Investigating the Potential for Ultraviolet Light to Modulate Morbidity and Mortality From COVID-19: A Narrative Review and Update

Abstract

During the COVID-19 (coronavirus disease of 2019) pandemic, researchers have been seeking low-cost and accessible means of providing protection from its harms, particularly for at-risk individuals such as those with cardiovascular disease, diabetes and obesity. One possible way is via safe sun exposure, and/or dietary supplementation with induced beneficial mediators (e.g., vitamin D). In this narrative review, we provide rationale and updated evidence on the potential benefits and harms of sun exposure and ultraviolet (UV) light that may impact COVID-19. We review recent studies that provide new evidence for any benefits (or otherwise) of UV light, sun exposure, and the induced mediators, vitamin D and nitric oxide, and their potential to modulate morbidity and mortality induced by infection with SARS-CoV-2 (severe acute respiratory disease coronavirus-2). We identified substantial interest in this research area, with many commentaries and reviews already published; however, most of these have focused on vitamin D, with less consideration of UV light (or sun exposure) or other mediators such as nitric oxide. Data collected to-date suggest that ambient levels of both UVA and UVB may be beneficial for reducing severity or mortality due to COVID-19, with some inconsistent findings. Currently unresolved are the nature of the associations between blood 25-hydroxyvitamin D and COVID-19 measures, with more prospective data needed that better consider lifestyle factors, such as physical activity and personal sun exposure levels. Another short-coming has been a lack of measurement of sun exposure, and its potential to influence COVID-19 outcomes. We also discuss possible mechanisms by which sun exposure, UV light and induced mediators could affect COVID-19 morbidity and mortality, by focusing on likely effects on viral pathogenesis, immunity and inflammation, and potential cardiometabolic protective mechanisms. Finally, we explore potential issues including the impacts of exposure to high dose UV radiation on COVID-19 and vaccination, and effective and safe doses for vitamin D supplementation.

Individual and Environmental Risk Factors for COVID- 19 Mortality in Elderly

“…Concerning weather parameters, previous studies reported that increase in UV index may lead to decrease COVID-19 mortality, which could be explained by the fact that atmospheric UV may have virucidal activity and are also necessary for vitamin D synthesis [5,23]. In our study, we could not report an association between UV index and COVID-19 mortality.…”

Diabetes increases the risk of COVID-19 in an altitude dependent manner: An analysis of 1,280,806 Mexican patients

“…UV radiation is a known germicidal that inactivates bacterial spores and mycobacteria [ 66 ], and the UV susceptibility coronavirus aerosols has been registered as 7 to 10 times that of other viral aerosols [ 67 ]. Thus, data collected to this date suggest that ambient levels of both UVA and UVB may be beneficial for reducing the severity and mortality of COVID-19 [ 68 ]. Other conditions, such as temperature and relative humidity, were inversely related to daily new cases and deaths.…”

Solar UV–B/A Radiation is Highly Effective in Inactivating SARS-CoV-2

“…In particular, about 10% of the photons emitted by the Sun in the range 290-315 nm (UV-B) and as much as 95% of those in the range 315-400 nm (UV-A), reach the Earth. The effect of these photons on Single-and Double-Stranded RNA/DNA viruses [10][11][12][13] and the possible role they play on the seasonality of epidemics [14][15][16][17][18][19][20][21][22][23][24][25], are nevertheless little studied and highly debated in alternative or complementarity to other environmental causes [23,[26][27][28][29][30][31][32][33][34][35][36][37][38][39]. Notably though, the effects of both direct and indirect radiation from the Sun needs to be considered in order to completely explain the effects of UV radiations in life processes (with e.g.…”