Indoor tanning triples the risk of skin cancer and causes widespread mutations in DNA

• The researchers examined thousands of medical records to compare skin cancer rates in people who used tanning beds and those who did not, then performed genetic analysis on 182 skin biopsies from both groups to track patterns of mutations.
• People who used tanning beds showed nearly twice as many DNA mutations as individuals in the control group.
• These mutations are found not only on commonly exposed skin, but also in areas of the body that rarely see sunlight, revealing how widespread tanning bed damage is.

Indoor tanning, skin cancer risks, and DNA damage

The use of tanning beds is associated with a nearly three-fold increase in the risk of developing melanoma, and for the first time, researchers have shown how these devices cause melanoma-related DNA damage across almost the entire surface of the skin, according to a new study led by Northwestern Medicine and the University of California, San Francisco.

Melanoma is the deadliest form of skin cancer and is responsible for about 11,000 deaths in the United States each year. For years, health experts have warned about the dangers of indoor tanning, yet the exact biological pathway linking tanning beds to cancer has not been fully determined. The indoor tanning industry, which is experiencing a resurgence in popularity, has pointed to this gap in knowledge to claim that tanning beds are no more dangerous than natural sunlight.

The new research “irrefutably” counters these arguments by showing that tanning beds, at the molecular level, change skin cells in ways that go beyond the effect of daily sun exposure, the authors say.

“Even in normal skin of indoor tanning patients, areas where there were no moles, we found DNA changes that represent precursor mutations that predispose to skin cancer,” said the study’s first author, Dr. Pedram Gerami, a professor of skin cancer research at Northwestern University Feinberg School of Medicine. “This has never been seen before.”

Skin cancer survivors who have previously used tanning beds and donated their skin biopsies to this work are available for interviews upon request.

The results were published December 12 in the journal Advancement of science.

Clinical ambiguity in younger melanoma patients

Jerami, who also directs the Skin Cancer Program in Dermatology at Northwestern University, has been treating people with skin cancer for two decades. During that period, he began to notice a striking pattern: an unusually high number of women under 50 who had multiple melanomas reported using tanning beds. It was suspected that frequent indoor tanning was the common factor linking these cases together.

To investigate this, Jerami and his team designed the epidemiological part of the study. They analyzed the medical records of about 3,000 people with a history of using tanning beds and compared them with nearly 3,000 individuals of the same age who had never used indoor tanning beds.

In this comparison, skin cancer was diagnosed in 5.1% of people who used tanning beds, versus 2.1% of those who did not. Even after the researchers took into account age, gender, sunburn history, and family history of melanoma, indoor tanning was still associated with a 2.85-fold increase in the risk of melanoma.

The study also found that people who used tanning beds were more likely to develop skin cancer in areas of the body that are usually protected from the sun, such as the lower back and buttocks. These observations supported the idea that tanning beds may cause DNA damage on a broader scale than regular sun exposure.

DNA sequencing reveals widespread mutations

To explore this possibility further, scientists have turned to advanced genomic tools. They used newer techniques to perform single-cell DNA sequencing on melanocytes (the pigment-producing skin cells where skin cancer starts) from three different groups of skin donors.

The first group consisted of 11 patients from Jerami’s clinic who had a long history of indoor tanning. The second group included nine individuals who had never used tanning beds but were similar in age, gender, and overall cancer risk. A third group of six cadaver donors provided additional skin samples to strengthen the control group.

In total, the team sequenced 182 individual melanocytes. They discovered that melanocytes from tanning bed users carried nearly twice as many genetic mutations as those in control groups and were more likely to harbor mutations associated with melanoma. In people who tanned indoors, these mutations also appeared in areas of the body that normally remain covered and not regularly exposed to sunlight, strengthening the conclusion that tanning beds cause a wide range of DNA damage.

“In outdoor sun exposure, maybe 20% of your skin is exposed to the most damage,” Jeramie said. “In tanning bed users, we saw the same serious mutations across almost the entire surface of the skin.”

Cancer survivor shares tanning bed toll

The study relied on the willingness of Gerami’s patients to donate skin biopsies. One participant, 49-year-old Heidi Tarr from the Chicago area, used tanning beds frequently as a teenager in high school — two to three sessions a week — because friends and celebrities at the time were doing it too and “I felt like that’s what made you beautiful.”

Years later, in her 30s and now a mother, she noticed a mole on her back and immediately feared it was serious. The spot turned out to be melanoma, which led to surgery, years of regular follow-up appointments and more than 15 additional biopsies as new moles appeared. “Biopsies can be painful, but psychological anxiety is worse,” she said. “You’re always waiting for the call that it’s melanoma again.”

After Jerami described the new research project, Tarr readily agreed to provide additional biopsies. “I value science, and I wanted to help,” she said. “If what happened to my skin can help others understand the real dangers of tanning beds, then this is important.”

“Injustice from the industry”

Seeing the genetic data and clinical trends together convinced Jerami of the need for stronger safeguards. “At the very least, indoor tanning should be illegal for minors,” he said.

“Most of my patients started tanning when they were young and weak and did not have the same level of knowledge and education they had as adults,” he said. “They feel wronged by the industry and regret the mistakes of their youth.”

Jeramie also believes tanning beds should carry warnings similar to those on cigarette packs. “When you buy a pack of cigarettes, it says this could lead to lung cancer,” he said. “We should have a similar campaign on the use of tanning beds. The World Health Organization has deemed that tanning beds contain the same level of carcinogens as smoking and asbestos. It is a Class 1 carcinogen.”

He recommends that anyone who used tanning beds frequently earlier in life have a full-body skin exam with a dermatologist and talk to their doctor about whether they should have ongoing routine skin checks.

Jeramy is a member of Northwestern University’s Robert H. Lurie Comprehensive Cancer Center.

The study, titled “Molecular Effects of Indoor Tanning,” was funded by the National Institutes of Health (grants R01 CA265786 and AR080626), the Department of Defense Melanoma Research Program (grant ME210014), a Melanoma Research Alliance Team of Science Award, a Dermatology Melanoma Research Alliance Fellows Award, a LEO Foundation Award for the Americas Region, and Cancer Center Support (grant P30CA082103). The IDP Foundation Award and the Greg and Anna Brown Family Foundation Award.