Puberty developing increasingly early

Childhood appears to be getting shorter and shorter for girls. A new study reveals that in the United States, the proportion of young white girls who develop signs of puberty at an early age has almost doubled since the late 1990s. The phenomenon has not been observed in black girls, although they typically reach puberty at an earlier age.

Childhood appears to be getting shorter and shorter for girls. A new study reveals that in the United States, the proportion of young white girls who develop signs of puberty at an early age has almost doubled since the late 1990s. The phenomenon has not been observed in black girls, although they typically reach puberty at an earlier age.

As part of this study, researchers monitored 1,200 American girls between 2004 and 2006. They noted that 10.4% of white seven-year-old girls had already reached the start of puberty, which is determined by the onset of breast development, a figure that is double what had been observed in 1997. A similar difference was noted among eight-year-old girls (18.3% vs. 10.5% in 1997).

No such evolution was noted among black girls, which suggests that the age of puberty onset has stabilized for that group. Hispanic girls and black girls nevertheless have a greater proportion of early puberty than white girls, namely 14.9%, 23.4% and 10.4%, respectively. And among eight-year-old girls, those figures were 30.9% (Hispanic girls), 42.9% (black girls) and 18.3% (white girls).

A combination of several factors could explain this evolution, but the two leading suspects are the obesity epidemic and exposure to chemicals present in the environment. According to one theory, excess body fat affects the levels of hormones that trigger puberty, as numerous studies have shown that girls with a higher body mass index tend to mature sooner. And then there are the chemicals in our environment (such as the infamous bisphenol A present in so many products made of rigid plastic), which could also influence the levels of hormones involved in the onset of puberty.

Early puberty could have several consequences, including an increased risk of developing breast cancer. Some studies also suggest that early development in girls may be linked with a less favourable body image, along with an increased risk of eating disorders, depression, suicide attempts and earlier sexual activity.