A History of Epidemiologic Methods and Concepts (review)

In 1996 the Wellcome Foundation and the Louis Jeantet Institute for the History of Medicine sponsored a conference in which historians and epidemiologists discussed the development of epidemiologic concepts and methods. Those papers and later contributions comprise this volume.

Epidemiology, according to Alfredo Morabia, is characterized by group comparisons that do not manipulate the exposures between the groups and by population thinking, by which he means that groups are more than the sum of their parts. Epidemiology is distinct from other sciences with similar concepts and methods because it has integrated them into a science to investigate the causes of health-related events in a population. Epidemiology as defined by these characteristics began in the eighteenth century, and its evolution continues.

Few would argue with Morabia. Epidemiology texts commonly cite from the Bible, antiquity, or Renaissance endeavors that we might call epidemiology, but whatever these "epidemiologists" were doing never caught on. Epidemiology began its sustainable development in the eighteenth century, as proto-epidemiologists solved population-level political or medical problems and developed the theoretical foundations of their praxis. Morabia stipulates that he is not presenting a history of epidemiology that explores how or why epidemiology emerged at that time or in those places. He has written instead what he calls an "epistemological perspective," and draws upon Jean Piaget: epidemiology began as "hands-on" work that used ratios, proportions, and rates to understand epidemics. He also incorporates Ian Hacking's observation that probabilistic thinking, epidemiology's backbone, emerged at the same time as epidemiology. Epidemiologists refined their concepts when they realized that group comparisons are prone to bias, confounding, or interaction and devised methods to control them. Most recently, epidemiologists have grappled with understanding efficient causality in epidemiology.

Other conference participants have presented historical papers. Wade Hampton Frost turned John Snow into epidemiology's first hero, around 1910. John Eyler focuses instead on Snow's contemporary, William Farr, whose miasmatic etiology of cholera presented to his contemporaries a more cogent explanation than did Snow's. Only when medical opinion beginning in the 1860s accepted Snow's theory of waterborne contagion did his work gain acceptance. Jan Vandenbroucke tells a similar story: on the Continent, Max von Pettenkofer's Bodentheorie needed displacement before Snow's contagionism could be accepted.

Snow and Farr participated in a nascent public health movement. Snow taught epidemiologists how to do "shoe-leather epidemiology" and to criticize rigorously methods and results. Farr by comparison studied numerical data to discern underlying regularities. Eyler shows how Farr's analysis of the Registrar-General's data improved the laws of mortality that Thomas Rowe Edmonds had devised in 1832. Burt Gerstman, Eyler, Gerry Hill, and Vandenbroucke show how Farr's On Prognosis (1838; complete text included in this volume) included a proto-version of longitudinal analysis and discriminated between risks and rates in a manner that modern epidemiologists rediscovered only in the 1970s. Farr's interest in statistics, Eyler asserts, was not influenced by Farr's study with Pierre Louis but by the then-current British belief that statistics strengthened arguments for reform.

Although Snow did little to control cholera, his methods informed a generation of British epidemiologists. Anne Hardy tells how British epidemiology, unlike German or American contemporaries who incorporated bacteriology into epidemiology, remained more observational, deductive, and population oriented. Only after World War I did a new generation integrate bacteriology into British epidemiology. This shift occurred not only because of bacteriology's increased scientific status, but also because of new institutional allegiances and as Hardy and Eileen Magnello show, new mathematical tools based on Karl Pearson's biometrics.

Papers by George Comstock on Wade Hampton Frost's tuberculosis cohort analyses and by Sir Richard Doll on the history of cohort studies point out how recently—since the mid-1930s—prospective studies have been systematically employed and thoroughly studied. Nigel Paneth, Ezra Susser, and Mervyn Susser show that case-control studies have their roots in late nineteenth-century clinical practice, and that...