Using Days Alive and Out of Hospital to measure inequities and possible pathways for them after cardiovascular surgery in Aotearoa New Zealand: study protocol for a secondary data analysis

INTRODUCTION: In Aotearoa New Zealand (NZ), socioeconomic status and being of Māori ethnicity are often associated with poorer health outcomes, including after surgery. Inequities can be partially explained by differences in health status and health system biases are hypothesised as important factors for remaining inequities. Previous work identified inequities between Māori and non-Māori following cardiovascular surgery, some of which have been identified in studies between 1990 and 2012. Days Alive and Out of Hospital (DAOH) is an emerging surgical outcome metric. DAOH is a composite measure of outcomes, which may reflect patient experience and longer periods of DAOH may also reflect extended interactions with the health system. Recently, a 1.1-day difference in DAOH was observed between Māori and non-Māori at a hospital in NZ across a range of operations. METHODS AND ANALYSIS: We will conduct a secondary data analysis using data from the National Minimum Data Set, maintained by the Ministry of Health. We will report unadjusted and risk-adjusted DAOH values between Māori and non-Māori using direct risk standardisation. We will risk adjust first for age and sex, then for each of deprivation (NZDep18), levels of morbidity (M3 score) and rurality. We will report DAOH values across three time periods, 30, 90 and 365 days and across nine deciles of the DAOH distribution (0.1-0.9 inclusive). We will interpret all results from a Kaupapa Māori research positioning, acknowledging that Māori health outcomes are directly tied to the unequal distribution of the social determinants of health. ETHICS AND DISSEMINATION: Ethics approval for this study was given by the Auckland Health Research Ethics Committee. Outputs from this study are likely to interest a range of audiences. We plan to disseminate our findings through academic channels, presentations to interested groups including Māori-specific hui (meetings), social media and lay press.