Association of serum vitamin D levels and dietary vitamin D intake with latent tuberculosis infection and long-term mortality: a population-based cohort study.

Background: Vitamin D plays a crucial role in immune function and respiratory infections, yet its association with latent tuberculosis infection (LTBI) and long-term mortality remains unclear. This study investigates the relationship between serum 25-hydroxyvitamin D levels, dietary vitamin D intake, LTBI risk and mortality.

Method: We analysed data from the 2011-2012 cycle of the US National Health and Nutrition Examination Survey, including 5286 adults (≥18 years) who underwent tuberculosis (TB) testing. Serum 25-hydroxyvitamin D levels were measured using high-performance liquid chromatography-tandem mass spectrometry, and dietary vitamin D intake was assessed via a 24-hour dietary recall. LTBI was defined as an induration>10 mm on the Tuberculin Skin Test or a positive QuantiFERON-TB Gold-In-Tube test. Mortality data were obtained through linkage with the National Death Index, with follow-up until 31 December 2019.

Results: Among 5286 participants, 708 (13.4%) had LTBI. Individuals with LTBI had significantly lower serum 25-hydroxyvitamin D levels than those without LTBI. A 10 nmol/L increase in serum 25-hydroxyvitamin D was associated with a 5% lower risk of LTBI (adjusted OR: 0.95, 95% CI: 0.92 to 0.99, p<0.05). Among LTBI participants, low serum 25-hydroxyvitamin D levels (<50 nmol/L) were independently associated with a higher risk of all-cause mortality (adjusted HR: 3.45, 95% CI: 1.33 to 8.90, p<0.05). However, dietary vitamin D intake was not significantly associated with LTBI risk or long-term mortality.

Conclusion: Vitamin D deficiency was associated with an increased risk of LTBI and long-term mortality in this population-based study. Although adequate serum 25-hydroxyvitamin D levels were linked to more favourable outcomes, the role of vitamin D supplementation in individuals with TB infection remains uncertain. Further research is needed to clarify these associations and guide evidence-based supplementation strategies for TB prevention and management.