Tanning Beds and Natural Sunlight Affect Melanocytes Differently

Tanning beds have long been popular for achieving a sun-kissed glow, but mounting evidence links indoor tanning usage to less glamorous consequences like wrinkles and skin cancer. The World Health Organization considers tanning beds to be carcinogens alongside hazards like asbestos or cigarette smoke; despite this, estimates suggest that millions of people, especially young women, continue to use them.

Because sunbed usage coincides with an increased incidence of melanoma, dermatologist Pedram Gerami from Northwestern Medicine sought to elucidate their molecular effects on skin cells. In a recent study, published in Science Advances, Gerami and his colleagues found that between tanning bed users and nonusers, those who tanned were more likely to have multiple melanomas on areas of the body with low amounts of sun damage.¹ Molecular analysis revealed that their skin cells harbored more pathogenic mutations, which may elevate melanoma risk. These findings highlight how tanning beds can affect skin cells differently than those who are exposed to natural, outdoor lighting.

The researchers formed two cohorts of nearly 3,000 individuals each: those with a history of tanning bed usage—who were more likely to be women—and a group of nonusers. The team observed that the tanning cohort was more likely to have multiple melanomas. The distribution of melanomas also differed. The tanning bed users more often had melanomas on areas of the body that typically receive less sunlight, such as the torso, compared to individuals exposed to natural sunlight.

These patterns led the team to suspect that indoor tanning increases the mutation burden in melanocytes, affecting a broader range of skin cells than natural sunlight typically reaches. When they collected normal skin biopsies from the upper or lower backs of both groups, single-cell genotyping revealed that tanning bed users had a higher mutation burden in melanocytes. Of these, the researchers found 40 pathogenic mutations predicted to disrupt a tumor-suppressor gene, along with increased expression of a gene commonly activated in cancer, compared to the control group of natural-sun exposure individuals.

Together, these findings reveal molecular and clinical differences between those who expose themselves to a tanning bed’s artificial ultraviolet radiation and natural sunlight. Further work is needed to dig deeper into these molecular changes, which may help to better inform the public about indoor tanning and that the pursuit of a tan can come with unintended consequences.