The hypothesis that men in high stress jobs have an increased risk of developing coronary heart disease was tested during an 18-year follow-up study from 1965-1983 of a group of 7,909 men of Japanese ancestry in Hawaii. Of the 7,909 men who completed the first examination at baseline, 4,673 were free of prevalent coronary heart disease (CHD), stroke, and cancer for the duration of the study, while 3,236 had incident CHD. Of the 4,579 men with higher stress jobs, 1,440 of them developed CHD; of the men with lower stress jobs, 1,796 of them developed CHD. What is the study design