Changing trends in indigenous inequalities in mortality: lessons from New Zealand

Methods Abridged period lifetables for Maori and non-Maori from 1951 to 2006 were constructed using standard demographic methods. Absolute [standardized rate difference (SRD)] and relative [standardized rate ratio (SRR)] mortality inequalities for Maori compared with European/Other ethnic groups (aged 174 years) were measured using the New Zealand Census-Mortality Study (an ongoing data linkage study that links mortality to census records) from 198184 to 200104. The SRDs were decomposed into their contributions from major causes of death. Poisson regression modelling was used to estimate the extent of socio-economic mediation of the ethnic mortality inequality over time. Results Life expectancy gaps and relative inequalities in mortality rates (aged 174 years) widened and then narrowed again, in tandem with the trends in social inequalities (allowing for a short lag). Among females, the contribution of cardiovascular disease to absolute mortality inequalities steadily decreased, but was partly offset by an increasing contribution from cancer. Among males, the contribution of CVD increased from the early 1980s to the 1990s, then decreased again. The extent of socio-economic mediation of the ethnic mortality inequality peaked in 199194, again more notably among males. Conclusion Our results are consistent with a causal association between changing economic inequalities and changing health inequalities between ethnic groups. However, causality cannot be established from a historical analysis alone. Three lessons nevertheless emerge from the New Zealand experience: the lag between changes in ethnic social inequality and ethnic health inequality may be short (5 years); both changes in the distribution of the social determinants of health and an appropriate health system response may be required to address ethnic health inequalities; and timely monitoring of ethnic health inequalities, based on high-quality ethnicity data, may help to sustain political commitment to pro-equity health and social policies.