Association between alcohol consumption and risk of developing tuberculosis in patients with diabetes: a nationwide retrospective cohort study

Background: Diabetes mellitus (DM) and alcohol consumption are risk factors for tuberculosis (TB). We investigated the association between alcohol consumption and TB development in individuals with type 2 DM (T2DM). Methods: Individuals who underwent the national health examination during 2009–2012 were screened using the Korean National Health Information Database. In total, 2,437,443 eligible individuals with T2DM were followed up until December 2018. We identified 21,275 individuals with newly developed TB. Alcohol consumption was evaluated based on the health examination questionnaire, and individuals were categorized into none (0 g/day), mild-to-moderate (1–29.9 g/day), and heavy (≥ 30 g/day) drinkers. Multivariate Cox proportional hazard models were used to estimate the adjusted hazard ratio (aHR) of risk factors for TB. Results: Mild-to-moderate alcohol drinkers had a lower risk of developing TB (aHR 0.92, 95% confidence interval [CI] 0.89–0.96), and heavy alcohol drinkers had a higher risk of developing TB (aHR 1.21, 95% CI 1.16–1.27) than nonalcohol drinkers. When categorized by an alcohol intake of 5 g/day, alcohol drinkers of < 5 g/day had the lowest risk (aHR 0.85, 95% CI 0.81–0.90). The risk increased with alcohol intake, resulting in ≥ 20 g/day as the threshold (20–25 g/day, aHR 1.09, 95% CI 1.02–1.16). Stratified analysis revealed that current smokers had an increased risk of developing TB even among mild-to-moderate drinkers. Conclusions: Heavy alcohol consumption has been linked to an increased risk of developing TB in patients with T2DM. In contrast, mild-to-moderate alcohol consumption was associated with a reduced risk of TB, except in current smokers, where it led to a higher risk of TB. The risk of TB substantially increased with alcohol intake of 20 g/day or more, following a J-shaped curve.