Smoking and coronary disease.

According to Feinstein,’ a “licensed” epidemiologist . . . “can obtain and manipulate the data in diverse ways that are sanctioned not by the delineated standards of science, but by the traditional practice of epidemiologists.” In this absence of “delineated standards” it is scarcely surprising that different investigators draw diametrically opposed conclusions. Thus we find on the one hand Shimkin’ proclaiming: “If there is any summit of achievement in cancer research during the past several decades, it must be the discovery, irrefutable proof, and obvious importance of the fact that tobacco smoking causes lung cancer in man and is associated with other severe hazards to health.” By contrast, Oldham” concludes “. I . we still do not know how cigarettes cause lung cancer, nor even, if we are particularly rigorous in our use of scientific logic, whether they do.” A similar confusion prevails in connection with ischemic heart disease. Perhaps the most detailed exposition of the thesis: “cigarette smoking is a cause of coronary heart disease,” is given in the recent report by the Surgeon General.’ Remarkably, the thesis rests on only two types of epidemiological evidence neither of which, nor both jointly, are adequate to establish cause. Inevitably, the first type of evidence concerns the positive, graded association that has generally, but not invariably, been observed between smoking and the risk of death from ischemic heart disease. Needless to say, the Surgeon General is well aware that association does not necessarily imply causation; the link could be explained