Number of Authors in Japanese Obstetrics and Gynecology Case Reports: A Preliminary Observation

I have long felt that articles from Japan have more authors than those from other countries. I showed this for obstetrics and gynecology (OBGYN) case reports. Author numbers naturally increase in “large-scale studies,” such as international multicenter original articles. High–impact-factor (IF) journals often publish such studies, so author-number comparisons should be made within similar IF ranges, preferably in a single journal. To reduce bias, I examined case reports (i) from a single journal (Case Reports in Obstetrics and Gynecology), (ii) with all authors from one university, and (iii) with the first author affiliated with an OBGYN department. Article retrieval is described in the Supporting Information. I focused on the four most frequently represented countries: Japan, the USA, Turkey, and Italy. The Kruskal–Wallis test, followed by pairwise Mann–Whitney U tests with Bonferroni correction, was used. Median values with interquartile ranges (IQRs) are presented, and all analyses were two-sided with p < 0.05 considered significant. The number of authors on Japanese reports was significantly higher than those from the USA, Italy, and Turkey: 7 (IQR 6–9) for Japan, compared with 4 (3–5) for the USA, 5 (4–6) for Turkey, and 6 (5–6) for Italy (all p < 0.01) (Table 1). A 1997 BMJ report [1] described that cardiology articles from Japan had significantly more authors than those from other countries, and a 2022 report [2] reconfirmed this trend. However, those studies contained potential biases (i–iii). I avoided these biases and still found that case reports from Japanese OBGYN departments had larger numbers of authors. I analyzed only one journal and compared Japan with three countries, so conclusions are impossible. Still, avoiding biases (i–iii), the data show a tendency. Discussing reasons is beyond this scope, but cultural differences may play a role [1]; culture also influences who becomes the corresponding author [3]. In my professorship, excluding a contributor is often difficult, as contributions exist along a spectrum, especially in case reports. Authorship is important regardless of article type [4]. These factual data may inform further discussion on appropriate author numbers. Shigeki Matsubara: conceptualization, investigation, writing – original draft, writing – review and editing, formal analysis. I thank doctors Yuri Matsubara (Department of Public Health, Dokkyo Medical University, Japan) and Daisuke Matsubara (Division of Community and Family Medicine and Department of Pediatrics, Jichi Medical University, Japan) for their help. The author has nothing to report. The author has nothing to report. The author has nothing to report. The author declares no conflicts of interest. The data that supports the findings of this study are available in the Supporting Information of this article. Data S1: Article retrieval and author numbers. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.