I've been wondering about sunscreen's effectiveness in reducing cancer risk.

The general impression I've gotten in my (admittedly brief) research on it seems: "If you know you'll be exposed for a long duration in the summer/spring, then yes, wear sunscreen. Otherwise, Vitamin D generation takes priority." (related)

I've looked around on lesswrong, and can't find any really all-encompassing informative posts about it. The most interesting comment I've seen was by Tem42, who references a study that claims that overall cancer rates are actually lower in southern states vs northern states.

Is my general impression correct enough? Or should people be lathering sunscreen all the time; or not at all?

Thanks in advance!

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If you regularly get sunburn, you should use sunscreen, because sunburn is unpleasant. Death isn't the only thing that matters. If you haven't noticed that you get sunburn or haven't thought about the possibility of using sunscreen or making simple interventions, like buying sunscreen, or putting it near sports gear as a reminder, there are great opportunities for improvement.

Whether to use sunscreen in situations where you won't get sunburn is controversial. But these situations are intermediate and it's probably less important to get them right than the extremes.

Added: maybe this sounds like trivial advice, but it's important to figure out what the typical advice actually means in terms of who it's aimed at (confer).

Great article about this topic: https://www.outsideonline.com/2380751/sunscreen-sun-exposure-skin-cancer-science

It does seem that using sunscreen doesn't offset the harms prevented by vitamin D.

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If you're worried about Vitamin D deficiency, it's quite easy to supplement. Why not do that (IF you're deficient) and wear sunscreen?

As someone who actually tries to follow dermatological recommendations for sunscreen use, it's pretty hard. You have to remember it every time you leave the house, be motivated enough to go through a tedious and bad-smelling task, cover *all* the exposed skin. If you're outside for a significant time, you have to remember to bring the sunscreen and reapply every hour. So, it's hard to believe that most people who spend time outside and wear sunscreen are actually doing it enough to avoid D exposure.

My read of the research is that the controllable risk factors for D deficiency are never going outside + poor diet + not supplementing, rather than overzealous sunscreen use.

A short answer is "Don't worry about Vitamin D unless you have a deficiency, avoiding UV damage to skin is more important". This doesn't necessarily mean sunscreen, could be taking a siesta during the peak UV times, wearing a proper hat and clothing etc. Something basic like staying out of the direct sunlight between 10am and 3pm ( more if you are in tropics or subtropics) would give you an approximate balance. If in doubt, there are plenty of UV meters on the market that would help you be more quantitative.

SSC's argument that the dermatologists' factual claims are wrong are the least of the problems. Even if the dermatologists really are experts at skin cancer, they aren't expert at the trade-offs.

On the other hand, if SSC is correct, that only eliminates one option that shminux gave. It doesn't necessarily reject the claim that you should stay out of certain sun conditions.

That was a great read.

figure out what was going on rather than desperately trying to multiply and divide all the numbers in the problem by one another.

That one hits home. I've been doing a bit of math lately, nothing too hard, just some derivatives/limits, and I've found myself spending inordinate amounts of time trying taking derivatives and do random algebra. Just generally flailing around hoping to hit the right strategy instead pausing to think first: "How should this imply that?" or "What does this suggest?" before doing rote algebra.

Well, weigh a throwaway comment by Scott against the consensus of dermatologists and skin cancer specialists.

So, social proof?

No, that's not what social proof means. I'm saying a throwaway comment by a non-expert has very little probative value. Now, I'd give it more weight if Scott were actually to write a post about this topic concluding that we should all stop wearing sunscreen, because knowing him there probably would be some serious thought and research put into that. But the post you linked to basically says "it's more complicated than you might think, but the consensus is still wear sunscreen."

That seems like a reason not to make a recommendation until someone trusted has done a proper lit review, not a reason to make an affirmative recommendation based on an old consensus with momentum behind it despite the glaringly obvious cultural and incentive problems that make the consensus likely to ignore new evidence.

But what about this? http://slatestarcodex.com/2014/05/23/ssc-gives-a-graduation-speech/

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UV meters! Thank you! Seems such an obvious idea in hindsight.

Why wonder blindly when you can quantify it. I'll look into getting one.

Or you could just look at the weather report, now that you know what to look for.

Yep. Just have to get into the habit of it.

(fixed the formatting a bit. if you want to use the markdown editor, go to your settings and check the box for that, but by default you can just hover over text and click the link button to put a link behind some text.)

I did that a couple minutes ago. Then tried to fix the formatting, and I think I then subsequently undid your formatting fixes.


Added: I fixed it again.

In the southern states, the sun feels hotter. People don't go out in the sun for a long time without sunscreen. In the northern states people think they are more fine. Consequently get more cancer. Also these results are slow to fruition because skin cancer takes a lifetime to develop.

Any sources for this?

I don't have a formal source, no.

I live in Australia. We know the sun here because it literally feels burning. I visited the northern states of america and I noticed that the sun didn't heat me up in the same way that it does in Australia. If I had to guess, this is about wavelengths of light that make it to the ground, not necessarily UV, but the IR ranges that feel a lot more like heat in the body body.

If heat keeps someone out of the sun that means less UV burn too.

Again - no source.


This source has a piece of information.

When we think about sunburn, we usually associate it with picnics and trips to the beach at the height of summer. But while it may seem like your days of dutifully donning sunscreen are still well ahead, the peak time when you're at risk for gettig a sunburn is actally... right now.

"UV rays become more intense in the spring, even before temperatures get warmer," the American Cancer Society warns. "People in some areas may get sunburned when the weather is still cool because they may not think of protecting themselves if it's not hot out."

It all has to do with the angle of the sun. According to the FDA, as the sun reaches a more direct angle, UV radiation strengthens. In the weeks preceding the summer solstice, that angle becomes more and more direct. Late spring and early summer are when UV rays are at their greatest, the CDC says.