Yet I eagerly read Elizabeth Weil's The Incredibly Shrinking Childhood in last week's New York Times magazine. The sub-title acknowledges some uncertainty (How early is too early for puberty?) though it doesn't question the timing of puberty so much as our preferences about when it should start.
We couldn't hope for a lengthy discussion of puberty without the requisite personal antecdote kicking off the article. This one features a mother fed up with traditional medicine whose 6 year-old daughter had pubic hair. Docs say girl hadn't actually starting puberty, deal with it. Mom goes on to found The Girl Revolution blog and sell her own brand of "craptastic-free" cosmetics for tweens. So naturally Mom, her daughter then 9, seeks help from an "applied kinesiologist" who attributes the early puberty to estrogens in the environment, sugar, insulin and stress along with voicing a few unsubstantiated claims about birth-control pills. He came upon his conclusions after a physical exam that found him holding small tubes of cortisol, estrogen and sugar over the girl's body.
At least he didn't read her palm or speak of chakras.
The holistic side show aside I can now get on with the evidence. I'm surprised by how little good, comparable data there is on the timing of puberty.
1960 British study of institutionalized children finds puberty (breast buds) begins at age 11.
1997 US study of 17,000 girls finds average age of breast buds in white girls (9.96) and black girls (8.87). At age 7, 5% of white girls had breast buds.
2010 US study finds breast buds at age 7 in 23% of black girls, 15% of Hispanic girls, 10% of white girls and 2% of Asian girls.
That's pretty much the big US studies. To be fair there've been numerous smaller projects on puberty but these haven't been exclusively dedicated to timing or didn't involve larger, representative samples.
Notice the huge gap between 1960 and 1997. Guess we were too worried about gender roles, building self-esteem and ADHD.
The 1960 study?
We can thank our current concern over earlier onset of puberty to Britain circa Post- WWII. Much of what we think of as normal puberty (including its timing and phases - pubic hair, breasts, period) comes from children living in an English orphanage starting in 1948. How frightening.
Pediatrician James Tanner originally planned on studying malnutrition in these kids but ended up documenting in addition to their general growth, their sexual development and giving the world not only the modern growth chart but The Tanner Scale that professionals still use to assess pubertal stages.
So the girls started developing breasts at age 11. Remember they lived in an orphanage during war time and were considered good candidates for studying malnutrition. I haven't read Tanner's original work in decades but I have to believe these kids weren't so well off, nutritionally or otherwise. Yet we're judging today's girls and boys by these likely malnourished children. I'd be amazed if that population resembles the US population today.
Returning to the late twentieth century. In 1997 the first large-scale US study discovered breasts developing earlier. Surprise. Aghast. More research. Sure there were some smaller studies between now and then but with mixed results that were difficult to compare due to different populations (countries even) and methods. The twenty-first century found groups of professionals on panels sorting through the mish-mash of studies. There appears to be a general consensus. A somewhat consensus that breast development is starting earlier and possibly menarche.
Here's the conclusion from a 2008 review study published in Pediatrics. Examination of US puberty-timing data from 1940 to 1994 for secular trends.
A majority of the panelists agreed that data are sufficient to suggest a trend toward an earlier breast development onset and menarche in girls but not for other female pubertal markers. A minority of panelists concluded that the current data on girls' puberty timing for any marker are insufficient. Almost all panelists concluded, on the basis of few studies and reliability issues of some male puberty markers, that current data for boys are insufficient to evaluate secular trends in male pubertal development. The panel agreed that altered puberty timing should be considered an adverse effect, although the magnitude of change considered adverse was not assessed.So here's the "consensus" in plain English:
Breasts: Looks like.
Boys: Who knows?
The earlier periods. It boils down to a difference of 3 months over several decades if not longer. Average age declined from about 12.8 to 12.5 years old. It's the kind of difference that's significant when we're talking a study of 17,000. If it were a smaller study it might not turn out significant. As a mother, I know, I could use every single one of those days. I'd like to delay that first for a year or five if I could.
Some researchers doubt this recent earlier breast development is a sign of actual puberty (as in hormonal activity) and suggest it could be a result of obesity. The NY Times piece goes over the evidence nicely. Also it addresses the potential causes of early puberty, including not just usual "environmental" suspects (estrogen-disruptors, BPA - mostly non-humans studies) but also obesity and a slew of social cultural factors that have been linked to early development in humans (e.g., living with a single parent, a step-father, early life stress, a father addicted to drugs). With all the current emphasis on toxins in the environment it's easy to down play the role of these other factors.
By the way, there is considerable differences across the globe in terms of puberty onset. According to a 2006 study girls in Denmark start considerably later with breast development at 10.88 years, menarche, 13.42. In Turkey the average age for breast buds is 7.74. Speaking of ethnicity, there's quite a range of average puberty onset just within the US. Anyhow maybe it's the Danes who are the freaks. Anyone?
Please let me know if you can think of a single positive thing about having a period. Please. I love how all the This Is How You Talk to Your Daughter Puberty Handbooks entreat moms to be positive but don't specify one positive. Help!
Examination of US puberty-timing data from 1940 to 1994 for secular trends: panel findings. Euling SY, Herman-Giddens ME, Lee PA, Selevan SG, Juul A, Sørensen TI, Dunkel L, Himes JH, Teilmann G, Swan SH. Pediatrics, 2008 Feb;121 Suppl 3:S172-91. Doi: 10.1542 (FREE)