Have geographical inequalities in cause-specific mortality in New Zealand increased during the period 1980-2001?

Aims: To monitor geographical inequalities in cause-specific mortality in New Zealand during the period 1980 to 2001, a time of rapid social and economic change.

Methods: Age-standardised rates of all-cause mortality, as well as for nine of the leading causes of death among males and females, were calculated for District Health Boards (DHBs) for the periods 1980-1982, 1985-1987, 1990-1992, 1995-1997, and 1999-2001. Geographical inequalities in health were evaluated using the DHB-level cause-specific Rate Ratio (RR; age standardised rates 1999-2001:1980-1982), and the Relative Index of Inequality (RII).

Results: Between 1980 and 2001, all-cause mortality rates fell for both males and females. However, age-standardised rates have risen for chronic obstructive pulmonary disease, diabetes mellitus, and cancer. The overall reductions in mortality rates have not been uniform across all regions as the all-cause mortality RR for each DHB ranged from 0.98 to 0.69 for males and 1.10 to 0.69 for females. The RRs for cause-specific mortality are more varied with large decreases and increases in mortality attributable to specific causes in some DHBs. There has also been a sharp rise in geographical inequalities in health measured using the RII, and this trend is consistent for most types of mortality.

Conclusions: Although overall mortality rates decreased over the 1980s and 1990s, this trend has not been consistent for all causes of mortality or in all regions of the country resulting in higher geographical inequalities in all-cause and most types of mortality.