Eco-Epidemiology and the Early Puberty Panic
Before the paper was even pre-published online the lead author of "Pubertal Assessment Method and Baseline Characteristics in a Mixed Longitudinal Study of Girls", Dr. Frank M. Biro, was giving interviews. The measured write up in The New York Times reported that "[s]ome researchers also suspect that environmental chemicals that mimic the effects of estrogen may be speeding up the clock on puberty, but that idea is unproved." Later however it quotes Dr. Brio, whose new project involves an attempt at correlating the subjects' hormone levels and chemical exposures, as saying "I think we need to think about the stuff we're exposing our bodies to and the bodies of our kids. This is a wake-up call, and I think we need to pay attention to it." From what I can see of the article it doesn't even purport to examine such an association and nothing about the data other than a crude sort of - our use of more and different chemicals may be going up (an assumption which is not assessed in the article) and onset of one prepubertal sign is going down - would even suggest such a hypothesis.
MSNBC took a far less measured approach. Whereas the NYTimes correctly reported that the study actually found no change in the onset of menses, MSNBC reported that "American girls are maturing earlier and earlier." Then it went on to write about all the possible perils of those who "go through puberty early" without disclosing that the 7 and 8 year old subjects had not in fact "gone through puberty" at all. And while MSNBC discusses the putative link between obesity and early puberty they quickly move on to a comment from Dr. Stanley Korenman (not one of the authors) who "says environmental exposure to estrogens in plastics, chemicals and foods has been going up" adding "and estrogens do stimulate breast development". All of this then prompts Dr. Biro to conclude "[u]ntil we know what the cause is, the best way to slow puberty may be to 'start living green'.
What's behind this belief that there's a simple answer to something like trends in the onset of puberty? Well, there's that whole third age of epidemiology business whereby many came to believe that changed and chronic conditions just had to be man-made. And there's also risk factor epidemiology which, if done often enough, is essentially guaranteed by the laws of probability to produce a study showing a statistically significant association between condition and chemical. Of course, as we've written before, that now 40 year old paradigm and the tool used to support it have been crumbling under the weight of erroneous predictions for the last 20 years. The problem was that causation was far more complex than most people expected and many of the tools needed to model causal networks had yet to be developed.
Enter eco-epidemiology. For a discussion of this new field you'll not find a better primer than "The Eco- in Eco-Epidemiology" and if you're really really interested and want to watch some lectures on the topic try The Yale Center for Eco-Epidemiology. For those beginning to doubt that nature is benign try the talks from "Zoonoses: Diseases from Nature". Finally, for those wanting the short version suffice it to say that causation, even for something like AIDS, is very very hard. A host of impacts from genes to culture determine who and how many will be infected. And genes shape cultures and culture may well shape genes . (h/t GNXP) Eco-epidemiology aims to deal with all of these multilayered causes.
Finally, back to the puberty panic. Our culture has changed in many ways over the last fifty years. For example resources have become more abundant. Elsewhere in nature when that happens critters exploit the opportunity by breeding sooner and more often. Why should we assume that we don't, albeit unconsciously, do the same? Eco-epidemiology aims to find all the contributors to the human condition and let the chips fall where they may.
