Temporal trends and age-period-cohort effects of tuberculosis incidence among older adults in western China, 2005–2020

Abstract

Abstract Background Tuberculosis remains a major public health challenge in China, and older adults in western China bear a disproportionate burden. This study examined the temporal trends in TB incidence among older adults in western China and assessed the independent effects of age, period, and cohort. Methods TB incidence data for adults aged 60 years and above in western China from 2005 to 2020 were obtained from China’s Tuberculosis Information Management System. Joinpoint regression was used to characterize temporal trends and identify change points overall and by sex and residence, reporting annual percentage change (APC) and average annual percentage change (AAPC). An age–period–cohort model using the intrinsic estimator method was conducted to estimate the independent age, period, and birth cohort effects. Results The age-standardized incidence rate (ASIR) decreased from 172.29 to 113.10 per 100,000, showing a non-significant declining tendency (AAPC=-2.91%, 95% CI: -5.95%, 0.22%), with higher rates in males and in rural areas. Declines were statistically significant among males (AAPC=-3.40%, 95% CI: -5.78%, -0.96%) and in urban areas (AAPC= -5.05%, 95% CI: -8.14%, -1.85%). Joinpoint analysis identified three change points, with a moderate decline during 2007–2015 (APC= -4.80%, 95% CI: -6.64%, -2.92%), a sharp decline during 2018–2020 (APC =-20.82%, 95% CI: -31.66%, -8.27%) and non-significant increases in 2005–2007 and 2015–2018. Age–period–cohort analysis showed an inverted U-shaped age effect, with the relative risk (RR) peaking at 70–74 years (RR = 1.132, 95% CI: 1.127, 1.136) and declining at 80–84 years (RR = 0.801, 95% CI: 0.796, 0.806). Period effects decreased over time, showing higher risks among males and urban residents during 2006–2010, but this pattern reversed during 2016–2020. Cohort effects generally declined, with the lowest risk in the 1956–1960 cohort (RR = 0.883, 95% CI: 0.877, 0.889). Conclusions TB incidence among older adults in western China showed a non-significant overall downward trend from 2005 to 2020, with marked reductions after 2018. Disparities by sex and residence, together with variations in age, period and cohort effects highlight the need for targeted TB prevention and control, particularly among older males and rural residents.