ABSTRACT
Several recent studies have demonstrated that low plasma 25(OH) vitamin D levels are associated with the risk of COVID-19 infection. The primary source of vitamin D production in humans is environmental UV radiation. In many viral respiratory diseases, peak infection rates are observed during winter due to reduced UV exposure and low temperatures. In Europe, the second wave of COVID-19 began early in the winter of 2020. Investigating the impact of seasonal temperature and UV exposure on COVID-19 transmission could thus aid in prevention and intervention. As such, we first performed a comprehensive meta-analysis of all related published literature based on the association between vitamin D and COVID-19, which supported the hypothesis that the low vitamin D level is a critical risk factor for COVID-19 infection. Next, to understand the potential impact of seasonal UV and temperature levels on COVID-19 cases, we analyzed meteorological data and daily COVID-19 cases per million in the populations of 26 European countries. We observed that low temperature, UV index, and cloud-free vitamin D UV dose (UVDVF) levels are negatively correlated with COVID-19 prevalence in Europe. Furthermore, a distributed lag nonlinear model was used to assess the nonlinear delayed effects of individual seasonal factors on COVID-19 cases. Such analysis highlighted the significantly delayed impact of UVDVF on the cumulative relative risk of COVID-19 infection. The findings of this study suggest that low UV exposure can affect the required production of vitamin D in the body, which substantially influences the dynamics of COVID-19 transmission and severity.
Subject(s)
Algorithms , COVID-19/transmission , Models, Theoretical , Seasons , Ultraviolet Rays , Vitamin D/blood , COVID-19/epidemiology , COVID-19/virology , Europe/epidemiology , Humans , Meta-Analysis as Topic , Observational Studies as Topic , Pandemics , SARS-CoV-2/physiology , Severity of Illness Index , TemperatureABSTRACT
Vitamin D deficiency is a worldwide pandemic. The aim of this study was to evaluate associations of plasma 25(OH)D levels with the likelihood of coronavirus disease 2019 (COVID-19) infection and hospitalization. The study population included the 14 000 members of Leumit Health Services, who were tested for COVID-19 infection from February 1st to April 30th , 2020, and who had at least one previous blood test for the plasma 25(OH)D level. 'Suboptimal' or 'low' plasma 25(OH)D level was defined as plasma 25-hydroxyvitamin D, or 25(OH)D, concentration below the level of 30 ng/mL. Of 7807 individuals, 782 (10.02%) were COVID-19-positive, and 7025 (89.98%) COVID-19-negative. The mean plasma vitamin D level was significantly lower among those who tested positive than negative for COVID-19 [19.00 ng/mL (95% confidence interval (CI) 18.41-19.59) vs. 20.55 (95% CI: 20.32-20.78)]. Univariate analysis demonstrated an association between the low plasma 25(OH)D level and increased likelihood of COVID-19 infection [crude odds ratio (OR) of 1.58 (95% CI: 1.24-2.01, P < 0.001)], and of hospitalization due to the SARS-CoV-2 virus [crude OR of 2.09 (95% CI: 1.01-4.30, P < 0.05)]. In multivariate analyses that controlled for demographic variables, and psychiatric and somatic disorders, the adjusted OR of COVID-19 infection [1.45 (95% CI: 1.08-1.95, P < 0.001)] and of hospitalization due to the SARS-CoV-2 virus [1.95 (95% CI: 0.98-4.845, P = 0.061)] were preserved. In the multivariate analyses, age over 50 years, male gender and low-medium socioeconomic status were also positively associated with the risk of COVID-19 infection; age over 50 years was positively associated with the likelihood of hospitalization due to COVID-19. We concluded that low plasma 25(OH)D levels appear to be an independent risk factor for COVID-19 infection and hospitalization.