GPT and chronic obstructive pulmonary disease: 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].