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Design, Rationale and Objectives
Design
The Cardiovascular Health Study (CHS) is a population-based longitudinal study of coronary heart disease and stroke in adults aged 65 years and older. Just over 5200 men and women (5201) were recruited from four communities: Forsyth County, North Carolina; Sacramento County, California; Washington County, Maryland; and Pittsburgh, Pennsylvania. An additional 687 African Americans were recruited after the initial baseline survey. The population from the Pittsburgh Field Center was entirely urban; and the other three Field Centers recruited a mixture of urban and rural populations.
Eligible participants were sampled from Medicare eligibility lists in each area. Those eligible included all persons living in the household of each individual sampled from the Health Care Financing Administration (HCFA) sampling frame, who were 65 years or older at the time of examination, were noninstitutionalized, were expected to remain in the area for the next three years, and were able to give informed consent and did not require a proxy respondent at baseline. Potentially eligible individuals who were wheelchair-bound in the home at baseline or were receiving hospice treatment, radiation therapy or chemotherapy for cancer were excluded.
Extensive physical and laboratory evaluations were performed at baseline to identify the presence and severity of CVD risk factors such as hypertension, hypercholesterolemia and glucose intolerance; subclinical disease such as carotid artery atherosclerosis, left ventricular enlargement, and transient ischemia; and clinically overt CVD. These examinations in CHS permit evaluation of CVD risk factors in older adults, particularly in groups previously under-represented in epidemiologic studies, such as women and the very old. The first of two examination cycles began in June 1989. Periodic interim contacts are schedules to ascertain and verify the incidence of CVD events, the frequency of recurrent events, and the sequellae of CVD.
Rationale
Risk factors for coronary heart disease (CHD) and stroke, and for other cardiovascular diseases (CVD), have been determined in middle-aged population groups, but the strength and importance of these factors in older individuals have not been clearly defined. Some studies have found conventional risk factors such as cholesterol and smoking, to weaken with advancing age. Other studies have found that there may even be a protective effect in the elderly of risk factors which have found to be important in younger populations. Conflicting findings raise the possibility that selective survival may significantly alter the importance of CVD risk factors in predicting the outcome or even the incidence of disease.
Objectives
The main objective of the study is to identify factors related to the onset of coronary heart disease and stroke. CHS is designed to determine the importance of conventional cardiovascular disease (CVD) risk factors in older adults, and to identify new risk factors in this age group, especially those that may be protective and modifiable. Other objectives are the following:
- To quantify associations of conventional and hypothesized risk factors with CHD and stroke.
- To assess the association of indicators of subclinical disease, identified by noninvasive measures such as carotid ultrasonography and echocardiography, with incidence of CHD and stroke.
- To quantify the association of conventional and hypothesized risk factors with subclinical disease.
- To characterize the natural history of CHD and stroke, and identify factors associated with clinical course.
- To describe the prevalence and distributions of risk factors, subclinical disease, and clinically diagnosed CHD and stroke.
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