evidence: Strong correlation between prevalence of severe vitamin D deficiency and population mortality rate from COVID-19 in Europe - PMID: 33721102 - PMCID: PMC7957444 - DOI: 10.1007/s00508-021-01833-y [...] Results: There were data sets from 10 countries that fitted the criteria and were analyzed. Severe vitamin D deficiency was defined as 25(OH)D less than 25 nmol/L (10 ng/dL). Pearson correlation analysis between death rate per million of population from coronavirus disease 2019 (COVID-19) and prevalence of severe vitamin D deficiency showed a strong correlation with r = 0.79, p = 0.007. Over time, correlation strengthened, and r coefficient asymptotically increased. After adjusting for countries' age structure and per capita health expenditures, multiple linear regression analysis showed that higher prevalence of severe vitamin D deficiency is associated with increased mortality. Each 1% increase in prevalence increased deaths by 55 per million (95% confidence interval, CI 8-102), p = 0.03. [...] Association between Average Vitamin D Levels and COVID-19 Mortality in 19 European Countries-A Population-Based Study.Nutrients. 2023 Nov 17;15(22):4818. doi: 10.3390/nu15224818. Nutrients. 2023. PMID: 38004213 Free PMC article. Review.