Trends, Demographic Characteristics, and Seasonal Patterns of Nonoperative and Operative Reduction for Intussusception: A Preliminary Nationwide Claims-Based Analysis from 2014 to 2023 in Japan.

Objective Nationwide population-based epidemiological data on intussusception in Japan are limited. This study aimed to preliminarily investigate the temporal trends, demographic characteristics, and seasonal patterns of intussusception reduction procedures using a comprehensive administrative database. Methods We analyzed data from the National Database of Health Insurance Claims and Specific Health Checkups (NDB) Open Data (2014-2023). The procedures were categorized as nonoperative or operative. The crude and age-adjusted procedure rates were calculated per 100,000 person-years. Temporal trends were assessed using linear and Poisson regressions. Seasonal variations (April 2019-March 2024) were evaluated using a one-way analysis of variance with post-hoc comparisons, and correlations with pediatric infectious diseases and meteorological variables were examined using Pearson's correlation coefficients. Results Over the decade, 42,173 procedures were performed, with an average annual rate of 3.4 per 100,000 person-years and an overall male-to-female ratio of 2.1:1. The age distribution was bimodal, with a major peak among children aged 0-4 years and a minor peak among adults aged ≥90 years. The annual procedure counts declined from 5,836 in 2014 to 3,735 in 2023. The age-adjusted nonoperative procedure rates decreased significantly, particularly among older adults (p <0.001). In 2023, nonoperative reductions accounted for 94.7% of all procedures, whereas operative procedures accounted for 5.3%. Nonoperative procedures demonstrated significant seasonal variation (p <0.05), particularly between spring and summer, and showed moderate positive correlations with pharyngoconjunctival fever and hand, foot, and mouth disease, as well as weak positive correlations with temperature. Conclusion This preliminary nationwide study provides contemporary epidemiological insights into the management of intussusception in Japan.