How much does health care contribute to health gain and to health inequality? Trends in amenable mortality in New Zealand 1981-2004.

OBJECTIVE To estimate the contribution of health care to health gain, and to ethnic and socio-economic health inequalities, in New Zealand over the past quarter century. METHOD Amenable and all-cause mortality rates by ethnicity and equivalised household income tertile from 1981-84 to 2001-04 were estimated from linked census-mortality datasets (the New Zealand Census-Mortality Study). Amenable mortality (deaths under age 75 from conditions responsive to health care) was defined using a classification recently developed for use in Australia and New Zealand. The contribution of health care to the observed improvement in population health status was estimated by the ratio of the difference in amenable to the difference in all-cause mortality over the observation period. RESULTS Trends in amenable causes of death were estimated to account for approximately one-third of the fall in mortality over the past quarter century, for the population as a whole and for all income and ethnic groups except Pacific peoples, for whom there was no reduction in amenable mortality. In 2001-04, amenable causes accounted for approximately one quarter of the mortality gap between all ethnic groups compared to the European/Other reference. DISCUSSION Our finding provides one indicator of the social impact of health care over this period. More importantly, that Pacific peoples seem to have benefited less than other ethnic groups calls for urgent explanation. Also, our finding that amenable causes account for about one quarter of current mortality disparities, clearly indicates that improvement in access to and quality of health care for disadvantaged groups could substantively reduce health inequalities.