There is limited evidence and lack of consensus whether second-hand smoke (SHS) increases risk of tuberculosis (TB), which has substantial implications for unrestricted smoking indoors and TB control policies. We aimed to establish the association between SHS and the risk of acquiring and worsening of TB in non-smokers. We identified 428 articles in the initial search and 12 comparative epidemiological studies met our inclusion criteria. Exposure to SHS was found to have a higher risk of TB infection [risk ratio (RR) 1·19, 95% confidence interval (CI) 0·90-1·57] compared to non-exposure; however, this did not reach statistical significance. There was marked variability (I 2 = 74%, P = 0·0008) between studies' results, which could be explained by the differences in the diagnostic criteria used. Exposure to SHS was found to be statistically significantly associated (RR 1·59, 95% CI 1·11-2·27) with the risk of TB disease. There was significant heterogeneity (I 2 = 77%, P = 0·0006) between studies' results, which was sourced to the internal characteristics of the studies rather than combining different study designs. We did not find any studies for SHS and TB treatment-related outcomes. Thus, we conclude that SHS exposure may increase the risk of acquiring TB infection and progression to TB disease; however, the evidence remains scanty and weak.
Tuberculosis (TB) is a deadly disease that still remains a global burden despite of worldwide measures to curb the disease. As of 2015, the goals of the WHO STOP TB Strategy (2006-2015) have been met and the new WHO End TB Strategy (2015-2030) has been implemented with aim of eradicating the disease. Following that, further studies have demonstrated that TB is a disease that cannot be controlled purely by anti-tuberculous medication alone. It is widely understood that various factors such as rising income inequality, overcrowding populations, compliance to healthcare and resistance pose great barriers to the eradication of disease. In many developing countries including Malaysia, TB is showing or re-emerging trend in both reported cases and resistance. Various predictors for poor disease outcome have been mentioned in the literature such as demographic factors, socioeconomic instability and severe comorbidities amongst the population. Therefore, a prompt review and understanding of the factors at play in the sequestration of TB cases in high risk groups may better inform preventative measures in the future.
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