[oaktrout]

True in women according to that study. Also they didn't ask specifically about sun exposure avoidance, they asked things like "Do you go abroad on holiday to swim and sunbathe". People on dialysis don't go abroad and people who can't swim secondary to poor health don't go swimming abroad. A poorly designed study with too many confounders imo.

[nradov]

The point is that for individual lifestyle decisions you can't take a reductionist approach and look at individual factors in isolation. Maybe moderate sunlight exposure causes DNA damage, but so what? Does it actually reduce lifespan (or healthspan)? Probably not, or at least we don't have any reliable evidence that it does.

[oaktrout]

I agree. I think it's also reductionist to say sun avoidance increases mortality, at least based on the evidence we have.

[ineptech]

They controlled for all the big health and lifestyle confounds, as described in the abstract, it was a huge study (1/5 of the female population of southern Sweden), they tracked the subjects for 20 years. Man if that's not good enough for you I don't think anything will be.

[oaktrout]

My issue with the study wasn't study size or duration, it was the questionarre. People who go to holiday in the mountains or go swimming are probably healthier. They could have just asked about sun exposure "how many days in the past month have you spent more than 2 hours in the sun". Also, why just study women? Did their analysis not pan out when they used men?

[ineptech]

They asked four questions that all pertain to sun exposure and weighted them into a single metric. Seemed pretty reasonable to me. You may find interesting a recent article on how academia's stance on the benefits/dangers of sun exposure has changed in the past few decades, including that study specifically, how it was received, and what criticisms and accolades it's received.

https://www.outsideonline.com/health/wellness/sunscreen-sun-...

[oaktrout]

"Outside online" does not seem like an unbiased source on this issue. Asking four questions that pertain to something does not make a good measure of that something. Agree to disagree on this one.

This is coming from someone who spends a lot of time in the sun. Melanoma was never going to have much of an impact on mortality at the population level, the incidence of high grade melanoma is far too low.

[ineptech]

> This is coming from someone who spends a lot of time in the sun.

Is it coming from someone with a lot of experience evaluating the protocols of epidemiological studies? Sunlight (whether too much or too little) affects us in all sorts of poorly-understood ways; that's why it's useful to do a big correlation study instead of just examining melanomas.

[oaktrout]

"Is it coming from someone with a lot of experience evaluating the protocols of epidemiological studies?"

It is, but I prefer to not involve my own credentials as a boring appeal to authority and focus on the argument at hand. I mentioned spending time in the sun to show I have no horse in the race. I only bring up melanoma because the cohort is “Melanoma In Southern Sweden”, but I think your point is fair regarding likely multifactorial causes.

“Sunlight (whether too much or too little) affects us in all sorts of poorly-understood ways; that's why it's useful to do a big correlation study instead of just examining melanomas”

Still, if I were designing a study to measure the impact of exercise on all cause mortality, I would not have a question like “Do you frequently jog to the farmers market to pick up vegetables?”. Half of the questions ask about going on vacation, maybe we are seeing that people who have enough time to “go abroad” twice a year live longer, I would believe that. I hope this is obvious and that even someone who doesn’t have “a lot of experience evaluating” these studies can see the flaw.

The study didn’t include any men!!! A study of women only might not generalize to the whole population, especially when it comes to all cause mortality. One obvious example: men have 1.5x higher risk of dying from melanoma than women. The study excluded individuals with a history of malignant melanoma.

The no-exposure group exercised less and had lower education, and there is a large risk for residual confounding that could have likely been accounted for by using categorical variables with more than 3 options.

Further criticisms include the “no exposure group” having much more women aged 55-64 (with likely much more comorbidities). They used length to follow up time to account for this which has no place in an observational study. The study excluded women who had a history of cancer.

I appreciate the work the authors did, but remain unconvinced that it is sunlight that caused lower mortality in their study.