The study described here was undertaken for two reasons. One reason was to ascertain whether smoking has an influence on death rates from lung cancer. The other reason was to ascertain whether smoking has an appreciable influence on the over-all death rate and, if so, what diseases are involved. The plan was to obtain smoking histories on a very large number of persons; to follow them for from three to five years; to ascertain the causes of death of those who died; and, finally, to correlate the mortality data with the previously obtained smoking histories. It was decided to limit the study to white men between the ages of 50 and 69, because this is the group in which the majority of deaths from lung cancer occur.
It was anticipated that the men would have to be followed for at least three years before an accurate estimate could be made
Hammond EC, Horn D. THE RELATIONSHIP BETWEEN HUMAN SMOKING HABITS AND DEATH RATESA FOLLOW-UP STUDY OF 187,766 MEN. JAMA. 1954;155(15):1316-1328. doi:10.1001/jama.1954.03690330020006