A study of adults ages 25 to 49 found the risk for the deadly skin cancer increased two to six times for women who tanned indoors, with the greatest odds seen for those who used tanning beds in their teens and 20s.
Even more stringent regulations
"All women who use indoor tanning are at risk of melanoma, but the strongest risk was among women who tanned in their 20s, who were about six times more likely to develop the disease, compared to women who didn't tan indoors," said lead researcher DeAnn Lazovich, an associate professor of epidemiology and community health at the University of Minnesota.
The findings support a recent U.S. Food and Drug Administration proposal to ban indoor tanning before age 18, Lazovich said. However, she added, "we need to do even more to reduce the melanoma epidemic that's been going on for a number of years".
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Lazovich suggested even more stringent regulations perhaps raising the tanning bed age to 21. Better yet, she said, "We could ban indoor tanning altogether, as Australia has done."
The report was published online in JAMA Dermatology.
According to the American Cancer Society, about 74,000 Americans were newly diagnosed with melanoma last year and nearly 10,000 died from it. The rate has been rising for 30 years, with women more likely than men to get this type of cancer, the study authors said in background notes. Many cases are caused by excess exposure to ultraviolet rays from the sun or other sources.
A clue to the cause
Lazovich and her colleagues set out to assess the possible connection between tanning beds, which are used more often by women than men, and melanoma. They collected data on nearly 700 men and women ages 25 to 49 who were diagnosed with the skin cancer between 2004 and 2007 and compared them with a similar number of "controls".
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Women in their 30s had more than three times the risk of melanoma if they tanned indoors, and women in their 40s had more than twice the risk, Lazovich said.
Also, women younger than 40 with melanoma reported starting indoor tanning earlier than women 40 to 49 at about age 16 versus 25, the study found.
Younger women with melanoma also reported more tanning sessions than older women, an average of 100 tanning sessions compared with 40 sessions for women diagnosed at 40 to 49, researchers said.
Melanoma location gives a clue to the cause, the researchers said. They used melanomas on the trunk, or torso, as a sign that these people had their chests and backs exposed during indoor tanning sessions.
The researchers found that about 33 percent of the women diagnosed before 30 had melanomas on their trunk, compared with 24 percent who were 40 to 49. Among the 63 women diagnosed with melanoma before age 30, only two said they had not used tanning beds, the researchers found.
Read: Sunscreen prevents melanoma
The researchers could not establish an association between indoor tanning in men, "partly because they are far less likely to tan indoors and there are many fewer men who get melanoma under 50", Lazovich said. "We didn't find very much going on among men, it was all among women."
Premature skin ageing
One of the challenges in preventing melanoma, she said, is changing the perception that tanned skin is attractive and seeing it for what it is, dangerous.
Gery Guy Jr, a health economist in the Division of Cancer Prevention at the U.S. Centres for Disease Control and Prevention, said, "Indoor tanning can and should be avoided."
Besides the risk for melanoma, indoor tanning can cause premature skin ageing, including wrinkling and age spots, and change skin texture, said Guy, who wrote an accompanying journal editorial.
The scientific evidence is "clear and overwhelming: every time you indoor tan you increase your risk of getting melanoma", Guy said. "And unlike the tan that is temporary, the increased risk of melanoma is permanent."
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