19) incidence and seasonally regulated androgen sensitivity. This potential relationship between SARS-CoV-2 infection and clock genes, coupled with previously reported effects of night shift work on health, leads us to hypothesize that night shift workers may be at an increased physiological risk of coronavirus disease-19 (COVID-19). Shift work, especially night shift work, has long been associated with several chronic health conditions. The mechanisms that drive these associations are not well understood; however, current literature suggests that the disruption of circadian rhythms may cause downstream hormonal and immune effects that render night shift workers more susceptible to disease. First, circadian rhythms may play a role in the mechanism of viral infection, as viral vaccines administered in the morning elicit greater immune responses than those administered in the afternoon. Next, increased exposure to light at night may inhibit the production of melatonin, which has been observed to enhance DNA repair and shown to upregulate expression of Bmal1, an established inhibitor of herpes simplex virus and influenza. Finally, abnormal immune cell and cytokine levels have been observed following night-shift work. These data suggest that further research is warranted and that high-risk occupations should be taken into consideration as public health policies are introduced and evolve.