Increasing prevalence despite decreasing incidence of ischaemic heart disease and myocardial infarction. A national register based perspective in Denmark, 1980-2009

Aims: Mortality from ischaemic heart disease (IHD) including acute myocardial infarction (AMI) in Denmark peaked around 1977, after which a marked decline has occurred as a result of decreasing incidence and increasing effect of treatment. IHD is a chronic, relapsing condition, and the effect of these changes on the prevalence of IHD is not known.

Methods and results: Changes in incidence and prevalence in 2000-2009 are presented, using nationwide data from public registers. An incident case is defined as a subject registered with a diagnosis of IHD/AMI and without a prior diagnosis for the past 20 years (beginning in 1980). A prevalent case is defined as a subject surviving the first year after the incident diagnosis. Regarding IHD, age-standardised incidence rates declined significantly from 2000 to 2009 for both sexes (females 445 to 340/100,000, males 822 to 678/100,000), reflecting a reduction in the annual number of new cases from 19.345 to 16.757. In contrast, prevalence rates increased slightly (females 2389 to 2616/100,000, males 5447 to 5579/100,000). Due to an increased proportion of elderly in the population, the number of prevalent cases increased from 125,000 in 2000 to 150,000 in 2009. The number of subjects having survived an AMI increased from 67,000 to 72,000. About 3% of the Danish population is afflicted by IHD.

Conclusion: Decreasing incidence, reduced case fatality and demographic development result in an increased prevalence of IHD, since the decline in incidence is more than offset by a larger decline in case fatality. The epidemic of IHD is far from over, in spite of the marked success of prevention and treatment.