Incidence of Tuberculosis in Chinese Adults with Type 2 Diabetes: A Retrospective Cohort Study in Shanghai

Background: Both type 2 diabetes mellitus (T2DM) and tuberculosis (TB) bring heavy disease burden around the world. Their causal relationship, however, remains unclear. In this study, we estimated incidence of TB in Chinese T2DM patients and evaluated the effect of glucose level on TB risk based on the management data in Shanghai. Methods: A retrospective cohort study was built based on the diabetes management system in Shanghai and included 240 692 adults aged 35 or above, diagnosed with T2DM between January 1, 2010 and December 31, 2015 and free of TB at diagnosis. Baseline information was from the system which was routinely collected for each patient at diagnosis of T2DM. Incident TB cases were identified through record-linkage with the Shanghai TB Surveillance System and Mandatory Notification System using the unique identification card number of each individual. Incidence of TB in all diabetes patients and by subgroups were calculated and compared. Multivariable Cox regression models with restricted cubic splines were used to evaluate the association of fast plasma glucose (FPG) level with the risk of TB. Findings: A total of 439 incident TB cases were identified in the cohort after an average of 3·83 years of follow-up. The overall incidence was 51·3/100 000 in diabetes patients and remained higher than that in general population from 2010 to 2015, with range from 44·5 to 76·4/100 000 vs. 28·1 to 31·0/100 000. The incidence was higher in men than in women (86·2 vs. 22·1 per 100 000), and was highest in patients with body mass index (BMI) <18·5 kg/m2 (215·2/100 000) or FPG≥10 mmol/L (143·2/100 000). The risk of TB was observed increasing with FPG increasing, particularly among those with normal BMI. Interpretation: Our results suggest that the risk of TB may increase as FPG increasing in normally weighted diabetes patients. Individualized screening strategy should be provided in Chinese diabetes patients to prevent and control TB. Funding Statement: The Three-year Action Plan on Public Health, Phase Ⅳ, Shanghai, China (15GWZK0801); The Study on Comprehensive Prevention and Treatment Model of Tuberculosis, Shanghai, China (2018ZX10715012). Declaration of Interests: The authors declared that there is no conflict of interest. Ethics Approval Statement: This study was approved by the Ethical Review Committee of Shanghai Municipal Center for Disease Control and Prevention. Since this was a retrospective study and all patients’ information used was routinely collected through the management system and the TB mandatory notification system, the requirement for informed consent was exempted by the committee mentioned above.