Japan's contribution to research in rheumatology

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.