Monthly Archives: June 2011

Unhealthful News 175 – You cannot avoid mosquitoes

Pretty insightful title, huh?

Those of us who write about public health with a libertarian bent (or what I prefer to call a humanitarian bent – we treat people as people, rather than mere biological processes, and care about what they care about) often point out that the behavioral preventive measures that the “health promotion” types favor are often not worth the costs.  But sometimes they are not even preventive.

I was just noticing the usual annual flurry of news stories about mosquitos and west nile virus (no link – I am not basing this on any particular story or claim).  Many of them offer suggestions about avoiding being exposed (lots of repellant, staying indoors at certain times of day), usually in conjunction with a warning about WNV being detected in mosquitoes in the local media market.  Some stories are about government efforts to eradicate the exposure vector with over-the-top chemical attacks on the local mosquitoes.  The problem is that it is probably impossible to avoid exposure to WNV.  Maybe I am thinking about this because I was just in northern Alberta feeding approximately 500 mosquitoes per day.  No WNV there, but if there was, I would definitely be exposed.  And during my time being outdoorsy in Texas, Minnesota, and other places, I have no doubt I have been exposed.  And so have most of you who have lived in places where it is endemic. 

At least that is my guess.  The last time I followed the science on this topic was about five years ago, and at that time no one had a good idea of what portion of the population in areas with WNV had antibodies (which proves exposure, though people without detectable antibodies may have been exposed too).  Maybe knowledge has improved since then, but I have not heard anything.  Anyway, the point is that it is a better assumption that everyone in areas with lots of WNV mosquitoes is eventually exposed than to make the usual assumption implicit in the news reports (and the public policy).

What is that assumption?  That only those people with diagnosed cases of west nile disease have been exposed.  This is absurd, but it is remarkably common among those people who are supposedly expert on infectious disease.  Think about numbers you hear, like 75% mortality rates for some exotic new disease.  What that means is that if you look at only the people who show up at a hospital because they are in critical distress from SARS, bird flu, etc., lots of them die.  Not exactly the same as what is being claimed, since thousands or millions may have gotten the infection but showed little or no symptoms.

So the precautions against WNV assume that most people who have never suffered a disease case from the virus must have not been exposed, so they should protect themselves (or the government should protect them) from exposure.  But, again, there is absolutely no basis for this assumption.  Frankly, it is kind of crazy.  It is pretty clear that, among people in endemic areas, what keeps someone from becoming a disease case is much more likely to be genetics or other personal characteristics, not the absence of exposure to the virus.

This is a case where you might choose to let the press off the hook (though it would be good if they were better at what they do) because they are being fed a steady stream of nonsense from the supposed experts.  You can avoid getting HIV by practicing safe behavior.  But if a substantial fraction of mosquitoes where you live carry WNV, it will find you (unless you can get them all to use condoms).  And as long as the experts keep up the fiction that avoiding exposure is the best way to prevent disease, we are unlikely to find a solution for the majority of people who are not willing to seal themselves up from bugs for months every year.  This naive fixation is annoying and absurd, and yet strangely true to form for official “public health” people.

Unhealthful News 174 – Many results in journals are wrong, and that’s ok

I received the following observation via twitter.  It looks like it had been RTed and perhaps MTed a few times, so I am not sure who first said it, and it does not matter.  I also do not know whether it was facetious or serious.  The suggestion was:

 Maybe we shouldn’t publish until results are replicated

The accompanying link was to a case of a researcher who fabricated data and the published papers have been withdrawn.

I can understand the frustration that causes a lot of non-scientists to complain that too much gets published that turns out to not be true.  Rarely is this because of something as blatant as fabricating data, though it is quite often for actions that ought to be considered similar, like researchers intentionally fishing for a model that gets the result they want and hiding that fact.  Sometimes, though, it is the completely honest and proper error that comes from random sampling or an unrecognized flaw in the study.  Readers want simple right answers, like they learned in high school science classes.  But science in action does not work that way.

Probably some of you immediately thought of the point I wanted to make about the above quote:  How, exactly, can anyone replicate something that has never been published?  They might stumble on the same analysis and do it themselves, but even then they would not know they had replicated something.  Why?  Because the way researchers let other researchers know that they have seen something that might be worth replicating is to publish it.  Scientific publication is primarily designed to be communication among scientific experts.

The problem is, then, when research results that, to non-experts, are barely more understandable than raw data are communicated to people who do not understand what they are:  They are just one cut at a question and might be different from the future received wisdom, or even the existing received wisdom.  And this even ignores the problem of readers not knowing how to interpret the results in a useful way, even apart from what other studies might show.

Everyone in sight is guilty here.  Researchers (and their institutions, and the journals) tout results to the press even when no one other than a few experts can really make sense or use of them.  Most health reporters do not know enough to critically assess results or put them in context, except in the way they cover politics (which is to say, treating it like a “he said, she said” game and finding someone to just assert that the result is wrong).  Science teachers create the mistaken impression that scientific results are always Truth.  And the public demands simpler answers than can really exist (though perhaps all the blame there lies with the others on the list).

As you can surmise from my writings, I think the crux of the problem is science reporters who simply do not understand science, and health researchers who …well… simply do not understand science.  But no one is going to get those groups to refrain from publishing until they know what they are doing.  And demanding replication of the errors will not help any — there is no shortage of that.

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.