Context: One of the risk factors for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is postulated to be vitamin D deficiency. To understand better the role of vitamin D deficiency in the disease course of COVID-19, we undertook a retrospective case-control study in the North West of England (NWE).
Objective: To examine whether hospitalisation with COVID-19 is more prevalent in individuals with lower vitamin D levels.
Methods: The study included individuals with results of serum 25-hydroxyvitamin D (25[OH]D) between 1 st April 2020 and 29th January 2021. Patients were recruited from two districts in NWE. The last 25(OH)D level in the previous 12 months was categorised as 'deficient' if less than 25 nmol/L and 'insufficient' if 25-50 nmol/L.
Results: 80,670 participants were entered into the study. Of these, 1,808 were admitted to hospital with COVID-19, of whom 670 died. In a primary cohort, median serum 25(OH)D in participants who were not hospitalised with COVID-19 was 50.0 [interquartile range, IQR 34.0-66.7] nmol/L versus 35.0 [IQR 21.0-57.0] nmol/L in those admitted with COVID-19 (p <0.005). There were similar findings in a validation cohort (median serum 25(OH)D 47.1 [IQR 31.8-64.7] nmol/L in non-hospitalised versus 33.0 [IQR 19.4-54.1] nmol/L in hospitalised patients). Age-, sex- and seasonal variation-adjusted odds ratios for hospital admission were 2.3-2.4 times higher among participants with serum 25(OH)D <50 nmol/L, compared to those with normal serum 25(OH)D levels, without any excess mortality risk.
Conclusions: Vitamin D deficiency is associated with higher risk of COVID-19 hospitalisation. Widespread measurement of serum 25(OH)D and treating any unmasked insufficiency or deficiency through testing may reduce this risk.
Keywords: COVID-19; Hospitalisation; Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); Vitamin D deficiency.
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