Spatial and temporal predictors of melanoma incidence in Austria: Results of en ecologic study.

Abstract

Objectives: Melanoma incidence increased in Austria in the last decades. Solar UV radiation increased until recently because of the damage to the ozone layer. With the restoration of the ozone layer UV radiation is predicted to decline again. If the increase in melanoma incidence were mostly due to the change in natural UV radiation we might expect declining incidence rates in the future. Exposure data: We assessed trends in UV annual cumulative doses at 9 fixed monitoring stations in Austria since 1961. There was strong inter-annual variation that was deemed not relevant for melanoma incidence. Apart from that, we observed an increase in annual cumulative UV dose of 1.2 kJ/m² per year consistently across stations. The only predictor of differences found between stations was the height above sea level with a gradient of 13.1 kJ/m² per 100 meter. Health data and methods: We obtained population data and melanoma incidences per 5-year age groups and gender for all 120 districts of Austria. We performed Poisson regression for each gender-age group with the gender-age specific population size as offset and year and height above sea level as predictor variables. Results: Averaged across strata melanoma incidence increased by 2% annually and by 20% per 100 m increase of height above sea level of the district. This fits well with the change in cumulative UV dose for these predictors. Effects were consistently stronger in younger age groups. Discussion and conclusions: Not only cumulative dose but also day-by day variability of UV radiation increased by year and by height above sea level with the strongest variation seen in summer. Since melanoma risk might be affected most strongly by peak exposures, for future scenarios not only cumulative average exposure but also variability and peak exposures would be of interest.