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(Stroke. 2008;39:1.)
© 2008 American Heart Association, Inc.

Editorials

The Importance of Epidemiological Studies Should Not Be Downplayed

From the University of Auckland (V.L.F.), New Zealand; and the University of Alabama at Birmingham (G.H.), Alabama, USA.

Correspondence to Valery L. Feigin, University of Auckland, Private Bag, 920193 Ferncroft St, Grafton Auckland, New Zealand 92019. E-mail v.feigin@ctru.auckland.ac.nz

Key Words: epidemiology

An extract of the first 250 words of the full text is provided, because this article has no abstract.

Epidemiology as the study of distribution and determinants of disease frequency in human populations can and should be considered a basic science in medicine. Indeed, epidemiological principles and methods (including methods of statistical analysis) form the basis of any medical research, from case reports and other descriptive studies to cohort studies and experimental clinical trials. A randomized controlled trial is no more than a cohort study in which the investigator(s) allocate the exposure being studied to the participants in a random manner.

The advancement of medical knowledge follows a process resulting in a "spectrum of evidence." Medical hypotheses are generated at the lowest level of evidence, where either clinical observations are made in a case-series or associations are observed in ecologic studies. An ecologic study is defined as an association study where associations between exposures and outcomes are made at the group level (ie, without jointly measuring exposures and outcomes in the same individuals). For example, it has been noted that individuals living in southern France and Italy have a unique diet (exposure), and also that they tend to have low rates of stroke and heart disease (outcome), suggesting a potential association of the diet and cardiovascular risk. Observations from these domains are considered weakest because of the lack of comparison groups in case-series and because multiple alternative pathways that can account for ecologic associations. The next level of evidence is considered the observational epidemiological studies that are generally classified as being (1) case-control, (2) cross-sectional, or (3) longitudinal cohort, . . . [Full Text of this Article]