Age-period-cohort analysis of pulmonary tuberculosis reported incidence, China, 2006-2020

Background: Tuberculosis (TB) poses a severe public health challenge in China and worldwide. This study evaluated the effects of age, period, and birth cohort on reported incidence trends of TB based on population and refined the characteristics of high-risk groups. Methods: Aggregate data that reported pulmonary tuberculosis (PTB) cases from China Tuberculosis Management Information System (TBIMS) from 2006 to 2020 were used to analyze effect coefficients through the age-period-cohort (APC) model based on intrinsic estimator (IE) method, and converted them into relative risk (RR) to estimate trends. Results: A total of 14.82 million cases of PTB were reported in China from 2006 to 2020, showing a continuous downward trend. The reporting rate increased with age by age group, with 70-74 years old being 2-3 times higher than that in 20-24 years old. APC analysis model showed that age effects were bimodal in 20-24 years old [RR = 2.29, 95% confidence interval (CI): 1.73-3.03] and 70-74 years old (RR = 1.95, 95% CI: 1.67-2.27), and lower than the overall average in the groups under 15 years old. Stratified results showed that the risk was higher for women under age 40 than men and higher for men over 40. The risk was higher in urban than in rural areas under 30 years old and slightly higher in rural than in urban between 30 and 64 years old. The risk for 15-34 years old was significantly higher in the east than in other regions. The period effects showed a decreasing trend, and the risk was higher in rural in recent years. Except for cohorts born in 1961-1965 and 2001-2005, where the RR increased, the later the cohort was born, the lower the risk. The cohort 1926-1930 in eastern had the highest risk (RR = 3.49, 95% CI: 2.44-4.98). Conclusions: The reported incidence of PTB continued to decline in China from 2006 to 2020. The young (20-24 years old) and the elderly (70-74 years old) were equally at high risk. There were differences in the age, period and cohort effects on PTB incidence among gender, urban-rural and regions. Our findings better reflected the characteristics of high-risk populations, thus contributing to the development of timely and effective intervention strategies, and providing clues for etiological research.