Variation of melanoma incidence with latitude in North America and Europe.

The relationship between melanoma incidence and latitude was investigated in North American and Europe, using the data collected by 43 population-based cancer registries. In North America melanoma incidence increased with decreasing latitude, supporting the role of UV light in the induction of melanoma. Within England the data from the National Cancer Registration scheme also showed that trend of decreased frequency of melanoma with decreasing latitude. In contrast, across Europe the trend was in the opposite direction, of increasing melanoma incidence with increasing latitude. It is suggested that across Europe there is a range of skin colour from dark in the south to light in the north, which gives rise to a range of susceptibility to the induction of melanoma by UV. The effect of this susceptibility must be large enough to overwhelm the opposing effect of decreased UV intensity at higher latitudes, and this emphasizes the dangers of excessive solar exposure to fair-skinned individuals. The populations of England may be a sufficiently random mix of skin colour, owing to repeated invasions, for the effect of UV intensity to be observed.