Gert van der Hoek
In Memoriam - Editor, Senior Moderator
1 MAY 2020, 2020
Abstract
Background: Research is ongoing to identify an effective way to prevent or treat COVID-19, but thus far these efforts have not yet identified a possible solution. Prior studies indicate the protective role of Ultraviolet-B (UVB) radiation in human health, mediated by vitamin D synthesis. In this study, we aim to empirically investigate the causal protective role of UVB radiation as measured by ultraviolet index (UVI) in reducing the number of deaths attributed to COVID-19 (COVID-19 deaths).
Methods: We carry out an observational study, applying a fixed-effect log-linear regression model to a panel dataset of 64 countries over a period of 78 days from 22 January 2020 onwards (n=4992). We use cumulative COVID-19 deaths as well as case-fatality rate as the main dependent variables to test our hypothesis and isolate the UVI effect from potential confounding factors such as underlying time trends, country-specific time-constant factors and time-varying factors such as weather.
Findings: After controlling for time-varying and time-constant factors, we find that a (permanent) one-unit increase in UVI leads to a 2.2% [p-value is less than 0.01] decrease in COVID-19 deaths (per day) as well as a 1.9% [p-value is less than 0.05] decrease in case fatality rate (per day). Our results are consistent across different model specifications.
Interpretation: We find a significant effect of UVI in reducing COVID-19 deaths, indicating evidence of the protective role of UVB radiation in mitigating COVID-19 deaths. If confirmed via clinical studies, then the possibility of mitigating COVID-19 deaths via sensible exposure to sunlight or vitamin D nutritional intervention will be very attractive because it is cost-effective and widely available.
Abstract
Background: Research is ongoing to identify an effective way to prevent or treat COVID-19, but thus far these efforts have not yet identified a possible solution. Prior studies indicate the protective role of Ultraviolet-B (UVB) radiation in human health, mediated by vitamin D synthesis. In this study, we aim to empirically investigate the causal protective role of UVB radiation as measured by ultraviolet index (UVI) in reducing the number of deaths attributed to COVID-19 (COVID-19 deaths).
Methods: We carry out an observational study, applying a fixed-effect log-linear regression model to a panel dataset of 64 countries over a period of 78 days from 22 January 2020 onwards (n=4992). We use cumulative COVID-19 deaths as well as case-fatality rate as the main dependent variables to test our hypothesis and isolate the UVI effect from potential confounding factors such as underlying time trends, country-specific time-constant factors and time-varying factors such as weather.
Findings: After controlling for time-varying and time-constant factors, we find that a (permanent) one-unit increase in UVI leads to a 2.2% [p-value is less than 0.01] decrease in COVID-19 deaths (per day) as well as a 1.9% [p-value is less than 0.05] decrease in case fatality rate (per day). Our results are consistent across different model specifications.
Interpretation: We find a significant effect of UVI in reducing COVID-19 deaths, indicating evidence of the protective role of UVB radiation in mitigating COVID-19 deaths. If confirmed via clinical studies, then the possibility of mitigating COVID-19 deaths via sensible exposure to sunlight or vitamin D nutritional intervention will be very attractive because it is cost-effective and widely available.