Why children become adults early

A recent issue of Pink magazine carried a feature on precocious puberty in a Maltese girl and discussed its associated problems, its diagnosis and treatment but no attempt was made to explain why this is an increasing phenomenon in both boys and girls.

In 1997, American researchers first reported a sharp decline in the age of puberty and, in 2003, Danish doctors at Copenhagen’s University Hospital confirmed a similar change in Europe. The last 200 years have seen a big drop in the age of puberty in the West. In the Leipzig choir, directed by J.S. Bach in the 1700s, the average age of voice break (late marker of male puberty) was about 18. Between the mid-19th and mid-20th century, the average age for female puberty dropped from 17 to under 14 in both America and northern Europe.

As nutrition and healthcare improved, the age of puberty dropped and from 1950 onwards it plateaued. In 1997, however, American researchers published a study of 17,000 girls that showed a sudden fall in the average age of puberty to 9.7 years and, among Afro-Americans, girls were hitting puberty at eight. Some were getting there at six, shortly after starting school. In 2002, a second study confirmed this trend.

A Danish study published last May (the first of its kind in western Europe) showed that, between 1991 and 2006, the age of girls’ breast development had dropped from 10.8 years to 9.8 years and they were, on average, having their first periods three months earlier. Their study of Danish boys showed a drop in the age of puberty by three and a half months over the same 15-year period. A China study last year reported the lowest-ever average age for breast development, 9.2 years. Dutch and Italian studies have shown similar findings to those in Danish boys.

This phenomenon presents dramatic challenges. Children who go into early puberty are prematurely sexualised and too immature to deal with the implications, such as being more vulnerable to sexual abuse, inappropriate sexual behaviour, sexually transmitted disease and teenage pregnancy. They are physically ready for sexual reproduction but mentally totally unprepared. They are also involved in more risk-taking behaviour, such as taking drugs, binge drinking and breaking the law. Recent Australian research has found increased aggression in girls who reached puberty early.

There may be long-term health problems for women because early puberty increases exposure to oestrogen, which might at least partly explain the increased incidence of breast and ovarian cancers in the West these last several decades. British research estimates that a girl who has her period a year later than her contemporaries has five per cent less risk of breast cancer in her lifetime.

A Norwegian 37-year study of 61,000 women has shown that girls reaching puberty early are more likely to develop type 2 diabetes. Those who got their first period at 10 or 11 had a 10 per cent higher mortality rate than those who got their period four years later.

The long-term risks for men are less proven. Although early puberty in boys might be related to the increased incidence of prostate cancer in the West, this apparent increased incidence might simply be due to better diagnosis in recent years.

It is now clear the age of puberty is falling fast in developed countries but there is no consensus on why this is happening. The focus is on environmental factors. Obesity, chemical and even absent fathers have been investigated (girls living apart from their father tend to get their first period earlier).

How puberty happens remains scientifically incompletely understood. One certainty is that it doesn’t occur until children reach a critical body weight. Periods tend to cease in anorexic girls and they seldom get pregnant. In parts of the world where malnutrition is still a problem, the average of girls’ puberty remains around 16. Once a critical body mass has been reached, a hormone (Leptin) message is sent from the fatty tissues to the brain, which then sends chemical messages to the sexual organs to develop and start producing oestrogen and testosterone. Other chemical messengers have been identified which are linked to the reproductive system. They encourage appetite, which may explain why the fridge is never full enough when children hit adolescence.

The American study of 1997 first raised the spectre of a connection between weight and early puberty and a recent Danish study showed that the heavier children were at seven, the earlier they entered puberty. A British study has found that the more weight a baby girl gains in the first year of life the earlier her first period starts.

But obesity alone doesn’t fully explain the age at puberty decline.

It could also be that early puberty triggers obesity. Danish schoolgirls who were heavier than they might have been a couple of decades ago showed no difference in body mass index between those growing breasts a year earlier and those that weren’t.

Obesity is an important risk factor but doesn’t fully explain this earlier puberty trend. Danish research is now concentrating on seven different chemicals called phthalates, which are endocrine disrupting chemicals (EDCs), believed to interfere with the way hormones work in our bodies. Researchers believe EDCs either mimic sex hormones or interfere with their metabolism and may therefore influence the commencement and progression of puberty.

They also believe EDCs are involved in early breast development. This is still an unproven hypothesis but what has changed in the environment these last 15 years needs to be studied.

The debate about EDCs is very controversial, with environmentalists on one side, big business on the other, and scientists caught in the middle. It is a very difficult area of research because we are all now exposed to a mixture of EDCs in our daily life and it’s likely that this chemical cocktail is passed from mother to baby in the womb.

The adverse effects of oestrogenic pollutants have been known since the early 1990s when British research found that male river fish were becoming feminised and man-made industrial chemicals in sewage were suspected of acting as female oestrogens. Some plant-derived products, like lavender and tea-tree oils, contain significant amounts of plant oestrogens (phyto-oestrogens). In 2007, an American study described how these two skin-applied oils (in healing balms, hair-gels or soap) could grow breasts in young boys (breasts returned to normal when phyto-oestrogen application stopped).

The key EDC suspects are the phthalates added to plastics to increase their flexibility, transparency and durability. They are found in anything from cellophane to shower curtains to toys and in food and drinks packaging.

Another suspect is Bisphenol A (BPA), a component of polycarbonate found in tin can lining, children’s feeding cups and plastic bottles (including baby ones). In animal experiments, BPA acts as a weak oestrogen and accelerates puberty. Denmark, Canada and the US are recommending a ban on BPA in baby bottles and feeding cups because of concern about its potential effects on the brain, behaviour and prostate gland in foetuses, infants and young children.

American children have a particularly high exposure to EDCs because 80 per cent of American beef is still treated with growth promoters. Exposure of children to sex hormone residuals in beef could contribute to the reduced pubertal age in America. American beef produced using anabolic sex hormones has been banned in Europe since 1989.

Research continues. We know little about how the human body copes with the chemicals that have made their way into our daily life.

A Danish study on EDCs to be published next year may leave us wiser about the role they play in turning children into adults before their time.

Prof. Cilia-Vincenti, a former lecturer of disease mechanisms at London and Malta universities and a former British Health Care Trust board director and Malta health service departmental chairman, maintains a long-standing interest in the nutritional, environmental and lifestyle factors affecting health and longevity.