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. Methods: Incidence was defined as first occurrence of a major coronary event, i.e. the sum of first CHD hospital admissions and out-of-hospital CHD deaths without a hospital admission for CHD in the preceding five years. Mortality was defined as the sum of deaths coded to CHD and deaths coded to related causes but with prior hospitalisation for CHD (in the preceding five years). Data were sourced from the New Zealand Health Information Service and record linkage was carried out using a unique national identifier, the National Health Index (NHI). Given estimates for incidence and mortality, multi-state lifetables were built and estimates for prevalence, survival, lifetable risk, and median age at onset extracted. Results: Estimated prevalence of CHD increased exponentially from around 2% for males and 0.5% for females at age 40-44 to peak at around 18% and 12% respectively at age 85-89. Median age at onset of CHD was 67.5 years for males and 77.5 years for females. Median survival duration was 9.5 years for males and 6.2 years for females. The lifetable risk of CHD was estimated at 35% for males and 28% for females. Conclusions: This study provides a complete and internally consistent picture of the descriptive epidemiology of CHD for the whole New Zealand population in 2001-03. This information will be useful for planning and funding of coronary prevention, treatment and rehabilitation services.