Coronary artery disease in US may no longer be declining
Authors: New York
Journal: BMJ (2008)

The US decline in coronary artery disease may have ended in the mid 1990s and the disease may even be increasing, reports an unusually comprehensive autopsy study from the Mayo Clinic and the University of British Columbia.

“Our finding that temporal declines in the grade of coronary artery disease at autopsy have ended, together with suggestive evidence that declines have recently reversed, provides some of the first data to support increasing concerns that declines in heart disease mortality may not continue,” the authors write.

A possible reason may be the recent epidemics of obesity and diabetes, which began at about the time when coronary artery disease blockages in their study were no longer declining.

The study, published in the Archives of Internal Medicine, reviewed the incidence of coronary artery disease among 515 residents aged 16 to 64 of Olmsted County, Minnesota, who died from accidents, suicide, homicide, or other unnatural causes from 1981 to 2004 (Arch Intern Med 2008;168:264-70).

Nearly all (96%) had autopsies and 82% (425 individuals) had grades assigned to blockages in the four main coronary arteries. The grades ranged from 0 (no blockage in the cross sectional lumen) to 5 (100% blockage).

“Over the full period, 8.2% of the 425 individuals had high-grade disease, and 83% had evidence of any disease,” the authors write. Analyses adjusted for the individuals’ age and sex showed declines during the study period in high grade disease, the average grade of disease, and any disease. The decline was consistent with the national decline in self reported myocardial infarctions in data up to 1994.

In this study, however, the authors write, “among these non-elderly individuals…declines in the grade of coronary artery disease ended after 1995, and there is suggestive evidence that the grade of coronary artery disease may have increased since 2000.”

Although the autopsy rate in the US is a low 8.3%, Olmsted County has always had a higher rate. The county has a population of about 125 000 and is predominantly white. Apart from the county seat, Rochester—home of the Mayo Clinic, it is relatively isolated from other metropolitan cities. Medical care is provided by the Mayo Clinic and the Olmsted Medical Center, and four affiliated hospitals. All autopsies were done at the Mayo Clinic’s pathology department.

In an accompanying editorial, Drs Jay Olshansky and Victoria Persky of the University of Illinois at Chicago write that previous studies had shown that incidence and mortality from coronary artery disease in the United States and in Olmsted County had declined through the 1980s and 1990s, though declines were smaller in the 1990s. The current study may show a reversal in the trend toward decline (Arch Intern Med 2008;168:261).

“If so, the reversal in trends in young adults could precede that in older individuals in the future. A recent article…estimated that approximately 47% of the decline in coronary artery disease deaths from 1980 to 2000 was attributed to treatments, whereas 44% of the decline was caused by changes in risk factors. However, these improvements were partially offset by 8% and 10% increases in deaths from obesity and diabetes mellitus, respectively,” they write.

Although the Olmsted study is limited, “the results are alarming enough to alert public health officials to begin monitoring younger cohorts for early signs of coronary artery disease with much greater vigilance,” they say.