Critique of the International Agency for Research on Cancer's meta-analyses of the association of sunbed use with risk of cutaneous malignant melanoma.

The International Agency for Research on Cancer (IARC) reported meta-analyses of the association of cutaneous malignant melanoma (CMM), finding significant correlations with ever use of sunbeds and first use of sunbeds prior to age 35 years; it did not claim that the associations showed causal links. However, some observational studies in the meta-analysis included individuals in the UK with skin phenotype at increased genetic risk of CMM without adjustment for skin phenotype. Treating the five UK studies separately from the other 14 corrected this oversight. In the original study, the summary relative risk (RR ) of CMM with respect to sunbed use was 1.15 (95% confidence interval [CI], 1.00-1.31). In this study, the similar RR was 1.20 (95% CI, 1.03-1.38). The RR for the five UK studies was 2.09 (95% CI, 1.14-3.84), whereas the RR for the other 14 studies was 1.09 (95% CI, 0.96-1.24). For first use of sunbeds prior to age 35 years, the IARC found a summary RR of 1.75 (95% CI, 1.35-2.36). This study plotted the RRs versus latitude of each study population, with a linear regression analysis carried out for all but the one UK study. The RR increased at 0.077 per degree of latitude and the regression explained 67% of the variance. It is also argued that factors other than sunbed use explain the increasing worldwide trends in CMM. Because solar-UV-simulating sunbeds induce production of vitamin D, the health benefits of their use greatly outweigh any possible risks.