Favourable trends in incidence of AMI in Norway during 2001-2009 do not include younger adults: a CVDNOR project

Aims Acute myocardial infarction (AMI) incidence reflects levels of risk factors in the general population and influences coronary heart disease mortality rates. We examined trends in AMI incidence in Norway during 2001-2009 and potential differences between sex and age groups. Methods All AMI hospitalizations (ICD9 410; ICD10 I21, I22) and coronary out-of-hospital deaths (ICD9 410-414; ICD10 I20-I25) in Norway for individuals 25 years were obtained during 1994-2009. Incident AMI was defined as a hospitalization or out-of-hospital death due to AMI with no prior hospitalization for AMI during the previous 7 years. Age-standardized and age-group specific rates were calculated and expressed per 100,000 persons. The annual changes in rates were obtained from Poisson regression analyses. The total change in incidence rates during 2001-2009 were then calculated based on the estimated annual change. Results We identified 148,522 incident AMIs (41% women; 21% out-of-hospital deaths) during 2001-2009. Incidence rates declined by 24% (incidence rate ratio, IRR, 0.76, 95% CI 0.75-0.78). Out-of-hospital death rates declined more than hospitalization rates (IRR 0.54, 95% CI 0.52-0.56 vs. IRR 0.84, 95% CI 0.82-0.85; p<0.001). The decline in incidence rates was observed among those 45 years or older. Among persons under 45 years, AMI incidence rates did not change significantly, while hospitalization rates increased with 11%. Conclusion AMI incidence rates declined during 2001-2009. The decline was due to reductions in rates of out-of-hospital deaths and hospitalizations in individuals 45 years or older. A worrying increase in hospitalization rates was observed in those younger than 45 years.