Chicago Peoples Gas Company Study
The Chicago Peoples Gas Study began in January, 1958 as a long-term observational study of an industrial cohort to examine coronary heart disease (CHD) without systematic intervention. The goal of the study was to determine incidence of CHD in a middle aged male population in respect to their entry characteristics 
Of the 1,594 male employees ages 40-59 at entry from the Chicago Peoples Gas Company, 1,465 agreed to the initial examination (92% response rate); 1,411 of 1.609 (88 %) ages 25-39 responded. The baseline examination included measurements of serum cholesterol, blood pressure, smoking status, weight, history of alcohol abuse, and an ECG. Socioeconomic information was obtained from personnel records. Subjects free of coronary heart disease were eligible for participation as a cohort.
At baseline, the middle-aged cohort had a mean diastolic blood pressure of 83.1 mm Hg and a mean cholesterol level of 237.5 mg/dL. 72.8% of the men were current smokers and 15.3% were former smokers. 
The cohort data were subsequently pooled with other longitudinal studies conducted in Chicago. Multivariate analyses after 12 to 30 years in the combined studies found independent positive relationships to CHD and all-causes deaths for: entry serum cholesterol and blood pressure level and cigarette use, for men and women of all age groups. 
“These findings indicate great potentials for prevention of the CHD epidemic and for increased longevity with health for men and women, through improved life-styles and consequent lower risk factor levels.”  (HB/FB)
 Liu K, Cedres LB, Stamler J, Dyer A, Stamler R, Nanas S, Berkson DM, Paul O, Lepper M, Lindberg HA, Marquardt J, Stevens E, Schoenberger JA, Shekelle RB, Collette P, Shekelle S, Garside D (1982). Relationship of education of major risk factors and death from coronary heart disease, cardiovascular diseases and all causes. Circulation 1982; 66: 1308-1314.
 Stamler, J, Dyer, AR, Shekelle, RB, Neaton, J, and Stamler, R. Relationship of baseline major risk factors to coronary and all-cause mortality, and to longevity: Findings from long-term follow-up of Chicago Cohorts. Cardiology 1993;82:191-222.