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.