Vitamin D and tuberculosis

To the Editor: Any role that vitamin D deficiency plays in increasing the risk of tuberculosis1,2 should not detract from the fact that infection with the causative organism is the necessary risk factor for disease, and decreasing the risk of infection initially will prevent disease even while factors that increase the risk of progression to active disease3 are present.

A letter in the Journal in 20132 suggested that vitamin D supplementation may decrease the incidence of tuberculosis. This was based on the distribution of tuberculosis notifications and vitamin D levels in Australia, and an earlier analysis by the authors of the effect of latitude on seasonality of tuberculosis in Australia.4

The cross-sectional studies on which the letter was based used grouped national data without adjusting for confounding from other factors associated with the variability of rates of tuberculosis infection across Australia. These include variability in relative proportions of migrants and Indigenous and non-Indigenous Australians and the differing age-related incidence of tuberculosis in these groups; the role of migrant screening programs in different jurisdictions and how this impacts on the stage of disease at diagnosis; and the timing of screening in relation to annual intakes of overseas students. These factors can variably confound associations with seasons, latitude and age.

There is no denying the need for a holistic approach that incorporates recognising and treating conditions that increase the risk of latent tuberculosis becoming active, and it is certainly important to tackle vitamin D deficiency in its own right. However, the major focus for decreasing the burden of tuberculosis remains the need to be aware of those populations with a disproportionately greater risk of primary tuberculosis infection and to ensure early diagnosis and management of the disease to prevent transmission initially.