Extract
Epidemiology is the study of the distribution and determinants of disease
frequency1. In the
fifth century BC, Hippocrates suggested that the development of human disease
might be related to the external and internal environment of an
individual1. In the
1600s and 1800s in England, John Graunt and William Farr quantified vital
statistics on the basis of birth and death
records1. In the
1850s, John Snow associated cholera with water contamination in London by
observing higher cholera rates in homes supplied by certain water
sources1.
Epidemiological methods gradually evolved with use of the case-control study
to demonstrate an association between smoking and lung cancer, use of the
prospective cohort study to determine risk factors for cardiovascular disease
in the Framingham Heart Study, and use of the randomized clinical trial for
the poliomyelitis
vaccine1. The
evidence-based medicine and patient-derived outcomes assessment movements
burst onto the scene of clinical medicine in the 1980s and 1990s as a result
of contemporaneous medical, societal, and economic influences. Pioneers such
as Sackett and Feinstein emphasized levels of evidence and patient-centered
outcomes
assessment2-10.
Work by Wennberg and colleagues revealed large small-area variations in
clinical practice, with some patients being thirty times more likely to
undergo an operative procedure than other patients with identical symptoms
merely because of their geographic
location11-16.
Additional critical research suggested that up to 40% of some surgical
procedures might be inappropriate and up to 85% of common medical treatments
were not rigorously
validated17-19.
Meanwhile, the costs of health care were rapidly rising to over two billion
dollars per day, increasing from 5.2% of the gross domestic product in 1960 to
16.2% in 199720.
Health maintenance organizations and managed care emerged. In addition,
increasing federal, state, and consumer oversight was brought to bear on the
practice of clinical medicine.