Abstract
In 2016 New Zealand’s Perioperative Mortality Review Committee (POMRC) reported that, between 2009-2013, Māori New Zealanders were 62% more likely to die within 30 days following an elective or waiting list procedure (adjusted odds ratio [OR]: 1.62, 95% CI 1.33-1.97) – even after adjusting for age, gender, deprivation and physical status (‘ASA’ score). Māori were also more likely to die following an acute procedure, although not to the same extent (OR: 1.23, 95% CI 1.18-1.36). In their concluding remarks, the Committee highlighted the urgent need for further research into the drivers of this substantial disparity, emphasising the need for future work to assess the impact of comorbidity.
Despite these stark disparities, there had been very little research examining the potential drivers of postoperative mortality disparities between Māori and non-Māori and there was an urgent need to:
• describe in detail the extent to which disparities in postoperative mortality exist between Māori and non-Māori, particularly for surgical procedures that are major causes of postoperative mortality and/or morbidity, and
• measure the extent to which any observed disparities are explained by patient-level, surgical quality-of-care and/or health system level factors.
We hypothesised that the factors that drive postoperative mortality among Māori may be different to the factors that drive postoperative mortality for non-Māori; also, that the magnitude of the impact of common factors (such as comorbidity) may differ between Māori and non-Māori. It was considered crucial that we understand where these differences lie, in order to best-inform any actions to address them.
Aim1: To describe current evidence regarding inequalities in postoperative mortality. While there was some international evidence on ethnic disparities in postoperative mortality, this had yet to be brought together in a cohesive review. We conducted a systematic review of the literature regarding disparities in postoperative mortality for indigenous peoples compared to non-indigenous to provide relevant context for the remainder of the study.
Aim 2: To compare postoperative mortality risk between Māori and non-Māori. We conducted a cohort study using national-level data to a) describe the crude rate of postoperative mortality in New Zealand, both overall and by surgical procedure, for both Māori and Non-Māori, b) compare the risk of postoperative mortality between Māori and non-Māori, adjusted for age and sex; and c) examine the extent to which key drivers such as deprivation and comorbidity might explain disparities in postoperative mortality between Māori and non-Māori.
Each of these Aims were achieved within the life of the Project. The steps taken toward this achievement, as well as the outcomes of each Aim, are separately detailed in subsequent sections of this final report. In addition, we have also detailed additional preparatory work within the life of the project that will help to facilitate our future work in this area.