Prognostic effect of tuberculosis on patients with occupational lung diseases

Occupational lung diseases are well recognized risk factors for tuberculosis (TB). However, little research investigated the effect of TB on the clinical course and outcome of occupational lung diseases.We conducted a 13-year observational study of a nationwide cohort to evaluate the risk and prognosis of TB among patients with occupational lung diseases in Taiwan.By using the Taiwan National Health Insurance database, occupational lung diseases cohort was identified according to diagnosis codes from 1998 to 2008 and prospectively monitored until the end of 2010, loss to follow-up, or death. Newly diagnosed TB, comorbidities, and demographic characteristics were evaluated as prognostic variables in the survival analysis of patients with occupational lung diseases using Cox proportional hazard regression models.A total of 12,787 study participants were enrolled with an average of 9.69 years of follow-up. Among them, 586 (4.58%) had newly diagnosed TB and 3180 (24.87%) died during follow-up. The incidence of TB was 473 per 100,000 person-years, and the risk of TB infection significantly increased over time. The independent risk factors for mortality included male gender (hazard ratio [HR]: 2.23, 95% confidence interval [CI]: 1.91-2.60), age (HR: 1.05, 95% CI: 1.05-1.06), TB (HR: 1.17, 95% CI: 1.01-1.37), congestive heart failure (HR: 1.44, 95% CI: 1.17-1.79), cerebrovascular disease (HR: 1.34, 95% CI: 1.15-1.57), chronic obstructive pulmonary disease (HR: 1.44, 95% CI: 1.33-1.56), and asthma (HR: 1.27, 95% CI: 1.15-1.40). In addition, patients with TB infections had worse outcomes in the survival analysis than those without TB (log-rank test P = 0.02).Despite the low prevalence of occupational lung diseases in Taiwan, patients with those diseases had a higher TB incidence than the general population did (473 vs 55 per 100,000 person-years). Furthermore, even with effective antimicrobial chemotherapy, TB infection was a prognostic factor leading to poor outcomes in the patients with occupational lung diseases. We recommend intensive medical surveillance of TB in these high-risk patients for better control of TB and improvement of occupational health in Taiwan.