Indoor tanning increases the risk for melanoma and should be avoided, according to investigators of a new case–control study from the state of Minnesota.
The study provides “strong evidence” that indoor tanning is a risk factor for melanoma, said lead author DeAnn Lazovich, PhD, associate professor of epidemiology and community health in the School of Public Health and Masonic Cancer Center at the University of Minnesota in Minneapolis. Here are the details from a report in MedScape:
In a variety of other work on the subject to date, including a 2006 report from the World Health Organization’s International Agency for Research on Cancer (IARC), a history of indoor tanning has been found to be only “weakly associated” with melanoma, Dr. Lazovich and colleagues report in their study published online May 26 in Cancer Epidemiology, Biomarkers & Prevention.
However, the IARC recently declared tanning devices to be carcinogenic.
In the new study, more than 90% of the participants were white and more than three quarters were very fair or fair skinned. A majority (62.9%) of the 1167 people who had melanoma and about half (51.1%) of the 1101 control subjects who did not have melanoma had tanned indoors at some point in their lives.
Just how much the risk for melanoma is increased by tanning depends on the device used and the amount of tanning undergone, said Dr. Lazovich, who spoke at a press teleconference held by the American Association for Cancer Research.
The melanoma risk was especially pronounced among users of ultraviolet (UV)B-enhanced devices, who had a 2-fold increase (adjusted odds ratio [OR], 2.86; 95% CI, 2.03 – 4.03), and users of primarily UVA-emitting devices, who had a 4-fold increase (adjusted OR, 4.44; 95% CI, 2.45 – 8.02).
“No device is safe,” said Dr. Lazovich, dispelling the belief that UVB devices are not carcinogenic. In general, melanoma risk increased with use, whether it was measured in hours, sessions, or years.
For instance, 1 to 9 hours of lifetime tanning resulted in a 46% increased risk (adjusted OR, 1.46; 95% CI, 1.15 – 1.85). But 50 or more hours resulted in a 3-fold increased risk (adjusted OR, 3.18; 95% CI, 2.28 – 4.43).
This study is the largest of its kind to date and “advances what we already knew on this subject,” said Dr. Lazovich.
Among the things the study revealed for the first time is the fact that there is a “dose-response relationship” between the amount of time spent indoor tanning and melanoma risk, and the fact that certain devices are riskier than others, she noted.
“It’s a very timely study,” said Allan Halpern, MD, chief of the dermatology service at Memorial Sloan-Kettering Cancer Center in New York City.
“There are more than 120,000 melanoma cases in the United States every year, and over 8,500 deaths,” said Dr. Halpern, who also spoke at the press conference.
Dr. Halpern called for the US Food and Drug Administration (FDA) to upgrade the regulatory designation of indoor tanning devices from category 1, which is “equivalent to a tongue depressor.” Dr. Halpern said that the agency is aware of the dangers of indoor tanning and has just issued a video on the subject. The FDA says that “any UV-emitting device should be avoided.”
The study should be used to educate teens and their parents, said Electra Paskett, PhD, associate director for population sciences at the Ohio State University Comprehensive Cancer Center in Columbus.
“A large proportion of indoor tanning bed users are teens,” she reported at the press conference. “We have to change the social norm,” she said about the widespread use of tanning among young people, likening the public health challenge to that of decreasing smoking and obesity.
“The study strengthens our hand with patients,” said Dr. Halpern. But he also admitted that any education effort is up against the “aesthetics of a tan,” which is coveted in youth culture.
He especially praised one dimension of the study: the inclusion of data on participants’ exposure to sunlight. “Industry always says that [tanning bed users] also go to the beach,” said Dr. Halpern.
However, in the study, lifetime sun exposure (high, medium, and low), including that from outdoor activities and jobs, was not associated with increased risk.
Industry Group Criticizes Study
The indoor tanning industry is a big business, note Dr. Lazovich and her coauthors.
According to the authors, a reported 30 million Americans visit indoor tanning salons each year and, in data from 116 American cities, the average number of tanning salons exceeds the average number of Starbucks or McDonalds.
An industry group criticized the study, calling it “reverse engineered,” and criticized Dr. Lazovich, calling her an “advocate” because of her past involvement with public health projects related to possible melanoma risk and indoor tanning.
“This study was designed and executed by an advocate, not a neutral party, and the advocate failed to properly disclose that she is not a neutral party,” said Joseph Levy, vice president of the International Smart Tan Network on the organization’s Web site blog.
“I am not an advocate, I am a cancer researcher,” said Dr. Lazovich during the press conference, adding that the study had grant support from the National Cancer Institute and the American Cancer Society.
The industry group also criticized the choice to study Minnesotans, calling them a “homogenous” group.
Dr. Lazovich defended the study sample, in which 98% of cases and 96% of controls were white, saying that it was “entirely appropriate to study those people most at risk.”
She also acknowledged that there “clearly was a genetic predisposition [for melanoma] among the participants.”
However, the study accounted for that by adjusting the odd ratios for the known risk factors for melanoma, she added.
The factors include skin color, freckles, moles, family history of melanoma, routine sun exposure, outdoor activity sun exposure, outdoor job exposure, mean sunscreen use, and number of lifetime painful sunbur
The International Smart Tan Network also cited “statistical irregularities” in the study.
The study says that 51% of the control group reported indoor tanning in the past. This seems very high, suggested the International Smart Tan Network. “Only an estimated 10% of the adult population in Minnesota utilizes indoor tanning facilities,” according to the organization’s blog, which calls the statistical variance between the 2 figures “so unlikely as to almost be impossible.”
The study authors report that control subjects were randomly selected from the Minnesota state driver’s license list (which includes people with state identification cards) and frequency-matched to cases in a 1:1 ratio on age (between 25 and 59 years) and sex.
The authors also address the high percentage of control group members who had formerly tanned or who currently tan.
“Although the prevalence of indoor tanning among participating controls (51.1%) is high compared with most other reports, we do not think this is due to differential selection of indoor tanners into the study,” they write.
“In a 2002 Minnesota statewide survey of adults, we found that overall, 36.3% of respondents reported indoor tanning use; prevalence was higher (42%) in the sample with the same age range as the current study,” they add.