A comparison of trends in melanoma mortality in New Zealand and Australia: the two countries with the highest melanoma incidence and mortality in the world

Mary Jane Sneyd,Brian Cox

doi:10.1186/1471-2407-13-372

Abstract

BackgroundNew Zealand and Australia have the highest incidence and mortality rates from cutaneous melanoma in the world. The predominantly fair-skinned New Zealanders and Australians both enjoy sun, tanned skin and the outdoors, and differences in these activities among generations have been important determinants of trends in melanoma mortality.We examined whether New Zealand trends in melanoma mortality mirror those in Australia, through detailed comparison of the trends in both countries from 1968 to 2007.MethodsFive-year age-specific and age-standardised mortality rates were calculated for each country for 5-year time periods. Tests for trends in age-specific rates were performed using the Mantel-Haenszel extension chi-square test. The age-adjusted mortality rate ratios for New Zealand/Australia were plotted against period of death to show relative changes in mortality over time. Age-specific mortality rates were plotted against period and the median year of birth to illustrate age-group and birth cohort effects. To compare the mortality of birth cohorts, age-adjusted melanoma mortality rate ratios were calculated for the birth cohorts in the quin-quennial tables of mortality rates.ResultsThe age-standardised mortality rate for melanoma increased in both sexes in New Zealand and Australia from 1968 to 2007, but the increase was greater in New Zealanders and women in particular. There was evidence of recent significant decreases in mortality in younger Australians and less so in New Zealand women aged under 45 years. Mortality from melanoma increased in successive generations born from about 1893 to 1918. In Australia, a decline in mortality started for generations born from about 1958 but in New Zealand there is possibly a decrease only in generations born since 1968.ConclusionsMortality trends in New Zealand and Australia are discrepant. It is too early to know if the pattern in mortality rates in New Zealand is simply a delayed response to melanoma control activities compared with Australia, whereby we can expect the same downward trend in similar age groups in the next few years. Specific research is needed to better understand and control the increases in mortality and thickness of melanoma in New Zealand.

Highlights

New Zealand and Australia have the highest incidence and mortality rates from cutaneous melanoma in the world
These represent the surface of melanoma mortality for the population during the years 1968–2007 in five-year age groups
Melanoma mortality was higher in New Zealand than in Australia in the most recent years, at older ages, for both men and women

Summary

Introduction

New Zealand and Australia have the highest incidence and mortality rates from cutaneous melanoma in the world. The predominantly fair-skinned New Zealanders and Australians both enjoy sun, tanned skin and the outdoors, and differences in these activities among generations have been important determinants of trends in melanoma mortality. We examined whether New Zealand trends in melanoma mortality mirror those in Australia, through detailed comparison of the trends in both countries from 1968 to 2007. New Zealand and Australia have the dubious distinction of having the highest incidence rates of and mortality rates from cutaneous melanoma in the world [1]. New Zealand has a range of latitude from Kaitaia (35°S) to Bluff (46°S), with summer UV indices from 13 to 8. An overall trend of decreasing melanoma incidence with increasing latitude occurs in both countries

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