SOURCE Girls reaching puberty increasingly early, finds US study
Obesity may be linked to finding that one in four black girls and one in 10 white girls in the US develop breasts by age seven
A US study shows that almost one in four black girls and one in 10 white girls had developed breasts by the age of seven.
The findings are the latest in a string of studies showing that girls in the US are reaching puberty sooner, with implications both for the social and emotional wellbeing of girls as well as for their physical health in later life. Early maturation has been shown to cause low self-esteem and doubts about body image, as well as greater rates of eating problems, depression and attempted suicide.
It is linked to earlier sexual experiences, and later on carries greater risks of breast cancer.
The researchers found that at the age of seven 23.4% of black girls, 14.9% of Hispanics and 10.4% of white girls had developed breasts.
At 8 those proportions had risen further to 42.9%, 30.9% and 18.3% respectively.
A similar survey completed in 1997 found the proportion of white girls who had developed breasts by seven was 5% — half of what it is today.
The proportion of black girls in that bracket has also shot up in the past decade, from 15% in 1997 to 23% today.
Studies have shown that in the 1700s girls began menstruation on average at about age 17-18, though that might be as much to do with widespread malnutrition as with other factors.
Experts point to several possible causes of the declining age of puberty.
Top of the list is obesity, as excessive body fat is understood to increase the levels of oestrogen that play a role in breast growth. One in three children
in the US are now obese or overweight, a rate that is rising despite efforts from Michelle Obama in the White House down to combat the epidemic.
Other areas of concern include environmental factors. Prime among those are chemicals known as endocrine disrupters that act on hormones to change bodily functions.
The precise role of chemicals on child development is still the subject of debate. But researchers believe that components of plastics such as bisphenol A, which has a similar structure to oestrogen, and is found in plastic bottles and in the lining of drinks cans, may be significant.
Phthalates, chemicals that disrupt the work of hormones, have also been pinpointed as possible culprits.
The study, published in the journal Pediatrics and led by a team from the Cincinnati children's hospital, was based on 1,239 girls aged six to eight. The sample was drawn from three areas across America: East Harlem in New York, Cincinnati and San Francisco.
The importance of diet and environmental factors is highlighted in the new study by region. Cincinnati had a much higher prevalence of the onset of breast development among 7 year olds (18.9%)
than either New York (15.3%) or San Francisco (11.6%).
San Francisco's relatively low ratings may have something to do with the city's emphasis on healthy eating, exercise and limited use of plastics and other harmful chemicals.