Girls now begin puberty aged 9 - links to chemicals - TIMES
Last modified: 2010-06-13 20:10:34
GROWING numbers of girls are reaching puberty before the age of 10, raising fears of increased sexual activity among a new generation of children.
Scientists believe the phenomenon could be linked to obesity or exposure to chemicals in the food chain, and is putting girls at greater long-term risk of breast cancer.
A study has revealed that breast development in a sample of 1,000 girls started at an average age of 9 years and 10 months - an entire year earlier than when a similar cohort was examined in 1991.
The research was carried out in Denmark in 2006, the latest year for which figures were available, but experts believe the trend applies to Britain and other parts of Europe. Data from America also point to the earlier onset of puberty.
Scientists warn that such young girls are ill-equipped to cope with sexual development when they are still at primary school.
"We were very surprised that there had been such a change in a period of just 15 years," said Anders Juul, head of the Department of Growth and Reproduction at the University hospital in Copenhagen, a world leader in the study of hormones and growth.
"If girls mature early, they run into teenage problems at an early age and they're more prone to diseases later on. We should be worried about this regardless of what we think the underlying reasons might be. It's a clear sign that something is affecting our children, whether it's junk food, environmental chemicals or lack of physical activity."
Hitting puberty early can mean longer exposure to oestrogen, which is a factor in breast cancer. There is also a greater risk of heart disease.
A number of artificially produced chemicals have been blamed for interfering with sexual development, notably bisphenol A, a plastic found in the lining of tin cans and babies' feeding bottles.
Juul's research team is now testing blood and urine samples from girls in the study to see if a direct link can be drawn between early sexual maturation and bisphenol A.
Another factor in puberty could be diet. Children are eating more than previous generations and growing bigger - and in many cases becoming obese.
There has been a steady lowering in the onset of puberty. In the 19th century, it was at about 15 for girls and 17 for boys.
The international standard for normal puberty in white girls was set in the 1960s at 12Å for the age when periods begin and at about 14 for boys when their voices break and their growth surges.
A more recent consensus in Britain has proved elusive. "Although we don't have clear data here, there is evidence the same thing [as in Denmark] is happening for reasons that we don't understand," said Richard Sharpe, head of the Medical Research Council's human reproductive sciences unit in Edinburgh.
"We don't know if this is the result of better nutrition or environmental factors, but it does create social problems for girls who are already living in a sexualised society."
Sharpe said boys had also been affected by the phenomenon. Choir schools have reported an increasing number of boys dropping out because their voices had broken at the age of 12 or 13.
Richard Stanhope, an expert in hormonal disorders in children who recently retired from Great Ormond Street hospital, said specialists in his field believed they were seeing more children going through early puberty.
"All the things we experience as teenagers are difficult enough to cope with, but when it happens at 10 or 11 it is much worse," he said.
"These children are also at a much higher risk of being sexually abused because it is hard for some adults to understand and behave appropriately towards them."
Girls who reach puberty early often find themselves teased at school. "I had to wear a bra at 9," said one girl, who did not want to be named. "I used to pretend to be ill to get out of changing for PE.
"The worst part was men coming on to me as though I was an adult when actually I was 11."
A study published in the journal Public Health Nutrition last Friday showed a link between high meat consumption and earlier puberty in girls.
Researchers at Brighton University found that 49% of girls who ate meat 12 times a week at the age of 7 had reached puberty by the age of 12 1/2, compared with 35% of those who ate meat four times a week or less.
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