Epidemiologic Studies of Birth Defects

Abstract

The term “epidemiology” was originally used to describe the study of epidemics. At first the word “epidemic” was confined to acute illnesses that appeared to “spread” within hours or days to afflict large numbers of people, but over the last half century the definition has broadened. Shortly after the Second World War it became apparent that some diseases, which probably had “incubation periods” of months or years, had become much more frequent than previously, and they began to be viewed as epidemics. Lung cancer and heart disease were the two conditions that appeared to prompt a dichotomy of epidemiology into infectious disease epidemiology (e.g., cholera, whooping cough, smallpox), and chronic disease epidemiology (e.g., lung cancer, heart attack). That dichotomy has been eliminated for many reasons, one of which is that epidemics of a number of chronic infections are now appreciated (e.g., kuru; Nathanson 1980).

This chapter is not intended to be a comprehensive historical review. Rather it is intended to focus on the state of the art in order to illustrate the difficulties encountered in conducting epidemiologic studies of substances like caffeine that are consumed by a large segment of the population, in the case of caffeine in a wide variety of beverages. The chapter begins with a general overview of problems encountered in conducting epidemiologic studies and continues (Sect. 5) with discussion of recent epidemiologic studies of caffeine and birth defects in the light of the problems each study poses