Association between vitamin D and incident herpes zoster: a UK Biobank study.

BACKGROUND: Vitamin D has immunomodulatory effects, but any association with herpes zoster (HZ) is unclear. AIM: To explore the association between vitamin D status and risk of incident HZ in adults in the UK. DESIGN AND SETTING: A cohort study involving participants of UK Biobank (a database containing the health information from half a million individuals) across England, Wales, and Scotland, who had at least one vitamin D testing result with linked primary care electronic health records. METHOD: The primary exposure was vitamin D status, categorised as deficient (<25 nmol/L), insufficient (25-49 nmol/L), or sufficient (≥50 nmol/L). The secondary exposures were self-reported vitamin D supplementation at baseline assessment and vitamin D prescription records. The outcome was diagnosed incident HZ, identified from linked primary care or hospital inpatient records. Weibull regression was used, adjusting for potential confounders, including demographic factors, comorbidities, and immunosuppression. RESULTS: In total, 177 572 eligible participants were included in the analysis, with a mean follow-up time of 10.1 years (standard deviation 1.9 years). No evidence showed that low vitamin D was associated with a higher incidence of HZ, compared with people with sufficient vitamin D (deficient: adjusted hazard ratio [HR] 0.99, 95% confidence interval [CI] = 0.90 to 1.10; insufficient: HR 1.03, 95% CI = 0.96 to 1.10). No evidence was found that supplementing vitamin D or receiving vitamin D prescription was associated with HZ incidence (supplementation: HR 0.88, 95% CI = 0.67 to 1.16; prescription: HR 1.11, 95% CI = 0.91 to 1.34). CONCLUSION: No association of vitamin D status, supplementation, or prescription with incident HZ was observed. No evidence supported vitamin D supplementation as a strategy to prevent HZ.