Based on an 8-year of age definition for precocity used by most clinicians, epidemiology studies have shown that the overall incidence of sexual precocity is estimated to be 1:5000 to 1:10,000 children. 
The condition of precocious puberty is far more common in girls than in boys with a female-to-male ratio of approximately 10:1. 
A number of factors appear to be related to early puberty. 
It is unclear why, but on average, black girls with precocious puberty seem to start puberty about a year earlier than white girls.
Occasionally, precocious puberty can be triggered by genetic mutations that affect the release of sex hormones. Most often these children have a parent or sibling with similar genetic abnormalities.
The reason here is also unclear, but children who are adopted from other countries outside the United States are 10 to 20 times more likely to develop precocious puberty.
There is an association between obesity in young girls and an increased risk of precocious puberty, though this may not be a direct link. However, obesity does not seem to be associated with early puberty in boys.
- Carel JC, Eugster EA, Rogol A, Ghizzoni L, Palmert MR, Antoniazzi F,et al.; ESPE-LWPES GnRH Analogs Consensus Conference Group. Consensus statement on the use of gonadotropin-releasing hormone analogs in children. Pediatrics. 2009;123(4):e752–62.
- Tirumuru SS, Arya P, Latthe P, Kirk J. Understanding precocious puberty in girls. Obstet Gynaecol. 2012;14(2):121-129. Doi: 10.1111/j.1744-4667.2012.00094.x.
- WebMD. Causes and consequences of early puberty. https://www.webmd.com/children/causes-symptoms?print=true. Accessed October 9, 2019.