Previous studies have shown only a weak correlation between indoor tanning and melanoma risk. In their study, Lazovich and colleagues attempted to address the limitations of earlier studies by utilizing a population-based case-control design. They enrolled two groups of Minnesota residents: 1,167 cases and 1,101 controls. Cases were identified from a statewide cancer registry; they were 25 to 59 years of age, 60% women, and had invasive cutaneous melanoma of any histological type. Controls were randomly chosen from lists of state driver's licenses and were matched to cases by age and sex. All participants completed a two-part exposure assessment that included a self-administered questionnaire, the answers to which served as the basis for telephone interviews. Information on other possible risk factors (such as the presence of freckles or moles, or a family history) was also collected.

Overall, 63% of cases and 51% of controls indicated use of indoor tanning. Melanoma occurred more often in those using indoor tanning than in those who'd never used tanning devices. Melanoma risk was directly related to frequency of tanning (total hours, sessions, or years), but not to the age at which tanning began. The relationship between frequency of tanning and risk of melanoma was demonstrated for each tumor site, including those that appeared on the trunk.

High-speed, high-intensity tanning devices were more likely to be linked to melanoma than were traditional devices and sunlamps; however, all devices contributed to melanoma risk. Also, indoor-tanning burns were more common among cases and resulted in melanoma risk similar to that from sunburns.