A recent study on tanning beds and melanoma has been making the rounds: "Indoor Tanning and Risk of Melanoma: A Case-Control Study in a Highly Exposed Population". The WSJ, Time, NPR, and USA Today have all covered it. The big statistic that everyone is throwing around is that "people who tanned indoors had a 74% higher chance of developing melanoma than those who hadn’t." Note that the reason this paper is such a big deal is because there has never been strong evidence that using tanning beds caused melanoma.
Well, I had the great pleasure of meeting Dr. Michael Holick today, and we discussed this very paper. You can view the full text here. Let's go the actual science and see what it says.
The 74% number comes from Table 3, second row, in the last column called multivariate adjusted OR (odds ratio). You'll see a 1.74 (hence, 74% more likely), plus a confidence interval. (This interval, or error bounds, simply indicates that if you ran this experiment 100 times, 95% of the time you'd expect this value to fall between 1.42 and 2.14.) The odds ratio for hours spent in a tanning bed increases to 3.18 (218% more likely) with duration of tanning bed use.
Well, from all the media hysteria, you'd expect that tanning beds would be the primary risk factor uncovered in the study. And you'd be wrong. Flip up to Table 2 and let's take a look at the odds ratios of other factors.
What color is your hair? Redheads have an OR of 3.53 -- which means red heads are 253% more likely to get melanoma. Compare that to the 74% number associated with ever having gone to the tanning salon. And even blondes are 117% more likely (2.17 OR). Having blonde hair or red hair has more to do with your risk of melanoma than whether you've ever gone to the tanning salon.
Having very fair skin increases your chances of melanoma by a whopping 450% (5.50 OR). Fair skin is 263% more likely, and even light olive skin is more important than having gone to the tanning salon.
Moles!!! If you have a bunch of moles you're 1,281% more likely to get melanoma. Having lots of moles is nearly 20X more important than whether you've gone to a tanning salon.
Lifetime Sun Exposure
Three measure of sun exposure show that high lifetime sun exposure decreases risk of melanoma (ORs of .85, .95, and .84).
Sun burns, on the other hand, do increase your risk of melanoma, comparable to tanning salon usage.
Mean Lifetime Sunscreen Use
Get this -- THE SAME STUDY THAT CONNECTS TANNING BEDS WITH MELANOMA ALSO CONCLUDES THAT HIGHER SUNSCREEN USAGE INCREASES YOUR RISK OF MELANOMA. Medium or High mean lifetime sunscreen usage increases your chances of getting melanoma by about 30%. But somehow "Sunscreen usage causes melanoma" is a less catchy headline than "Tanning beds cause melanoma".
My point is not that there are no risks to tanning beds. My point is that the biggest risk factors for melanoma are NOT tanning bed usage and are NOT sun exposure. It's having moles. And red hair or blonde hair. And fair skin.
So how about we do some science that actually tries to understand what's going on, instead of attention-grabbing headlines that confuse and scare people.