# Trends in central precocious puberty incidence in Japan during the COVID-19 pandemic

## TL;DR

This study shows that the incidence of central precocious puberty in Japanese girls increased during the COVID-19 pandemic and remained high afterward.

## Contribution

The study provides multicenter evidence from Japan on the pandemic's impact on CPP incidence in girls.

## Key findings

- CPP incidence in girls increased significantly during the pandemic compared to pre-pandemic years.
- Elevated CPP incidence in girls persisted into the post-pandemic period.
- CPP patients consistently showed higher degrees of overweight compared to national reference values.

## Abstract

The incidence of central precocious puberty (CPP) has reportedly increased worldwide during the coronavirus disease 2019 (COVID-19) pandemic; however, multicenter data from Japan remain limited. This study aimed to evaluate temporal changes in the incidence and clinical characteristics of CPP before, during, and after the pandemic.

We conducted a multicenter retrospective observational study across four pediatric endocrinology centers in Kanagawa, Japan. Newly diagnosed CPP cases from 2018 to 2023 were categorized into three periods: pre-pandemic (2018–2019), pandemic (2020–2021), and post-pandemic (2022–2023). Incidence rate ratios (IRRs) were calculated using quasi-Poisson regression, with population size included as an offset. Clinical characteristics—including age at diagnosis, bone age, degree of overweight, and hormone profiles—were compared across periods using the Kruskal–Wallis test.

A total of 118 children (94 girls and 24 boys) were diagnosed with CPP during the study period. Among girls, CPP incidence increased significantly during the pandemic compared with the pre-pandemic period [IRR 2.47; 95% confidence interval (CI): 1.29–5.03]. In boys, incidence also increased with a statistically significant IRR; however, the estimate was accompanied by wide confidence intervals owing to the small number of cases. Elevated incidence rates in girls persisted into the post-pandemic period. No significant differences were observed across periods in age at diagnosis, degree of bone age advancement, degree of overweight, or basal and stimulated hormone levels. Nevertheless, the cohort consistently exhibited higher degrees of overweight compared with national reference values.

This multicenter study demonstrates a significant increase in CPP incidence among girls during the COVID-19 pandemic in Japan, with sustained elevation in the post-pandemic period. Although clinical characteristics remained largely unchanged, the consistently higher degree of overweight underscores the need to consider lifestyle and environmental factors that may have been exacerbated during the pandemic. Ongoing surveillance and reevaluation of CPP diagnostic criteria may be warranted to address emerging epidemiological trends.