Evidence? (Your chart merely shows correlation, not causation.)
Powers &8^]
There is no hard evidence of this, but it is a little more than just a “correlation.”
Chronically sun-exposed individuals have a neutral or diminished risk for melanoma.
Intermittently high-exposed individuals have a somewhat higher risk for melanoma.
If it were the sun (UV) causing melanoma, this would not be the case.
If it were sunscreen, it would be.
If it were getting sunburned that causes melanoma, use of sunscreen would diminish the risk.
No one has posted a link to the column yet?
I believe the increase in skin cancer is caused by the increased use of cell phones. I mean, look at the charts. Cell phones cause cancer. That and the increased use of air bags in autos.
Over a million mummified bodies found in Egypt. I don’t know what most people call that, but I call it data!
I thought it was caused by gluten and vaccinations.
It’s more complicated than this. For instance, chronic sun exposure has been shown to double the risk of getting one type of melanoma (lentigo maligna melanoma).
Add in the heightened risk of other skin cancers (squamous cell carcinoma and basal cell carcinoma) and chronic overexposure to sun (especially without sunscreen protection) is not a good idea (even if you avoid skin cancer, the damage from lots of sun over time prematurely ages you and does not contribute to a flattering appearance).
Not necessarily. The primary culprit is thinking you’re protected when you are not. If you start applying sunscreen and think that will protect you for 6 hours, but it absorbs or sweats off in 30 minutes, and you don’t keep applying more, you’re going to get the sunburn exposure and going to get it more frequently because you are taking more opportunities to get in the sun/more exposure when you do get in the sun.
No. It’s caused by Youtube Kitty Cat videos. The data proves it!
Of course it’s more complicated. If it weren’t it wouldn’t be controversial. But it is controversial, and Cecil’s column makes the issue appear way more black and white than it is according to the available studies.
You cite a “for instance” wrt to UV and lentigo maligna melanoma as if this is one of many examples proving a relationship between UV and melanoma. LMM is pretty much the only example, and in any case this was a limited study done by some derm residents using some generous extrapolations (what state you live in determines your UV exposure) and applies to that very specific subtype of melanoma which accounts for about 15% of all melanomas. (And, I think, there is broad agreement that LMM’s precurson, LM, is UV damage-related.)
This study rose to the level of a Poster at a dermatology meeting. That doesn’t mean it’s wrong, but neither is it earth shattering.
Finally, you sort of forgot this line from your cite:
"Overall, women and men born in an area of high UV index faced a 37 percent higher risk of LMM and a much lower relative risk of other melanoma subtypes, Dr. Linos says. "
Dermatologists have it drilled into them as gospel that UV causes melanoma. That’s just plain wrong. UV actinic damage causes skin cancers such as basal and squamous cell, and increases the relative risk of lentigo maligna subtype of melanoma on the order of 1.5 or so. The discussion of lentigo maligna is beyond the scope of this post, but precisely because it is in sun exposed areas and has only a 5% or so transformation to “melanoma,” it sort of sits in its own category.
And 85% of melanomas probably have nothing to do with chronic UV exposure. To date the only available literature supports no such contention, since for chronically UV-exposed skin, the effect seems to be protective.
I think that in this post you forgot to emphasize the following:
“There is no doubt that intermittent, intense sun exposure - the kind that frequently leads to sunburn, for example, on tropical vacations - is associated with the development of many melanomas”
Yes - chronic, lower level sun exposure doesn’t pose the same melanoma risk - but it does put people at markedly higher risk of other skin cancers and prematurely ages the skin.
Physicians need to do their part to explode myths about skin cancer - including pervasive ones that suggest that skin cancer is not related to sun exposure, and that sunscreen is harmful.
I have already presented cites showing some data that intermittent exposure to sun is associated with a higher risk of melanoma.
But you are missing the whole point!
It’s not a question of whether or not the intermittently exposed have a higher incidence (and fwiw, the notion that those are the folks who got sunburned is an assumption, since the chronically exposed could just as easily get burned along the way).
It’s a question of causality, not simply concluding post hoc ergo propter hoc.
If UV caused melanomas, we’d see a high incidence of melanoma in people exposed to a lot of UV. If sun screen causes melanoma, we’d see a high incidence of melanoma in people using a lot of sun screen. If UV increases LMM and is protective against the 85% of other melanomas, what kind of evidence is that sun exposure is net harmful?
I have no idea what causes melanoma. But there is no more evidence that it is the sun’s UV than that it is some other factor such as sun screen. And the fact that chronic exposure to UV is protective should make the knee-jerk association with UV fail the sniff test for an assumption of causation.
Beyond that, instead of reading a Snopes opinion about an article, why not read the original publication? It’s here and it basically says women who don’t get as much sun have excess mortality.
“The mortality rate amongst avoiders of sun exposure was approximately twofold higher compared with the highest sun exposure group, resulting in excess mortality with a population attributable risk of 3%.”
The irony, of course, is that the reason they had the 20-year data to look at in the first place was because of the sun/melanoma panic leading to the MISS study. Now that’s irony!
Physicians should be all about exploding myths and relaying instead what the data show. For melanoma it’s a fascinating nest and I recommend sticking to original literature since the Sun=Danger myth is so friggingly and pervasively ingrained that nearly every lay author and frankly a great many medical authors take it as a default position.
Even worse, the available data show that avoiding the sun may be a greater risk than not avoiding it, melanoma be damned.
In the old days a Cecil column would have tackled and analyzed the fine points. This one doesn’t. It just spouts the superficial assumptions.
One other quick point: Be careful not to conflate “melanoma” with “skin cancer.” Sure; most melanomas start in the skin. But no reasonable student of the topic thinks ordinary skin cancers (basal and squamous, e.g.) are unrelated to UV exposure. Neither are they in the same league as melanoma for lethality.
At issue for me are two points:
- Is being in the sun overall beneficial or harmful?
- Is UV exposure the cause of melanoma?
See above.
If instead, you just make a point that “sun causes skin cancer,” you have not given a patient enough information to decide whether or not to avoid the sun. In fact, all you’ve done is leave an impression that one should stay out of the sun. That impression has been left with many of the masses, who are slathering up with sunscreen or staying inside.
Should the turn to the Straight Dope column on “skin cancer” they aren’t going to leave with the straight dope, and will instead be just as ignorant about the data as when they started.
Another aspect to changing rates that Cecil only hints at - rapid (from an evolutionary perspective) changes in where populations live. Skin pigmentation adaptations to irradiance levels take many generations but we have moved around lots over the past centuries with some dark skinned people living in low intensity areas and paler people living in higher irradiance locations. IOW, there is a geographic and lifestyle mismatch between location skin pigment characteristics.
See here (pdf) for a discussion.
Talk about missing the point.
It’s not a matter of “stay indoors, don’t get exercise and have low vitamin D levels” versus “enjoy all the sun and tanning bed exposure you want”. Based on the evidence we have, there’s ample reason to employ moderation.
We have excellent evidence that skin cancer causation is related to degree of sun exposure. The epidemiology is at least as good as that showing smoking is related to various cancers.
Any physician who tells or implies to patients that using sunscreen and moderating their sun exposure is likely to have an equivalent impact on their health as getting chronically tanned/sunburned is doing a severe disservice to them. It is clear that skin cancer risk overall is tied to lots of sun exposure. This is not a he-said-she-said matter (remember, the skin cancers that are non-controversially tied to sun exposure (squamous cell and basal cell carcinoma) are way way more common than melanoma).
There’s a lot of crankery out there that suggests sunscreen is somehow toxic and part of a plot by Big Pharma (or at least Big Coppertone) to cause cancer. It has been aided and abetted (sometimes unwittingly) by otherwise knowledgeable physicians (here’s looking at you, Bernard Ackerman).
Physicians ought to be about opposing crankery with good evidence, not enabling dangerous behavior.
Regarding hype about sunscreen harm - it runs the gamut from “respectable” sources like Dr. Oz, all the way into the deeply crazy (Natural News).
For a science-based look at benefits and potential risks, try (surprise!) Science-Based Medicine.
I am not trying to persuade you that sunscreen is harmful.
I am pointing out that there is no more data that UV causes melanoma than that sunscreen does (wrt the 85% of non-LMM melanoma).
I’m not sure Dr Oz is a respectable source, but your mileage may vary.
Feel free to post any scientific cite related to sun exposure and melanoma if you want to help me understand the data better.
I prefer the original rather than a lay distillation.
And once again, if you conflate “melanoma” and “skin cancer” you are going to get very confused about UV and melanoma, for the reasons I mention above.
And as a last point, did you have a cite showing exposure to the sun is net dangerous? Something to offset the MISS study I set forth above?
If you don’t, in your opinion what sort of behaviour should physicians be encouraging based on evidence regarding sun exposure?
Then you need to stop making comments like this:
There is zero evidence that sunscreen causes melanoma or any other cancer. On the other hand, there is evidence that sun exposure (intermittent, strong) increases risk of melanoma in general, plus the previously described link between lentigo maligna melanoma and sun exposure.
This should not be so difficult to understand.
Melanoma (including the 85% you are stressing) is caused by sun damage from UV. Melanin is protective to melanoma. Melanin is activated by chronic sun exposure. Intermittent sun exposure leaves melanin lower, leaving greater risk for the times that the light skinned are exposed.
Sun screen blocks UV. However, sun screen needs to be applied thoroughly to cover the skin, and it has problems with (a) washing off, (b) soaking into the skin, and (c) the chemicals being physically changed by the UV to make them cease working. All three problems mean that, regardless of the SPF, sun screen needs to be reapplied frequently, at least once an hour, and needs to be applied liberally. This page discussing application says that the standard test amount is 2 mg/cm[sup]2[/sup], but many people only apply 0.5 to 1.3 mg/cm[sup]2[/sup]. That means they get less protection than the people rating the SPF expect.
This page says use 1 oz for your legs, arms, neck, and face. That’s about a palmful. I’m not sure reading that but I think it means 1 oz for each of those, as opposed to 1 oz total.
Light-skinned people with chronic sun exposure get tanned, which protects them better than light-skinned people with intermittent exposure. Tanning also protects against sunburn.
You seem to be saying that the connection between protection from sunburn associated with melanin and the protection from melanoma associated with melanin is just a coincidence, and the real culprit is sun screen use.
Another confounding factor is that UV is divided into UVA and UVB by wavelength. Roughly speaking, UVA is skin damaging UV and UVB is burning UV. Traditionally, chemical sun screens have only been concerned with stopping the burn, or blocking UVB. Mineral sunscreens (zinc oxide, titanium dioxide) block both. The FDA is proposing new guidelines to label protection for both UVB and UVA.
If sun screens have largely been concerned with only blocking UVB and not blocking UVA, but UVA is also cancer causing, then there is risk for cancer even when using sun screens. This could lead to people getting more exposure to the sun but thinking they are protected during the intermittent exposure, whereas those with chronic exposure get the additional protection of melanin. Thus, the risk pattern to melanoma that you cite with regards to the intermittent sun exposure being riskier than chronic exposure to the sun.
I read the study from your cite. That study is examining the role of vitamin D deficiency in mortality. They state:
Nowhere in the paper do they refute that claim. They also state:
I’m not sure how that is supposed to support your position that UV does not cause MM.
Another quote from the paper:
In other words, very low sun exposure is linked to more aggressive melanomas with shorter survival times. Explain again how that is the fault of sun screen.
I will point out that looks somewhat like a contradiction: low sun equals melanoma, but intermittent sun equals melanoma. However, that is balancing the risks of low vitamin D against the risks of UV exposure. They point out the characteristics of the melanomas for the two conditions tend to differ.
From the Dr Oz page decrying the chemicals in sun screen:
Even that page says 20 minutes a day is sufficient sunlight, and more is detrimental.
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Some sun is good, a lot of sun is bad.
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UV causes melanoma, but the protection of melanin means intermittent exposure leads to more cases than chronic exposure, and sun screen has not been great at limiting exposure to all bands of UV, so people think they are protected because they are protected from burns, but are getting more exposure via UVA so are at greater risk for melanoma.
Read the articles in Post 13 and let me know how you came to this conclusion based on available literature.
As to overall mortality, you are really confused. The Swedish study from the MISS data looked at overall mortality, and the raw data is that more sun exposure diminishes overall mortality, even taking into account any increase in mortality from malignant melanoma.
While I appreciate you taking time to link out to various consumer oriented cites, I’m not interested in them. If you have some literature cites you want to parse out, I’ll try to take a look at them for you.
Your notion that people with chronic exposure get tanned, and that this is what protects them, is a postulate. It may or may not be right, but there is no direct support for it.
What has happened with the UV hoopla is the broad impression by the public that one should never get tanned, and avoid the effects of UV at all costs, with heavy application of sunblock and staying out of the sun where possible. This is unsupported as a route to avoid melanoma or reduce your overall mortality.
To summarize: the available literature shows chronic sun exposure will reduce your mortality and diminish your overall chance of getting melanoma.
As with any literature, this may be wrong. But it is the current state of the science.