Vitamin D and COVID-19 infection and mortality in UK Biobank

Purpose Low blood 25-hydroxyvitamin D (25(OH)D) concentration has been proposed as a potential causal factor in COVID-19 risk. We aimed to establish whether baseline serum 25(OH)D concentration was associated with COVID-19 mortality, and inpatient confirmed COVID-19 infection, in UK Biobank participants. Methods UK Biobank recruited 502,624 participants aged 37–73 years between 2006 and 2010. Baseline exposure data, including serum 25(OH)D concentration, were linked to COVID-19 mortality. Univariable and multivariable Cox proportional hazards regression analyses were performed for the association between 25(OH)D and COVID-19 death, and Poisson regression analyses for the association between 25(OH)D and severe COVID-19 infection. Results Complete data were available for 341,484 UK Biobank participants, of which 656 had inpatient confirmed COVID-19 infection and 203 died of COVID-19 infection. 25(OH)D concentration was associated with severe COVID-19 infection and mortality univariably (mortality per 10 nmol/L 25(OH)D HR 0.92; 95% CI 0.86–0.98; p = 0.016), but not after adjustment for confounders (mortality per 10 nmol/L 25(OH)D HR 0.98; 95% CI = 0.91–1.06; p = 0.696). Vitamin D insufficiency or deficiency was also not independently associated with either COVID-19 infection or linked mortality. Conclusions Our findings do not support a potential link between 25(OH)D concentrations and risk of severe COVID-19 infection and mortality. Randomised trials are needed to prove a beneficial role for vitamin D in the prevention of severe COVID-19 reactions or death.