New research in the journal Paediatrics shows obesity
is the largest predictor of earlier onset puberty in girls, which is affecting
white girls much sooner than previously reported.
The multi-institutional study strengthens a
growing body of research documenting the earlier onset of puberty in girls of
"The impact of earlier maturation in
girls has important clinical implications involving psychosocial and biologic
outcomes," said Frank Biro, MD, lead investigator and a physician in the
Division of Adolescent Medicine at Cincinnati Children's Hospital Medical Centre.
"The current study suggests clinicians may need to redefine the ages for
both early and late maturation in girls."
Girls with earlier maturation are at risk
for a multitude of challenges, including lower self-esteem, higher rates of
depression, norm-breaking behaviours and lower academic achievement. Early
maturation also results in greater risks of obesity, hypertension and several
cancers – including breast, ovarian and endometrial cancer.
The study was conducted through the Breast
Cancer and Environmental Research Program, established by the National
Institute of Environmental Health Science. Paediatrics is the journal of the
American Academy of Paediatrics.
Researchers at centres in the San Francisco
Bay Area, Cincinnati and New York City examined the ages of 1 239 girls at the
onset of breast development and the impact of body mass index and
race/ethnicity. The girls ranged in age from 6 to 8 years at enrolment and were
followed at regular intervals from 2004 to 2011. Researchers used
well-established criteria of pubertal maturation, including the five stages of
breast development known as the Tanner Breast Stages.
The girls were followed longitudinally,
which involved multiple regular visits for each girl. Researchers said this
method provided a good perspective of what happened to each girl and when it
Researchers found the respective ages at
the onset of breast development varied by race, body mass index (obesity), and
geographic location. Breast development began in white, non-Hispanic girls, at
a median age of 9.7 years, earlier than previously reported. Black girls
continue to experience breast development earlier than white girls, at a median
age of 8.8 years. The median age for Hispanic girls in the study was 9.3 years,
and 9.7 years for Asian girls.
Body mass index was a stronger predictor of
earlier puberty than race or ethnicity. Although the research team is still
working to confirm the exact environmental and physiological factors behind the
phenomenon, they conclude the earlier onset of puberty in white girls is likely
caused by greater obesity.