Written by Catharine Paddock PhD
Doctors and researchers writing in the American Journal of Preventive Medicine argue it is time to push the message that UV tanning causes – as opposed to merely being associated with – skin cancer.
They note that when the US Surgeon General finally announced that smoking causes lung cancer in 1964, there was a shift in awareness and policymaking, followed by a decline in smoking and lung cancer rates.
Dr. Robert P. Dellavalle, associate professor of dermatology at the University of Colorado School of Medicine and senior author of the paper, says:
“It’s time for the Surgeon General to say the same thing about UV tanning.”
In July 2014, the acting Surgeon General Dr. Boris Lushniak announced in a Call to Action to Prevent Skin Cancer that indoor tanning is “strongly associated with increased skin cancer risk.”
In their paper, Dr. Dellavalle and colleagues explain why there is a strong case for changing “strongly associated with increased skin cancer risk” to “causes skin cancer.”
Their argument is that UV (ultraviolet) tanning meets the same criteria for being considered a cause of skin cancer as smoking does as a cause of lung cancer.
The authors say changing the words so the endorsed public message clearly says “UV tanning causes skin cancer” will save lives.
When arguing the case for showing something causes a disease, experts use a nine-point system devised in 1965 by British epidemiologist Sir Austin Bradford Hill, the pioneer of the randomized clinical trial, who with Richard Doll proved the connection between smoking and lung cancer.
UV tanning – like smoking – meets eight of the “Bradford Hill” criteria
Dr. Dellavalle and colleagues explain that both smoking and UV tanning meet eight of the nine “Bradford Hill” criteria for establishing them as causes of cancer:
- Strength: The authors argue that while the association between smoking and lung cancer is stronger (smokers are 35% more likely to get lung cancer than nonsmokers), in terms of epidemiology, the large body of evidence that shows people who use UV tanning beds have a 16% higher risk of skin cancer is also strong
- Consistency: Dr. Dellavalle and colleagues say yes – the association between UV tanning and skin cancer is consistent across all studies and is not limited to a particular group or nationality
- Specificity: The authors say yes – there is a one-to-one relationship between UV exposure and skin cancer and this has been established for some time
- Temporality: This is perhaps the most obvious of the criteria as far as UV tanning and skin cancer is concerned. The answer is yes, studies show that use of tanning beds precedes increased risk of skin cancer
- Biological gradient: With smoking the answer is yes – the more you smoke, the higher your risk of lung cancer. The authors say the same is true of UV tanning – each additional tanning bed session per year increases the risk of melanoma by 1.8%
- Plausibility: Yes, there is a clear biological explanation – UV rays from tanning beds cause changes to DNA deep inside the skin and this can cause cells to become cancerous
- Coherence: Yes, data from lab studies agree with findings from population studies – they point to similar conclusions
- Experiment: This is where there is some difficulty because just as it is clearly unethical to ask people to smoke to see if they develop lung cancer, it is unethical to ask people to use tanning beds to see if they get skin cancer. All you can do is follow the ones that already do this, which does not constitute a randomized clinical trial. Dr. Dellavalle says this is “a primary advantage for the tanning industry, which claims that there is lack of true science behind cancer-causing claims”
- Analogy: Bradford Hill said in some circumstances “it would be fair to judge by analogy.” Citing the effects of thalidomide and rubella, he said we would “surely be ready to accept slighter but similar evidence with another drug or another viral disease in pregnancy.” Dr. Dellavalle and colleagues argue this point with reference to people with skin types that burn easily – their cancer risk is higher. This is analogous to tanning as a whole – the more burned you get, the higher your risk of skin cancer.
‘Reduce UV exposure and you reduce skin cancer’
Another point that the authors make is that, in the case of most cancers, the chances of developing them are down to genetic mutations, but in the case of smoking with lung cancer and tanning with skin cancer these are preventable diseases. Dr. Dellavalle says, “reduce smoking and you reduce lung cancer; reduce UV exposure and you reduce skin cancer.”
He also points out that people are far more likely to grasp the message if you say indoor tanning causes cancer than if you say something convoluted about “association” and concludes:
“Tanning beds cause skin cancer. It is time to now more openly announce this causality.”