Jessica* still plays with dolls; her mum still tucks her into bed every night, and brushes her hair for school in the morning. Jessica is nine years old – a little girl – but every month Jessica bleeds just like a woman.

 

She has breasts, too, while all her friends are as flat-chested as a boy. But although Jessica is different from her friends, she is not all that different. Throughout the western world nine year old girls are entering puberty and getting their periods. It is common enough that nine is within the range of “normal”.

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Between the middle of the nineteenth century and the middle of the twentieth, the average age of menarche (the commencement of menstruation) had fallen from 17 years to 13 years. The cause of this has been attributed to less disease, plentiful calories and changes in environmental conditions. The age of sexual maturation in girls has varied throughout our history: “humans, evolving in hunter-gatherer societies, developed the ability to reproduce at younger ages in response to plentiful calories.”1

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While the average age of menarche hasn’t fallen much more – among US Caucasian girls it is currently 12.6 years and among African-American girls 12.1 years – today, girls as young as nine starting their periods is common, and in her comprehensive review of early puberty in US girls, Dr Sandra Steingraber says that “the onset of puberty itself, as measured by the appearance of breasts and pubic hair, shows signs of a more dramatic ongoing decline for both African-American and Caucasian girls.”1

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In 1997, research published in the journal Pediatrics found that at the age of three years, 1% of Caucasian American girls and 3% of African-American girls had started breast and/or pubic hair development.2 By the age of eight this had increased to almost 15% and 48% respectively.

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In 2010, Dr Frank Biro and colleagues found that there had been a further significant increase in Caucasian girls who had started breast development at the age of eight although there was little change in the proportion of African-American girls with breast development.3

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The falling age of puberty in girls is not just about our daughters growing up faster; early puberty is associated with significant physical and psycho-social risks and we need to understand why it is happening and what we can do about it.

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The Risks

Those who reach puberty and sexual maturity earlier:

• suffer more psychosocial and health problems such as anxiety, depression, eating disorders and adjustment disorders, and are more likely to attempt suicide;

• are more prone to early drug abuse, cigarette smoking and alcohol use;

• are more likely to have earlier sexual intercourse and are at a higher risk for teenage pregnancy;

• have an higher risk of breast cancer;

• have a higher risk of polycystic ovary syndrome. 1

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Our media regularly report on this country’s high rates of teen pregnancy and substance abuse among young women, in particular binge drinking, and the increased risk of breast cancer is a major public health concern in a country in which 2600 women are diagnosed every year and 600 women die from the disease.

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Steingraber writes that “menarche before age 12… raises breast cancer risk by 50 percent compared to menarche at 16. Conversely, for each year menarche is delayed, the risk of breast cancer declines by 5 to 20 percent.”1 Early menarche may also increase the risk of death from breast cancer.

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In addition, “early [breast development] – which is sometimes, but not always, coupled with early menarche – seems to influence breast cancer risk in and of itself. The tempo of puberty may also affect later breast cancer risk: a long period between breast budding and first ovulation creates a wide ‘estrogen window’ that is thought to be favorable to the future development of breast cancer… Girls who enter puberty with breast budding as the presenting event may be more likely to develop breast cancer in later life than girls whose puberties manifest with pubic hair.”1

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Why is it Happening?     

Although improved diet may have been responsible for the drop in age at menarche between the 19th and mid 20th centuries, the causes have become far more complex since the 1960s. For girls, environment from point of conception onwards influences the timing of puberty, and the process is inherently susceptible to disruption. Risk factors for early puberty include:

• low birth weight and premature birth;

• being overweight or obese; and

• environmental exposures to endocrine-disrupting chemicals.

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Other factors suspected of being risk factors include:

• formula feeding in infancy;

• physical inactivity;

• psycho-social stressors, including father absence and family dysfunction; and

• television viewing and media use.

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It is clear that all of these known and suspected factors are essentially to do with our lifestyles and environmental exposures to chemicals. Considering these factors, it would seem that for some girls early puberty is inescapable. There is also a complex interplay among these risk factors with such things as formula feeding, inactivity, and television viewing and media use contributing to obesity.

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Environmental Oestrogens

Numerous studies have linked early sexual maturity in animals and humans to exposure to oestrogenic or endocrine disrupting chemicals (EDCs) such as bisphenol A, phthalates, parabens and a wide range of pesticides and other industrial chemicals. In one study, scientists found that girls with the highest pre-natal exposures to Polychlorinated Biphenyls (PCBs) and DDE hit puberty eleven months earlier than girls with lower exposures.4

Sandra Steingraber writes that “recent studies demonstrate the exquisite sensitivity of children to sex hormones even during the quiescent period between [infancy] and adolescent puberty.” She goes on to say that “prepubertal girls are highly sensitive to sex hormone exposures, which may influence the timing of pubertal maturation.”

 

Her report then details numerous studies describing early sexual development following accidental exposures to EDCs and pubertal development in response to low-level background exposure to EDCs, and hormones in meat and milk in the US.

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What Can We Do?

First and foremost we need more information. We need to understand more about puberty and the internal mechanisms which control it. Dr Steingraber says we need to understand more about how chemical exposure during pregnancy may influence the process, what role breast milk plays in the endocrine system and the role of EDCs during childhood.

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Critcally, Dr Steingraber says “much chemical testing remains to be done. Currently, chemicals are not tested for their ability to disrupt the endocrine system before they are allowed into the marketplace.”

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We need our governments to take action to lower the body burden of EDCs, including phasing out chemicals such as bisphenol A and phthalates.

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In terms of what we can already do, tackling the childhood obesity problem is important. We need to increase rates of breast-feeding, the lack of which is associated with childhood and adolescent obesity, and we need to improve childhood diets, raise physical activity levels and reduce the hours that children spend in front of TVs and computers.

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Finally, Dr Steingraber points out that “early puberty in girls is not a trend that will be reversed by single actions by single-purpose agencies. It is a multi-causal threat to the well-being of girls and women that ultimately requires a comprehensive, integrated, unified response.”

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* Jessica is not a real girl but she could be one of many girls facing puberty far too early for her emotional and social development.

 

1 Steingraber, S, 2007: The Falling Age of Puberty in U.S. Girls, Breast Cancer Fund, US

2 Herman-Giddens, ME, et al., 1997: Pediatrics, 99(4): 505-512, 1997.

3 Biro, F, et al., 2010: Pediatrics Volume 126, Number 3, September 2010

4 Boyce, N, 1997: New Scientist, August 2, 1997, pg. 5.

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Copyright © 2012, Sue Claridge