Impact of fine particulate matter on latent tuberculosis infection and active tuberculosis in older adults:a population-based multicentre cohort study

BACKGROUND AND AIM: Evidence showed that air pollution was associated with an increased risk of tuberculosis (TB), an infectious disease caused by bacillus Mycobacterium tuberculosis (MTB). However, the associations of air pollution with latent TB infection (LTBI) and subsequent active TB development have not yet been investigated to date. This study aimed to study the impact of long-term exposure to ambient particulate matter with an aerodynamic diameter less than 2.5 μm (PM2.5) on the acquisition of LTBI and on the risk of subsequent active disease development among rural older adults from a multicentre cohort. METHOD: A total of 4789 older adults were included in a population-based, multicenter, prospective cohort study (LATENTTB-NSTM) from 2013 to 2018. The level of long-term (1- to 3-year) exposure to PM2.5 for each participant was assessed by aggregating satellite-based estimates at a daily time scale and 1 km resolution. Logistic regression and time-varying Cox proportional hazards models with province-level random intercepts were employed to assess associations of long-term exposures to PM2.5 with the risk of LTBI and subsequent development of active TB, respectively. RESULTS: Out of 4789 participants, 3283 were LTBI-free at baseline, among whom 2805 completed the one-year follow-up and 127 of them developed newly identified LTBI. No significant associations were identified between long-term exposure to PM2.5 and the risk of LTBI. And among 1506 participants with LTBI at baseline, 30 active TB cases were recorded during the 5-year follow-up. Particularly, an increment of 5 μg/m3 in 2-year moving averaged PM2.5 was associated with a 42.7% increased risk of active TB (HR = 1.427, 95% CI: 1.073-1.897). CONCLUSIONS: Our findings suggest that long-term air pollution might be considered as a neglected risk factor for active TB development from LTBI, especially for those living in developing or less-developed areas where the air quality is poor.