Minnesota Business and Professional Men’s Study
The Minnesota Business and Professional Men study was the first systematic cohort study of characteristics measured in healthy participants for their value in predicting heart attacks. It had no a priori hypotheses, but measured a number of potential risk factors. The study focused on a group consisting of a single socioeconomic class and only attempted to describe differences within that group. The main purpose of the study, undertaken by Dr. Ancel Keys and his team of researchers, was to compare pre-CHD development characteristics of men who developed CHD to those who did not develop CHD.
In a prospective cohort design, the researchers examined a group of approximately 300 men aged 45-55 years and 200 men younger than 45. The majority of participants were obtained through a listing of 1000 men stable in their employment whose names were provided by their corporations and the University of Minnesota. Of these men, 916 responded to the initial solicitation (91.6% response rate). After determining eligibility to participate, the 50 most overweight, 50 most underweight and 50 most physically active men were selected to participate. A random drawing provided the remaining 150 subjects. The subjects were first examined in fall of 1947, and a few were excluded for pre-existing medical conditions. Several others withdrew, bringing the final number of participants to 281. These subjects received an annual physical over the 15 year duration of the study and again in 1983.  During these physicals, measurements of blood pressure, weight and urinalysis were taken, as well as a blood sample and ECG. Serum cholesterol was estimated using the Bloor method. Skinfold thickness measurements were taken in 1948, 1949, 1951 and 1954. Medical history was carefully assessed to determine if any changes had been made in the subject’s “natural characteristics,” like radical alterations to diet or physician prescription to antihypertensive drugs.
From 1948-1963, 32 deaths occurred in the cohort, 17 of which were attributed to coronary heart disease. Myocardial infarction occurred in 22 men. Seven subjects developed angina pectoris with ECG ischemia, and two cases of angina without ECG were also reported. One subject died a sudden ischemic death. Compared to the general male U.S. population, this mortality was quite low. U.S. Vital statistics suggested that for a sample of the general population the size of the study population, 72 deaths should be expected over the 15 year period. The investigators attributed this difference in mortality to the recruiting procedures used in the study.
After 35 years of follow-up, 183 subjects died, 110 were alive, and one could not be located. Entry body fatness, indicated by body mass index, skinfold thickness at three sites, relative girth, and body density did not differ significantly among 35-year dead from the living when analyzed in multiple regression.  Analysis based in 1983 data was also conducted to ascertain the effect of HDL cholesterol level on longevity. Surviving subjects did not differ in mean HDL from the men who died but they had higher values of HDL than the men who had died of CHD. Subjects who had died of cancer had significantly higher HDL cholesterol than subjects who had died of CHD. 
In terms of risk factors examined, the investigators found an increasing risk of developing CHD with each higher class of cholesterol level, thus signaling its importance when considered singly. They also found that the combination of high systolic blood pressure and high body weight (above the 80th centile) also was highly significant. The investigators also examined a number of other variables in comparison to other study populations in Framingham, MA, Chicago, Los Angeles and Albany, NY. Each study population consisted of individuals from a variety of backgrounds. The Minnesota Businessmen Cohort had lower levels of serum cholesterol than any other cohort, however, across cohorts, as serum cholesterol level increased, so did risk for developing CHD. Strengths of the study include a long follow-up period. A weakness of the study was the inadequate sample size for coronary endpoints, and that the data could not be generalized to any larger groups than those of high socioeconomic status who were successful in business and professional life. (HB)
 Keys, A., Taylor, H.L., Blackburn, H., Brozek, J., Anderson, J.T., and Simonsen, E., 1963. Coronary heart disease among Minnesota business and professional men followed fifteen years. Circulation, 28 (9), 381-395.
 Keys, A., 1989. Longevity of man: relative weight and fatness in middle age. Annals of Medicine, 21 (3), 163-8.
 Keys, A., 1988. High density lipoprotein cholesterol and longevity. Journal of epidemiology and community health, 42 (1), 60-5.