Frequent tanning bed users may have up to an eight times greater risk for melanoma than people considered at high risk for melanoma who don’t use tanning beds, according to a new study that also showed how tanning beds alter melanoma-linked DNA on the molecular level and damage areas of skin not usually exposed to the sun.
“Our study demonstrates that at the molecular level, tanning bed users have more mutations in their skin cells than people in the general population who are twice their age,” lead study author Pedram Gerami, MD, director of the Skin Cancer Institute of Northwestern and the melanoma clinic at Northwestern University in Chicago, told Medscape Dermatology.
“Further, tanning bed users have more mutations in their skin cells than other high-risk patients who have not used tanning beds, even after controlling for other risk factors associated with melanoma,” he said.
Case-Control Study Results
The study, published on December 12 in the journal Science Advances, involved a case-controlled analysis of adult patients seen at Northwestern’s dermatology service, 2925 of whom had no tanning bed use and 2932 who had at least 10 such exposures.
All patients were considered at high risk for melanoma, Gerami said, because both the case and control cohorts were drawn from his group’s high-risk clinic at Northwestern. The tanning bed nonusers, matched by age to the tanning bed cohort, served as the epidemiologic control cohort. Nearly 90% of the tanning cohort were women compared with 57% of the control group. Those in the tanning cohort were more likely to have a history of sunburn (71.2% vs 50.3%) and a family history of melanoma (18.1% vs 16.8%).
In the study, melanoma was diagnosed in 5.1% of tanning bed users vs 2.1% of nonusers (P < .001). After adjusting for age, sex, family history of melanoma, and sunburn history, tanning bed use was associated with an increased risk for melanoma (odds ratio, 2.85; 95% CI, 2.0-3.99).
In addition, patients who had 10-50 tanning bed sessions had almost a threefold greater risk for melanoma than the control cohort, with the risk increasing exponentially with greater exposures. Those with 51-100 sessions had a fourfold greater risk; patients with 101-200 sessions had about a sixfold greater risk; and patients with more than 200 sessions had an eightfold greater risk.
“There really are parallels to smoking because it’s not that difficult to accumulate 200 exposures,” Gerami said. “If you go once a week for 4 years, that’s 200 exposures, and that is not an uncommon story.”
The study comparisons were between two high-risk groups, he noted. “So, if you were to then try to compare that to the general population, you could just imagine it’s going to be considerably higher,” he said.
What’s more, the study found that tanning bed users were more likely than those exposed only to sunlight to have melanoma over multiple body areas and to develop melanoma on body sites with low cumulative sun damage — such as the lower back and buttocks — compared with nonusers (76.1% vs 61.2%).
For people tanning outdoors, the upper shoulders and back “seem to be preferentially damaged,” Gerami said. “That surface area of the body probably doesn’t constitute 20% of your total body surface area, so now imagine that same level of high-intensity exposure not to 15%-20% of your body surface area, but closer to 90%-plus of your body surface area.”
Besides the epidemiologic component, the study also included a molecular analysis of shave biopsy skin samples from 11 tanning bed users compared with skin samples from nine patients in the original control cohort and six cadavers representative of the general population. The cadavers were nearly twice as old as the tanning cohort (78.3 years vs 43.6 years). The mutation burden of melanocytes was almost twofold higher among the tanning bed users than in the other two groups, and melanocytes from tanning bed users were more likely to have melanoma-linked mutations.
“It’s clear that tanning bed usage causes some diffuse DNA damage to skin cells,” Gerami said, and “explains this high predilection for melanoma and also the predilection for multiple melanomas.”
The trends for tanning bed use in the US are mixed. The study quoted 20-year-old data indicating that more than 30 million people use tanning beds in the US yearly. More recent data on tanning bed usage were not available, although a 2020 study reported that tanning bed use internationally declined 70% among adolescents and 35% in adults in the 10 years after the International Agency for Research on Cancer classified artificial tanning devices as carcinogenic.
However, in the US, more tanning salons are in business. According to the market research organization IBISWorld, 27,318 tanning salons operate in the US, up from 22,000 in 2023 and an increase of more than 11,000 since earlier this century.
A 2014 meta-analysis estimated more than 400,000 cases of skin cancer may be related to indoor tanning in the US each year, causing 245,000 basal cell carcinomas, 168,000 squamous cell carcinomas, and 6200 melanomas.
Commentary
Hillary C. Tsibris, MD, medical director of melanoma dermatology at the Dana-Farber Cancer Institute in Boston, said the Northwestern study is notable for the large number of patients with quantified tanning bed exposure, detailed information on additional ultraviolet exposure and melanoma risk factors, and the use of an age-matched control population.
But she noted the second control group of cadaveric skin samples “differed in several important melanoma risk factors, including history of melanoma, hair color, sunburn history, age, and tanning ability.” These differences in baseline characteristics, she noted, may affect the reported differences in skin mutational burden and melanoma driver mutation frequency.
“Hopefully, studies such as this one will help to emphasize that, contrary to marketing claims, tanning bed use is not safer than natural sunlight exposure and, in contrast, raises the mutational burden and melanoma risk in areas of the skin that receive low levels of cumulative sun damage,” Tsibris told Medscape Medical News.
The study was independently supported. Gerami and Tsibris reported having no relevant financial relationships.
https://www.medscape.com/viewarticle/study-sheds-new-light-tanning-bed-melanoma-risks-2025a1000z84
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