Within a large community-based population, the incidence of MI decreased significantly after 2000, and the incidence of STEMI decreased markedly after 1999. Reductions in short-term case fatality rates for MI appear to be driven, in part, by a decrease in the incidence of STEMI and a lower rate of death after non-STEMI, based on research published June 10 in the New England Journal of Medicine.
Robert W. Yeh, MD, from the cardiology division at Massachusetts General Hospital, Harvard Medical School in Boston, and colleagues identified 46,086 patients at least 30 years of age in a community-based population (Kaiser Permanente Northern California beneficiaries), who were hospitalized for 18,691,131 person-years of follow-up from from 1999 and 2008.
The researchers calculated adjusted age- and sex-adjusted incidence rates for MI overall and separately for STEMI and non-STEMI. They identified patient characteristics, outpatient medications and cardiac biomarker levels during hospitalization from health plan databases, and ascertained 30-day mortality from administrative databases, state death data and Social Security Administration files.
The investigators found that age- and sex-adjusted incidence of MI increased from 274 cases per 100,000 person-years in 1999 to 287 cases per 100,000 person-years in 2000, and it decreased each year thereafter, to 208 cases per 100,000 person-years in 2008, representing a 24 percent relative decrease over the study period. Likewise, the age- and sex-adjusted incidence of STEMI decreased throughout the study period (from 133 cases per 100,000 person-years in 1999 to 50 cases per 100,000 person-years in 2008).
Thirty-day mortality was significantly lower in 2008 than in 1999, according to the authors.
However, revascularization rates increased across all patient populations, Yeh and colleagues reported. The proportion of patients who underwent revascularization within 30 days after MI increased from 40.7 percent in 1999 to 47.2 percent in 2008. Among patients with STEMI, 49.9 percent underwent revascularization in 1999 as compared with 69.6 percent in 2008. Among patients with non-STEMI, 33.4 percent underwent revascularization in 1999 as compared with 41.3 percent in 2008.
Interestingly, the authors wrote that the use of cardiac biomarkers also increased over the study period. The proportion of patients with MI who were known to have undergone troponin I testing increased from 53 percent in 1999 to 84 percent in 2004, with stable testing rates between 2004 and 2008. The proportion of patients who underwent CK-MB testing decreased from 75 percent in 1999 to 56 percent in 2008. Yet, the use of peak CK-MB levels and the CK-MB index decreased significantly over time among patients with MI who were tested overall, as well as among patients with non-STEMIs. There was no consistent trend for peak CK-MB levels among patients with STEMIs.
“The use of certain cardioprotective medications (e.g., statins, beta-blockers and aspirin) has increased over time, and these agents may have beneficial effects beyond their effect on risk factors and may contribute to a lower severity of subsequent cardiac events,” wrote Yeh and colleagues.
The authors concluded that the lower incidence of MI—particularly STEMI—is “probably explained, at least in part, by substantial improvements in primary prevention efforts, and these trends occurred despite the increased sensitivity of new biomarkers for the diagnosis of MI and the increasing prevalence of selected cardiovascular risk factors.”
Despite the progress reported in Yeh et al’s study, in the accompanying editorial, Jeremiah R. Brown, PhD, and Gerald T. O'Connor, PhD, wrote that “variations in socioeconomic factors are associated with disparities in attaining reductions in cardiovascular risk factors.” For instance, among people living below the poverty level, the rate of high cholesterol levels has increased by 0.4 percentage points, while the levels among people living above the poverty level have decreased by 0.4 to 2.2 percentage points.
Brown and O’Connor, from Dartmouth Institute for Health Policy and Clinical Practice in Lebanon, N.H., wrote that despite the availability of statins and other pharmacologic agents—including aspirin, beta-blockers and ACE inhibitors or angiotensin-receptor blockers—to modify the risk factors for coronary heart disease, the rate of improvement has “slowed down or stopped.”
They noted that heart disease remains