[psychometry]

>But the people/populations using more sunscreen are also having more skin cancer

Um, you missed the most obvious explanation (assuming that's even true): People who have an elevated risk of skin cancer (due to geographic location and/or skin type) are likely to use more sunscreen for that very reason, but despite their sunscreen use they're still at an elevated risk of cancer because sunscreen cannot eliminate all risk.

It's really no different than saying that people who are receiving more IV chemotherapy are also dying of cancer more often than people who aren't.

[gojomo]

This sort of confounder is common, but we have in the US a population that, over the decades, is (pre-exposure) no more pale/susceptible-to-burns.

The public has been bombarded for decades with the health message to avoid the sun, and a deep tan has become less fashionable. (My younger friends, especially, treat minimizing tans/exposure as an almost religious obligation.)

Sunscreens have broadened the wavelengths they block – they used to mostly skip UVA, thinking it harmless – and upped their SPF factors. (In the 1980s, I recall SPF15 as the max - now it's SPF30, SPF80, SPF100.) Sales & usage of sunscreen keep growing.

But melanoma case rates are still on a long-term rising trend. Deaths have finally improved slightly in the last few years - likely from earlier detection & better treatment.

If the population's generally the same, but slathering on far more sunscreen every decade – but cases still go up & mortality barely budges – there's little hint of effective protection.

[lotsofpulp]

> If the population's generally the same, but slathering on far more sunscreen every decade – but cases still go up & mortality barely budges – there's little hint of effective protection.

It is not so simple to come to this conclusion. You would have to establish that time spent in sun per person has not gone up, that per person use of sunscreen (good quality sunscreen) has gone up by a measurable amount, that it is being used properly, and the cancer is happening on areas where sunscreen was used. In addition, you would have to control for people living longer.

Note that the US population in less sunny and cold areas (Midwest and Northeast) has stalled for 3 decades compared to explosive growth in population in the South and West (sunny, warm areas).

[gojomo]

The shifting of population regionally, and the aging of the population, are both good points to consider for proper controls. (In Australia, a fair-skinned population in high-UV latitudes suffers melanoma rates 50% or higher than the US. Accordingly, the promotion of sun-avoidance & sunscreen is even more intense than the US. Their age-adjusted malanoma rate reporting shows the same increase, from the 1980s through 2016: https://www.canceraustralia.gov.au/affected-cancer/cancer-ty...).

But as a longtime observer of trends, I'm pretty confident: people of all ages are conspicuously, consciously avoiding the sun more than in the 60s-80s. Indoor time has risen. Our palest most-sun-sensitive subgroups haven't increased as a proportion of the population - they've shrunk, compared to darker-skinned populations with lower base rates of melanoma.

If contra my impressions, sun exposure time has gone up, that could be due to overconfidence in sunscreens, one of the effects I'm concerned about.

If sunscreens provided the protection claimed, & this drumbeat of "slather it on always!" was an effective message, shouldn't there have been some dent in melanoma rates over the decades?

Lung cancer deaths have gone down with smoking warnings & reduced sales.

Motor vehicle deaths per mile traveled have gone down with new rules & education.

Melanoma rates seem to go up no matter how much more sunscreen is touted, is sold/used, or is strengthened in SPF or formats/staying-power.

[nomel]

The majority of my family has had skin cancer (we don't tan, we burn). It's usually in places you can't put sunscreen, like eyelids, close to the lips, etc.