• Users Online: 247
  • Print this page
  • Email this page

Table of Contents
Year : 2021  |  Volume : 7  |  Issue : 4  |  Page : 477-482

CiteSpace-based metrical and visualization analysis of tai chi chuan an algesia

1 Acupuncture and Tuina School, Chengdu University of Traditional Chinese Medicine, Chengdu, China
2 School of Medical Information Engineering, Chengdu University of Traditional Chinese Medicine, Chengdu, China
3 Centre for Health, Activity, and Rehabilitation Research, School of Physiotherapy, University of Otago, Dunedin, New Zealand

Date of Submission14-Feb-2021
Date of Decision22-Mar-2021
Date of Acceptance22-Mar-2021
Date of Web Publication08-Jun-2021

Correspondence Address:
Prof. Hai-Yan Yin
Acupuncture and Tuina School, Chengdu University of Traditional Chinese Medicine, Chengdu 610075
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2311-8571.317994

Rights and Permissions

Objective: The objective of the study was to explore the research status and hot topics that are most studied about in Tai Chi Chuan (TCC) analgesia through a metrical and visualization analysis of the literature and provide some references for the experimental research on the analgesic effect of TCC and its clinical applications. Methods: The literature on TCC analgesia was collected from the Web of Science database, and the metrical and visualization analysis was performed using the CiteSpace. 5.6.R4 software in terms of publication outputs, countries, institutions, keywords, highly cited articles, and highly cited journals. Results: The number of annual publications gradually increased over time. The five research groups presented stable cooperative relationships and more publications. The authors ranked as top 1 were from America rather than China, which has more publications. The most common keywords were Tai Chi, randomized controlled trial, older adults, exercise, pain, low back pain, quality of life, management, etc. The literature on knee osteoarthritis and fibromyalgia had the highest citation frequency. The journals with high citation frequency included Cochrane Database System Review, Pain, and Plos One. Conclusions: Increasing attention has been paid to TCC analgesia. Randomized controlled trials, older adults, low back pain, and quality of life were found to be most studied in this field. Investigating clinical efficacy and conducting meta-analyses could be a promising direction in the future. The international cooperation and literature quality of TCC analgesia should be further strengthened.

Keywords: CiteSpace, metrical analysis, Tai Chi Chuan, pain, visualization analysis

How to cite this article:
Mao YQ, Zhang F, Song HB, Li YF, Tang JF, Yang P, Liu LZ, Tang Y, Yu SG, Yin HY. CiteSpace-based metrical and visualization analysis of tai chi chuan an algesia. World J Tradit Chin Med 2021;7:477-82

How to cite this URL:
Mao YQ, Zhang F, Song HB, Li YF, Tang JF, Yang P, Liu LZ, Tang Y, Yu SG, Yin HY. CiteSpace-based metrical and visualization analysis of tai chi chuan an algesia. World J Tradit Chin Med [serial online] 2021 [cited 2021 Nov 29];7:477-82. Available from: https://www.wjtcm.net/text.asp?2021/7/4/477/328761

  Introduction Top

Tai Chi Chuan (TCC), also known as “Tai Chi,” “Taiji Chuan,” or “Taiji Quan,” is a centuries-old meditative martial art that originated in China and has become increasingly popular in the West. TCC has been developed into five schools: Chen, Yang, Wu, Wu, and Sun. After the founding of the People's Republic of China, a 24-form simplified TCC was created and popularized by the State Sports Commission. On December 17, 2020, it was inscribed on the United Nations Educational, Scientific, and Cultural Organization's representative list of the intangible cultural heritage of humanity, indicating that TCC has become a valuable asset for the world. TCC consists of a series of gentle movements that strengthen and relax the body and mind, based on theories of traditional Chinese medicine (TCM), such as meridian, qi, blood, and Daoyin. Several studies have shown that TCC can generate therapeutic benefits in a variety of diseases,[1] such as chronic pain,[2] hypertension,[3] diabetes,[4] Parkinson,[5] cognitive disorders,[6] rheumatoid arthritis,[7] knee osteoarthritis,[8] insomnia,[9] anxiety and depression,[10] fall prevention,[11] and fibromyalgia.[12] It is noteworthy that a large number of publications on TCC have been published. Thus, it is important to quickly grasp the most commonly studied topics and trends in this field to obtain reference information for future studies.

CiteSpace, created by Chen and his team in early 2004, is a web-based Java application that supports visual exploration with knowledge discovery in bibliographic databases.[13],[14] This software shows the structure, regularity, and distribution of scientific knowledge with some information regarding countries, institutions, journals, authors, keywords, and references.[15] Compared with other bibliometric analysis software, CiteSpace is more intuitive in identifying the key points and important trends from the existing literature.[15],[16] Therefore, this article intended to use CiteSpace to analyze the research topics that are most studied about and the trends in the field of TCC analgesia and provide some references for TCC analgesia research from the perspective of bibliometric analysis.

  Methods Top

The retrieval data for measurements and statistical analysis were screened from the Web of Science Core Collection. The search formula was set to TS = (“Tai Chi” OR “Taiji” OR “Tai Chi Chuan” OR “Taijiquan” OR “Taichi Chuan”) AND (“pain”). The period from January 1982 to October 2020 was selected. A total of 428 records were retrieved.

The analysis was carried out using Microsoft Office Excel 2020 and CiteSpace. 5.6.R4 software. CiteSpace was used to perform statistical analysis and generate a visual illustration graph (also called a knowledge map) using different types of terms such as author, institution, country, keywords, journal, and citation frequency. The parameters of CiteSpace were set as follows: time slicing (from 1982 to 2020, 1 year per slice), term source (title, abstract, author, and keywords), node types (select author, institution, country, keyword, category, cited author, and cited journal in turn), strength (cosine), scope (within slices), map clarity (Top n = 50, or TOP n = 30), and pruning parameter (Pathfinder).

  Results Top

Analysis of publication outputs

The number of annual publications on TCC analgesia is shown in [Figure 1]. Only one study was published between 1982 and 1992. From 1992 to 2005, a slight increase was observed with approximately two to six publications per year. Since 2006, a clear upward trend was noted, with an increase from nine studies in 2006 to 68 in 2019. In general, there is an upward trend [red line in [Figure 1] in the publication outputs for TCC analgesia.
Figure 1: The number of annual publications of TCC analgesia

Click here to view

Analysis of leading countries

The analysis results of countries with high publication outputs contributing to TCC analgesia are displayed in [Figure 2]. Among the 17 involved countries, the United States (3.03) had the highest number of studies, with 194 publications, followed by China (2.11), Australia (0.22), Canada (0.08), the United Kingdom (0.12), Spain (0.11), and South Korea (0.11). Thus, it can be concluded that the United States, China, Australia, and Canada made significant contributions to the research of TCC analgesia
Figure 2: Visualized map of the leading countries contributed to TCC analgesia

Click here to view

Analysis of leading institutions

[Figure 3] shows a visualized knowledge map of the authors' countries and their collaboration network regarding the literature on TCC analgesia. It shows that 341 nodes refer to the authors' countries, 550 links mean the collaboration network, and the different colors indicate clusters of intimate relationships. Eighty-one institutions were involved in the network. As shown in [Figure 3], the top five institutes with publications include the Harvard Medical School, Tufts University, Harvard University, Brigham and Women's Hospital, and Fujian University of TCM. Most of the institutes belong to the United States, China, and Hong Kong. The United States has the largest number of institutions., indicating that the United States played an important role in this field, consistent with the leading countries analysis above. However, it should be pointed out that there is a large opportunity for collaboration in TCC analgesia research between these institutes and countries.
Figure 3: Visualized map of the leading institutes contributed to TCC analgesia

Click here to view

Analysis of Key words

Keywords represent highly refined research content and are important indicators of the research themes and hot topics that are extensively studied. There were 215 keywords extracted from 428 articles with 215 nodes and 439 links by CiteSpace, as shown in [Figure 4]. The top eight frequently occurring keywords in the literature on TCC analgesia were Tai Chi, randomized controlled trial, older adult, exercise, low back pain, quality of life, and management, suggesting that these may be hot spots that are extensively studied in this field. Among these keywords, “exercise” (0.12), “randomized controlled trial” (0.1), “low back pain” (0.15), and “balance” (0.11) are key nodes because their betweenness centrality is ≥0.1, which means they may play an important role in linking other keywords.

Keyword burst analysis was carried out to track hot spots and research trends. A burst term refers to a word or an article whose citation appears to rise suddenly over a period of time, which could be regarded as an important index for deducing the research frontier in the field of characteristic research.[15],[16] Six keywords with the strongest citation bursts were extracted in this study. [Figure 5] shows a list of burst terms sorted according to their occurrence period. The red bars indicate the duration of the citation burst, whereas the blue bars represent the time interval. As shown in [Figure 5], the burst keywords on TCC analgesia in the time sequence from 2000 to 2020 are Chuan, clinical trial, mindfulness, rheumatoid arthritis, disease, and meta-analysis, which have had relatively high burst strength. Rheumatoid arthritis, disease, and meta-analysis are the burst keywords in the past 3 years, which implies the future development direction and trend in this field.
Figure 4: Visualized map of keywords on TCC analgesia

Click here to view
Figure 5: Top six keywords with the strongest citation bursts on TCC analgesia

Click here to view

Analysis of highly cited articles

Studies with high citation frequency are called high-cited articles, which is one of the most important indicators of bibliometrics. As listed in [Table 1] (in order of citation frequency), the top five high-cited articles on TCC analgesia were published from 2009 to 2012, and all were related to randomized controlled clinical trials, focusing on osteoarthritis[17],[19],[20] and fibromyalgia.[18],[21] The article named “Tai Chi is effective in treating knee osteoarthritis: A randomized controlled trial[17] had the highest citation frequency of 56.
Table 1: The top five articles with high citation frequency

Click here to view

Analysis of highly cited journals

The highly cited journal analysis showed the contribution of each journal to TCC analgesia, which also reflects the best source of research in this field to a certain extent. As shown in [Table 2], the top five journals with high citation frequencies are Cochrane Database System Review, Pain, Plos One, Archives of Physical Medicine and Rehabilitation, and Clinical Rehabilitation. In general, compared with the literature in other research fields, neither the citation frequency nor the impact factor of articles on TCC analgesia is very high.
Table 2: The top five journals with high citation frequency

Click here to view

  Discussion Top

From the analysis of publication outputs, we found an upward trend in the publication of studies on TCC analgesia. This result indicates that TCC analgesia has received increasing attention.[2],[7],[8],[12],[22],[23] The reasons for the upward trend may be as follows: (1) With the development of modern scientific research and increasing emphasis on health, the research on TCC and pain itself has been constantly deepening and expanding. (2) The aging population is growing exponentially worldwide, followed by financial difficulties in medical care costs, especially due to the increase in chronic diseases that occur easily in older adults, such as pain, diabetes, cardiovascular disease, and cancer. These trends have compelled scientists to explore economical and effective medical treatments.[24] It has been recognized that TCC is a low-cost physical fitness exercise and has proven to be useful for many diseases. Therefore, TCC may be a potential method to cope with global population aging problems.[25],[26],[27] (3) The opioid misuse and addiction public health crisis is rapidly evolving worldwide[28] and should not be ignored. Opioids are a type of analgesic or medication used to control pain sensations. Therefore, alternative approaches are needed to replace opioid therapy for pain to deal with opioid crises.[29] TCC, as a low-cost, nonaddictive, and multifunctional exercise, has received increasing attention.

It should be noted that the United States had the most publications on TCC analgesia, instead of China, where TCC has originated from and has been practiced for centuries. This could be because most of the publications on TCC analgesia in China were in Chinese. However, this may also be because the opioid crisis was especially urgent in the United States.[29] This crisis pushed the United States to explore efficient, cost-effective, and nonpharmaceutical management methods for pain.

The most popular keywords of TCC analgesia were “Tai Chi,” “randomized controlled trial,” “older adult,” “exercise,” “pain,” “low back pain,” “quality of life,” and “management.” They represented the topics that were most studied about in the field of TCC analgesia. Among these keywords, we paid special attention to “randomized controlled trials.” A large number of randomized controlled trials on TCC, and not only on TCC analgesia, suggest that most of the studies on TCC analgesia focused on the efficacy of TCC in pain management. Only a few studies have focused on mechanism research.[30] In the future, efficacy will be a priority in TCC analgesia research. The other keyword we focused on is “older adults.” It has been reported that older adults have a high frequency of chronic pain.[31],[32] It is estimated that 60%–75% of people over the age of 65 have persistent pain, which is far higher for older people.[33] Substantial evidence suggests that older adults are the primary benefit group from TCC. First, compared to some other exercises, Tai Chi is a noncompetitive, self-paced system of gentle physical exercise and stretching. It involves a series of movements performed in a slow, focused manner, accompanied by deep breathing. Some studies have shown the TCC treatment plans for analgesia. A training program of three 60-min sessions a week for 12 weeks has been shown to be effective for chronic nonspecific low back pain;[34] a training program of two 60-min sessions a week for 12 weeks reportedly has therapeutic effects for fibromyalgia;[18] and a 12-week Tai Chi program was reported to significantly lower pain severity in older adults with chronic multisite musculoskeletal pain.[35] Therefore, Tai Chi is a low-side effect and multifunction exercise and may be suitable for older adults, especially for those with chronic pain.

Overall, chronic pain, including neck pain,[36] shoulder pain,[37] waist pain (low back pain),[34] leg joint pain,[7],[8] and multisite pain[35] can be relieved by TCC.[2] “Low back pain” was found to be one of the most common keywords, while the highly cited articles were focused on “rheumatoid arthritis” and “fibromyalgia.” We could infer that although there were more publications on TCC and lower back pain, there is much scope for development in this field, and more high-quality research is needed.

As mentioned in the keyword burst analysis, “Chuan,” “clinical trial,” “mindfulness,” “rheumatoid arthritis,” “disease,” and “meta-analysis” appeared in chronological order from 2000 to 2020. It also indicated that the hot spots most studied about in this field included the confirming effect of TCC analgesia. Among these keywords, “rheumatoid arthritis,” “disease,” and “meta-analysis” were the up-to-date burst keywords. This implies that these words might be commonly studied hot spots in the next few years. A meta-analysis is a survey in which the results of the studies included in the review are statistically similar and are combined and analyzed as if they were one study.[38] The emergence of “meta-analysis” in the burst-keyword analysis means that the number of articles in a clinical trial on TCC analgesia has accumulated to some extent. It would be pertinent to conduct a systematic review to support evidence-based conclusions on TCC analgesia. However, not all the meta-analysis conclusions on TCC analgesia could apply enough support for TCC analgesia, mainly due to the low data quality of some clinical trials. Therefore, more high-quality studies designed and conducted according to the CONSORT statement[39] are needed in the future.

Our study had some limitations. The quantity of the included literature is not sufficient compared to some other CiteSpace-analysis publications. Hence, the conclusion from this study is only preliminary and approximate, aiming to provide references from the perspective of bibliometric analysis. In the future, we could integrate the Chinese selected terms we were interested in, but some other terms might be useful for analysis and should be considered.

  Conclusions Top

This study demonstrated that attention to TCC analgesia has increased recently, in which randomized controlled trials, older adults, low back pain, and quality of life might be the hot topics that are most studied about in this field. Investigating clinical efficacy and conducting meta-analysis could be a promising direction in the future. The international cooperation and literature quality of TCC analgesia should be further strengthened.

Financial support and sponsorship

This work was supported by the Science and Technology Department of Sichuan Province (2018HH0123, 2021YFH0096), the 2019 Internationalization Incentive Fund, Division of Health Sciences, University of Otago, and the Sino-German Center for the Promotion of Science (GZ919).

Conflicts of interest

There are no conflicts of interest.

  References Top

Solloway MR, Taylor SL, Shekelle PG, Miake-Lye IM, Beroes JM, Shanman RM, et al. An evidence map of the effect of Tai Chi on health outcomes. Syst Rev 2016;5:126.  Back to cited text no. 1
Kong LJ, Lauche R, Klose P, Bu JH, Yang XC, Guo CQ, et al. Tai chi for chronic pain conditions: A systematic review and meta-analysis of randomized controlled trials. Sci Rep 2016;6:25325.  Back to cited text no. 2
Lee SH, Kim BJ, Park IH, Hwang EH, Park EJ, Jang I, et al. Effects of taichi on grade 1 hypertension: A study protocol for a randomized controlled trial. Trials 2020;21:177.  Back to cited text no. 3
Lee MS, Jun JH, Lim HJ, Lim HS. A systematic review and meta-analysis of tai chi for treating type 2 diabetes. Maturitas 2015;80:14-23.  Back to cited text no. 4
Li F, Harmer P, Fitzgerald K, Eckstrom E, Stock R, Galver J, et al. Tai chi and postural stability in patients with Parkinson's disease. N Engl J Med 2012;366:511-9.  Back to cited text no. 5
Yue C, Yu Q, Zhang Y, Herold F, Mei J, Kong Z, et al. Regular tai chi practice is associated with improved memory as well as structural and functional alterations of the hippocampus in the elderly. Front Aging Neurosci 2020;12:586770.  Back to cited text no. 6
Mudano AS, Tugwell P, Wells GA, Singh JA. Tai Chi for rheumatoid arthritis. Cochrane Database Syst Rev 2019;9:CD004849.  Back to cited text no. 7
Hu L, Wang Y, Liu X, Ji X, Ma Y, Man S, et al. Tai Chi exercise can ameliorate physical and mental health of patients with knee osteoarthritis: Systematic review and meta-analysis. Clin Rehabil 2021;35:64-79.  Back to cited text no. 8
Li H, Chen J, Xu G, Duan Y, Huang D, Tang C, et al. The effect of tai chi for improving sleep quality: A systematic review and meta-analysis. J Affect Disord 2020;274:1102-12.  Back to cited text no. 9
Shuai Z, Christine K, Sara L, Peter M, David S, Chris Z. The effects of twelve weeks of tai chi practice on anxiety in stressed but healthy people compared to exercise and wait-list groups – A randomized controlled trial. J Clin Psychol 2018;74:83-92.  Back to cited text no. 10
Deborah B, Laddie S, Judy C, Maegen B. Balance and functional outcomes for older community-dwelling adults who practice tai chi and those who do not: A comparative study. J Geriatr Phys Ther 2019;42:209-15.  Back to cited text no. 11
Staud R. Tai chi reduced severity of fibromyalgia symptoms at 24 weeks compared with aerobic exercise. Ann Intern Med 2018;168:JC70.  Back to cited text no. 12
Synnestvedt MB, Chen C, Holmes JH. CiteSpace II: Visualization and knowledge discovery in bibliographic databases. AMIA Annu Symp Proc 2005;2005:724-8.  Back to cited text no. 13
Chen C, Chen Y. Searching for clinical evidence in CiteSpace. AMIA Annu Symp Proc 2005;2005:121-5.  Back to cited text no. 14
Yan WT, Lu S, Yang YD, Ning WY, Cai Y, Hu XM, et al. Research trends, hot spots and prospects for necroptosis in the field of neuroscience. Neural Regen Res 2021;16:1628-37.  Back to cited text no. 15
[PUBMED]  [Full text]  
Li Y, Fang R, Liu Z, Jiang L, Zhang J, Li H, et al. The association between toxic pesticide environmental exposure and Alzheimer's disease: A scientometric and visualization analysis. Chemosphere 2021;263:128238.  Back to cited text no. 16
Wang C, Schmid CH, Hibberd PL, Kalish R, Roubenoff R, Rones R, et al. Tai Chi is effective in treating knee osteoarthritis: A randomized controlled trial. Arthritis Rheum 2009;61:1545-53.  Back to cited text no. 17
Wang C, Schmid CH, Rones R, Kalish R, Yinh J, Goldenberg DL, et al. A randomized trial of tai chi for fibromyalgia. N Engl J Med 2010;363:743-54.  Back to cited text no. 18
Fransen M, Nairn L, Winstanley J, Lam P, Edmonds J. Physical activity for osteoarthritis management: A randomized controlled clinical trial evaluating hydrotherapy or Tai Chi classes. Arthritis Rheum 2007;57:407-14.  Back to cited text no. 19
Brismée JM, Paige RL, Chyu MC, Boatright JD, Hagar JM, McCaleb JA, et al. Group and home-based tai chi in elderly subjects with knee osteoarthritis: A randomized controlled trial. Clin Rehabil 2007;21:99-111.  Back to cited text no. 20
Jones KD, Sherman CA, Mist SD, Carson JW, Bennett RM, Li F. A randomized controlled trial of 8-form Tai chi improves symptoms and functional mobility in fibromyalgia patients. Clin Rheumatol 2012;31:1205-14.  Back to cited text no. 21
Hall A, Copsey B, Richmond H, Thompson J, Ferreira M, Latimer J, et al. Effectiveness of tai chi for chronic musculoskeletal pain conditions: Updated systematic review and meta-analysis. Phys Ther 2017;97:227-38.  Back to cited text no. 22
Peng PW. Tai chi and chronic pain. Reg Anesth Pain Med 2012;37:372-82.  Back to cited text no. 23
Kennedy BK, Berger SL, Brunet A, Campisi J, Cuervo AM, Epel ES, et al. Geroscience: Linking aging to chronic disease. Cell 2014;159:709-13.  Back to cited text no. 24
You T, Ogawa EF, Thapa S, Cai Y, Yeh GY, Wayne PM, et al. Effects of Tai Chi on beta endorphin and inflammatory markers in older adults with chronic pain: An exploratory study. Aging Clin Exp Res 2020;32:1389-92.  Back to cited text no. 25
Northey JM, Cherbuin N, Pumpa KL, Smee DJ, Rattray B. Exercise interventions for cognitive function in adults older than 50: A systematic review with meta-analysis. Br J Sports Med 2018;52:154-60.  Back to cited text no. 26
Chang YK, Nien YH, Tsai CL, Etnier JL. Physical activity and cognition in older adults: The potential of Tai Chi Chuan. J Aging Phys Act 2010;18:451-72.  Back to cited text no. 27
Skolnick P. The opioid epidemic: Crisis and solutions. Annu Rev Pharmacol Toxicol 2018;58:143-59.  Back to cited text no. 28
Coussens NP, Sittampalam GS, Jonson SG, Hall MD, Gorby HE, Tamiz AP, et al. The opioid crisis and the future of addiction and pain therapeutics. J Pharmacol Exp Ther 2019;371:396-408.  Back to cited text no. 29
Liu J, Chen L, Tu Y, Chen X, Hu K, Tu Y, et al. Different exercise modalities relieve pain syndrome in patients with knee osteoarthritis and modulate the dorsolateral prefrontal cortex: A multiple mode MRI study. Brain Behav Immun 2019;82:253-63.  Back to cited text no. 30
Domenichiello AF, Ramsden CE. The silent epidemic of chronic pain in older adults. Prog Neuropsychopharmacol Biol Psychiatry 2019;93:284-90.  Back to cited text no. 31
Cruz-Almeida Y, Fillingim RB, Riley JL 3rd, Woods AJ, Porges E, Cohen R, et al. Chronic pain is associated with a brain aging biomarker in community-dwelling older adults. Pain 2019;160:1119-30.  Back to cited text no. 32
Molton IR, Terrill AL. Overview of persistent pain in older adults. Am Psychol 2014;69:197-207.  Back to cited text no. 33
Liu J, Yeung A, Xiao T, Tian X, Kong Z, Zou L, et al. Chen-style tai chi for individuals (aged 50 years old or above) with chronic non-specific low back pain: A randomized controlled trial. Int J Environ Res Public Health 2019;16:517.  Back to cited text no. 34
You T, Ogawa EF, Thapa S, Cai Y, Zhang H, Nagae S, et al. Tai Chi for older adults with chronic multisite pain: A randomized controlled pilot study. Aging Clin Exp Res 2018;30:1335-43.  Back to cited text no. 35
Lauche R, Stumpe C, Fehr J, Cramer H, Cheng YW, Wayne PM, et al. The effects of tai chi and neck exercises in the treatment of chronic nonspecific neck pain: A randomized controlled trial. J Pain 2016;17:1013-27.  Back to cited text no. 36
Fong SS, Ng SS, Lee HW, Pang MY, Luk WS, Chung JW, et al. The effects of a 6-month Tai Chi Qigong training program on temporomandibular, cervical, and shoulder joint mobility and sleep problems in nasopharyngeal cancer survivors. Integr Cancer Ther 2015;14:16-25.  Back to cited text no. 37
Mittal N, Goyal M, Mittal PK. Understanding and appraising systematic reviews and meta-analysis. J Clin Pediatr Dent 2017;41:317-26.  Back to cited text no. 38
Boutron I, Altman DG, Moher D, Schulz KF, Ravaud P; CONSORT NPT Group. CONSORT statement for randomized trials of nonpharmacologic treatments: A 2017 update and a CONSORT extension for nonpharmacologic trial abstracts. Ann Intern Med 2017;167:40-7.  Back to cited text no. 39


  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]

  [Table 1], [Table 2]


    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

  In this article
Article Figures
Article Tables

 Article Access Statistics
    PDF Downloaded24    
    Comments [Add]    

Recommend this journal