Trends in malignant melanoma of skin in New Zealand.

Incidence and mortality rates for malignant melanoma of skin in the New Zealand non-Maori population over the past 30 years were analysed in relation to sex, age, birth cohort and time. In both sexes, the age-standardized incidence rates increased approximately exponentially with time, with an annual increment of 7.5%. The age-standardized mortality rates increased approximately linearly with time, resulting in a two- to three-fold increase over 30 years, as compared with an eight- to nine-fold increase in the incidence rates. Descriptive birth cohort analysis shows different patterns of increase for incidence and mortality rates. The main difference is that, whereas incidence rates have continued to increase in recent birth cohorts, mortality rates have stabilized. The explanation for this difference is uncertain.