Simone Ribero, Dan Glass, Massimo Mangino, Abraham Aviv, Tim Spector, Veronique Bataille

Lower Vitamin D serum levels are linked to increased melanoma risk and poorer survival. Naevus counts are associated with both melanoma risk and survival and to leucocyte telomere length. Vitamin D is also linked to telomere biology with higher levels of Vitamin D in individuals with longer leucocyte telomere length despite adjusting for age. Using the TwinsUK data, we explored the association between naevus count, leucocyte telomere length and Vitamin D serum levels. Increasing Vitamin D levels were associated with increasing naevus count: serum levels were 73.3 nmol/l in individuals with less than 50 naevi compared to 78.8 nmol/l in individuals with more than 50 naevi (p = 0.002). In the final regression model, using naevus count as a continuous variable, Vitamin D remained associated with higher naevus counts despite adjustment for age, weight, height, season of sampling and twin relatedness (p = 0.02). Further adjustment for leucocyte telomere length, decreased the magnitude of the association but it remained significant so leucocyte telomere length is not the sole driver of this association. Having large numbers of naevi is associated with higher Vitamin D serum levels.