None of the studies used to vilify indoor tanning have ever been designed to isolate and measure the effects of non-burning UV exposure. That is the problem. Most research on the risks of UV exposure comes from retrospective survey data (often self-administered surveys) – studies that cannot reliably isolate independent variables, such as assessing whether subjects sunburned repeatedly or exposed themselves responsibly. That limitation, especially as it relates to studies on sunbed use, is becoming more and more important in revealing the need for better study models.
Consider: There are many applications for sunbed use today – (1) Medical use of sunbeds to treat cosmetic skin diseases, (2) Home use of sunbeds for self-treatment of cosmetic skin diseases and suntanning, and (3) Professional sunbed salon usage of sunbeds under the supervision of a trained operator. Unfortunately, research on this topic often mixes these groups together incorrectly.
For example, a 2006 meta-analysis by the World Health Organization (WHO) alleged that sunbed usage increased the risk of melanoma 75 percent for those who start tanning before age 35. But of the 688 subjects in that meta-analysis, 344 used either home sunlamps or dermatologic sunbeds in a doctor’s office – categories that produced the greatest risk.
Subsequent meta-analyses of the data have been subject to the same complications – they use the same data sets and self-administered retrospective surveys. Organizations that have lobbied against sunbed usage have promoted these studies without acknowledging these critical distinctions or the limitations of retrospective surveys. And these limitations are acknowledged in the US Government’s own reports. The US Preventative Services Task Force’s 2012 report, “Behavioral Counseling to Prevent Skin Cancer” states:
“We found very few studies that examined the relationship between exposure to indoor tanning devices and risk for squamous cell and basal cell carcinoma, after adjusting for all important confounders. Results generally suggest no association. However, a slightly larger body of higher-quality evidence suggests that ‘regular’ or ‘early’ use of indoor tanning devices may increase the risk for developing melanoma (range OR, 1.55 to 2.3). Most of these studies used crude measures of indoor tanning exposure.
Of the four studies that found a statistically significant association between indoor tanning exposure and melanoma, only two adjusted for both skin phenotype and some measure of sun exposure, while one adjusted for skin phenotype and number of sunburns and one adjusted for only skin phenotype. These studies suggest that regular or higher frequency indoor tanning or use at a younger age may increase risk for melanoma. The one study that examined sunlamp and tanning bed exposure separately found a statistically significant trend (p=0.02) for frequent sunlamp use (≥6 times) and melanoma risk (OR, 1.54 [CI, 0.93–2.57]), but not for frequent tanning bed use (≥10 times) and melanoma risk (OR, 1.25 [CI, 0.79–1.98]). However, the study investigators stated that while no association with tanning bed use was found, sufficient lag time may not have elapsed to assess a potential effect, given the more recent use of tanning beds.”
Even the United States Surgeon General does not use the term “causes” in discussing UV exposure’s relationship with skin cancer. In fact, when asked what might be causing the recent higher number of reported incidences of skin cancer in the U.S., then-Acting Surgeon General Dr. Boris Lushniak (himself a dermatologist) said the following in a transcribed interview with the Washington Post:
Lushniak: It’s difficult to say. We’ve seen increases [in melanoma cases] – almost a tripling over the last 30 years. And of course, the question is, is it based upon ultraviolet exposure? Increased outdoor activities? The indoor tanning industry and artificial sources of ultraviolet radiation? From our perspective, the real concern is that this is an increase, and we need to do something about it.
Washington Post: But we don’t know for sure what’s causing the increase?
Lushniak: In essence, we really don’t. From the epidemiological surveillance perspective, we see the numbers increasing. But in terms of looking at specific [causes] of that, it’s still difficult to determine.”
We acknowledge that there are risks associated with overexposure to the sun and sunbeds, including skin cancer. But it’s important that we keep these risks in perspective while determining public health policy decisions. Discussion of the nuance and critical confounding factors in the research isn’t happening yet. It’s time for a balanced discussion about the risks of UV exposure from any source – sunbeds or the sun.