Researchers have previously established that girls have been experiencing puberty earlier over the past few decades. And now, a new study, published in the journal Pediatrics, suggests that obesity is playing a role in this trend.
Experts say that girls who begin puberty earlier are at risk for lower self-esteem, higher rates of depression and lower academic achievement. Additionally, early maturation increases risks for obesity, hypertension and several cancers, including breast, ovarian and endometrial cancer.
The study, which was conducted through the Breast Cancer and Environmental Research Program, established by the National Institute of Environmental Health Science, followed 1,239 girls aged 6 to 8 from 2004 to 2011.
Researchers at health centers in the San Francisco Bay Area, Cincinnati and New York City examined the ages at which breast development began and the impact of body mass index (BMI) and race/ethnicity. They used criteria of "pubertal maturation," including the Tanner Breast Stages, which outlines five stages of breast development.
Lead investigator Dr. Frank Biro, a physician at Cincinnati Children's Hospital Medical Center, says:
"The impact of earlier maturation in girls has important clinical implications involving psychosocial and biologic outcomes."
BMI and early maturation
The longitudinal study shows that white girls are entering puberty at younger ages than previously reported. Researchers say BMI may be a factor.
During the course of the study, the girls were followed longitudinally - meaning there were multiple regular visits - which the researchers say provides a good understanding of what happened to each girl at specific times.
The researchers found that the ages of onset of breast development varied by race, BMI and geographic location.
By race, breast development began:
- In black girls at an average age of 8.8 years
- In Hispanic girls at an average age of 9.3 years
- In Asian girls at an average age of 9.7 years, and
- In non-Hispanic white girls at an average age of 9.7 years.
The researchers note that the age of 9.7 years for white girls is earlier than previously reported.
They say that BMI served as a stronger link to early puberty than either race or ethnicity. Though the team is conducting further research to identify the specific environmental and physiological factors behind this trend, they suggest the earlier start of puberty in white girls is likely due to greater obesity.
"The current study suggests clinicians may need to redefine the ages for both early and late maturation in girls," says Dr. Biro.
In 2012, Medical News Today reported on a study suggesting that like girls, boys are reaching puberty 6 months to 2 years earlier than a few decades ago.