Indoor tanning and non-melanoma skin cancer: A systematic review and meta-analysis

Background: Non-melanoma skin cancer (NMSC), including basal cell carcinoma (BCC) and squamous cell carcinoma of the skin (SCC), is by far the most common human malignancy. Indoor tanning is a known risk factor for malignant melanoma and is ranked as a Class 1 carcinogen by the World Health Organization. Yet the data on NMSC are less clear, primarily because small individual studies have resulted in varied effect estimates. Methods: We conducted a systematic review and meta-analysis of studies that assessed the effect of indoor tanning on development of NMSC. Literature review using PubMed (1966 – present) and Embase (1974 – present) identified 13 published case-control studies which quantitatively examined exposure to indoor tanning and development of NMSC. After applying inclusion/exclusion criteria, 9 studies were included in this analysis. Results for BCC were reported separately from SCC. Summary odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using a random-effects model. Results: Nine studies provided data of NMSC risk among participants who reported “ever” exposure to indoor tanning compared to those “never” exposed. A positive association between indoor tanning and risk of both BCC (summary OR 1.23, 95% CI 0.94-1.62) and SCC (summary OR 1.76, 95% CI 1.22-2.54) was found. Heterogeneity between studies was non-significant for both outcomes. Conclusion: These results indicate an increased risk of both BCC and SCC associated with exposure to indoor tanning. Our findings contribute to the growing body of evidence on the harms of indoor tanning and should be incorporated in public health campaigns to reduce exposure to this carcinogen.