Abstract
PurposeLow 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.MethodsUK 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.ResultsComplete 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.ConclusionsOur 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.
Highlights
In the hunt for modifiable COVID-19 risk factors, vitamin D has gained a lot of attention both in the media and within the scientific community [1]
Proponents of such a link cite a few early studies that present circumstantial evidence. They are either ecological, at an individual level but unable to fully adjust for potential confounders, or they measured 25-hydroxyvitamin D (25(OH)D) concentration once patients were already hospitalised with COVID-19 which introduces reverse causation, as vitamin D is a negative acute phase reactant [2]
A recent review conducted by the Scientific Advisory Committee on Nutrition found insufficient evidence to support recommending vitamin D supplementation to prevent acute respiratory tract infections in the general UK population [6]
Summary
In the hunt for modifiable COVID-19 risk factors, vitamin D has gained a lot of attention both in the media and within the scientific community [1] Proponents of such a link cite a few early studies that present circumstantial evidence. Some of the variables that were associated with increased COVID-19 risk in our sample, for example lower socioeconomic status, being Black or South Asian, or being overweight or obese, are associated with lower vitamin D. This suggests that the positive findings of other studies may. Another recent study of UK Biobank data replicated this finding [8], but it would be more informative to relate 25(OH)D concentration to COVID-19-related mortality
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