‘No safe way to suntan, new NICE guidance warns.’ The BBC headline was repeated by most of the media and reflected some alarming new advice on skin cancer. The nub of it was that people should expose their arms and legs to short busts of sunlight only — long enough to get a hit of vitamin D, but not long enough to change the colour of your skin.
The guidelines aren’t based on any new evidence and don’t represent a change in thinking. Instead they are an attempt to reflect current consensus among the experts. I have to admit I was shocked that a bit of sunbathing is actually considered risky behaviour. But is it true — and how much does it raise your risk of skin cancer?
The truth is the experts don’t know. The clear evidence relates to sunburn, not tanning. A meta-analysis published in the Annals of Epidemiology in 2008 found that getting a painful sunburn every two years of your life triples your chance of a melanoma.
Another study found that if you had 26 or more ‘painful’ or ‘severe’ sunburns in your lifetime your risk would double or triple.
To put this into perspective, the lifetime risk of developing a malignant melanoma is one in 52 for men and one in 54 for women.
As a rough estimate, then, getting sunburnt frequently will raise your risk to slightly less than three in 52 (for men) or slightly less than three in 54 (for women) — slightly less, that is, because the original lifetime risk figures encompass everyone, including the perennially sunburnt, so to simply triple the figure would be to overstate the risk.
Another key factor is your skin type. People with very fair skin (classed as ‘type 1’) have double the risk of a melanoma compared to people with dark skin (‘type 6’).
When it comes to skin cancer risk and tanning, the picture is hideously complex. Many skin cancers are caused by exposure to ultraviolet light (either through sunshine or sun beds). Ultraviolet light also causes skin to darken. So a tan is evidence of exposure to a carcinogen — it is the skin ‘trying to protect itself’. But that’s a good thing, too: a tan will protect against future exposure to UV. That is why people with naturally dark skin are at lower risk. There is some evidence that outdoor workers, who spend a lifetime in the sun, are at lower risk too.
Mark Elwood, professor of cancer epidemiology at the University of Auckland, explained:
Epidemiological evidence shows that ‘intermittent sun exposure (from holidays, etc) is more of a risk factor for most melanoma than continuous sun exposure (from long-term outdoor employment): maybe in the latter situation, the protective mechanisms outweigh the initial carcinogenic dose.
He stressed that, for most people, these ‘protective mechanisms’ will not apply, and the NICE guidance is ‘probably a reasonable, if over-simplified, statement’.