Heart attacks declined 24 percent in Kaiser Permanente northern California since 2000

Oakland, Calif. (June 9, 2010) – Heart attacks declined by 24 percent within a large, ethnically diverse, community-based population since 2000, and the relative incidence of serious heart attacks that do permanent damage declined by 62 percent, according to a Kaiser Permanente Division of Research study in the current issue of the New England Journal of Medicine.

The reductions in death after heart attack are driven in part by the decline in incidence of more severe heart attacks known as ST-elevation myocardial infarction, as well as a lower mortality rate after less severe non-ST-elevation heart attacks, explained Alan S. Go, MD, the lead investigator of the study and director of the Comprehensive Clinical Research Unit at the Kaiser Permanente Division of Research in Oakland, Calif. Go explains that ST-elevation heart attacks are diagnosed by a specific electrocardiogram finding that indicates more severe injury to the heart muscle.

This study of more than 46,000 patients in Northern California aged 30 years and older who suffered a heart attack is the first study to provide a contemporary population view of heart attack incidence in a large, diverse community. Previous studies focused on selected subgroups and/or populations with limited diversity and have not separately examined ST-elevation and non-ST-elevation heart attacks. It is also the first to examine the possible influence of widespread use of cardiac biomarkers (particularly troponin) on heart attack trends, which might be expected to lead to an increase in the reported rate of heart attacks, particularly non-ST-elevation heart attacks.

"This research provides new insights into the changing landscape of heart attack incidence and associated outcomes in the community," Go said. "Despite our ability to more easily diagnosis heart attacks using sensitive biomarkers, we found a consistent trend of fewer severe ST-elevation myocardial infarctions over the past decade—the type of heart attack we particularly want to prevent."

Heart attacks with ST-elevation are a true emergency, most often requiring an immediate procedure to open the blocked artery, noted Robert W. Yeh, MD, an interventional cardiologist at the Massachusetts General Hospital and Harvard Medical School who was the first-author of the study. "These findings are welcome news for those of us in the cardiology community. Perhaps we have turned the corner on preventing the most severe presentation of heart disease."

Researchers identified 46,086 patients aged 30 and older within Kaiser Permanente in Northern California who were hospitalized for heart attacks between 1999-2008 and found the age- and sex-adjusted incidence of heart attack increased from 274 per 100,000 in 1999 to 287 per 100,000 in 2000, then declined each year thereafter to 208 per 100,000 in 2008 (24 percent decline between 1999 and 2008). However, the age- and sex-adjusted incidence of ST-elevation myocardial infarction declined by 62 percent from 133 per 100,000 in 1999 to 50 per 100,000 in 2008. Age- and sex-adjusted incidence of non-ST-elevation myocardial infarction also declined since 2005, which followed widespread implementation of sensitive cardiac testing known as troponin I, which helps diagnose heart attacks. Thirty-day mortality was significantly lower in 2008 compared with 1999.

Because the study population is within an integrated delivery system, it provided an accurate assessment of total membership at any point in time and comprehensive identification of those hospitalized for heart attack. The population has broad age, gender, and ethnic diversity and is highly representative of the local and statewide population. Researchers also demonstrated that the results were consistent after removing the possible effects of different types of patients joining or leaving the health plan membership over time.

Additional authors on the study are Stephen Sidney, MD, MPH; Malini Chandra, MBA, MS; Mike Sorel, MPH and Joe V. Selby, MD, MPH, with the Kaiser Permanente Division of Research. Funding for the study was provided by the Schering-Plough Future Leaders in Cardiovascular Medical Research Grant and The Permanente Medical Group, whose 7,000 physicians provide care for 3.3 million Kaiser Permanente members in Northern California.

The Kaiser Permanente Division of Research conducts, publishes, and disseminates epidemiologic and health services research to improve the health and medical care of Kaiser Permanente members and the society at large. It seeks to understand the determinants of illness and well-being and to improve the quality and cost-effectiveness of health care. Currently, DOR's 500-plus staff is working on more than 250 epidemiological and health services research projects.

Massachusetts General Hospital (www.massgeneral.org), established in 1811, is the original and largest teaching hospital of Harvard Medical School. The MGH conducts the largest hospital-based research program in the United States, with an annual research budget of more than $500 million and major research centers in AIDS, cardiovascular research, cancer, computational and integrative biology, cutaneous biology, human genetics, medical imaging, neurodegenerative disorders, regenerative medicine, systems biology, transplantation biology and photomedicine.

About Kaiser Permanente

Kaiser Permanente is committed to helping shape the future of health care. We are recognized as one of America's leading health care providers and not-for-profit health plans. Founded in 1945, our mission is to provide high-quality, affordable health care services and to improve the health of our members and the communities we serve. We currently serve 8.6 million members in nine states and the District of Columbia. Care for members and patients is focused on their total health and guided by their personal physicians, specialists and team of caregivers. Our expert and caring medical teams are empowered and supported by industry-leading technology advances and tools for health promotion, disease prevention, state-of-the art care delivery and world-class chronic disease management. Kaiser Permanente is dedicated to care innovations, clinical research, health education and the support of community health. For more information, go to: www.kp.org/newscenter.