Rising incidence of central precocious puberty in Thailand: a nationwide population-based study before, during, and after the COVID-19 pandemic (2018–2024)

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 personyears).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 peri-pubertal age groups.Further studies are required to determine whether these patterns reflect pandemic-related factors or an earlier onset of puberty.