Japan's share of research output in urology and nephrology

Background: Recent studies have documented Japan's share of articles in different biomedical fields. However, Japan's contribution to urology and nephrology is not known. Methods: Seven journals in this field with the highest impact factors were selected to obtain relevant data. In June 2002, we searched the Medline database to obtain country affiliation details of articles published in the selected journals during 1991-2000. The proportion of articles with a higher grade of evidence (randomized controlled trials or clinical trials, cohort studies and case-control studies) were also generated and compared to the average values for all articles published in these journals. Results: Of the total number of articles (22 232), Japan's share of research output for the selected journals in urology and nephrology was 6% (1335 articles) and it ranked second in the world following the USA (56.5%). The recent increase in the share was statistically significant for Japan, Austria, France, Germany, Spain and Turkey. The proportion of articles with a high grade of evidence was lower for articles originated in Japan than for the total number of articles. Conclusion: Japan's contribution to urology and nephrology research is within the range of its contribution to other biomedical fields. However, the number of high quality clinical research conducted in Japan in this field was small.