Diabetes mellitus is associated with tuberculosis. A cohort of 42,116 clients aged 65 years or more, enrolled at 18 Elderly Health Service centers in Hong Kong in 2000, were followed up prospectively through the territory-wide tuberculosis registry for development of tuberculosis from 3 months after enrollment to December 31, 2005, by use of their identity card numbers as unique identifier. The effects of diabetes mellitus and diabetic control on tuberculosis risk were assessed with adjustment for sociodemographic and other background variables. Diabetes mellitus was associated with a modest increase in the risk of active, culture-confirmed, and pulmonary (with or without extrapulmonary involvement) but not extrapulmonary (with or without pulmonary involvement) tuberculosis, with adjusted hazard ratios of 1.77 (95% confidence interval: 1.41, 2.24), 1.91 (95% confidence interval: 1.45, 2.52), 1.89 (95% confidence interval: 1.48, 2.42), and 1.00 (95% confidence interval: 0.54, 1.86), respectively. Diabetic subjects with hemoglobin A1c <7% at enrollment were not at increased risk. Among diabetic subjects, higher risks of active, culture-confirmed, and pulmonary but not extrapulmonary tuberculosis were observed with baseline hemoglobin A1c > or =7% (vs. <7%), with adjusted hazard ratios of 3.11 (95% confidence interval: 1.63, 5.92), 3.08 (95% confidence interval: 1.44, 6.57), 3.63 (95% confidence interval: 1.79, 7.33), and 0.77 (95% confidence interval: 0.18, 3.35), respectively.

A cohort of 42,655 clients that were first registered with the Elderly Health Service in 2000 were followed prospectively through the tuberculosis (TB) notification registry until the end of 2002. A total of 286 active TB cases (186 culture confirmed) were identified. The annual TB notification rates were 735, 427, and 174 per 100,000 among current smokers, ex-smokers, and never-smokers, respectively (p < 0.001). The trend in TB risk persisted after the control of background characteristics using Cox proportional hazards analysis (adjusted hazard ratios [HRs]: 2.63, 1.41, and 1, p < 0.001). In comparison with never-smokers, current smokers had an excess risk of pulmonary TB (adjusted HR, 2.87; 95% confidence interval [CI], 2.00-4.11; p < 0.001), but not extrapulmonary TB (adjusted HR, 1.04; 95% CI, 0.33-3.30; p = 0.95). Among the current smokers, those who developed TB smoked more cigarettes per day than those who did not (13.43, SD 8.76 vs. 10.96, SD 7.87, p = 0.01). A statistically significant dose-response relationship was observed with respect to active TB and culture-confirmed TB (both p < 0.05). Smoking accounted for 32.8% (95% CI, 14.9-48.0%), 8.6% (95% CI, 3.3-15.1%), and 18.7% (95% CI, 7.7-30.4%) of the TB risk among males, females, and the entire cohort, respectively. Approximately 44.9% (95% CI, 20.7-64.6%) of the sex difference was attributable to smoking.

The impact of smoking on tuberculosis outcome was evaluated in a territory-wide treatment programme.16 345 consecutive patients undergoing chemotherapy for active tuberculosis in government chest clinics in Hong Kong from 2001 to 2003 were followed up prospectively for 2 years for treatment outcome and subsequently tracked through the territory-wide tuberculosis notification registry for relapse until the end of 2012.Smoking was associated with more extensive lung disease, lung cavitation and positive sputum smear and culture at the baseline. In both current smokers and ex-smokers, sputum smears and cultures were significantly more likely to remain positive after 2 months of treatment. Both categories of smokers were significantly less likely to achieve cure or treatment completion within 2 years. Overall, 16.7% of unsuccessful treatment outcomes were attributable to smoking, with the key contributor being default in current smokers and death in ex-smokers. Among successful treatment completers, there was a clear gradient (hazard ratios of 1.00, 1.33 and 1.63) of relapse risk from never-smokers to ex-smokers and current smokers, with an overall population attributable risk of 19.4% (current smokers: 12.2%; ex-smokers: 7.2%).Smoking adversely affects baseline disease severity, bacteriological response, treatment outcome and relapse in tuberculosis. Smoking cessation likely reduces relapse and secondary transmission. @ERSpublications Smoking adversely affects treatment response in TB. Smoking cessation reduces relapse and secondary transmission.

A consistent seasonal pattern was found, with variable amplitudes of fluctuation in different subgroups and differing disease characteristics in different seasons. These observations are suggestive of the presence of a seasonal disease-modifying factor.