The role of vitamin D in the prevention of coronavirus disease 2019 infection and mortality
Authors: Lee Smith
Petre Cristian Ilie
Simina Stefanescu
Journal: Aging Clinical and Experimental Research (2020)
Discipline: CLINICAL MEDICINE
Keywords: COVID-19; Calcitriol; Cholecalciferol; SARS-CoV2; Vitamin D.
Affiliations: Research and Innovation Department, The Queen Elizabeth Hospital Foundation Trust, King's Lynn, UK. ., The University of East Anglia, Norfolk, UK., The Cambridge Centre for Sport and Exercise Sciences, Anglia Ruskin University, Cambridge, UK.

Abstract:  WHO declared SARS-CoV-2 a global pandemic. The present aim was to propose an hypothesis that there is a potential association between mean levels of vitamin D in various countries with cases and mortality caused by COVID-19. The mean levels of vitamin D for 20 European countries and morbidity and mortality caused by COVID-19 were acquired. Negative correlations between mean levels of vitamin D (average 56 mmol/L, STDEV 10.61) in each country and the number of COVID-19 cases/1 M (mean 295.95, STDEV 298.7, and mortality/1 M (mean 5.96, STDEV 15.13) were observed. Vitamin D levels are severely low in the aging population especially in Spain, Italy and Switzerland. This is also the most vulnerable group of the population in relation to COVID-19. It should be advisable to perform dedicated studies about vitamin D levels in COVID-19 patients with different degrees of disease severity. 

Retracted: No

PubPeer comments:
 The figures quoted in the abstract of this article  mean levels of vitamin D (average 56 mmol L, STDEV 10.61) in each country and the number of COVID-19 cases 1 M (mean 295.95, STDEV 298.7, and mortality 1 M (mean 5.96, STDEV 15.13 are not the same as the figures in the results section  mean vitamin D (average 56.79 nmol L, STDEV 10.61) and number of cases of COVID-19 1 M population in each country [average 1393.4, STDEV 1129.984, r(20)u2009=u2009u2212 0.4435; p valueu2009=u20090.050], and between the mean vitamin D levels and the number of deaths caused by COVID-19 1 M (Fig. 1) [average 80.42, STDEV 94.61, r(20)-valueu2009=u2009u2212 0.4378; p valueu2009=u20090.05) Could the authors please comment on the discrepancy between these values? , 
 Many of the references in the article appear to be incorrect. The authors state We searched the literature for the mean levels of vitamin D in each country [3]. Reference 3 does not contain information on vitamin D levels by country. Reference [6] does contain this information and so it is likely the correct source of the data in the present paper. Even if this is correct, it is still unclear how the values from this paper were selected. For example, in reference [6], the average vitamin D levels in Norway from two separate studies are reported, Cashman 2015 and Cashman 2016. Why did the authors of the present study use the value from Cashman 2016 (65 nmol l) rather than Cashman 2015 (71 nmol l)? In reference [6], there are also two values quoted for Sweden (68.7 and 78). It appears that in this case, the authors of the present study decided to use the mean of these values in their report (73.5). What s more, the values for Sweden were exclusively sampled from elderly people, whereas others (such as the UK) were sampled across the population, from babies to adults. It is possible that these sampling biases contribute to the variation in quoted Vitamin D levels in the present study, meaning that the values are not representative of the general population in each country , 
 Most importantly, even if we take the data for vitamin D levels used in the present study as accurate, if we update the data with the current coronavirus statistics (based on https: www.worldometers.info coronavirus 10-05-20), we see that the correlation between deaths M and vitamin D levels is getting weaker as the pandemic progresses.   R = -0.3933 p= 0.08 , 
 (Continued) Update using the most recently available numbers (20-05-10)  We see that the correlation is even weaker than before. The p-value represents the likelihood of whether or not the correlation seen is simply due to chance. A low p-value indicates a strong correlation, and a high p-value suggests a random distribution. In biology a p-value lower than 0.05 is typically considered significant . A p-value of 0.05 suggests a 5% chance that the correlation is just random. If we plot the p-values for the correlation between death M and Vitamin D levels over time, we can see that the correlation between these number is getting weaker and weaker, seriously calling into question the value of this study.  , 
 The difference between a direct correlation between vitamin D levels and COVID-19 outcome (e.g. deaths) and the inverse correlation proposed by the authors is not significant, as judged by the correlation coefficients.  , 
 I recalculated the correlations based on data from 22 June 2020. Vitamin D vs CC per million: R2 = 0.2048, p = 0.0451 Vitamin D vs C-deaths per million: R2 = 0.1214, p = 0.1321 Even the  correlation between Vitamin D levels and confirmed cases per million is very weak. If mean Vitamin D levels would be of clinical relevance, I would rexpect a correlation to deaths rather than to infection (confirmation). But the correlation to c-deaths is weaker. It might be quite obvious that the black box  hospital and national medical usances is the most relevant factor that could overrule any relevant effect of the corona virus infection. Nonetheless, the lack of reasonable correlation with mean levels does not exclude a reasonable correlation to low levels. ,