In total, 1890 articles on POD were found in the WoS core database. The top-100 cited ones are shown in the supplementary materials (Supplementary Sheet 1).
Citation Times and Publication Year
The selected articles were published between 1981 and 2022. As shown in Figure 1, with a number of 11, 2011 was the most productive year for highly cited articles. Citations ranged from 83 to 718 in the WoS Core Collection. However, the usage of these articles was relatively low with the highest count of 140 and the lowest count of 3 since January 2013. The highest usage count was 20 in the last 180 days. The above-mentioned information could be found in the Supplementary Sheet 1. We also displayed the 10 most frequently cited articles in Table 1 and the 10 most constantly used articles since January 2013 in Table 2 respectively.
Study Type
All the 100 articles were clinical related studies. There were 73 original studies and 27 secondary studies. As shown in Figure 2A, there were 2 retrospective database analysis studies, 14 reviews, 18 randomized controlled trials (RCTs), 1 pilot study, 9 meta-analysis or systematic review studies, 4 guidelines, 42 cohort studies, 3 case-control studies, and 7 case reports or case series studies. Furthermore, 73 studies had high-level evidence, whereas 27 studies had low-level evidence (Figure 2B).
Country/Region and Institution
Information on the author, institution, and country of the articles was analyzed. The United States of America (USA) was the most productive country with 54 top-100 cited articles (Table 3). Germany ranked second (13), followed by Canada (9), the United Kingdom (UK) (7), China (7), Denmark (6), and the Netherlands (6) (Table 3). The top-10 institutions of publication counts are presented in Figure 3A. Harvard University, with 16 articles devoted to the greatest contribution of the 100 publications. The second is the University of California with 14 publications, while Johns Hopkins University and Beth Israel Deaconess Medical Center came third with 9 publications. We also analyzed the co-authorship of organizations using VOSviewer. Figure 3B shows the network visualization of the organizations’ co-authorships. The 207 organizations formed 52 clusters, and different colors represent different clusters, as shown in Figure 3B. In the figure, nodes refer to organizations, circle color refers to clustering, and link thickness refers to co-authorship strength. For example, Harvard University, Beth Israel Deaconess Medical Center, Hebrew Rehabilitation Center for Aged, Brown University, Mount Sinai Hospital, and Brigham and Women’s Hospital formed blue clusters and had a strong co-authorship, while the University of California, Purdue University, and Duke University constructed the yellow cluster. The largest cluster included 20 items and the smallest cluster included 1 item.
Author Analyses
The Top-11 authors was presented in the Table 4. Marcantonio Edward R published 11 articles and ranked No. 1 in terms of article number, followed by Leung Jacqueline M (10) and Inouye Sharon K (9). The 11 authors all come from USA. To better reflect the contribution and influence of author’s research, we also analyzed the co-citation of authors by VOS viewer and presented the network visualization in Figure 4. Inouye Sharon K had the most citations and strongest co-citation strength. Marcantonio Edward R also had a strong interaction with other researchers.
Journal, IF and JCR Category Quartile
These articles came from 47 journals, top journals such as Lancet, New England Journal of Medicine, JAMA-Journal of the American Medical Association and the British Medical Journal. The highest IF was 168.9, while the lowest was 1.018. The mean IF of these journals was 18.04. The JCR categories included: (1) Anaesthesiology, (2) Surgery, (3) Geriatrics & Gerontology, (4) Medicine, General & Internal, (5) Gerontology, (6) Psychiatry, (7) Critical care medicine, (8) Cardiac & Cardiovascular systems, (9) Respiratory system, (10) Clinical neurology, (11) Orthopedics, (12) Multidisciplinary sciences, (13) Psychology, (14) Peripheral vascular disease, and (15) Neurosciences. Except 1 journal did not have a location in JCR Category Quartile system, 30 journals were in the Q1 zone, 10 in Q2, 5 in Q3, and 1 in Q4. Besides, the top-10 journals on IF are shown in Table 5.
Keywords Analyses
Finally, we conducted a co-occurrence analysis of all keywords through VOSviewer to reveal the impacts and trends. The more frequently a keyword is used, the closer relationship will be between the two keywords in co-occurrence analysis. The minimum number of occurrences of a keyword was set as 3 and 84 keywords were screened out. The keywords formed 6 clusters and the network visualization of keywords co-occurrence is shown in Figure 5A. The keyword with highest appearance (31) and link strength (193) was “delirium”(Figure 5B). The top-10 co-occurrence keywords also included “risk-factors”, “surgery”, “confusion assessment method”, “elderly patients”, “hip fracture”, “intensive care unit”, “cardiac surgery”, “general anesthesia” and “risk” Figure 5B). In order to better understand the trends in research topics over time, we used CiteSpace to analyze the keywords burst. In Figure 6, 25 keywords with the highest burst strength are shown in the first column. The keywords with the longest citation burst duration are “open-heart surgery” and “prognosis”. They were widely focused from 1992-2005. In most recent years, “double blind” and “cardiac surgery” have become booming research topics. It is worth noting that this was the second outbreak of the keywords “cardiac surgery.”