# Vitamin D Status, Fasting Blood Glucose, and Latent Tuberculosis Infection in a High-Risk Population in Ulaanbaatar, Mongolia

## TL;DR

This study found that low vitamin D levels are linked to latent tuberculosis infection in high-risk groups in Mongolia, especially when combined with high blood sugar.

## Contribution

The study identifies a significant interaction between vitamin D deficiency and high blood glucose in increasing latent TB risk among household contacts in Mongolia.

## Key findings

- 47% of participants had latent tuberculosis infection.
- Lower vitamin D levels were independently associated with higher odds of LTBI in household contacts.
- The link between vitamin D and LTBI was stronger in those with higher blood glucose levels.

## Abstract

Background: Mongolia is experiencing a rapid epidemiologic transition in which high burdens of micronutrient malnutrition, infection, and cardiometabolic disease are simultaneously prevalent. This cross-sectional study sought to understand how nutritional, lifestyle, and cardiometabolic risk factors are distributed among a population at high-risk for tuberculosis (TB), comprising household contacts (HHCs) and healthcare workers, (HCWs) in Ulaanbaatar, Mongolia, and how these factors are associated with TB infection. Methods: A total of 196 HHCs and 241 HCWs were assessed for latent TB infection (LTBI) using the QuantiFERON-TB Gold Plus (QFT-Plus) assay and for diabetes using fingerprick samples for fasting blood glucose. Participants also underwent assessments of their diet and physical activity, nicotine dependence, body mass index, and serum 25(OH)D concentration. We examined associations between assessed risk factors and LTBI using multivariate logistic regression. Results: The prevalence of LTBI was 47% for both HHCs and HCWs. A total of 54% percent of HHCs and 68% of HCWs had low physical activity levels; 63% of HHCs and 95% of HCWs were overweight or obese; 7% of HHCs and 4% of HCWs had impaired or diabetic fasting blood glucose [FBG]; and 49% of HHCs and 70% of HCWs were vitamin D deficient. In a multivariable analysis of HHCs, LTBI was independently associated with lower serum [25(OH)D], and the odds ratio (OR) was 3.18 (95% CI 1.38–7.79; p = 0.009). In contrast, the probability of LTBI did not differ significantly between vitamin D-deficient and non-deficient HCWs, and the OR was 0.89 (95% CI 0.59–1.37; p = 0.42). In a pooled analysis of HHCs and HCWs, the probability of LTBI did not significantly differ between vitamin D-deficient vs. non-deficient participants. The association between serum [25(OH)D] and LTBI among HHCs and HCWs was significantly modified by fasting blood glucose (FBG), such that a lower vitamin D status was significantly more common among those in the highest tertile of FBG than among those in the lowest tertile of FBG. Conclusions: Nutritional, lifestyle, and cardiometabolic risk factors are highly prevalent among HHCs and HCWs with TB in Ulaanbaatar, Mongolia. These findings underscore the importance of simultaneously controlling TB infection, malnutrition, and cardiometabolic risks among HHCs and HCWs to reduce the disease burden in Mongolia.