THE INTERFACE OF EPIDEMIOLOGIC METHODS Interface of Genetics and Epidemiology

Genetic epidemiology is a hybrid discipline with a relatively short history of less than 50 years. The first mention of "epidemiologic genetics" can be found in the 1954 book by Neel and Schull (1), who suggested that the two parent disciplines must consider each other's strategies when studying common diseases such as cancer, diabetes, and heart disease that reflect joint effects of both genes and environmental factors. The hybrid discipline of genetic epidemiology emerged slowly over the next two decades, but the pace of interaction between genetics and epidemiology has accelerated recently. Epidemiology, the methodological science of public health, is the older of the two parent disciplines and has its roots in use of vital records or observational data to identify causal agents and/or mechanisms of disease transmission during the "bacteriologic revolution" of the 19th century. Epidemiology's history of systematic study design for observational data sparked development of numerous statistical approaches to test hypotheses and make causal inferences (2). The broader field of public health builds its combined intervention and health policy efforts upon sound epidemiologic findings. Savitz et al. (3) argued that epidemiology as a discipline must strive to maintain its scientific objectivity and independence from public health policy initiatives. Modern genetics (the biologic science of inheritance) can be traced to Gregor Mendel, an Austrian monk whose plant breeding experiments in the middle of the 19th century produced the underlying paradigm for genetics (4). The value of Mendel's experimental