The girls are not alone in puberty. According to the survey, boys are also published in the medical journal JAMA Pediatrics. The body mass index of children in children can play a role.
The researchers reviewed health records at schools and assessed trends in height and growth for 4090 boys born in Sweden between 1947 and 1996. The boys born later in this 50-year period previously suffered puberty. For every decade born later, boys reached the highest altitude rate or PHV, a puberty study mark, 1.5 months earlier.
The age at PHV was becoming increasingly younger for boys who were born later, from about 14.2 years in 1947 to 13.7 years in 1996.
"It's a big difference … this is a secondary school compared to high school," said Dr. Breuner was not involved in the study.
Part of the previous puberty trend can be attributed to an increase in BMI in childhood over time, a study found. The weight gain in childhood, based on the calculation of the body weight index at the age of 8 years, was associated with the previous puberty time in boys, but did not explain the overall picture. (Body mass index is the weight of a person in kilograms divided by a square of height in meters. For children and teenagers, BMI is age-related and gender-specific.)
Even after adjusting the body mass index in childhood, researchers have seen that PHV's age was 1.2 months earlier for every decade born later.
Other factors of the previous puberty period could be diet, a socio-economic environment, or exposure to hormone-depleting chemicals, researchers said, but did not directly evaluate them.
Among the limitations of the study: The participants were a relatively homogeneous group of white Swedish boys whose body mass index ranged from 12.3 to 29.3 – lower than the range for boys in the United States.
These findings can only be "carefully extrapolated to a more difficult and more heterogeneous population of adolescents from the US", Dr. Vanessa Curtis of the University of Iowa and dr. David Allen from the University of Wisconsin.
The study has limitations
This is not the first study to discover the early onset of puberty in boys. A study in 2012 showed that boys in the United States developed sexually six months to two years earlier than medical textbooks say. However, in this study, the size of genitals and the production of sperm were used as puberty, but not for PHV.
Whilst puberty in girls is usually indicated by the age at which it first begins with menstruation, objective measurements for puberty in boys have not been found in studies. PHV indicates the age of the greatest growth growth, which usually occurs two years after puberty in boys. In a previous study, researchers estimated PHV as a puberty marker.
"For boys, there is no reliable appropriate marker for puberty, and therefore studies on trends at puberty among boys are rare," said Maria Bygdell, MD, Claes Ohlsson and dr. Jenny Kindblom from the University of Gothenburg in Sweden. .
In addition PHV may not be accurate measurements, as researchers were unable to measure secondary sexual characteristics, such as changes in voice or hair growth, to confirm the onset of puberty. PHV was also unable to measure whether boys had reached sexual maturity earlier.
Researchers did not look at trends since 1996, but since then, teenagers have had greater exposure to device screen times and had more mental health problems to be considered in future studies, Breuner said.
However, these findings can still be managed by pediatricians who may need to be "more willing to discuss" things such as normal physical changes, the use of drugs and alcohol, gender and mental health "in the younger years," Breuner said.
Although the study showed that boys are the previous time for puberty, it is still not as early as in girls who are usually affected by puberty two years ago, which, according to Breuner, was already found in previous studies. Early puberty in girls was associated with an increased risk of diabetes and breast cancer.
Long-term effects on early puberty in boys are not yet known and will be important for the treatment, researchers warned.
™ & © 2019 Cable News Network, Inc., Time Warner. All rights reserved.