To test the hypothesis that indoor tanning without burns prevents sunburn and subsequent skin cancer, researchers at the Masonic Cancer Center, Department of Dermatology, and Division of Epidemiology and Community Health, University of Minnesota, Minneapolis used data from a case-control study on indoor tanning and the risk of melanoma. The researchers had detailed information on indoor tanning and sun exposure for the study participants and excluded those who experienced a burn while tanning indoors.
A total of 1167 melanoma patients were matched to 1101 control subjects by sex and age. All participants completed a questionnaire and telephone interview. In analyses adjusted for sociodemographic factors (eg., age, sex, income, education), eye, hair, and skin color, number of freckles and moles, family history of melanoma, and lifetime sun exposure and sunscreen use, they found that melanoma patients reporting zero lifetime burns were nearly four times more likely to be indoor tanners than control subjects. In addition, melanoma patients with zero sunburns reported having started tanning indoors at younger ages and used indoor tanning over more years than other patients who had experienced sunburn, suggesting that greater total exposure contributed to the findings.
The researchers write that their results demonstrate "...that indoor tanning, even when used in a way that does not produce burns, is a risk factor for melanoma."