MC1R and non-melanoma skin carcinoma: Although this reduced the sample size for our analysis, it is unlikely to have introduced systematic bias, as a comparison of those with (n = 676) versus without (n = 270) clinical skin examinations showed no statistically significant differences on predictors including sex, self-reported nevi, hair colour, MC1R genotype, previous non-melanoma skin cancer, and childhood blistering sunburns.