Olmsted County Study

Background/Question: Elveback and Connolly and other researchers at the Mayo Clinic created the Olmsted County Study partly in response to the national decline in mortality from coronary heart disease in the United States. This study used a population sample from Olmsted County to study cardiovascular disease trends in Olmsted County and compare them to national findings.

Population/Methods: To determine the study population, medical records from the virtually complete local coverage by Mayo Clinic hospitals were screened for a diagnosis of angina pectoris, myocardial infarction, or sudden unexpected death from 1950 to 1975. There were 3,080 incident coronary cases during the study period, and for each case information collected included age, sex, height, weight, initial manifestation, electrocardiographic information, laboratory data, associated diseases, antihypertensive medication, and follow-up information.

Results: The incidence trends seen in Olmsted County followed mortality trends seen on a national level. Improved case-fatality and survival rate in the 1970’s contributed, along with a fall in sudden deaths, to the decline in coronary mortality rates. Incidence was higher for males than for females (ratio 2.2) and incidence peaked between 1955 and 1959 but mortality continued to increase for another decade. Later follow-ups of this population group saw a stabilization of sudden deaths and incidence while survivorship in angina patients improved.

Conclusions/Discussion: This population study was uniquely effective in completeness of follow up and initial design because the population was relatively isolated from other urban centers, medical care was virtually self-contained within Rochester, MN, and most medical care was provided by the Mayo Clinic. The Olmsted County Study was among the first, along with the DuPont Study and Minnesota Heart Survey, to show an actual decrease in CHD incidence as well as mortality rates in U.S. men, but an increase in the 1980s in women. It also recognized a plateau in stroke mortality rates in the 1990s. (FB/HB)