Western Collaborative Group Study (WCGS): 25-Year Follow-up of Cardiovascular Disease Morbidity and Mortality
To conduct a 25-year follow-up of the surviving participants in the Western Collaborative Group Study, the first large prospective study of coronary heart disease risk factors to incorporate direct assessment of Type A behavior.
|Study Start Date:||July 1985|
|Estimated Study Completion Date:||June 1990|
The WCGS began in 1960 with 3,524 male volunteers who were employed by 11 California companies. Subjects were 39 to 59 years old and free of heart disease as determined by electrocardiogram. After the initial screening, the study population dropped to 3,154 and the number of companies to 10 because of various exclusions. The cohort comprised both blue- and white-collar employees. At baseline the following information was collected: socio-demographic including age, education, marital status, income, occupation; physical and physiological including height, weight, blood pressure, electrocardiogram, and corneal arcus; biochemical including cholesterol and lipoprotein fractions; medical and family history and use of medications; behavioral data including Type A interview, smoking, exercise, and alcohol use. Later surveys added data on anthropometry, triglycerides, Jenkins Activity Survey, and caffeine use. Average follow-up continued for 8.5 years with repeat examinations. During the 8.5 year follow-up, coronary heart disease occurred in 257 of the initially disease-free group, of whom 50 died of coronary heart disease. There were 90 non-coronary disease deaths. Multiple logistic analyses confirmed the roles of blood pressure, serum cholesterol and cigarette smoking as risk factors. The study also found that Type A behavior, as assessed by a Structured Interview, was associated independently with the risk of coronary heart disease and constituted a 2:1 risk.
In 1982, Dr. Richard Brand and Dr. David Ragland at the School of Public Health, University of California at Berkeley, conducted a Mortality Follow-up of the 3,014 WCGS subjects living in 1969. The purpose of the 1982 follow-up was to locate the original participants, determine vital status, and obtain information about the health status of the participants who were still alive, and cause of death of participants who had died between 1969 and 1982. All individuals contacted were asked to participate in the proposed 25-year follow-up physical examination. At that time in 1983 there were 2,534 surviving subjects. All data gathered by the 1982 Mortality Follow-up were used in the 25-year follow-up.
The follow-up evaluated the power of cardiovascular disease risk factors, as measured in 1960, to predict coronary heart disease morbidity and mortality over 25 years and to predict stroke. It also evaluated the power of changes in cardiovascular disease risk factors as observed across the seven repeat exams from 1960 to 1969, to predict long-term morbidity and mortality and provided the basis for a potential future follow-up of an aging cohort.
The 25-year follow-up extended the existing database by adding current risk factor status and cardiovascular disease morbidity data collected by physical examinations and personal interviews. The new data included physical, physiological, and biochemical variables, health behavior, medical and family history, and Type A behavior. Existing mortality records were updated and used to determine cause of death and, where possible, the extent of cardiovascular pathology.