Changes in life expectancy in Aotearoa New Zealand: a cause-specific decomposition analysis over 20 years

Life expectancy in Aotearoa New Zealand has increased over recent decades, but these increases have not been distributed equally across population groups. Examining how changes in cause-specific mortality have contributed to changes in life expectancy can improve understanding of evolving mortality patterns and persistent inequities. This study quantified the contribution of major causes of death to changes in life expectancy over approximately two decades.

Mortality data from the New Zealand Mortality Collection and population estimates from Statistics New Zealand were used to calculate life expectancy at birth for Māori, Pacific, Asian, and European and Other populations for the periods 2001-2003 and 2020-2022. Changes in life expectancy were decomposed by age and cause of death using the Arriaga method. Deaths were grouped into major disease categories and selected individual causes to estimate their contribution to the change in life expectancy.

Life expectancy increased for all ethnic groups, with the largest absolute increases observed among Māori. Improvements were driven primarily by reductions in mortality at adult and older ages. Across all ethnic and sex groups, declines in cardiovascular disease and cancer mortality accounted for more than half of the total change in life expectancy. Reductions in mortality from diabetes and smoking-related conditions also contributed to increases among Māori and Pacific peoples. Despite these improvements, substantial ethnic inequities in life expectancy remain.

Increases in life expectancy in Aotearoa New Zealand between 2001-2003 and 2020-2022 were driven largely by reductions in mortality from major non-communicable diseases, primarily cardiovascular disease and cancer. Māori experienced some narrowing of the life expectancy gap relative to European and Other populations, whereas the gap for Pacific peoples remained largely unchanged. Despite overall improvement, substantial inequities persist. Further increases are likely to depend on strengthening primary prevention, particularly reductions in smoking and cardiovascular risk factors, alongside improved participation in screening and early detection programmes, including the potential role of lung cancer screening, and ensuring equitable access across care pathways.