The Epidemiology and Management of Ischaemic Heart Disease in New Zealand: A Series of National Routine Health Data-Linkage Studies

Abstract

This thesis comprises a series of eight data-linkage studies that examined the epidemiology and management of ischaemic heart disease (IHD) in New Zealand over the last 12 years. Using individual-level linkage of routinely collected national data on almost the entire population, the first three studies investigated long-term statin use, acute revascularisation and case fatality in people hospitalised with acute coronary syndromes (ACS). The latter five studies were focused on all hospitalised and fatal IHD, examining pre-hospital IHD case fatality and contemporary trends in IHD hospitalisations, deaths, incidence and prevalence. The research demonstrated that most patients with ACS received appropriate evidence-based management. Approximately 65% of patients underwent angiography and 80% were dispensed a statin on discharge. Compared to Europeans, however, Māori and Pacific patients were 20% less likely to undergo revascularisation and 10-20% less likely to be maintained on a statin up to three years post discharge. Ethnic inequities in case fatality were also apparent. Compared to Europeans, Māori and Pacific patients were 50% more likely to experience a prehospital IHD death or die within 28 days of IHD hospitalisation, and twice as likely to die in the year following ACS hospitalisation. Analyses of trends in IHD between 2005 and 2016 demonstrated that IHD hospitalisation and mortality rates have been declining by 3-6% annually in men and women in all age groups, in those with and without a history of IHD and in all major ethnic groups. IHD prevalence is also declining in parallel with IHD incidence. Taken together, these findings indicate that primary and secondary prevention efforts in New Zealand have been successful. In spite of this success, however, ethnic inequities in IHD outcomes remain a major concern. Māori and Pacific people die from IHD at approximately twice the rate of Europeans, yet they experience fewer IHD hospitalisations for every IHD death, suggesting that there are important barriers to care for the highest needs groups in this country. To ensure that New Zealand continues to make gains in IHD, a concerted effort to improve outcomes and achieve equity for all ethnic groups, and in particular, Māori and Pacific, are needed.