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Observational Studies 1 (2015) 137-140 Submitted 3/15; Published 8/15 William G. Cochran and the 1964 Surgeon General’s Report Norman Breslow norm@u.washington.edu Department of Biostatistics University of Washington Seattle, WA 98195, USA By the late 1950’s the causal connection between cigarette smoking and lung cancer was well established. Several excellent retrospective (case-control) and prospective (cohort) studies had been published that led the US Surgeon General to declare “excessive smoking is one of the causative factors of lung cancer” (Burney 1959). The next few years brought new evidence of this and other major health effects of smoking. Although “medical opinion had shifted significantly against smoking” (United States Surgeon General’s Advisory Committee Report, 1964), no concerted action had yet been taken to alert the public to its dangers. The Federal Trade Commission (FTC) was clamoring for guidance on how to regulate the labeling and advertising of tobacco products. Accordingly, in 1962, Surgeon General Luther Terry selected an advisory committee of ten members to revisit the scientific evidence and produce a technical report on the health hazards of smoking. Representatives of government, medicine and industry, including some from the Tobacco Institute Inc., submitted a list of over 150 candidates for possible appointment to the committee. Each organization reserved the right to veto, without explanation, any name on the list. People who had taken a position on the issue, which included all those who performed the studies under review, were excluded from consideration. The committee on smoking and health ultimately comprised eight physicians, one chemist and one statistician, William Cochran. Reputed to be a “statistician you could talk to,” Cochran was by then well known for prior service on several national advisory committees dealing with prominent science policy issues: the effectiveness of the battery additive ADX2; an evaluation of the Kinsey report on sexual behavior; and the planning of the Salk polio vaccine trial (Meier, 1984). His acceptability to all the organizations responsible for proposing candidates may have been helped by the fact that he was a heavy smoker (Colton, 1981). Indeed, smokers made up half the committee. Cochran’s influence on the report and its conclusions was enormous. Although none of its chapters were attributed to individual committee members, he was known in particular to have written Chapter 8, Mortality, and its appendices. This chapter reviewed seven large cohort studies of smoking and mortality in men. In his recent bestseller, Siddartha Mukherjee (2010) stated: The precise and meticulous Cochran devised a new mathematical insight to judge the trials [studies]. Rather than privilege any particular study, he reasoned , perhaps one could use a method to estimate the relative risk as a composite number through all the trials in the aggregate. (This method, termed meta-analysis, would deeply influence academic epidemiology in the future.) c ⃝2015 Norman Breslow. Breslow Table 26 of Chapter 8 contained the key results. Its importance to the overall evaluation of the evidence was apparent from the fact that an abridged version appeared as Table 2 in Chapter 4, Summaries and Conclusions. For each of 25 specific causes of death, and for all causes, the table listed for each of the seven studies the observed numbers of deaths in smokers, the expected numbers and their ratio. Following principles of indirect standardization , the expected numbers were the sum over age categories of the age-specific death rates among non-smokers times the age-specific person-years of observation for smokers. Age adjustment was essential. Since smokers were younger than non-smokers, their crude death rates were less than those for non-smokers. Cochran’s innovation was to present two summaries of the seven mortality ratios for each cause of death. The first was a summary mortality ratio, where the expected number was obtained by pooling the age-specific data over studies. The second was simply the median of the mortality ratios for the seven studies . These were remarkably consistent: 10.8 vs. 11.7, respectively, for lung cancer; 1.7 vs. 1.7 for coronary artery disease, the most common cause of death; and 1.68 vs. 1.65 for all causes. In...

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