Elsevier

Public Health

Volume 129, Issue 4, April 2015, Pages 396-402
Public Health

Original Research
Painting a picture of trans-Tasman mortality

https://doi.org/10.1016/j.puhe.2015.01.015Get rights and content

Highlights

  • We compare observed rates of mortality for Australia and New Zealand.

  • We examine the changes over time, by age and sex.

  • New Zealand has moved from better to worse mortality rates relative to Australia.

Abstract

Objectives

The determinants of health and mortality inequalities in New Zealand and Australia have been subjected to research, with the influence of a range of socio-economic and demographic influences (deprivation, social class, ethnicity) receiving notable attention. Both countries are considered privileged, positioned amongst the world leaders in rankings of mortality and life expectancy. This paper reports on observed rates of mortality and views how the countries have fared over time with respect to one another.

Study design, observational, methods

This study derives comparable rates of mortality for both New Zealand and Australia, disaggregated by age and sex for the time period 1948–2008. The age-standardised rates are visualised using the Lexis mapping software program, showing the relative differences between the countries over time whilst simultaneously highlighting age, period and cohort effects.

Results

Relative to Australia, New Zealand had advantageous rates of mortality across almost all age groups between the years 1948 and 1980 (approximately). For both sexes, a dramatic reversal of fortunes in New Zealand has followed relative to Australia. For example, for younger males in New Zealand, the reversal is startling. Over the time period observed, males aged 10–20 years in New Zealand have moved from an advantageous position of having a mortality rate 20% lower than Australia to a relative position of 50% higher.

Conclusions

The social and economic forces in both New Zealand and Australia which may have driven the divergence require further scrutiny. It is argued here, that the changing fortunes of the populations are linked to the process of selective migration and the large-scale population movements between the countries facilitated by the Trans-Tasman Travel Arrangement. These findings have important implications for policy formation and service planning, if the inequality in mortality between the areas of study is to be addressed.

Introduction

It has been established that the health of people is affected by the place in which they live. There is international evidence around the determinants of health and mortality inequalities,1, 2 with multiple socio-economic and demographic factors such as wealth, education and ethnicity linked with poor health outcomes. Much of the current literature has examined inequalities between groups within countries; these groups often defined based on their gender, social or ethnic identities and their spatial distribution. One emerging trend, within more affluent countries in particular, is of greater gender inequalities3 that have seen women take on a favourable position (relative to men) in terms of both life expectancy and mortality rates.4

There have been many studies of the inequalities in health outcomes between people and places within New Zealand and Australia. Differences in health and mortality have been highlighted within each country in terms of socio-economic factors5, 6, 7, 8, 9, 10, 11 including deprivation, social class and racial or ethnic factors.12, 13, 14, 15, 16 There is also evidence, within the field of health geography, that the places and spaces where people live are important contributors to health outcomes.17 Within New Zealand and Australia there have been noticeable improvements in mortality and life expectancy that see both countries rank among the worlds' best in measures of both.18

Just as sub-national variation in health outcomes exists within Australia and New Zealand, there is evidence of changes in the relative position between countries over time.4, 19 A study of male and female mortality rates among affluent countries over time shows falling mortality rates for both sexes during the study period 1850–1999.4 These changes are not consistent for both groups, as a widening gap in mortality ratios has seen women of all ages move to a much more favourable position over time. This trend has noticeably accelerated in the past 70 years. Mortality comparisons have also been drawn between specific countries. An observational study of mortality inequalities between England and Wales compared to Scotland for the period 1925–2005 suggests that the gap between the two groups has widened over time. This study19 showed the divergence over time within Great Britain particularly for younger men.

Given the geographic proximity and similarities in colonial origins of present day New Zealand and Australia it is somewhat surprising that comparisons of health outcomes between the two countries have been limited to date. Both countries share a history of European settlement in the 18th–19th century and today have distinct indigenous populations living alongside European and migrant groups. There are also similarities in the recent economic trajectories of both countries with export driven economies and simultaneous periods of recession. Australia, on the back of its mineral exports and large population base, has however grown to become one of the largest and wealthiest nations worldwide, while New Zealand has a much smaller economy focused on areas such agriculture. Migration between the two is open with citizens of both countries able to live and work in the other, largely without restriction due to the Trans-Tasman Travel Arrangement of 1973. Such agreements between the respective Governments of each country date back nearly a century, and the rates of migration which they facilitate are known to be influenced by the economic conditions in each of the countries.20

Both New Zealand and Australia currently rank highly in international comparisons of national performance in health, education and quality of life, as well as in economic, civil and political freedoms. This study does not focus upon the effects of migration; rather it aims to illuminate longer-term health trends between New Zealand and Australia in terms of mortality at each age, for males and females over time. It is important to clarify how the current position in terms of mortality may have arisen, if it has always been this way and if not, how changes have occurred and to which people.

Section snippets

Methods

The data for this study were collected from the Human Mortality Database (a full methods protocol can be found elsewhere21). The data contain age specific death rates for both New Zealand and Australia from 1948 to 2008 by single year of age and sex. This data were then read into, transformed and output from the statistical software R.22 This was then used to create Lexis maps using the Lexis software program. This paper also follows the methodological approach used elsewhere4, 19 to compare

Results

The figures presented visualise the relative mortality over time (1948–2008) for males (Fig. 1) and females (Fig. 2) respectively comparing relative mortality between New Zealand and Australia. For men, Fig. 1 shows that New Zealand enjoyed a relative advantage across almost all ages from the start of the period in 1948 to approximately 1980. From 1980 onwards the relative morality slowly shifted to a positive of relative disadvantage for New Zealand for older men, whereas for younger males

Discussion

The reversal from a position of relative mortality advantage to one of significant disadvantage compared with Australia, particularly for younger New Zealand men and women, indicates a major shift in health differential between the two countries. These changes could be indicative of an on-going overall decline in the health and well-being of New Zealanders, a notable rise in the health and well-being of Australians, or a combination of both these effects. Fig. 1, Fig. 2 suggest that this

Acknowledgements

This research uses estimates obtained from the Human Mortality Database (HMD). The HMD is sponsored by the University of California, Berkeley, and the Max Planck Institute for Demographic Research. The HMD is available at www.mortality.org or www.humanmortality.de (data downloaded in June 2013).

The software used to draw the Lexis maps was Lexis 1.1, written by Kirill Andreev (available at http://www.demogr.mpg.de/books/odense/9/cd/default.htm).

Ethical approval

None sought. Data used in this study are rates

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