The objectivity, validity and credibility of research in clinical medicine can be enhanced by the appropriate involvement of epidemilogy. However, the overall contribution of epidemiology to clinical research, either as a methodology or as a resource for research, has been poorly quantified. We therefore assessed the involvement of epidemilogy in influential publications in the field of clinical medicine, and made an international comparison on a quantitative basis. The 500 most frequently cited papers published during 1981-96 in the field of clinical medicine in the US, the UK, and Japan were compared in terms of epidemilogical involvement using pre- determined criteria. The three criteria were based on the indexing of relevant MeSH keywords, publication types, or the departmental affiliations of the authors. For all three criteria, the proportion of clinical papers with epidemiological involvement was the highest in the US, followed by the UK, whereas it was the lowest in Japan. The difference was almost four-fold between the US and Japan. There was also an increasing trend of epidemiological involvement in publications of clinical medicine over the years, which was more apparent in the US than in either the UK or Japan. These findings may reflect inter-country differences in resources as well as in the stance towards evidence-based health sciences.
J Epidemiol, 2001 ; 11:41-45