Age, period, and cohort effects of Clonorchis sinensis infection prevalence in the Republic of Korea: Insights and projections.

Background: With decades of containment efforts, the prevalence of C. sinensis infection in Korea has shown a declining trend. However, well-tailored intervention assessments remain challenging, particularly when considering the potential impacts of cohort variations in raw freshwater fish consumption behavior, a major transmission route to humans, on this observed decline. Methodology: We applied an age-period-cohort modeling approach to nationally representative C. sinensis infection prevalence data from 1981–2012 in Korea to assess age, period, and cohort effects on its secular trend and to project the age-stratified prevalence up to 2023. Principal findings: Our analysis suggests that both cohort and period effects have substantially contributed to the declining prevalence of C. sinensis infection in Korea. Age-stratified projections up to 2023 suggest a decline in prevalence across all age groups, while those aged over 40 are anticipated to maintain prevalences above the elimination threshold of 1%. Conclusions: Our study highlights the importance of incorporating cohort effects into intervention assessments aimed at controlling C. sinensis infection. The effectiveness of interventions remains evident in Korea despite adjusting for the cohort effect. This approach, applicable to other endemic countries, would provide valuable insights for intervention assessments and inform future public health planning to eliminate C. sinensis infection. Author summary: Clonorchis sinensis (C. sinensis) infection, a neglected chronic parasitic infection, continues to be a significant public health concern with severe implications. Despite ongoing containment efforts leading to a decline in prevalence in Korea, assessing interventions remains challenging, due to variations in infection risk across different birth cohorts, driven by generational differences in raw freshwater fish consumption. We applied the age-period-cohort modeling approach to nationally representative C. sinensis infection prevalence data from 1981–2012 in Korea. Our analysis showed both cohort and period effects have significantly contributed to the observed decline in the prevalence of C. sinensis infection in Korea throughout the study period. Notably, the effectiveness of interventions remains evident even after adjusting for the cohort effect. Projections of age-stratified prevalence up to 2023 suggest a downward trend across all age groups. However, those aged over 40 are expected to maintain a prevalence exceeding 1%, highlighting the imperative for ongoing sustained efforts toward disease elimination. The age-period-cohort modeling framework offers broad applicability in other liver fluke endemic countries, particularly where data on host reservoirs beyond humans is limited. This approach provides valuable insights for future public health planning and resource allocation, aiming to mitigate the disease burden in affected regions. [ABSTRACT FROM AUTHOR]