Abstract
Background: Nationwide data on the incidence of central precocious puberty (CPP) and premature thelarche (PT), a benign variant of pubertal development, are limited.Purpose: To evaluate trends in CPP and PT incidence among Thai children before, during, and after the COVID-19 pandemic.Methods: This cross-sectional population-based study used National Health Security Office (NHSO) claims data from 2018 to 2024. CPP and PT were identified using ICD-10-TM (International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Thai Modification) codes. Annual incidence rates (AIRs) were calculated for each NHSO-insured population, while incidence rate ratios (IRRs) were estimated using quasi-Poisson regression.Results: A total of 6,782 girls and 189 boys with CPP, and 1,594 girls with PT, were included. Among girls, the CPP AIR increased from 15.0 per 100,000 person-years in 2018 to 51.7 in 2021 and remained elevated during 2022–2024 (44.1–47.7). The IRR was 2.27 (95% confidence interval [CI], 1.82–2.83) for pandemic versus prepandemic, and 1.06 (95% CI, 0.89–1.26) for postpandemic versus pandemic period. An age-stratified analysis showed the greatest increase among girls aged 8 to <9 years. Among boys, the CPP AIR remained low and stable (0.6–1.0 per 100,000 person-years). The female-to-male IRR was 43.0 (95% CI, 33.5–55.3). The incidence of PT in girls increased from 7.2 in 2018 to 14.6 per 100,000 person-years in 2024, with the largest increase observed among those aged 7 to <8 years.Conclusion: The incidence of CPP among Thai girls increased during the COVID-19 pandemic and remained elevated thereafter, whereas the incidence of PT increased gradually. Both trends were most pronounced in peripubertal age groups. Further studies are required to determine whether these patterns reflect pandemic-related factors or an earlier onset of puberty.