Indoor tanning beds sharply increase the risk of melanoma, the deadliest kind of skin cancer, and the risk increases over time, U.S. researchers said on Thursday, and others experts called for tighter regulation.
They said people who use any type of tanning bed for any amount of time are 74 percent more likely to develop melanoma, and frequent users are 2.5 to 3 times more likely to develop the skin cancer than people who never use them.
The study confirms prior research linking indoor tanning beds with melanoma, and answers any lingering questions about whether the practice is safe, or if the risk depends on the type of tanning bed used.
"We found that it didn't matter the type of tanning device used; there was no safe tanning device," said DeAnn Lazovich of the University of Minnesota, whose study appeared in the journal Cancer Epidemiology, Biomarkers and Prevention.
Studies had suggested younger people were at greater risk, but Lazovich said the risk rises with frequency of use, regardless of age, gender or the device used.
"The increased risks we have reported are the risks associated with indoor tanning above and beyond any other known risk factors for melanoma," Lazovich said in a telephone briefing.
Dr. Allan Halpern, chief of dermatology at Memorial Sloan-Kettering Cancer Center in New York, told the briefing that melanoma cases are on the rise in the United States and the findings strengthen the case for regulating tanning beds.
He said the World Health Organization already classifies tanning beds as a human carcinogen, but in the United States, tanning beds are considered a class 1 medical device — "which is the equivalent of tongue depressors," he said.
The FDA has been reconsidering this classification and on Wednesday the agency released a video saying the use of any ultraviolet or UV-emitting device for the purpose of tanning should be avoided.
"I'm hopeful it will be very helpful in the hands of the U.S. Food and Drug Administration to move forward to regulate this industry," said Halpern, who was not involved in the research.
For the study, Lazovich and colleagues studied 1,167 people diagnosed with melanoma and compared them with 1,101 people who did not have melanoma.
The team asked people which type of tanning bed they had used — those that emit UVA radiation or UVB radiation.
They found that melanoma risk was about 3 times greater among people who had used tanning beds that emit UVB rays and 4.4 times greater for UVA-emitting devices.
They also found that risk increased with use.
They defined frequent use as people who used indoor tanning for more than 50 hours, or more than 100 sessions, or for more than 10 years.
"Most reports were not able to adjust for sun exposure, confirm a dose-response, or examine specific tanning devices," Lazovich said. "Our population-based, case-control study was conducted to address these limitations."
Melanoma accounts for about 3 percent of skin cancer cases but causes most skin cancer deaths, and doctors have few effective treatments to offer once the disease has spread.
According to the American Cancer Society, 68,000 people were diagnosed with melanoma in 2009, and 8,650 died of it.