ACS incidence dips in all but the most elderly

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Incidence of acute coronary syndrome (ACS) declined in Medicare beneficiaries in most age groups between 1992 and 2009, researchers reported online Aug. 11 in JAMA Internal Medicine.

Gautum R. Shroff, MBBS, of the Hennepin County Medical Center in Minneapolis, and colleagues analyzed a 5 percent Medicare sample between 1992 and 2009 to identify patients hospitalized for ACS. They found the incidence among patients between the ages of 64 and 74 years dropped from 56 percent to 50 percent. The rate for patients older than 84 years, though, rose from 11 percent to 15 percent.

Overall, annual unadjusted incidence remained at 2.4 percent to 2.5 percent until 2002. At that point, it began to slip lower steadily to 1.7 percent in 2009. Incidence of unstable angina dipped steadily from 1.5 percent to 0.6 percent in the study period while acute MI fluttered between 1.2 percent and 1.4 percent. Acute MI incidence in patients older than 84 increased from 2.8 percent in 1992 to 3.4 percent in 2002. Between 2002 and 2009, it then dropped to 2.6 percent.

Shroff et al credited prevention strategies for the declines. They pointed out that the incidence of acute MI was higher in their research compared with other community-based studies, and that the issue should be studied further.

“[T]he trend of declining ACS incidence was driven primarily by a reduction in unstable angina diagnoses, probably reflecting more frequent diagnosis of AMI [acute MI] relative to unstable angina due to expanded use of more sensitive cardiac biomarkers and changing definitions of ACS,” they proposed.