"The growing popularity of artificial tanning (for non medical reasons) among adolescents and young adults is cause for concern," says first author Margaret R. Karagas, PhD, a DMS epidemiologist who is associate professor of community and family medicine and associate director of the Center for Environmental Health Sciences at Dartmouth.
She published the findings in the Feb. 6 issue of the Journal of the National Cancer Institute with co-authors Stephen Spencer, MD, DMS professor of medicine and of surgery; Martin Weinstock, MD, PhD, Brown Medical School professor of dermatology and epidemiology, and Dartmouth researchers Virginia Stannard, RN, MEd, Leila Mott, MS, and Mary Jo Slattery, RN, MS.
Millions of Americans visit tanning salons each year, and the majority of users are adolescents or young adult women. Although some studies suggest that tanning device use might contribute to the incidence of melanoma, an aggressive form of skin cancer, results to date are not definitive.
Few studies have looked at the association between tanning devices and the more prevalent skin cancers: basal cell and squamous cell carcinoma, which together are the most common malignancy in humans. Karagas and colleagues have previously reported an increasing trend in the incidence rates of these cancers.
"We know that ultraviolet radiation (UVR) exposure that comes from the sun is a major cause of skin cancer. Tanning lamps mimic sunlight and provide such an intense, concentrated dose of UVR, we would predict that people who use these devices may get skin cancers," Karagas said. "Also, tanning lamp users often get a burn like a sunburn, and sunburns are linked to the risk of all three skin cancers: basal cell, squamous cell and melanoma."
The Dartmouth study was a statewide collaboration with dermatologists that involved almost 1,500 residents of New Hampshire between the ages of 25 and 74. The investigators interviewed people about their past tanning device usage, history of sun exposure, tendency for sunburn, previous radiation treatment and smoking history. Participants included more than 800 men and women who were newly diagnosed with the two skin cancers: 603 with basal cell carcinoma and 293 who with squamous cell carcinoma; and 540 who were free of skin cancer.
Overall, people who reported any use of tanning lamps were 2.5 times more likely to develop squamous cell carcinoma and 1.5 times more likely to develop basal cell carcinoma than those who did not use tanning lamps, the team found. Other factors, including past sunburns, sunbathing and sun exposure, did not appear to explain the excess risk of either type of skin cancer associated with tanning lamps.
Tanning device use was most frequently reported by women younger than 50 in the study. Moreover, the risk of basal cell and squamous cell carcinoma increased with younger age at use (20% and 10%, respectively, for each decade younger participants were when they began using a tanning device).
This finding also makes sense, explains Karagas. "Sun exposure early in life also appears to play an important role in risk of skin cancer." The authors call for "an appropriate public health response," particularly considering the popularity of tanning among the young -- one prior study of high schoolers found that at least half of the girls reported using a commercial tanning bed at least four times in the past year. Suggestions from the public health and medical community have included restricting tanning device use in minors and requiring written informed consent from adults.
The use of tanning devices may contribute to the incidence rates of basal cell and squamous cell carcinoma, the researchers conclude. "This was an observational study that suggests what physicians and epidemiologists expected, based on their knowledge of the relationship between sun exposure and skin cancers," Karagas says.
She and her colleagues plan a more in depth investigation of the effects that frequency of tanning lamp use and amounts of ultraviolet emissions have on the incidence of skin cancer. Their work is funded by the National Cancer Institute.
Journal
JNCI Journal of the National Cancer Institute