Introduction Heavy alcohol consumption increases the risk of active tuberculosis (TB). However, the relation between lower levels of alcohol intake and TB risk remains unclear. We aimed to evaluate the association between alcohol intake and risk of active TB and assess whether the associations were modified by smoking status, which is another risk factor for active TB.
Methods The Singapore Chinese Health Study is a prospective cohort of 63 257 adults aged 45–74 years recruited from 1993 to 1998. Information on alcohol intake and smoking history was collected at recruitment. Active TB cases were identified via linkage with National TB Notification Registry.
Results During a mean follow-up of 16.8 years, 1249 incident cases of active TB were identified. Among non-smokers, compared with total abstinence, participants who had monthly to weekly intake of alcohol had reduced TB risk (HR 0.70, 95% CI 0.55 to 0.89), but this reduction in risk with low-dose drinking was not observed among current smokers (HR 0.96, 95% CI 0.77 to 1.18; p for interaction=0.02). Comparatively, drinking 2+ drinks daily was associated with increased TB risk among current smokers (HR 1.51, 95% CI 1.11 to 2.05). This increased risk was not observed among non-smokers (HR 0.93, 95% CI 0.49 to 1.77) and the interaction between alcohol intake and smoking status was of borderline significance (p for interaction=0.08). In joint effect, compared with those who neither smoked nor drank, the risk of active TB increased from 1.82 (95% CI 1.57 to 2.10) in current smokers who were non-drinkers to 3.16 (95% CI 2.35 to 4.24) in current smokers who also drank 2+ drinks daily.
Conclusion While low intake of alcohol may protect against active TB among non-smokers, drinking 2+ drinks daily could act synergistically with smoking to increase the risk of active TB in current smokers.
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Contributors AZS and W-PK contributed to the conception and design of the study and analysis of data. CBEC, Y-TW, J-MY and W-PK participated in the acquisition of data. AZS, CBEC, Y-TW, J-MY and W-PK were involved in the interpretation of the data and drafting of intellectual content. All authors read and approved the final manuscript and W-PK was responsible for the integrity of the work as a whole. W-PK is the guarantor.
Funding This work was supported by the United States National Cancer Institute, National Institutes of Health (grant numbers UM1 CA182876 and R01 CA144034). W-PK is supported by the National Medical Research Council, Singapore (NMRC/CSA/0055/2013). The sponsors have no role in: the study design; the collection, analysis or interpretation of data; the writing of the report or in the decision to submit the article for publication.
Competing interests All authors have completed the ICMJE uniform disclosure form at and declare: support from the National Institutes of Health for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.
Ethics approval The Institutional Review Boards of the National University of Singapore and University of Pittsburgh approved the conduct of the SCHS. The present study was approved by the Institutional Review Board of the National University of Singapore. All participants gave informed consent.
Provenance and peer review Not commissioned; internally peer reviewed.
Data sharing statement No additional data available.
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