Modern Trends in Myocardial Infarction

Heart disease, and in particular coronary heart disease, is the leading cause of death worldwide but rates have actually been declining since the 1950s likely due to reductions in smoking prevalence and the availability of effective treatments for hypertension.  Consequently, rates of death from acute myocardial infarction (MI) have also been falling but there is less data to characterize trends over the last decade which has seen the widespread introduction of effective and timely reperfusion strategies and the increased use of statins, beta-blockers, ACE inhibitors and dual antiplatelet therapy.
Examining data from Kaiser Permanente Northern California, a patient group of over 3 million people, the authors identified all hospitalizations in patients 30 years of age or older between 1999 and 2008 in whom the primary diagnosis was myocardial infarction.  Age and sex-adjusted incidence rates were calculated for myocardial infarction overall and separately for ST-segment elevation and non-ST-segment elevation MI.  In all 46,086 hospitalizations were identified during 18,691,131 person-years of follow-up.  Over the study period the incidence of myocardial infarction showed a very impressive 24% relative decrease from 274 cases per 100,000 person-years to 208 cases per 100,000 person-years in 2008 with an even more impressive decline in the rate of ST elevation MI from 133 cases per 100,000 person-years in 1999 to 50 cases per 100,000 person-years in 2008 (P<0.001 for linear trend).  Accompanying this was a significant fall in 30-day mortality (adjusted OR, 0.76; 95% CI, 0.65 to 0.89) driven both by the decrease in ST-elevation MI and a lower rate of death after non-ST-elevation myocardial infarction.
While this data is heartening and reflects the massive progress made in the delivery of treatment for acute coronary syndromes over the last decade and progress in reducing smoking and cholesterol levels, a note of caution needs to be sounded and this study may well be reflecting a nadir in the trends for myocardial infarction.  In this same period, there has been an insidious rise in the rate of hypertension from 30.0% to 31.3%, in the prevalence of type 2 diabetes mellitus from 9.4% to 10.2% and the rate of obesity has increased by 3.0 percentage points, from 31.1% to 34.1%.  These worrying trends may well stop and even reverse the gains in population health seen over the past decades.

Conclusion:

In this study both the incidence of and mortality form myocardial infarction was seen to drop over the last decade.  However, an increase in the prevalence cardiovascular risk factors may reverse this trend in the future.

• Yeh RW, Sidney S, Chandra M, Sorel M, Selby JV and Go AS.  Population trends in the incidence and outcomes of acute myocardial infarction.  N Engl J Med. 2010 Jun 10;362(23):2155-65.

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