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Mortality rates from coronary heart disease (CHD), and from acute myocardial infarction (AMI), in particular, have been declining steadily since the 1970s.1 2 Data from the MONICA study suggest that two-thirds of this decline can be attributed to changes in the incidence of first CHD events.1 Since the end of the MONICA study, CHD incidence has been monitored through national registries based on continuous updating of routinely collected data from hospital records.3 These data, however, are not without limitations. In this issue of Heart, Chan et al4 show that data from total hospital admissions can be misleading (see page 1589). Previous reports based on the same data showed a marked increase in hospital admissions for AMI, signalling a new epidemic of CHD.5 In a thorough reanalysis, Chan et al demonstrate that this is solely due to an increase in AMI readmissions and changes in diagnostic practices, rather than an increase in the incidence of first AMI.4 In fact, as in several other Western populations,1 2 the incidence of first AMI has been declining steadily in New Zealand since 1993.
Figure 1 shows data from the European World Health Organization (WHO) regional office on total CHD hospital admissions in selected European countries, based on national hospital registries.6 These data do not routinely distinguish first from recurrent admissions. The figure would appear to point to relatively small changes in CHD admissions during the past 5 years in the Netherlands, Spain and Italy, an increase in Denmark and a decline in Sweden. To what extent do these trends reflect changes in first CHD events, readmissions or diagnostic practices? To understand the relevance of this question, it is essential to reflect on the rationale for CHD surveillance.
RATIONALE FOR MONITORING TRENDS IN HOSPITAL ADMISSIONS
Trends in CHD admissions are usually used as …