Skin cancer, sunscreen, and connecting the dots

There is skin cancer in my family.  My grandfather has had it, and occasionally a doctor will try to tell me that I am genetically predisposed to it because of this.  While I try to practice good sun habits, I am dubious about the “genetic predisposition” argument.  You see, my grandfather spent several years in the early 40’s hanging out in the sun in the Phillipines while monitoring Japanese aircraft activity.  He thinks that’s more responsible for his skin cancer than genes.  I do too.

Regardless, you might say, it’s a good idea to wear sunscreen right?  Of course.  Except it may not help.

As it turns out, sunscreen formulas that prevent sunburn may not be equally good at preventing cancer.  And you may not be putting enough on.  And they may have chemicals in them that actually increase your cancer risk rather than decrease it.  Huh.

I’ve talked before about making sure you connect all the dots, not just proving disjointed ideas.  We know that sunscreen prevents sunburn, and people who get sunburns are more likely to get skin cancer.  The troubling part is that there is no proof that people who wear sunscreen get less skin cancer.  It’s tempting to jump from A to C, but you have to remember things can go wonky when you don’t remember the stop at B.

Regardless of the data, sunburns are painful, and I’m still very Irish, so I would recommend sunscreen in general…but lets not oversell the good it might be doing.

Circumventing the Middle Man

Well, my post on justifiable skepticism (Paranoia is just good sense if people actually are out to get you) certainly was the big winner for traffic/comments this week.  I was happy to see that…I had a lot of fun putting that graph together and thought the outcomes were pretty striking.  Thanks to Maggie’s Farm for linking to it.

It was my post on food deserts however, that got me the most IRL comments.  Both my mother and my brother commented on it, and not terrifically positively.  In retrospect, I wasn’t very clear about the points I was trying to make, though to be fair I had spent a lot of the day on an airplane.

My issue with food desert research, or any similar research, is that what we’re really talking about is a proposed proximate cause to a larger issue: obesity.  In my experience, just having people tell you why they think something’s happening, isn’t good enough to prove that’s the actual reason.  Thus my quibble with much of the theorizing about obesity problems….you have to make sure that what you’re theorizing is the cause is actually the cause (or one of the causes) before you start dumping money in to it.  You cannot make the middle man the holy grail if you haven’t established that it’s really a cause.

Unfortunately, people love to jump on good ideas before truly establishing this link.

Example:  A few years ago, it was discovered that 22% of school children were eating vending machine food.  This school had an obesity problem, the food in the vending machines was unhealthy, so a push began to remove vending machines from schools.  Schools balked, as they make money from vending machines, but the well being of children came first…..until of course this study came out proving that reducing access to vending machines didn’t actually effect obesity rates.   Oops.

It’s really a simple logic exercise…proving that kids are (a) obese and (b) eating from vending machines does  not actually prove that getting rid of (b) will reduce (a).

That’s why I liked the research in to the difference food deserts make in obesity.  It’s a question that needs to be asked more often when trying to address a large issue:  are we sure that the issue we’re trying to address will actually help the issue we were concerned about it the first place???


If you haven’t established that it will, then be careful with how you proceed.  Addressing food deserts (or vending machines or whatever) is  a means to an end, and you shouldn’t confuse it with the end itself…unless you have really good data backing you up.