Unhealthful News 173 – Believable information about nearsightedness (and why)

I need a little positivity in my life today, so I am going to write it.  Perhaps the most interesting health news story of the week was not in the news, but was an op-ed in the New York Times that argued that spending time out in the sun is the way to prevent a child from becoming nearsighted.  The authors make a good case and it seems convincing.  It is kind of interesting why it is convincing.

The authors clearly demonstrate that they are engaged in good scientific reasoning.  This is not a case of a reporter blindly transcribing something he does not understand.  (I should also mention that the authors are credentialed experts, but frankly that does not impress me.  People with those credentials write a lot of garbage too.)  They start with the observation that nearsightedness has increased dramatically in Americans over 40 years.  But particularly insightful is that they observe that there is a strong genetic component, which is pretty much common knowledge, but allude to the fact that any highly nearsighted prehistoric ancestors would have been selected out of the gene pool.  Thus, our ancestors must not have been nearsighted and so there is an environmental cause alongside the genetic cause (my words, not theirs, but they make the point precisely without the jargon).

They then point out a couple of studies that support the “playing outdoors a lot as a kid protects against nearsightedness” hypothesis.  In a typical health news story, this is all you would see.  You would then be left wondering if these studies really represented the most convincing body of evidence, or if the authors just like their results.  It is still possible that these authors are pushing a pet claim that is really not so well supported.  I know little about the subject, so could not judge. 

So why do I trust them?  Well, I understand evolutionary biology and gene-environment interactions in the abstract, and they explain those parts of the story correctly, with a precision that comes from simplifying without dumbing down.  The do not explicitly point this out, but their explanation can explain the quantity of the effect that has been seen (because the changes in being outdoors are that great), unlike many such stories where something causes a large percentage increase in risk but still only accounts for a small fraction of the total.  They also respond to the common belief and most obvious alternative hypothesis, that staring at books and screens caused the problem.  The respond with a mere assertion that this is not true, which leaves the reader a bit dissatisfied.  We can hope that if they could have afforded another few hundred words they would have explained the claim a bit.  But the mere fact that they recognize what most people would think when told “nearsightedness has an environmental cause and is increasing in Americans”, and they bring it up themselves, is a good sign.  Acknowledging the best alternative hypothesis to their own does not prove they are credible, of course, but the typical practice – failing to even mention it, hoping readers will not think of it – would prove they are not.

On the critical side, they write the phrase “four times less likely”.  You know what they mean, but if you think about it, that phrase really does not work.  It does not really hurt their scientific credibility.

So, good news for my baby, who may avoid sharing my experience of having to memorize where the soap before getting into the shower (no glasses) because I cannot see it.  And it is good to see health science writing that inspires confidence, and to be able to sort out why that is.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s