Low alanine aminotransferase as a risk factor for chronic obstructive pulmonary disease in males

Alanine aminotransferase (ALT) levels reflect skeletal muscle volume and general performance, which are associated with chronic obstructive pulmonary disease (COPD) development and prognosis. This study aimed to investigate ALT levels as a risk factor for COPD development. This 13-year population-based retrospective observational cohort study included 422,452 participants for analysis. We classified groups according to the baseline ALT levels (groups 1–5: ALT (IU/L) < 10; 10–19; 20–29; 30–39; and ≥ 40, respectively). The incidence of COPD was the highest in group 1, decreasing as the group number increased in males, but not in females. The Cox regression analysis in males revealed that a lower ALT level, as a continuous variable, was a significant risk factor for COPD development [univariable, hazard ratio (HR): 0.992, 95% confidence interval (CI): 0.991–0.994; multivariable, HR: 0.998, 95% CI: 0.996–0.999]. In addition, COPD was more likely to develop in the lower ALT level groups (groups 1–4; < 40 IU/L), than in the highest ALT level group (group 5; ≥ 40 IU/L) (univariable, HR: 1.341, 95% CI: 1.263–1.424; multivariable, HR: 1.097, 95% CI: 1.030–1.168). Our findings suggest that males with low ALT levels should be carefully monitored for COPD development.