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Excessive exposure to solar ultraviolet (UV) is the main cause of skin cancer. Specific prevention should be further developed to target overexposed or highly vulnerable populations. A better characterisation of anatomical UV exposure patterns is however needed for specific prevention. To develop a regression model for predicting the UV exposure ratio (ER, ratio between the anatomical dose and the corresponding ground level dose) for each body site without requiring individual measurements. A 3D numeric model (SimUVEx) was used to compute ER for various body sites and postures. A multiple fractional polynomial regression analysis was performed to identify predictors of ER. The regression model used simulation data and its performance was tested on an independent data set. Two input variables were sufficient to explain ER: the cosine of the maximal daily solar zenith angle and the fraction of the sky visible from the body site. The regression model was in good agreement with the simulated data ER (R(2)=0.988). Relative errors up to +20% and -10% were found in daily doses predictions, whereas an average relative error of only 2.4% (-0.03% to 5.4%) was found in yearly dose predictions. The regression model predicts accurately ER and UV doses on the basis of readily available data such as global UV erythemal irradiance measured at ground surface stations or inferred from satellite information. It renders the development of exposure data on a wide temporal and geographical scale possible and opens broad perspectives for epidemiological studies and skin cancer prevention.

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Seasonal variation in cutaneous melanoma incidence with a summer peak is poorly understood. It has been hypothesized to be due to increased diagnosis in summer or a late-promoting effect of sun exposure. We analyzed the characteristics of incident cases of cutaneous melanoma and their outcome by season of diagnosis in the population of New South Wales, Australia. Cases of melanoma (25,845 cases; 10,869 females and 14,976 males) were registered by the New South Wales Central Cancer Registry in 1989 to 1998. There was significant seasonal variation in incidence (P < 0.0001, Nam test). The summer to winter ratio was greater for women, younger people, lesions on the limbs, and superficial spreading melanoma. Melanomas were thicker in winter than in summer (medians 0.75 and 0.70 mm, respectively; P < 0.0001, Kruskal-Wallis test). Cases were followed for a median of 63 months and 2,710 (10.5%) died from their melanoma. Fatality from melanoma was lower for melanomas diagnosed in summer than winter (relative fatality = 0.72; 95% confidence interval, 0.65-0.81); the 5-year survival rate was 92.1% for diagnosis in summer and 89.0% for diagnosis in winter. This result remained significant after adjustment for year of diagnosis, age, sex, Breslow thickness, anatomic location, and histologic type (relative fatality = 0.82; 95% confidence interval, 0.72-0.94). Seasonality in melanoma incidence is probably caused mainly by increased and earlier diagnosis in summer, although a late-stage promotional effect of sun exposure cannot be excluded completely. Earlier diagnosis may also reduce fatality when melanoma is diagnosed in summer. Independence of variation in fatality with season from seasonal variation in thickness, however, suggests that sun exposure around the time of diagnosis decreases fatality of melanoma