To distinguish solarium use with and without risk behavior on melanoma incidence and all- cause mortality. -A report from the large MISS Cohort

Background: Artificial ultraviolet radiation (UVR) from solarium use has been linked to melanoma in some studies, while others report lower overall mortality. Whether melanoma risk is due to solarium use itself or to associated behaviors indicating intermittent solar overexposure remains unclear. Methods: The Melanoma of Southern Sweden (MISS) cohort included ~ 29,000 women enrolled in 1990 and followed for up to 34 years. Solarium use and sun exposure habits were assessed at baseline and after 10 years. Participants were categorized as non-users, solarium users without, or with indicators of intermittent solar overexposure. Cox proportional hazards models estimated hazard ratios (HRs) for melanoma and all-cause mortality. Sensitivity analyses, attributable risk, and restricted mean survival time (RMST) over 25 years were evaluated. Results: Solarium use without indicators of solar overexposure was not associated with melanoma risk. Solarium users with overexposure indicators had a higher melanoma risk (HR 1.60, 95% CI 1.30–2.00). Both solarium user groups had ~ 18% lower all-cause mortality than non-users. Approximately one-third of melanomas among solarium users was attributable to solar overexposure. Over 25 years, solarium users had an RMST nearly 10 months longer than non-users. Conclusions: Melanoma risk among solarium users appears driven by intermittent solar overexposure rather than solarium use itself, while solarium use was associated with lower all-cause mortality. Our findings indicate that prevention efforts should focus on reducing intermittent UV overexposure behaviors.