The objective of this study is to investigate the degree of Japan's contribution to the research in rheumatology in the past decade. Articles published in 1991-2000 in highly reputed journals in rheumatology and general medicine were assessed through the MEDLINE database. Then, the number of articles having an affiliation with a Japanese institution was counted and summed up as a whole and also separately for each journal with statistical time trend analysis. The proportions of randomized controlled studies (RCT), case-control/cohort studies, and case reports in articles from Japan were also determined. Of total articles in rheumatology, Japan's contribution to the research reported in journals of rheumatology was 5.7% and ranked fourth in the world; in journals of general medicine, it was 1.2% and ranked eighth. The recent increase in contribution was significant (P = 0.01). Compared with other countries, the proportions of RCTs (1.1%) and case-control/cohort studies (6.4%) were smaller and that of case reports similar (5.9%) among the articles from Japan. In conclusion, we should determine and remove the factors that restrain high-quality clinical research to achieve a more significant contribution of Japan to research in rheumatology.
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