Boys in the United States are beginning to see the first signs of puberty from six months to two years earlier than previously observed, according to a new study published Saturday in Pediatrics. The study is the first to look at the onset of puberty for U.S. boys in 25 years and seems to mirror similar findings that have already been well documented in girls, points out the Wall Street Journal. The difference appears most pronounced in African-American boys, who are starting to see the first signs of puberty at 9.1 years. The average for Hispanic boys is 10 and 10.1 years for white boys, compared with the average age of 11.5 in previous studies.
The study has been a long time coming and is widely considered to be the most comprehensive attempt to measure puberty in U.S. boys. Still, experts cautioned that since previous studies were smaller or approached the issue through a different light, it might not be so easy to pinpoint how much earlier boys are developing, points out the New York Times.
The study involved 212 practitioners across the country who recorded information on genital size and the appearance of pubic hair, generally thought to be the first signs of puberty, in 4,100 boys. Part of the reason why it took so long to carry out the study, years after a similar trend was seen in girls, is that it is more difficult to identify the onset of puberty in boys, notes CNN.
The researchers did not attempt to answer the question why so the reasons behind this earlier onset of puberty remain a mystery. There are theories that it could be related to obesity rates, physical inactivity, and chemicals used in food production. “But those are just theories, and they remain unproven,” cautions the Associated Press.