As of March 4, 2023, 1836 pieces of documents were retrieved. Only “Article” and “Review” were selected as article types, excluding editorials, letters, news, and other non-academic, retracted, and duplicated studies. Meanwhile, the language was limited to English, resulting in 1531 articles.
3.1 Annual publication and citation trends
Publication and citation trends of literature related to atrial fibrillation and cognitive dysfunction from 1997 to 2022 were shown in Fig. 1. The straight square referred to the annual publication volume, while the broken line represented the annual total citation frequency. The number of literature in relevant fields showed an increasing trend. At the end of the 20th century, researchers began to cover this field, but over the course of more than the after decade, it received insufficient attention. From 1997 to 2011, the number of publications in this field remained flat, with the annual number of publications ranging from 4 to 32. In 2012, the annual number of published articles exceeded 50 for the first time and has since entered a period of rapid growth, with a decrease in 2014 and 2017. The number of annual publications peaked at 204 in 2022, representing an annual growth rate of 9.09%.
3.2 Distribution of countries
Analyzing the global distribution of literature can help identify which countries have made critical contributions to this field so that you can track it closely. Studies on atrial fibrillation and cognitive dysfunction were distributed in 106 countries worldwide, among which European and American countries accounted for a large proportion. The United States led the world with 511 articles, accounting for 33.4 percent of the total, followed by the United Kingdom (191), Italy (181), China (155), Germany (115), Canada (115), Sweden (102), and Netherlands (101). In addition, Australia (98), Japan (80), Spain (77), France (72), and Denmark (54) also posted more than 50 articles. The rose chart in the lower left corner of Fig. 2 intuitively showed the number and proportion of publications by countries, while the world map represented countries’ collaboration networks. The nodes in the figure referred to the countries corresponding to the map. The denser the lines, the more the country communicated and cooperated with other countries.
3.3 Leading institutions
Understanding leading institutions can help us better track academic frontiers and seize opportunities for collaboration and exchange. So far, a total of 2906 research institutions around the world have participated in studies in this field. We used VOSviewer to visualize organizations with no less than 10 publications. As shown in network visualization (Fig. 3), 84 organizations met the criteria and were grouped into four clusters, represented by four colors. In this diagram, the size of the label and circle was determined by the weight of the occurrences of documents and the lines between items represented links. Distance between two institutions approximately indicated the relatedness of links. Generally, the closer two institutions are located to each other, the stronger their relatedness. According to the number of documents published by research institutions, Karolinska Institute, Harvard University, and Boston University ranked among the top three, University of Washington, the University of Liverpool, Johns Hopkins University, University of Massachusetts, University of Minnesota, Mayo Clinic, and Mcmaster University rounded out the top 10.
However, overlay visualization has different meanings for the size and color of circles (Fig. 4). The size is determined by total link strength; the more frequent and extensive the cooperation, the larger the circle. The color is determined by the Z-score (calculated by subtracting the mean and dividing by the standard deviation) of the item. A positive score means the item is ahead, while a negative score means it is behind. The absolute value of the score indicates how far the project deviates from the data center. The colors range from yellow (highest score) to green to blue (lowest score). The color bias toward yellow indicates that the institute has gotten active in this field recently.
The prominent institutions with high total link strength included the University of Liverpool, Karolinska Institute, Boston University, Aalborg University, Harvard University, and so on. In particular, the University of Liverpool and Aalborg University have been pooling their efforts in this field in recent years. Besides, Institutions such as Liverpool Heart & Chest Hospital, Northeastern University, University of Mississippi, Yonsei University, University of Basel, University Hospital Basel, University of Utah, and University of Bern are also famous for research on atrial fibrillation and cognitive dysfunction.
3.4 Prominent journals
We used a bibliometric online analysis platform pair to identify prominent journals in this field. Journal Impact Factor (JIF) and Journal Citation Reports™ (JCR) quartile reflect the quality and influence of the journal. Journals’ categories, based on the Science Citation Index Extension (SCIE), reflect the journal’s subject preferences. The journal categories are mainly Cardiac &Cardiovascular Systems, Clinical Neurology, and Geriatrics & Gerontology.
A total of 1531 articles were distributed in 554 journals. Table 1 showed the countries, impact factors, and quartiles of the top 10 journals with more than 15 publications. The journal with the most significant number of relevant publications was Stroke (61, 3.98%), followed by the Journal of Alzheimer’s Disease (36, 2.35%), Journal of the American Heart Association (33, 2.16%), and American Journal of Cardiology (28, 1.83%). Among the top 10 journals regarding the number of publications, 3 were distributed in Q1, and 5 were in Q2. More than half of these journals were from the United States, and 4 belonged to European countries. It is worth noting that Stroke (10.170, Q1) and Neurology (11.800, Q1) had impact factors of more than 10. Meanwhile, Stroke (7479), Neurology (1834), Journal of The American Geriatrics Society (967), American Journal of Cardiology (789), and Journal of Alzheimer’s Disease (732) were also in the top 10 cited journals.
Table 1
Top 10 journals on atrial fibrillation and cognitive dysfunction
No. | Journal | Category | TP (%) | Country | JIF2022 | JCR |
1 | Stroke | • Clinical Neurology • Peripheral Vascular Disease | 61(3.98) | USA | 10.170 | Q1 |
2 | J Alzheimers Dis | Neurosciences | 36(2.35) | Netherlands | 4.160 | Q2 |
3 | J Am Heart Assoc | Cardiac & Cardiovascular Systems | 33(2.16) | USA | 6.106 | Q2 |
4 | Am J Cardiol | Cardiac & Cardiovascular Systems | 28(1.83) | USA | 3.133 | Q3 |
5 | J Am Geriatr Soc | Geriatrics & Gerontology | 26(1.70) | USA | 7.538 | Q1 |
6 | Neurology | Clinical Neurology | 26(1.70) | USA | 11.800 | Q1 |
7 | Int J Cardiol | Cardiac & Cardiovascular Systems | 20(1.31) | Ireland | 4.039 | Q2 |
8 | PLoS One | Multidisciplinary Sciences | 18(1.18) | USA | 3.752 | Q2 |
9 | J Stroke Cerebrovasc | • Peripheral Vascular Disease • Neurosciences | 17(1.11) | USA | 2.677 | Q3 |
10 | Front Cardiovasc Med | Cardiac & Cardiovascular Systems | 16(1.05) | Switzerland | 5.846 | Q2 |
TP, Total number of publications; JCR, Journal Citation Reports. |
Figure 5 showed the changes in the number of journal publications during different periods with cluster graphs. Work in atrial fibrillation and cognitive dysfunction in Stroke, American Journal of Cardiology, Journal of the American Geriatrics Society, and Neurology began early, dating back to the late 20th century.
Journals that have increased their interest in this area in recent years were Journal of Alzheimer’s Disease, Journal of the American Heart Association, International Journal of Cardiology, Plos One, Journal of Stroke & Cerebrovascular Diseases, and Frontiers In Cardiovascular Medicine. Since 2015, the number of published papers in Stroke, Journal of Alzheimer’s Disease, Journal of the American Heart Association, Journal of the American Geriatrics Society, Journal of Stroke & Cerebrovascular Diseases, and Frontiers In Cardiovascular Medicine had increased significantly compared to previous periods. Simultaneously, Frontiers In Cardiovascular Medicine had achieved breakthroughs of zero.
3.5 Most impactful authors
Table 2 listed the top ten authors related to AF and cognitive dysfunction, all of whom had published no less than 15 articles. Lip GYH (University of Liverpool, England) (48) is the most prolific author, followed by Gottesman RF (Johns Hopkins University, USA) (24), Mcmanus DD (University of Massachusetts, USA) (22), Alonso A (Emory University, USA) (20), Bunch TJ (University of Utah, USA) (20). Eight of the top ten authors were from the United States, the other two came from the UK and South Korea, and all belonged to different organizations.
Table 2
Top 10 authors with no less than 15 publications on AF and cognitive dysfunction
No. | Author | Publications(%) | Institutions | Countries |
1 | Lip GYH | 48(3.14) | ·The University of Liverpool ·Liverpool Cardiovascular Science Center | England |
2 | Gottesman RF | 24(1.57) | Johns Hopkins University | USA |
3 | Mcmanus DD | 22(1.44) | University of Massachusetts | USA |
4 | Alonso A | 20(1.31) | Emory University | USA |
5 | Bunch TJ | 20(1.31) | University of Utah | USA |
6 | Chen LY | 15(0.98) | University of Minnesota Twin Cities | USA |
7 | Jacobs VR | 15(0.98) | University of North Carolina | USA |
8 | Joung B | 15(0.98) | ·Yonsei University ·Severance Cardiovasc Hospital | South Korea |
9 | May HT | 15(0.98) | Intermountain Medical Center | USA |
10 | Saczynski JS | 15(0.98) | Northeastern University | USA |
We built a collaborative network based on authors whose number of published papers was more than or equal to 7; of the 12 587 authors, 84 met the thresholds. Some of the 84 authors in the network were not connected; the result finally showed that a total of 57 authors were divided into seven clusters (Fig. 6). The authors in each column belonged to the same collaborative group, and the lines between them indicated their cooperation relationships. The size of nodes is proportional to the number of authors’ publications. The more yellow the node color is, the more closely the corresponding author has paid attention to this field in recent years. Lip GYH was the author who published the most articles and had the highest total association strength, and Joung B is part of a group that has been the most active in this field recently. Among the top 10 authors, Gottesman RF worked closely with Chen LY and Alonso A, while Mcmanus DD worked more with Saczynski JS. Meanwhile, although Bunch TJ, Jacobs VR, and May HT published many papers, they had relatively little research cooperation.
When two documents appear together in the reference catalog of the third document, the two documents form a co-citation relationship. Author co-citation analysis means that two authors are cited by a third author simultaneously, reflecting the similarity of research direction and density between authors[34]. The researchers used VOSviewer to visualize the collaborative network of 167 authors with 40 or more co-citations (Fig. 7). The authors with the highest co-citation frequency were Lip GYH (351), Bunch TJ (311), Wolf PA (270), Ott A (253), and Kalantarian S (228). All 167 authors were divided into four groups. The green one mainly consisted of Lip GYH, Wolf PA, Friberg L, Kirchhof P, Connolly SJ; the red cluster included Ott A, Folstein MF, Gorelick PB, Jefferson AL, Qiu CX, and others; the yellow group was mostly made up of authors such as Vermeer SE, Wardlaw JM, Pantoni L; the blue one was posed of Bunch TJ, Kalantarian S, Chen LY, Jacobs V, Kim D, and other co-workers.
3.6 Highly cited reference analysis
Highly cited articles in a particular field often reflect the breakthrough of research focus and the change of research direction in this field. Table 3 showed the top 10 cited literature in AF and cognitive function. The article with the highest number of citations was “Global, regional, and national age-sex specific all-cause and cause-specific mortality for 240 causes of death, 1990–2013: a systematic analysis for the Global Burden of Disease Study 2013” (Naghavi M, et al., 2015) (4637)[35], which pointed out that the age-standardized mortality rate of atrial fibrillation was increasing. Five of the top 10 papers suggested that atrial fibrillation was associated with cognitive dysfunction or dementia (#2, #3, #6, #7, #10). Notably, “Atrial fibrillation and dementia in a population-based study. The Rotterdam Study” firstly put forward that dementia and subtypes of Alzheimer’s disease and vascular dementia may be related to atrial fibrillation even if no clinical strokes had occurred, which opened the way for research into AF and cognitive dysfunction. The other four of the top 10 papers described the epidemiological characteristics of mortality, morbidity, risk factors, related pathophysiological pathogeneses, and clinical outcomes of atrial fibrillation or dementia (#1, #4, #5, #9). After adjusting for atrial fibrillation and other relevant variables, the remaining paper found that higher glucose levels may be a risk factor for dementia, even among persons without diabetes (#8).
Table 3
Top 10 highly globally cited documents
No. | Article Title | Journal | First Author | Year | TCs |
1 | Global, regional, and national age-sex specific all-cause and cause-specific mortality for 240 causes of death, 1990–2013: a systematic analysis for the Global Burden of Disease Study 2013[35] | Lancet | Naghavi, M | 2015 | 4637 |
2 | Vascular Contributions to Cognitive Impairment and Dementia A Statement for Healthcare Professionals From the American Heart Association/American Stroke Association[45] | Stroke | Gorelick PB | 2011 | 2276 |
3 | A multicenter risk index for atrial fibrillation after cardiac surgery[46] | Jama-Am Med Assoc | Mathew JP | 2004 | 843 |
4 | Projections on the number of individuals with atrial fibrillation in the European Union, from 2000 to 2060[47] | Eur Heart J | Krijthe, BP | 2013 | 701 |
5 | Incidence of Dementia over Three Decades in the Framingham Heart Study[48] | N Engl J Med | Satizabal CL | 2016 | 567 |
6 | Vascular risk factors for Alzheimer’s disease: an epidemiologic perspective[49] | Neurobiol Aging | Breteler MMB | 2000 | 514 |
7 | Atrial fibrillation and dementia in a population-based study. The Rotterdam Study[36] | Stroke | Ott A | 1997 | 509 |
8 | Glucose Levels and Risk of Dementia[50] | N Engl J Med | Crane PK | 2013 | 498 |
9 | Atrial Fibrillation: Epidemiology, Pathophysiology, and Clinical Outcomes[51] | Circ Res | Staerk, L | 2017 | 470 |
10 | Poststroke dementia[52] | Lancet Neurol | Leys D | 2005 | 461 |
TCs, Total number of citations of total publications. |
20 important articles in the relevant data set and their citation relationships were shown in Fig. 8. The results displayed that “Atrial fibrillation and dementia in a population-based study. The Rotterdam Study” (Ott A, 1997) received the most citations from other articles[36]. Ultimately, half of the articles were cited in “Atrial fibrillation as a risk factor for cognitive decline and dementia” (Singh-Manoux A, 2017)[17]. Among the 20 papers, 5 of them had more than 100 local citations. They were “Atrial fibrillation and dementia in a population-based study. The Rotterdam study” (Ott A, 1997) (189)[36], “Cognitive impairment associated with atrial fibrillation: a meta-analysis” (Kalantarian S, 2013) (165)[37], “Atrial fibrillation is independently associated with senile, vascular, and Alzheimer’s dementia” (Bunch TJ, 2010) (142)[38], “Atrial fibrillation and incidence of dementia: a systematic review and meta-analysis” (Kwok CS, 2011) (121)[39], and “Atrial fibrillation and the risk of incident dementia: a meta-analysis” (Santangeli P, 2012) (103) respectively[40], indicating that these papers were of landmark significance in the field of AF and cognitive dysfunction.
References with citation bursts referred to those references that are frequently cited by scholars in a specific field over a while. We listed 25 references with intense citation bursts identified by CiteSpace (Fig. 9). Except for the first citation burst, which occurred in 1998, titled “Atrial fibrillation and dementia in a population-based study. The Rotterdam Study”[36], the remaining 24 citation breaks occurred in 2010 and later. It is worth noting that “Cognitive impairment associated with atrial fibrillation: a meta-analysis” was the document with the most vigorous burst (Strength = 30.18), bursting from 2013 to 2018[37]. In addition, there are also four articles ongoing citation burst, titled “Less dementia with oral anticoagulation in atrial fibrillation” (Kalantarian S, 2013)[41], “Risk of dementia in stroke-free patients diagnosed with atrial fibrillation: data from a population-based cohort” (Kim D, 2019)[42], “Atrial Fibrillation and Cognitive Function: JACC Review Topic of the Week” (Diener HC, 2019)[43], and “2020 ESC Guidelines for the diagnosis and management of atrial fibrillation developed in collaboration with the European Association for Cardio-Thoracic Surgery (EACTS): The Task Force for the diagnosis and management of atrial fibrillation of the European Society of Cardiology (ESC) Developed with the special contribution of the European Heart Rhythm Association (EHRA) of the ESC” (Hindricks G, 2021)[44].
3.7 Analysis of keywords and subject areas
A co-occurrence network diagram of keywords was visualized in VOSviewer (Fig. 10). 94 keywords that appeared at least 20 times were clustered according to the research direction and roughly divided into 4 categories. The first cluster was the largest cluster, with 33 keywords marked in red, related to the mechanism of atrial fibrillation and cognitive dysfunction, including “cognitive impairment,” “dementia,” “Alzheimers-disease,” “hypertension,” “small vessel disease,” and “vascular risk factors.” The green cluster contained 29 keywords, focusing on epidemiological factors such as “risk factors,” “age,” “population,” “prevalence,” “mortality,” and “prediction.” Cluster 3 with 18 keywords represented by the blue circle concentrated on surgical treatment and postoperative outcomes of atrial fibrillation. The keywords included “atrial fibrillation,” “stroke,” “cognitive function,” “outcome,” “catheter ablation,” “follow-up,” “quality of life,” and “depression.” The last cluster in yellow, looked at the use and management of anticoagulants in patients with AF and consisted of 14 items, for example, “warfarin,” “anticoagulation,” “management,” and “guidelines.”
Combining the high-frequency words with their years of appearance can help us understand the changes in research direction and trends, to capture the research hotspots and frontiers. Figure 11 showed the hot words burst over the years. The circle size represents the frequency of the keywords, the abscissa corresponds to the year of their outbreaks, and the ordinate corresponds to the content of the keywords. The blue horizontal lines represent the period of the high-frequency hot words. As shown to us, new outbreak keywords included “fibrillation,” “midlife,” “recommendation,” “outcomes,” “catheter ablation,” and “epidemiology.” The most frequent hot words were risk factors, atrial fibrillation, dementia, stroke, Alzheimer’s-disease, and cognitive impairment, and the most intense years were 2017 and 2018.
With the help of the bibliometric tool, a thematic map was created, which can help researchers explore potential research areas. Its horizontal axis represents centrality, meaning relevance degree and the vertical axis represents density, which can also be considered as the degree of research development. In the first quadrant are motor themes, which are both critical and well-developed. The second quadrant is niche themes, which have developed well but are relatively unimportant for the current research. The third quadrant contains emerging or declining themes that are relatively marginal within the current field. The fourth quadrant represents basic themes, which are essential but not yet well developed. As was shown in Fig. 12, the prevalence of dementia and stroke was the most relevant research topic in this field and had been well-developed. Research on the management of anticoagulants such as warfarin and stroke prevention was well developed, and this theme was important. Other themes were highly relevant but had yet to see a rush of research, such as the relationships among blood pressure, mild cognitive impairment, and Alzheimer’s-disease, risk factors for cognitive impairment in patients with atrial fibrillation, and epidemiologic topics such as risk, mortality, and prevention.