Vitamin D Deficiency and Severe Dengue Fever: A Systematic Review and Meta-Analysis.

Vitamin D affects immune function and possibly, dengue severity, but evidence is inconsistent. Observational studies comparing vitamin D levels between severe and nonsevere dengue were systematically searched. A random-effects meta-analysis was conducted. Heterogeneity was quantified using I2. Subgroup and sensitivity analyses were performed. Six studies with 1,130 participants were included. The pooled odds ratio (OR) for severe dengue with vitamin D deficiency was 1.77 (95% CI: 0.75-4.16, P = 0.194) with substantial heterogeneity (I2 = 61.6%). A subgroup analysis showed a significant association in children (OR: 51.20, 95% CI: 3.12-842.95). Excluding an outlier yielded a significant fixed-effect OR of 1.67 (95% CI: 1.04-2.67, P = 0.034) with reduced heterogeneity (I2 = 46.1%). Vitamin D deficiency might be linked to higher odds of severe dengue, especially in children, but confirmation requires larger sample sizes. Establishing causality and assessing vitamin D supplementation in high-risk groups require prospective studies.