3 ms·

Here’s my hypothesis: it’s not total sun exposure that causes issues, it’s inconsistent sun exposure. Those of us in northern climates experience an annual cycl

by chongli 11mo ago

Here’s my hypothesis: it’s not total sun exposure that causes issues, it’s inconsistent sun exposure. Those of us in northern climates experience an annual cycle of very high and then nonexistent sun exposure. This causes our skin to stop producing melanin during the winter and then leaves us vulnerable to sunburn in the spring and summer. If we had year-round sun then our skin would consistently maintain melanin levels and we wouldn’t have sunburn. I’d love to know if there are any studies trying to answer my question.

ch4s3 11mo ago
It’s just sunburns that cause skin cancer. It’s really that simple.
- seattle_spring 11mo ago
  That's .. just not true at all.
  - ch4s3 11mo ago
    While the cause is UV exposure, sunburns drive most of the actual risk.[1] so it not technically true that skin cancer is only caused by sunburns, most melanomas come from sunburns. There’s a very linear dose response. [1] https://pmc.ncbi.nlm.nih.gov/articles/PMC2873840/ https://pmc.ncbi.nlm.nih.gov/articles/PMC2873840/
    - DANmode 11mo ago
      More accurately, “sunburn events”.
tomtomistaken 11mo ago
This, and we are staying inside most of the time, so when spring arrives, we won't have gradual exposure but exposure all at once on the first sunny weekend we decide to get some sun.
- VBprogrammer 11mo ago
  Funny story. I started doing the couch to 5k running plan a few years back in January. Come March I realised I'd actually managed to get a tan (living in the outskirts of London, UK being further north than practically all of the inhabited North Americas). Just being outside in whatever the weather consistently for 30 minutes or so every other day.
dgfl 11mo ago
This is precisely the picture that I seemed to get when looking at this in depth some time ago. Most meta-reviews highlight a correlation between _number of blistering sunburns_ and melanoma. Not between actual amount of UV exposure. You may think that they’re the same, but they’re not. In fact, the same meta-review was noticing weak anti-correlation between chronic sun exposure and melanoma, I.e. people who work outside shirtless actually have better odds than baseline. Most risk seems to come from occasional exposure to extremely strong sunlight compared to your day-to-day baseline. Practically speaking, if your skin is able to tan, absorbing as much sunlight as your environment allows for most of the year, with the intrinsic gradual build-up over spring, should be harmless if not even beneficial. Of course, this highly depends on your genetics and your location. Avoid sunbathing around the equator regardless. And if you’re physically unable to tan, as some people do, then this might not be true either. I couldn’t determine that as easily.
- ch4s3 11mo ago
  I’ve read the exact opposite of this claim in tons of papers. What are you looking at?
  - coldtea 11mo ago
    Probably ones not sponsored by the Big Sunscreen
  - dgfl 11mo ago
    For example this one: https://doi.org/10.1093/ije/dyp166 https://doi.org/10.1093/ije/dyp166 It’s a decently big meta-review. It cites studies which more or less say exactly what I said very early, e.g. https://doi.org/10.1007/BF02071515 https://doi.org/10.1007/BF02071515 I might be completely wrong, of course. I’d rather be proven wrong than stay ignorant, so please do share the studies you had in mind.

by chongli 11mo ago

ch4s3 11mo ago

It’s just sunburns that cause skin cancer. It’s really that simple.

seattle_spring 11mo ago
That's .. just not true at all.
- ch4s3 11mo ago
  While the cause is UV exposure, sunburns drive most of the actual risk.[1] so it not technically true that skin cancer is only caused by sunburns, most melanomas come from sunburns. There’s a very linear dose response. [1] https://pmc.ncbi.nlm.nih.gov/articles/PMC2873840/ https://pmc.ncbi.nlm.nih.gov/articles/PMC2873840/
  - DANmode 11mo ago
    More accurately, “sunburn events”.

tomtomistaken 11mo ago

This, and we are staying inside most of the time, so when spring arrives, we won't have gradual exposure but exposure all at once on the first sunny weekend we decide to get some sun.

VBprogrammer 11mo ago
Funny story. I started doing the couch to 5k running plan a few years back in January. Come March I realised I'd actually managed to get a tan (living in the outskirts of London, UK being further north than practically all of the inhabited North Americas). Just being outside in whatever the weather consistently for 30 minutes or so every other day.

dgfl 11mo ago

This is precisely the picture that I seemed to get when looking at this in depth some time ago. Most meta-reviews highlight a correlation between _number of blistering sunburns_ and melanoma. Not between actual amount of UV exposure. You may think that they’re the same, but they’re not. In fact, the same meta-review was noticing weak anti-correlation between chronic sun exposure and melanoma, I.e. people who work outside shirtless actually have better odds than baseline. Most risk seems to come from occasional exposure to extremely strong sunlight compared to your day-to-day baseline. Practically speaking, if your skin is able to tan, absorbing as much sunlight as your environment allows for most of the year, with the intrinsic gradual build-up over spring, should be harmless if not even beneficial. Of course, this highly depends on your genetics and your location. Avoid sunbathing around the equator regardless. And if you’re physically unable to tan, as some people do, then this might not be true either. I couldn’t determine that as easily.

ch4s3 11mo ago
I’ve read the exact opposite of this claim in tons of papers. What are you looking at?
- coldtea 11mo ago
  Probably ones not sponsored by the Big Sunscreen
- dgfl 11mo ago
  For example this one: https://doi.org/10.1093/ije/dyp166 https://doi.org/10.1093/ije/dyp166 It’s a decently big meta-review. It cites studies which more or less say exactly what I said very early, e.g. https://doi.org/10.1007/BF02071515 https://doi.org/10.1007/BF02071515 I might be completely wrong, of course. I’d rather be proven wrong than stay ignorant, so please do share the studies you had in mind.