Screening for Cardiovascular Disease: A Comparison of Maori and non-Maori Risk Profiles

Abstract

Māori, the indigenous population of New Zealand (NZ), have poorer cardiovascular health outcomes compared to non-Māori. However, there is a paucity of documented cardiovascular risk profiles in rural Māori communities and urban Māori communities outside NZ’s largest city of Auckland. The overall study, the Hauora Manawa / Community Heart Study was designed to assess prevalence of CVD and associated risk factors, to identify objective markers of CVD risk and to monitor interventions and associated outcomes within a rural and urban Māori and an urban non-Māori community. The scope of this thesis was to compare the cardiovascular risk factor profiles of rural and urban Māori cohorts and an urban non-Māori community sample age- and gender-matched to the urban Māori.

Participants, aged between 20 - 64 years were randomly selected from the NZ electoral roll. A total of 252 rural Māori, 243 urban Māori and 256 urban non-Māori participants attended screening. Ethnicity was self-declared at interview. Demographic, personal and family medical history, lifestyle factors, accessing health services, established CVD risk markers, insulin resistance (IR) (impaired fasting glucose (IFG), HOMA-IR, MacAuley formula) and metabolic syndrome (ATPIII definition) were compared across the cohorts. Non-established CVD biomarkers (circulating and genetic) were investigated for associations with CVD risk factors in this study. Descriptive statistics, analysis of variance (ANOVA), χ2-tests, logistic and linear regression models were used to determine statistical associations (p < 0.05). Correction for multiple testing was applied.

Our findings illustrated a clear gradient of CVD risk factors across the community cohorts. Rural Māori carried the greatest burden of cardiovascular risk compared with their urban counterparts, despite the majority of participants within each community accessing primary healthcare services. Overall, rates of previously diagnosed cardiac history were comparable across the three cohorts; however salient risk factors common to rural and urban Māori were higher BMI, current smoking, pre-diabetes, type 2 diabetes (DM2), hypertension (HTN), dyslipidaemia (DL) and gout. Rates of treatment were comparable between the cohorts; however therapeutic targets at screening were sub-optimally achieved, particularly blood pressure, total cholesterol and LDL-cholesterol targets. Poor glycaemic control was observed in rural Māori participants with DM2. Similar rates of undiagnosed HTN and DL were observed across the cohorts. Metabolic-associated markers (creatinine and urate) were associated with existing cardiac history and DM2 in rural and urban Māori, whilst two DM2-associated genetic markers (rs5943634 and rs9465871) were associated with higher HbA1c across all cohorts.

In conclusion, this study highlighted that despite having similar rates of engagement with primary healthcare services, elements of cardiovascular profiles differed between rural and urban Māori cohorts, but levels of risk factors were generally greater than in non-Māori. Circulating and genetic markers showed few associations with CVD risk factors in this study and these findings require validation in larger Māori cohorts to determine their clinical relevance. In summary, opportunistic and early screening of CVD risk factors and intensive management to reach cardiovascular therapeutic targets are critical in reducing the cardiovascular burden among Māori.