Incidence and spatial trends of idiopathic central precocious puberty in France: a nationwide epidemiologic study

Introduction A large number of known or suspected endocrine disrupting chemicals (EDCs) are present ubiquitously in the environment and in consumer products, usually in trace amounts. Low doses exposures of the general population to certain EDCs are now proven in France. Early environmental exposure to EDCs could affect the development of reproductive functions: idiopathic central precocious puberty (ICPP) is a pathology increasingly studied for its possible causal link with EDCs exposure. The aim of this study was to estimate the incidence of ICPP and to describe spatial trends in France. Methods The incidence rates of ICPP were estimated using the French national health insurance information system (SNIIRAM) which provides nationwide exhaustive data on patient expenditure. Incident cases of ICPP were identified by the first refund of GnRH agonists, for girls less than 9 years and boys less than 10 years, in metropolitan France, from 2011 to 2013. Spatial distributions of these incidences were assessed by models allowing structured and/or unstructured spatial heterogeneity. Results A total of 3 519 girls were identified, corresponding to about 1 173 new cases of ICPP in girls per year. The female annual incidence during the studied period is 2.68 per 10 000 girls younger than 9 years. During the same period a total of 352 boys were identified, corresponding to about 117 new cases per year. The male annual incidence is 0.28 per 10 000 boys younger than 10 years. Spatial structured heterogeneity is observed across the country, with similar patterns for both genders. Conclusions The national incidences of ICPP among girls and boys were estimated for the first time in France. They are consistent with the results of the few available similar studies, especially the Danish nationwide study. We will discuss several hypotheses that could explain the observed spatial pattern, including suspected risk factors (environmental exposure, nutrition) and variations in medical practices.