Something unexpected: Sunbathers live longer (2016)

What's interesting about this study in Swedish women is that if you look at the results section the high sun exposure group has the highest disposable income and most years of education. Low exposure has the lowest disposable income and least years of education. Probably because for Swedish women high sun exposure means travel which is expensive.

It's hard to say if the study measures sun exposure or the ability to stay healthy with a higher income & better education.

"Fewer non-cancer deaths" is about what I expected: getting more sun gets you more vitamin D (especially important if you live closer to the poles than to the equator, and the study was done in Sweden), but getting too much sun increases your risk of skin cancer. Since vitamin D is an important part of the body's immune system, you're less likely to catch various diseases (or, more accurately, more likely to fight them off effectively before feeling sick) if you have enough vitamin D.

I once watched a video of a medical guy giving a lecture on why people should take vitamin D supplements (he was from Minnesota, which is quite far north of the equator). He had a memorable line, "There's no such thing as flu season, there's only vitamin-D deficiency season." In the summer, he said, Minnesotans who work outside actually get enough vitamin D from skin exposed to sunlight. But in the winter, pretty much nobody in Minnesota gets enough sunlight on their skin: even if the sun is shining that day, everyone is bundled up in warm clothing!

Also, the darker your skin is, the more sun exposure you need to get enough vitamin D. So if an African and a European get the same amount of sunlight, the European's body will produce more vitamin D from it, because the African's skin has a lot more melanin. So dark-skinned people are more likely to need vitamin D supplements (whereas light-skinned people such as me are more likely to get skin cancer; there are pros and cons to having more or less melanin).

Most people, unless they live in the tropics, would probably benefit from taking vitamin D supplements during the winter. And all year long if you work indoors.

If this was truly the case we'd probably see massive differences between countries depending on latitude, no? And yet life expectancy is strongly correlated with gdp per capita.

https://ourworldindata.org/grapher/life-expectancy-vs-gdp-pe...

The abstract refers only to “sun exposure,” but it really did focus on sunbathing:

> Four predetermined questions were posed regarding sun exposure: (i) How often do you sunbathe during the summertime? (never, 1−14 times, 15−30 times, >30 times); (ii) Do you sunbathe during the winter, such as on vacation to the mountains? (no, 1−3 days, 4−10 days, >10 days); (iii) Do you use tanning beds? (never, 1−3 times per year, 4−10 times per year, >10 times per year); and (iv) Do you go abroad on vacation to swim and sunbathe? (never, once every 1–2 years, once a year, two or more times per year).

Another factor is the location of the study in Sweden. In summer the typical peak UV index in Sweden is 5 whereas in Australian summers the UV index is often 11+.

New study finds people that follow the least number of studies live the longest.

People who take time to de-stress living longer, seems entirely unsurprising.

(2016)

This feels to be strongly in the “correlation does not imply causation” bucket. Something like being in the sun means you’re outside and therefore not sedentary fits with our current understanding of health and might balance out the increase in mortality due to skin cancers