Craig Wright

Explaining trends in coronary heart disease hospitalisations in New Zealand: trend for admissions and incidence can be in opposite directions

Background: A recent increase in the absolute number of hospitalisations for acute myocardial infarction (AMI) in New Zealand may signal a new epidemic of coronary heart disease (CHD). Objective: To quantify the impact of factors other than incidence of disease on these national hospitalisation trends. Methods: A total of 324 663 electronic records of New Zealand public CHD hospitalisations from 1993 to 2005 were examined. Repeat admissions were identified by record linkage using a unique national health identifier for each patient. Results: Hospitalisations for AMI increased by about 8% a year throughout the 13-year study period. Interhospital transfers increased by 117% over the study period, while readmissions increased by 42%. By 2005 over 60% of all admissions for CHD were readmissions. After accounting for readmissions, hospital transfers and population changes, the age-standardised first AMI hospitalisation rate peaked in 1995 and has since declined by 15%. Reciprocal trends in AMI and angina hospitalisations were seen, indicating changing diagnostic criteria. Overall hospitalisation rates for first CHD events remained relatively steady at about 216.4 events per 100 000 between 1993 and 2000 and subsequently declined by 25% to 162.2 events per 100 000 in 2005. Conclusion: Recent trends in hospitalisation rates for AMI are significantly influenced by factors other than underlying changes in CHD incidence. Increasing absolute numbers of admissions coded as AMI in New Zealand between 1993 and 2005 can be accounted for by increases in readmissions, increases in interhospital transfers, changes in diagnostic criteria for AMI and in demography.

Four out of ten patients are not taking statins regularly during the 12 months after an acute coronary event.

Background: In New Zealand, a setting in which national guidelines recommend statins for all patients with coronary heart disease (CHD) and cost barriers are low, patterns of use of these drugs are unknown. We investigated dispensing rates after hospital discharge for acute CHD event. Design: Retrospective cohort study. Methods: Drug dispensing, hospital diagnosis, and mortality records were linked by unique identifier for all New Zealanders aged 35–84 years after discharge following acute CHD event in 2007. We defined the statin dispensing ratio (SDR) as the proportion of days that 15,506 patients aged 35–84 years were dispensed such agents during the 12 months post discharge. An SDR ≥0.8 (80% or more days covered) was considered optimal. Results: Overall, 59% of the cohort had an SDR ≥0.8. Of patients dispensed statins in the 3 months before admission (n = 5506), almost all (99%; 5466) continued treatment during follow up and 82% had an SDR ≥0.8. In contrast, for patients not dispensed statins before admission (n = 8014), only two–thirds started statins during follow up and only 44% had an SDR ≥0.8. Of all patients with low statin dispensing (SDR <0.8), about one–quarter were not dispensed any lipid-lowering drugs, one-quarter received alternative lipid-lowering drugs, one-quarter stopped statins, and the remaining quarter were intermittent statin users. Conclusion: In a setting with few barriers to statin treatment, about 40% of patients had suboptimal statin dispensing during the year after hospital treatment for CHD. This study has identified four significant categories of suboptimal adherence that could inform quality improvement programmes.

Can the incidence and prevalence of coronary heart disease be determined from routinely collected national data? Population-based estimates for New Zealand in 2001--03.

Objective: To produce internally consistent estimates of coronary heart disease (CHD) incidence, prevalence, survival and mortality as a decision aid for service planning and resource allocation.

Ethnic differences in cause specific mortality among hospitalised patients with diabetes: a linkage study in New Zealand

Study objective: To describe patterns of excess mortality among patients with diabetes in three ethnic groups. Design: A linkage study of national hospital discharge records to death records. Setting: New Zealand. Participants: The study included 74 847 patients (11 268 Māori, 5730 Pacific, and 57 849 non-Māori/non-Pacific) aged over 25 years with a hospital discharge diagnosis of diabetes between 1988 and 2001. By the end of 2001, 29 295 (39%) of the cohort had died. Based on the underlying cause of death, standardised mortality ratios (SMRs) (95% confidence intervals) were calculated for each ethnic group and sex. Main results: Comparing the mortality patterns of patients with diabetes to the general population of the same ethnic group, adjusting for age and calendar period, all cause SMRs were higher for Māori women and men: 3.80 (95% CI: 3.64 to 3.97) and 3.44 (95%CI: 3.30 to 3.58) than for Pacific (men: 2.41 (95%CI: 2.21 to 2.61); women: 2.23 (95%CI: 2.06 to 2.41)) and non-Māori/non-Pacific (men: 2.98 (95%CI: 2.93 to 3.04); women: 2.99 (95%CI: 2.93 to 3.04)) people. SMRs were significantly raised for several causes of death, including cardiovascular disease and many site specific cancers. Conclusions: The pattern of excess mortality among Māori with diabetes may relate to severity of disease. This needs further investigation, as the excess mortality may be amenable to intervention.

The future of population registers: linking routine health datasets to assess a population's current glycaemic status for quality improvement

Objectives To determine the diabetes screening levels and known glycaemic status of all individuals by age, gender and ethnicity within a defined geographic location in a timely and consistent way to potentially facilitate systematic disease prevention and management. Design Retrospective observational study. Setting Auckland region of New Zealand. Participants 1 475 347 people who had utilised publicly funded health service in New Zealand and domicile in the Auckland region of New Zealand in 2010. The health service utilisation population was individually linked to a comprehensive regional laboratory repository dating back to 2004. Outcome measures The two outcomes measures were glycaemia-related blood testing coverage (glycated haemoglobin (HbA1c), fasting and random glucose and glucose tolerance tests), and the proportions and number of people with known dysglycaemia in 2010 using modified American Diabetes Association (ADA) and WHO criteria. Results Within the health service utilisation population, 792 560 people had had at least one glucose or HbA1c blood test in the previous 5.5 years. Overall, 81% of males (n=198 086) and 87% of females (n=128 982) in the recommended age groups for diabetes screening had a blood test to assess their glycaemic status. The estimated age-standardised prevalence of dysglycaemia was highest in people of Pacific Island ethnicity at 11.4% (95% CI 11.2% to 11.5%) for males and 11.6% (11.4% to 11.8%) for females, followed closely by people of Indian ethnicity at 10.8% (10.6% to 11.1%) and 9.3% (9.1% to 9.6%), respectively. Among the indigenous Maori population, the prevalence was 8.2% (7.9% to 8.4%) and 7% (6.8% to 7.2%), while for ‘Others’ (mainly Europeans) it was 3% (3% to 3.1%) and 2.2% (2.1% to 2.2%), respectively. Conclusions We have demonstrated that the data linkage between a laboratory repository and national administrative datasets has the potential to provide a systematic and consistent individual level clinical information that is relevant to medical auditing for a large geographically defined population.

The burden of coronary heart disease in Māori: population-based estimates for 2000-02

Objective: To estimate coronary heart disease (CHD) incidence, prevalence, survival, case fatality and mortality for Māori, in order to support service planning and resource allocation.