Author Number May Matter in Determining Author Order

Hashimoto et al.'s recent paper [1] hit the point: “the customary assignment of department directors as the last, regardless of actual contribution, warrants reconsideration.” Indeed, Hashimoto et al.'s original article [2] showed that some countries tend to list department directors as the last author and the second author often serves as the corresponding author. I claimed that the second-to-last author, often a division leader and having led the study, should become the last author when warranted [3]. I share observations focusing on the author's number and the department director's role. First, the number of authors sometimes seems excessive, which complicates author order. In a four-authored paper, the first, second, second-to-last, and last authors all carry importance [1-3], and order may pose little problem. After retirement, most of my papers have been single- or two-authored, where author order does not exist. Second, several factors expand author number. (1) “Contribution” can be interpreted flexibly. For example, in a retrospective surgical study based on charts, senior surgeons who performed many operations are often included, even if they contributed little conceptually. (2) Excluding some doctors within a division can be difficult for the director. Directors may believe that “going together” strengthens bonds. (3) In Japan, first-authored papers are mandatory for board certification [4]. Residents therefore become first authors, even when their contribution is uncertain, further inflating author lists. In all these situations, staff cannot openly question authorship, and decisions rest entirely with directors. Conversely, author numbers may be too small for some multicenter studies. The Journal of Obstetrics and Gynaecology Research, a journal with which I am familiar, limits authors to 10. I examined multicenter studies (2014–2024) with ≥ 5 affiliations (n = 41): < 8 authors (7 articles), 9 (4), 10 (11), 11 (3), and > 12 (16). The sharp drop from 10 to 11 authors (11 → 3 articles) may reflect this policy. Importantly, listed authors are often department directors, whereas doctors who contributed substantially appear unlisted. Again, directors' judgments are decisive. My previous study showed that directors largely stop writing first-authored papers just after appointment [5]. While education becomes their priority, I sense a difference in their views on authorship before and after directorship. Author number can be excessive, and directors almost always occupy the last position. In multicenter studies, directors are listed even when author numbers are limited. I do not intend to criticize individuals; author number and order depend on directors' responsibility. ChatGPT-5 was used for grammar checking. The author has nothing to report. The author has nothing to report. The author declares no conflicts of interest. Data sharing is not applicable to this article as no new data were created or analyzed in this study.