Tanning beds mutate nearly your entire skin and triple melanoma risk

For the first time, scientists have demonstrated how tanning beds cause fundamental DNA damage across almost the skin's entire surface that results in a threefold risk of developing melanoma. It puts beyond doubt the dangers associated with using these devices.

Scientists from Northwestern Medicine and the University of California, San Francisco wanted to better understand the relationship between indoor tanning and cancer development, particularly with these machines rising in popularity among younger generations. A recent study found that there are more tanning salons in Florida than McDonald's outlets, and that up to 40% of teenage girls and 20% of 18- to 29-year-olds have used one of these devices in the previous 12 months.

The researchers looked at the medical records of 32,315 patients seen by the Dermatology service at Northwestern University, with 7,474 of these individuals having reported tanning bed usage. The extent of use was detailed in 2,932 patients, which formed the study's “epidemiological case” cohort. Then, for a control cohort, the researchers randomly selected 2,925 people from the 24,841 patients with no history of tanning bed usage.

They found that melanoma was diagnosed in 5.1% of indoor tanners compared with 2.1% of non-users. After adjusting for variables – age, sex, sunburn and family history – tanning bed use resulted in a 2.85-fold increase in melanoma risk. These users were also more likely to develop skin cancers on parts of their body that had rarely been exposed to sun, such as the lower back and buttocks.

“In outdoor sun exposure, maybe 20% of your skin gets the most damage,” said study first author Dr. Pedram Gerami, professor of skin cancer research at Northwestern University. “In tanning bed users, we saw those same dangerous mutations across almost the entire skin surface.”

Delving further, the team conducted single-cell DNA sequencing on the pigment-producing skin cells where melanoma originates, known as melanocytes, from three donor groups. Group one featured 11 patients with a long history of using tanning beds. Group two included nine patients who had never used one but matched for age, sex and cancer risk. And group three featured skin from six cadavers as further controls.

And this is where it got really interesting – and somewhat frightening. With 182 individual melanocytes sequenced, the researchers quickly noticed that the cells of indoor tanners contained almost twice the number of mutations as the control samples, and these changes were more likely to be melanoma-linked ones. And the damage was more likely to be in those shielded-from-the-sun areas of the body.

“Even in normal skin from indoor tanning patients, areas where there are no moles, we found DNA changes that are precursor mutations that predispose to melanoma,” said Dr. Gerami. “That has never been shown before.”

In fact, the melanomas they develop are much like those seen in people who have inherited a genetic risk of skin cancer.

"Young tanning bed users, without a family history of melanoma, periodically develop multiple melanomas on body sites that receive low cumulative sun damage," the team noted. "The presentation of tanning bed-induced melanomas is reminiscent of familial melanoma."

Tanning beds first hit the US market in the 1970s, and by the mid-2010s, had grown into a US$3-billion-a-year industry. As of 2013, an estimated 7.8 million women and 1.9 million men in the US hit the "sunbed" each year, usually frequently. According to the World Health Organization, tanning beds are are a Group 1 carcinogen, meaning there is sufficient scientific evidence that they cause cancer in humans. (Smoking, alcohol and processed meats are also in this group.)

“When you buy a pack of cigarettes, it says this may result in lung cancer,” he said. “We should have a similar campaign with tanning bed usage."

In 2015, the FDA attempted to ban people under the age of 18 from using tanning beds and require all adults to sign a consent form acknowledging that they know the risks that come with this specific ultraviolet light exposure. But 10 years on the responsibility has fallen to state and local governments to restrict or ban the service. California was the first state to ban indoor tanning for minors in 2012, and since then, 43 more states have banned or at least restricted tanning bed use for those under 18.

Australia, which has the highest rate of melanoma in the world, banned the use of tanning beds outright in 2015, but it wasn't the first country to do so. Brazil banned cosmetic indoor tanning in 2009, but allows it for some medical conditions. It's worth noting that the tanning bed industry lobby in these countries was relatively small at the time of the bans – however, both Europe and the US have powerful lobby groups fighting more US restrictions.

"Given the high levels of mutational damage in skin cells from tanning bed users, it is difficult to justify marketing claims that the spectra of UV radiation in tanning beds are safer than natural sunlight," the study's researchers concluded. "Another popular claim by tanning advocates is that a pre-vacation tan can photoadapt skin in anticipation of recreational sun exposure. However, we see that tanning bed usage raises the mutation burden and risk of melanoma particularly in skin cells that receive low cumulative sun damage.

"Tanning bed exposures are often thought of as a substitute for natural UV radiation despite differences in the maximum doses, UV content, body sites exposed, and patterns of melanoma that arise," they said. "Our work highlights unique ways in which tanning beds shape the mutational landscapes of skin cells, helping to explain the distinctive presentations of melanoma in this patient population."

Melanoma – the deadliest type of skin cancer – kills an estimated 11,000 people in the US every year.

The research was published in the journal Science Advances.

Source: Northwestern University