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Do I have to spell it out? The observation is that sunscreen sales and melanoma rates are correlated. That's probably true, but it doesn't tell us anything abo

Do I have to spell it out? The observation is that sunscreen sales and melanoma rates are correlated. That's probably true, but it doesn't tell us anything about causation, one way or the other. Perhaps sunscreen is ineffective against melanoma. Or perhaps melanoma rates are rising because sunscreen use causes melanoma. Or perhaps sunscreen sales are rising because melanoma rates are rising. (As someone who has just watched a close relative die of metastatic melanoma, I assure you that the experience really inspires you to wear sunscreen and go to the dermatologist. Every time I get a pimple, I have to fight the desire to visit the emergency room.) Perhaps sunscreen sales and melanoma rate would be completely unrelated, if they weren't both driven by an external cause. Perhaps they're both caused by population increases in the Sun Belt, or by other demographic changes. Perhaps sunscreen is highly effective against melanoma, but there are still lots of older patients who got all their sun in the 1940s, 50s, and 60s before sunscreen was invented, and those patients are still getting melanoma at large rates. Or perhaps sunscreen is completely ineffective, but we won't know until the people who used it as kids reach their sixties. Or perhaps sunscreen causes melanoma... but it takes more than fifty years to do so. Perhaps sunscreen causes autism! I guess that's what this article is trying to suggest. As you can see, pulling hypotheses out of one's ass is easy to do, and it's fun for the whole family. It's also uninformative. Scientific studies would be informative. I'm sure there are lots and lots and lots of published studies which address hypotheses like these. It's a pity that the article didn't cite any of those studies.

kingkongrevenge 18y ago
If you want to dismiss correlation altogether you should really just argue that all medical research and discussion is useless (which I wouldn't consider an absurd position). You can tear apart pretty much any correlation backed assertions with "what-ifs." One simply must be reasonable. If sunscreen sales clearly negatively correlated to melanoma, that would be a point worthy of consideration in this discussion, no? It is reasonable to consider this lack of correlation as a piece of evidence in support of the discussed framework. Apply your own grain of salt: this is not a scientific publication and the audience is assumed to be a reasonable person. There would be practically nothing to say in the "non-sciences" (medicine, economics, etc.) if one were not allowed to admit "circumstantial evidence."
- mechanical_fish 18y ago
  I'm not dismissing this correlation. I was even generous enough to assume that it's not being made up. (Only half of it is cited, and the citation is to a Newsweek article which has no footnotes of its own.) I'm just finished with it. It doesn't have much explanatory power. It fits a big universe of hypotheses, some of which I have outlined above. It's provocative, which is not the same thing as conclusive. But consider me provoked. I'm curious. Bring on the science. Until someone brings some more studies to the table there's really not much more to say. I'd rather spend my afternoon getting some carefully modulated sun exposure. ;)
jcl 18y ago
It seems likely, at least, that sunscreens are ineffective against melanoma. Via a link on the Slip-Slop-Slap Wikipedia page (http://en.wikipedia.org/wiki/Slip-Slop-Slap http://en.wikipedia.org/wiki/Slip-Slop-Slap): "While few epidemiologic studies have examined the relationship of sunscreen use and skin cancer, two studies suggest that sunscreens may not be effective in preventing skin cancer. A large case-control study showed higher risks of melanoma in men who used sunscreens, and a large prospective study showed a higher incidence of basal cell carcinoma in women who used sunscreens. The excess risks in the latter study persisted after multiple adjustment for differences in skin type and time spent outdoors." -- "Could Sunscreens Increase Melanoma Risk?" http://www.ajph.org/cgi/reprint/82/4/614 http://www.ajph.org/cgi/reprint/82/4/614
- mechanical_fish 18y ago
  Hooray, links to data! This is from 1992 and earlier, though. One wonders if there has been any more progress in recent years. And here is where I get to rant about my own pet peeve: Why should I be surprised that so few people know how to properly cite scientific literature? That literature is locked behind paywalls! I'm not going to even bother using PubMed on this, and it's only partly because I don't care. It's mostly because, even if I turn up a definitive set of review papers in Nature on this very topic, I won't be able to read them without paying $15 each, or whatever.
  - jcl 18y ago
    I'm not sure if you are referring to the article I quoted or to its references... but the page that I linked to let me download the article directly for free, despite a sidebar link that purportedly also allows you to purchase the article. (I was surprised, too.) I, too, wonder if there aren't more recent studies. The two studies cited were from 1985 and 1990, though; if that's the most they could come up with in 1992, it sounds like the area is sparsely researched.
    - mechanical_fish 18y ago
      The references, of course. It's hard to operate without them. Particularly when you're outside of your own field, and can't just name the various schools of thought -- and the major authors and manuscripts associated with them -- off the top of your head.

kingkongrevenge 18y ago

If you want to dismiss correlation altogether you should really just argue that all medical research and discussion is useless (which I wouldn't consider an absurd position). You can tear apart pretty much any correlation backed assertions with "what-ifs." One simply must be reasonable. If sunscreen sales clearly negatively correlated to melanoma, that would be a point worthy of consideration in this discussion, no? It is reasonable to consider this lack of correlation as a piece of evidence in support of the discussed framework. Apply your own grain of salt: this is not a scientific publication and the audience is assumed to be a reasonable person. There would be practically nothing to say in the "non-sciences" (medicine, economics, etc.) if one were not allowed to admit "circumstantial evidence."

mechanical_fish 18y ago
I'm not dismissing this correlation. I was even generous enough to assume that it's not being made up. (Only half of it is cited, and the citation is to a Newsweek article which has no footnotes of its own.) I'm just finished with it. It doesn't have much explanatory power. It fits a big universe of hypotheses, some of which I have outlined above. It's provocative, which is not the same thing as conclusive. But consider me provoked. I'm curious. Bring on the science. Until someone brings some more studies to the table there's really not much more to say. I'd rather spend my afternoon getting some carefully modulated sun exposure. ;)

jcl 18y ago

It seems likely, at least, that sunscreens are ineffective against melanoma. Via a link on the Slip-Slop-Slap Wikipedia page (http://en.wikipedia.org/wiki/Slip-Slop-Slap http://en.wikipedia.org/wiki/Slip-Slop-Slap): "While few epidemiologic studies have examined the relationship of sunscreen use and skin cancer, two studies suggest that sunscreens may not be effective in preventing skin cancer. A large case-control study showed higher risks of melanoma in men who used sunscreens, and a large prospective study showed a higher incidence of basal cell carcinoma in women who used sunscreens. The excess risks in the latter study persisted after multiple adjustment for differences in skin type and time spent outdoors." -- "Could Sunscreens Increase Melanoma Risk?" http://www.ajph.org/cgi/reprint/82/4/614 http://www.ajph.org/cgi/reprint/82/4/614

mechanical_fish 18y ago
Hooray, links to data! This is from 1992 and earlier, though. One wonders if there has been any more progress in recent years. And here is where I get to rant about my own pet peeve: Why should I be surprised that so few people know how to properly cite scientific literature? That literature is locked behind paywalls! I'm not going to even bother using PubMed on this, and it's only partly because I don't care. It's mostly because, even if I turn up a definitive set of review papers in Nature on this very topic, I won't be able to read them without paying $15 each, or whatever.
- jcl 18y ago
  I'm not sure if you are referring to the article I quoted or to its references... but the page that I linked to let me download the article directly for free, despite a sidebar link that purportedly also allows you to purchase the article. (I was surprised, too.) I, too, wonder if there aren't more recent studies. The two studies cited were from 1985 and 1990, though; if that's the most they could come up with in 1992, it sounds like the area is sparsely researched.
  - mechanical_fish 18y ago
    The references, of course. It's hard to operate without them. Particularly when you're outside of your own field, and can't just name the various schools of thought -- and the major authors and manuscripts associated with them -- off the top of your head.