Previous tuberculosis modifies spirometry outcomes among small-scale gemstone miners in Tanzania: a cross-sectional, clinic-based study
File(s)
Accepted version
Author(s)
Howlett, Patrick
Type
Journal Article
Abstract
Introduction
Small-scale miners are known to experience high silica exposures, associated with high rates of silicosis and Tuberculosis (TB). TB has been shown to worsen underlying impairment of lung function in miners. We describe the spirometry outcomes, according to previous TB status, among a large cohort of small-scale miners attending a screening centre.
Methods
We collected cross-sectional spirometry and clinical data from consecutive miners and ex-miners, with negative Xpert TB results, attending a screening clinic in Northern Tanzania, between February 2018 and December 2020. Spirometry values assessed using the ATS/ERS 2019 quality criteria and compared to GLI 2022 global (GLIgl) reference values. We used multiple linear regression to model excess Forced Expiratory Volume in 1 second (FEV1) and Forced Vital Capacity (FVC) loss using
16 an a priori interaction between duration of work and previous TB.
Results
Of 542 participants, 80 (15%) reported previous TB. At least moderate (z-score ≤−2.5) FEV1 reductions were present in 51% of participants with previous TB and 18% of those without previous TB. For FVC, respective values were 34% and 10%. A miner with TB and 10 years of work was modelled to have lost 1405 (95% CI 1134, 1676) mls of FEV1 and 1342 (95% CI 1042, 1641) mls of FVC compared to GLIgl reference values. For miners without previous TB, the corresponding excess FEV1 and FVC losses were 693 (95% CI 581, 804) mls and 624 (95% CI 504, 743) mls, respectively.
Discussion
Unmeasured silicosis may partially explain some of the observed effect of previous TB. However, this does not change our observation of a clinically significant burden
of abnormal spirometry in a clinic-based population of small-scale miners. Reducing silica-exposures and preventing TB are key to improving lung health in miners.
Small-scale miners are known to experience high silica exposures, associated with high rates of silicosis and Tuberculosis (TB). TB has been shown to worsen underlying impairment of lung function in miners. We describe the spirometry outcomes, according to previous TB status, among a large cohort of small-scale miners attending a screening centre.
Methods
We collected cross-sectional spirometry and clinical data from consecutive miners and ex-miners, with negative Xpert TB results, attending a screening clinic in Northern Tanzania, between February 2018 and December 2020. Spirometry values assessed using the ATS/ERS 2019 quality criteria and compared to GLI 2022 global (GLIgl) reference values. We used multiple linear regression to model excess Forced Expiratory Volume in 1 second (FEV1) and Forced Vital Capacity (FVC) loss using
16 an a priori interaction between duration of work and previous TB.
Results
Of 542 participants, 80 (15%) reported previous TB. At least moderate (z-score ≤−2.5) FEV1 reductions were present in 51% of participants with previous TB and 18% of those without previous TB. For FVC, respective values were 34% and 10%. A miner with TB and 10 years of work was modelled to have lost 1405 (95% CI 1134, 1676) mls of FEV1 and 1342 (95% CI 1042, 1641) mls of FVC compared to GLIgl reference values. For miners without previous TB, the corresponding excess FEV1 and FVC losses were 693 (95% CI 581, 804) mls and 624 (95% CI 504, 743) mls, respectively.
Discussion
Unmeasured silicosis may partially explain some of the observed effect of previous TB. However, this does not change our observation of a clinically significant burden
of abnormal spirometry in a clinic-based population of small-scale miners. Reducing silica-exposures and preventing TB are key to improving lung health in miners.
Date Acceptance
2025-11-29
Citation
BMJ Open Respiratory Research
ISSN
2052-4439
Publisher
BMJ Publishing Group
Journal / Book Title
BMJ Open Respiratory Research
Copyright Statement
Copyright This paper is embargoed until publication. Once published the Version of Record (VoR) will be available on immediate open access.
License URL
Publication Status
Accepted