Association between vitamin D and COVID-19 infection and mortality in Taiwanese patients

Vitamin D plays a role in immune regulation and may influence coronavirus disease 2019 (COVID-19) outcomes. This study examined the association between serum vitamin D levels and COVID-19 infection and mortality in symptomatic patients in Taiwan.

This retrospective cohort study included symptomatic patients who underwent COVID-19 real-time polymerase chain reaction (RT-PCR) assay between 2020 and 2023. Serum 25-hydroxyvitamin D (25(OH)D) levels were categorized as deficient (<20 ng/mL), insufficient (20-30 ng/mL), or sufficient (≥30 ng/mL). Logistic regression models were used to evaluate the impact of vitamin D levels on COVID-19 infection and mortality, adjusting for potential confounders including age, sex, and comorbidities.

Among the 481 participants (mean age: 58.2 years; 66.7% female), 96 (19.96%) tested positive for COVID-19. Vitamin D level was not associated with COVID-19 infection (odds ratio [OR] = 1.00, 95% CI, 0.99-1.02; p = 0.687); however, vitamin D deficiency significantly increased the risk of COVID-19-related mortality (OR = 10.68; 95% CI, 1.18-96.45; p = 0.035). The mortality rate in patients aged 65 to 74 years was higher compared to those aged 19 to 44 years (OR = 12.91; 95% CI, 1.29-128.83; p = 0.029).

Vitamin D levels were not associated with susceptibility to COVID-19 infection. However, vitamin D deficiency, particularly in older patients, was associated with an increased risk of mortality among those diagnosed with COVID-19. These findings support the role of vitamin D in reducing COVID-19 mortality and emphasize the importance of maintaining sufficient levels in high-risk populations.