Ancel Keys Lecture.

W hen I was a young doctor, we used to explain to our patients with atherosclerotic problems that unfortunately their arteries were wearing out: We did not need to seek causes because it was a result of old age.We were vaguely aware that the incidence rate varied in different populations, but no one saw this as an intellectual challenge; we were fatalists.It is to the Framingham group that we owe our understanding that this disease does not strike indi- viduals haphazardly like lightning; rather, it strikes very selectively and is drawn by identifiable risk factors.But it was Ancel Keys who led us to confront the more fundamental question, namely, why did the western epidemic of heart disease occur in the first place?Why do population incidence rates vary?Keys raised the debate regarding these questions in cardiology and preventive medicine to a new level.He did not merely provide some of the main answers; he also taught us to investigate the problems of a mass disease from a new viewpoint -that of the sick population.To honor his achievement by giving this first Ancel Keys Lecture is a weighty and anxious responsibility.My qualification for attempting the task is simply a keen awareness of the importance of his contribution.I shall first examine the preventive approach to individuals based on identifying and correcting their risk factors; then, I shall turn to the more basic and powerful population approach, which tackles the underlying causes of high incidence rates, and I shall explore the implications of some new data.My principal conclusion is that the two approaches are neither opposite nor even independent but rather highly interactive. Prevention in IndividualsMedicine is concerned primarily with patients, and preventive medicine is concerned with preventing people from becoming patients.Our profession is strongly oriented toward the problems of individuals and a wish to prevent them from changing from normal, healthy people into sick people.This leads us to think of the sick as a distinct group and of disease as a defined entity that is separate from normalcy.Indeed, the basis of clinical diagnosis is the assump- tion that with respect to each disease, the world is divided into just two classes -those who have it and those who do not.