A case study evaluating the effect of clustering, publication bias, and heterogeneity on the meta-analysis estimates in implant dentistry.

Meta-analyses may provide imprecise estimates when important meta-analysis parameters are not considered during the synthesis. The aim of this case study was to highlight the influence of meta-analysis parameters that can affect reported estimates using as an example pre-existing meta-analyses on the association between implant survival and sinus membrane perforation. PubMed was searched on 7 July 2021 for meta-analyses comparing implant failure in perforated and non-perforated sinus membranes. Primary studies identified in these meta-analyses were combined in a new random-effects model with odds ratios (ORs), confidence intervals (CIs), and prediction intervals reported. Using this new meta-analysis, further meta-analyses were then undertaken considering the clinical, methodological, and statistical heterogeneity of the primary studies, publication bias, and clustering effects. The meta-analyses with the greatest number and more homogeneous studies provided lower odds of implant failure in non-perforated sites (OR 0.49, 95 % CI = [0.26, 0.92]). However, when considering heterogeneity, publication bias, and clustering (number of implants), the confidence in these results was reduced. Interpretation of estimates reported in systematic reviews can vary depending on the assumptions made in the meta-analysis. Users of these analyses need to carefully consider the impact of heterogeneity, publication bias, and clustering, which can affect the size, direction, and interpretation of the reported estimates.

Overview of systematic reviews on periodontal-orthodontic interactions: A comprehensive literature analysis.

The aims of this research were to investigate the methodological quality of systematic reviews on periodontal-orthodontic interactions (i.e. reviews of primary research broadly defined as any including both periodontic and orthodontic components) and to provide a mapping of the researched topics. We searched four major databases (PubMed, Lilacs, Web of Science, and Embase) for systematic reviews of periodontal-orthodontic interactions. We used the AMSTAR-2 tool (the acronym is derived from 'a measurement tool to assess systematic reviews') to assess the methodological quality of the included systematic reviews. Individual AMSTAR-2 ratings were tabulated, and the percentage per item was calculated. To assess the association between the AMSTAR-2 percentage score and the overall confidence in the systematic review results, an ordinal regression model was used. We initially retrieved 973 documents, and 43 systematic reviews were included. Systematic reviews of interventions were the most prevalent (n = 26, 60.5%). Most of the systematic reviews did not report a meta-analysis (n = 25, 58.1%). In addition, most of the studies included in the systematic reviews had an unclear or high risk of bias. Most of the systematic reviews were rated as having critically low or low overall confidence (n = 34, 79.1%). A significant correlation was found between the AMSTAR-2 percentage score and overall confidence in the results. The methodological quality of systematic reviews on periodontal-orthodontic interactions can be improved. The limitations of our study include potential language bias and an arbitrary classification of the topics researched.

Education and learning: potential methodological and ethical issues in systematic reviews containing a meta-analysis: some critical reading suggestions for junior doctors.

Junior doctors make clinical decisions regularly; therefore, they need to adequately interpret the evidence supporting these decisions. Patients can be harmed if clinical treatments are supported by biased or unreliable evidence. Systematic reviews that contain meta-analyses of randomized controlled trials are a relatively low-biased type of evidence to support clinical interventions. Therefore, it is reasonable to think that doctors will likely select this type of study to answer clinical questions. In this article, doctors are informed about potential methodological and ethical issues in systematic reviews that contain a meta-analysis that are sometimes not easily identified or even overlooked by the current tools developed to assess their methodological quality or risk of bias. The article presents a discussion of topics related to data extraction, accuracy in reporting, reproducibility, heterogeneity, quality assessment of primary studies included in the systematic review, sponsorship, and conflict of interest. It is expected that the information reported will be useful for junior doctors when they are reading and interpreting evidence from systematic reviews containing meta-analyses of therapeutic interventions, mainly those doctors unfamiliar with methodological principles.

Methodological quality of umbrella reviews in endodontics: A cross-sectional study.

INTRODUCTION: In endodontics, the number of umbrella reviews has increased significantly over the last few years, but there is no evidence that they were methodologically sound. The aim of the current study was to appraise the methodological quality of umbrella reviews in endodontics, and to identify possible predictive factors associated with methodological quality. METHODS: Umbrella reviews published in the discipline of endodontics until December 2023 were included. The methodological quality of the reviews was evaluated using a checklist consisting of 11 items. Each item in the checklist was evaluated by two independent assessors who assigned a score of '1' if it was fully addressed, '0.5' if it was partially ddressed, and '0' if it was not addressed. Bootstrapped multiple linear regression analysis was used to examine the association between the total scores awarded and five predictor variables (a priori protocol registration, year of publication, number of authors, journal impact factor (IF) and continent of the corresponding author). The statistical significance level was set as 5%. RESULTS: A total of 27 reviews were included. Ninety-six per cent of the reviews adequately reported: eligibility criteria for selecting the reviews, details of the reviews, techniques for assessing the risk of bias or methodological quality of the individual systematic reviews they included. Only 30% of the reviews adequately managed overlapping primary studies within individual systematic reviews. Among the five predictors analysed, a priori protocol registration and journals with IFs were associated with significantly greater total methodological quality scores. DISCUSSION: Several methodological shortcomings in the umbrella reviews published within the field of endodontics were revealed. Umbrella reviews published in journals with IFs and those with protocols registered a priori had significantly superior methodological quality scores. CONCLUSION: In endodontics, authors intending to publish umbrella reviews should consider the limitations revealed in this study and follow the appropriate rules to ensure their reviews comply with the highest standards and provide accurate and dependable information and conclusions.

Reporting of flow diagrams in randomised controlled trials published in periodontology and implantology: a survey.

BACKGROUND: Item 13 of the CONSORT guidelines recommends documentation of the participant flow in randomised clinical trials (RCTs) using a diagram. In the medical literature, the reporting of the flow of participants in RCTs has been assessed to be inadequate. The quality of reporting flow diagrams in periodontology and implantology remains unknown. The aim of this study was to assess the reporting of flow diagrams in RCTs published in periodontology and implantology journals. MATERIALS AND METHODS: RCTs published between 15th January 2018 and 15th January 2022 in twelve high-ranked periodontology and implantology journals were identified. Trial characteristics at the RCT level were extracted. The flow diagram included in each RCT was assessed for completeness of reporting in relation to published criteria and the CONSORT flow diagram template. RESULTS: From the 544 eligible articles, 85% were single-centre, 82% of parallel-group design and 79% investigated surgical interventions. Three-hundred and fifteen (58%) articles were published in CONSORT endorsing journals. A flow diagram was reported in 317 (58%) trials and reporting was more common in periodontology (73.1%). Overall, 56% of publications with a flow diagram reported a complete CONSORT flow diagram, while in 44% of flow diagrams, at least one point from the CONSORT reporting template was missing. Reasons for loss to follow-up (69.7%) and exclusions from the RCT analysis (86.4%) were poorly reported. CONCLUSION: The reporting of flow diagrams in periodontology and implantology RCTs was sub-optimal. Greater awareness of the importance of fully completing the participant CONSORT flow diagram is required.

ASSESSMENT OF THE FREQUENCY OF REPORTING DENTAL PATIENT-REPORTED OUTCOMES (dPROs) IN A SAMPLE OF RANDOMIZED CONTROLLED TRIALS ON ROOT COVERAGE PROCEDURES.

OBJECTIVE: Dental patient-reported outcomes (dPROs) are important for understanding the impact of proposed therapies on patients' oral health. The aims of the present study were to investigate the frequency of the reporting of dPROs in randomized controlled trials (RCTs) of root coverage procedures and to assess associations between the study/article characteristics and the reporting level of the dPROs. METHODS: The PubMed database was searched for RCTs of root coverage procedures in March 16, 2022 and articles published up to March 2022 were included. Information on the types of outcomes and the characteristics of the studies/articles were extracted and reported as frequencies and percentages. Univariate and multivariate binary logistic regression analyses were performed to investigate the associations between the study/article characteristics and the reporting level of dPROs. RESULTS: The search initially identified 387 articles, and after applying the eligibility criteria, 135 articles reporting 135 RCTs were included. A combination of dPROs and non-dPROs was reported in 61.5% of the selected trials, while 37.8% of the trials reported only non-dPROs. Pain or discomfort was the most frequently reported dPRO (n = 58, 43% of the RCTs). More recently published RCTs reported more dPROs. The country of the first author (odds ratio [OR]: 4.39; 95% CI: 1.76-10.95; P < .01), protocol registration (OR: 0.36; 95% CI: 0.16-0.83; P = .02), and RCT type (OR: 0.38; 95% CI: 0.17-0.83; P = .02) were significantly associated with the reporting level of the dPROs. CONCLUSIONS: Researchers in recent years seem to be paying more attention to the importance of dPROs. RCTs in which the first authors were from developed countries, registered trials, and RCTs with a parallel design were more likely to report dPROs than RCTs with first authors from developing countries, unregistered trials, and RCTs with a split-mouth design.

Methodological assessment of systematic reviews of in-vitro dental studies.

BACKGROUND: Systematic reviews of in-vitro studies, like any other study, can be of heterogeneous quality. The present study aimed to evaluate the methodological quality of systematic reviews of in-vitro dental studies. METHODS: We searched for systematic reviews of in-vitro dental studies in PubMed, Web of Science, and Scopus databases published up to January 2022. We assessed the methodological quality of the systematic reviews using a modified "A MeaSurement Tool to Assess systematic Reviews" (AMSTAR-2) instrument. The 16 items, in the form of questions, were answered with yes, no, or py (partial yes). Univariable and multivariable linear regression models were used to examine the association between systematic review characteristics and AMSTAR-2 percent score. Overall confidence in the results of the systematic reviews was rated, based on weaknesses identified in critical and non-critical AMSTAR-2 items. RESULTS: The search retrieved 908 potential documents, and after following the eligibility criteria, 185 systematic reviews were included. The most researched topics were ceramics and dental bonding. The overall rating for the confidence in the results was critically low in 126 (68%) systematic reviews. There was high variability in the response among the AMSTAR-2 items (0% to 75% positively answered). The univariable analyses indicated dental specialty (p = 0.03), number of authors (coef: 1.87, 95% CI: 0.26, 3.47, p = 0.02), and year of publication (coef: 2.64, 95% CI: 1.90, 3.38, p < 0.01) were significantly associated with the AMSTAR-2 percent score. Whereas, in the multivariable analysis only specialty (p = 0.01) and year of publication (coef: 2.60, 95% CI: 1.84, 3.35, p < 0.001) remained significant. Among specialties, endodontics achieved the highest AMSTAR-2 percent score. CONCLUSIONS: The methods of systematic reviews of in vitro dental studies were suboptimal. Year of publication and dental specialty were associated with AMSTAR-2 scores. The overall rating of the confidence in the results was low and critically low for most systematic reviews.

COMBINATION OF Nd:YAG AND Er:YAG LASERS MIGHT IMPROVE PERIODONTAL PROBING DEPTHS AND CLINICAL ATTACHMENT LEVELS, BUT THE LEVEL OF EVIDENCE IS VERY WEAK.

ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION: Estrin NE, Moraschini V, Zhang Y, Romanos GE, Sculean A, Miron RJ. Combination of Nd:YAG and Er:YAG lasers in non-surgical periodontal therapy: a systematic review of randomized clinical studies. Lasers Med Sci. 2022 Apr 1. doi: 10.1007/s10103-022-03548-6. Epub ahead of print. PMID: 35364744. SOURCE OF FUNDING: There was no statement on the source of funding. TYPE OF STUDY/DESIGN: Systematic review with meta-analysis.

A new method for testing reproducibility in systematic reviews was developed, but needs more testing.

BACKGROUND: To develop and test an approach to test reproducibility of SRs. METHODS: Case study. We have developed an approach to test reproducibility retrospectively while focusing on the whole conduct of an SR instead of single steps of it. We replicated the literature searches and drew a 25% random sample followed by study selection, data extraction, and risk of bias (ROB) assessments performed by two reviewers independently. These results were compared narratively with the original review. RESULTS: We were not able to fully reproduce the original search resulting in minor differences in the number of citations retrieved. The biggest disagreements were found in study selection. The most difficult section to be reproduced was the RoB assessment due to the lack of reporting clear criteria to support the judgement of RoB ratings, although agreement was still found to be satisfactory. CONCLUSION: Our approach as well as other approaches needs to undergo testing and comparison in the future as the area of testing for reproducibility of SRs is still in its infancy.

Watching the watchers: A report on the disclosure of potential conflicts of interest by editors and editorial board members of dental journals.

Reporting potential conflicts of interest (COIs) by all parties involved in the publication process is of pivotal importance to increase trust in research. The present study assessed the disclosure of potential COIs of editors and editorial board members of high-ranked dental journals. From 28 April 2021 to 05 May 2021, the websites of 91 dental journals classified by impact factor (IF) were scrutinized to obtain information on the reporting of COI forms of editors and board members, and whether these individuals reported their detailed curriculum vitae (CV). The COI forms were assessed to understand the potential financial and non-financial COIs of editors and board members. Only 11 (12.1%) journals reported COI forms of editors-in-chief (EICs) and associate editors (AEs). No journal reported a COI form of the editorial board members. Of the 100 editors (EICs plus AEs), 25 (25.%) declared connections to for-profit organisations, and seven (7%) to not-for-profit organisations. Five (5%) editors (all AEs) reported non-financial COIs, and 35 (35%) editors reported nothing to declare. Nine (9.9%) journals reported a short CV of editors, which were not informative regarding potential COIs. Editors and editorial board members of high-ranked dental journals should report in more detail their potential COIs.

Prediction intervals should be included in meta-analyses published in dentistry.

This focus article aims to highlight the value of reporting prediction intervals (PIs) in random effects meta-analysis and to assess the prevalence of PI-reporting in periodontology and implant dentistry meta-analyses. We searched in the PubMed database for meta-analyses published in the fields of periodontology and implant dentistry. We selected meta-analyses related to primary outcomes with at least three trials. Additionally, we extracted information on the type of the meta-analysis model (fixed or random) and whether the random effects meta-analyses included PIs in addition to the 95% confidence intervals. Three-hundred and forty-nine meta-analyses were found in 94 systematic reviews. Two-hundred and sixty-three (75.4%) subgroup and full meta-analyses used the random-effects model, 81 (23.2%) used fixed-effect methods, and 5 (1.4%) did not specify the model used. In 75 systematic reviews, we found 231 meta-analyses with three or more trials (173 full meta-analyses and 58 subgroup meta-analyses). Only one systematic review reported PIs. Interpretation of the results of random effects meta-analyses which ignore heterogeneity can be misleading. Heterogeneity should be explored, and two common approaches include subgroup analyses and meta-regression. Random effects meta-analyses should include PIs because they convey the extent of heterogeneity in treatment effects across studies in a clinically relevant context.

LOW-LEVEL LASER THERAPY MAY REDUCE THE RISK OF SEVERE ORAL MUCOSITIS IN PATIENTS RECEIVING CHEMOTHERAPY OR RADIOTHERAPY.

ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION: Peng et al. Low-level laser therapy in the prevention and treatment of oral mucositis: a systematic review and meta-analysis. Oral Surg Oral Med Oral Pathol Oral Radiol. 2020 Oct;130(4):387-397.e9. doi: 10.1016/j.oooo.2020.05.014. Epub 2020 Jun 5. SOURCE OF FUNDING: Sichuan University Post-doctoral Research and Development Fund (grant No. 19 XJ0008) TYPE OF STUDY/DESIGN: Systematic review with meta-analysis.

PRESUMED PREDATORY JOURNALS ARE ABUNDANT IN ORAL HEALTH.

OBJECTIVE: to identify characteristics of presumed predatory (PP) journals, presumed legitimate open access (PLOA) journals, and presumed legitimate subscription (PLS) journals published in dentistry. METHODS: We assessed presumed predatory (PP), presumed legitimate open access (PLOA) and presumed legitimate subscription (PLS) journals using indicators reported in the literature consisting of 29 items in the form of questions in a cross-sectional setting. The indicators formed the basis for the 13 salient characteristics of PP journals that were used to generate scores. Greater scores would imply that the journal was more likely to be predatory compared to lower score journals. Associations between predatory score and journal type were examined using the non-parametric Kruskal-Wallis test, and classification to the 3 groups based on the article characteristics was implemented using the random forest approach. RESULTS: From the 580 potentially eligible journals, 431 dental journals were included: 226 PP (52%), 111 (26%) PLOA, and 94 (22%) PLS. There were significant differences in the predatory score among the three groups; PP journals had the highest mean score and PLS journals the lowest mean score. Mention or reporting to be indexed in the Directory of Open Access Journals (DOAJ) database and journals´website with distorted or blurry images were the most influential variables for accurate classification into a predatory category or not. CONCLUSIONS: The present study found that some specific characteristics such as distorted images and grammatical errors are more prominent in PP dental journals.

A systematic review on bacterial community changes after periodontal therapy with and without systemic antibiotics: An analysis with a wider lens.

BACKGROUND: This systematic review aimed to provide a comprehensive view on microbial community shifts after periodontal therapy with and without systemic antibiotics, conducted in randomized controlled trials (RCTs). METHODS: Search functions in PubMed, Scopus, the Web of Knowledge, and the Cochrane Oral Health Library databases were used to locate studies published up to December 2018 that reported at least two bacteria before and after periodontal therapy. Gray literature and manual searching were done. Information about reported bacteria in those studies were extracted, and a descriptive microbial community analysis was conducted to observe trends and influencing factors on microbial dynamics. Methodological aspects were examined, including the bacterial detection method, heterogeneity of procedures, and risk of bias (RoB) of the studies. RESULTS: The 30 included studies reported 130 different bacterial genera. Four different detection methods were reported: cultivation, polymerase chain reaction, DNA-DNA-checkerboard hybridization, and 16S rDNA amplicon sequencing. No general compositional change between the antibiotic and placebo groups could be found after therapy on the community level. Fifty-five bacteria were reported in two or more studies. Of those, 24 genera decreased and 13 increased more frequently after antibiotic use. Great heterogeneity between procedures and variability in RoB were found among the studies. CONCLUSIONS: Microbial shifts occurred regardless of the use of antibiotics. Antibiotic therapy seems to induce more changes in single bacteria. The heterogeneity in methods and reporting of the included studies preclude clinical recommendations on the use or not of adjunctive antibiotics. The present results may guide further research on the topic.

Reporting and handling of incomplete outcome data in implant dentistry: A survey of randomized clinical trials.

AIM: To assess the reporting and handling of incomplete outcome data in randomized clinical trials (RCTs) published in implant dentistry. MATERIALS AND METHODS: We included RCTs on interventions related to the treatment with dental implants and presented any form of missing data. PubMed, SCOPUS and Cochrane databases were searched for studies published between May 2015 and May 2018. Reporting and handling of missing data at the study level were evaluated using a series of relevant questions. Descriptive data were reported, and univariable analyses were performed to evaluate the association of study variables with quality of reporting and data handling. RESULTS: One-hundred and thirty-seven RCT reports were included from the 7,116 initially retrieved publications. The reporting of incomplete outcome data varied greatly among the trials and for the different questions. The range of adequately reported questions was between 3.64% (question: comparison of baseline characteristics of all randomised participants) and 100% (question: explicit reporting of missing data). The complete case analysis was the most used (45.3%) approach for incomplete outcome data handling. CONCLUSIONS: Randomized studies in implant dentistry have room for improvement in both the reporting and the handling of incomplete outcome data.

The (in)adequacy of translational research in dentistry.

Translational research, as the name suggests, "translates" research findings into clinical practice to improve the health of human beings. The translational process builds on information from experiments conducted at a basic level (i.e., in vitro and/or animal studies) and progresses over experimental human studies for efficacy, efficiency, and safety to implementation. Therefore, all steps in the process should be based on studies conducted with the highest methodological quality possible in order to provide accurate and useful information. Furthermore, the systematic dissemination of new procedures/techniques should be done only when they have been proven to be effective and safe. This focus article describes examples of new techniques/procedures in dentistry that have not resulted from an adequate translational research process since the initial evidence was published. These procedures are generally characterised by lack of good evidence, particularly on their potential harms, and lack of adequate chronological order, regarding the translational research process (i.e., human research being conducted before animal research). Even so, they seem to be widely disseminated, and their promotion involves a wide range of sources, including social media. Some guidance is proposed to improve the quality of the translational research process in dentistry, as well as the level of awareness of all parties involved with the use of this research: clinicians, researchers, and patients. By improving the translational research process, optimization of the application and use of these resources, with less risk to the patients, is expected.

Systematic reviews in orthodontics: Impact of the PRISMA for Abstracts checklist on completeness of reporting.

INTRODUCTION: This study evaluated and compared the completeness of reporting of abstracts of orthodontics systematic reviews before and after the publication of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for Abstracts Checklist (PRISMA-A). METHODS: Abstracts of systematic reviews and meta-analyses in orthodontics published in PubMed, Latin American and Caribbean Health Sciences Literature, and the Cochrane Database of Systematic Reviews databases before March 23, 2018, that met the predefined inclusion and exclusion criteria, were evaluated using the 12 items of PRISMA-A, scoring each item from 0 to 2. Abstracts were classified into 2 groups: before and after publication of the PRISMA-A checklist. Three calibrated evaluators (intraclass correlation coefficient and kappa > 0.8) assessed the scores for compliance with the checklist. The number of authors, country of affiliation of the first author, performance of meta-analysis, and topic of the article were recorded. A regression analysis was performed to assess the associations between abstract characteristics and the PRISMA-A scores. RESULTS: Of 1034 abstracts evaluated, 389 were included in the analysis. The mean PRISMA-A score was 53.39 (95% CI, 51.83-54.96). The overall score for studies published after the publication of the checklist was significantly higher than for studies published before (P ≤ 0.0001). The components returning significantly higher scores after publication of PRISMA-A were title (P = 0.024), information from databases (P = 0.026), risk of bias (P ≤ 0.0001), included studies (P ≤ 0.0001), synthesis of results (P ≤ 0.0001), interpretation of results (P = 0.035), financing and conflict of interest (P ≤ 0.0001), and registration (P ≤ 0.0001). These results showed the positive effect of PRISMA-A had on the quality of reporting of orthodontics systematic reviews. Nevertheless, the poor adherence revealed that there is still need for improvement in the quality of abstract reporting. CONCLUSIONS: The quality of reporting of abstracts of orthodontic systematic reviews and meta-analyses increased after the introduction of PRISMA-A.

Laser Therapy as an Adjunct Treatment for Peri-Implant Mucositis and Peri-Implantitis Provides No Extra Benefit for Most Clinical Outcomes.

ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION: Laser therapy for treatment of peri-implant mucositis and peri-implantitis: an American Academy of Periodontology best evidence review. Lin GH, López del Amo, FS, Want H-L. J Periodontol 2018;89(7):766-82. SOURCE OF FUNDING: Sponsored by J. Morita USA (Irvine, California). TYPE OF STUDY/DESIGN: Systematic review with meta-analysis.

Appraisal of systematic reviews on the management of peri-implant diseases with two methodological tools.

AIM: This study aimed to evaluate and compare the performance of two methodological instruments to appraise systematic reviews and to identify potential disagreements of systematic review authors regarding risk of bias (RoB) evaluation of randomized controlled trials (RCTs) included in systematic reviews on peri-implant diseases. MATERIAL/METHODS: We searched Medline, Web of Science, Cochrane Library, PubMed Central, and Google Scholar for systematic reviews on peri-implant diseases published before July 11, 2017. Two authors independently evaluated the RoB and methodological quality of the systematic reviews by applying the Risk of Bias in Systematic Reviews (ROBIS) tool and Assessing the Methodological Quality of Systematic Reviews (AMSTAR) checklist, respectively. We assessed the RoB scores of the same RCTs published in different systematic reviews. RESULTS: Of the 32 systematic reviews identified, 23 reviews addressed the clinical topic of peri-implantitis. A high RoB was detected for most systematic reviews (n=25) using ROBIS, whilst five systematic reviews displayed low methodological quality by AMSTAR. Almost 30% of the RoB comparisons (for the same RCTs) had different RoB ratings across systematic reviews. CONCLUSIONS: The ROBIS tool appears to provide more conservative results than AMSTAR checklist. Considerable disagreement was found among systematic review authors rating the same RCT included in different systematic reviews.

A survey of prevalence of narrative and systematic reviews in five major medical journals.

BACKGROUND: Systematic reviews may provide less biased evidence than narrative reviews because they observe a strict methodology, similarly to primary studies. Hence, for clinical research questions, systematic reviews should be the study design of choice. It would be important to evaluate the prevalence and characteristics of narrative and systematic reviews published in prominent medical journals. Researchers and clinicians give great value to articles published in such scientific journals. This study sought to evaluate the prevalence and characteristics of narrative and systematic reviews in the five highest-ranked general medical journals and investigate the associations among type of review, number of citations, and impact factor (IF). METHODS: We surveyed the five highest-ranked medical journals (The New England Journal of Medicine, The Lancet, The Journal of the American Medical Association, The BMJ, and Annals of Internal Medicine) for narrative and systematic reviews published between June 2015 and June 2016. We independently selected and extracted the data from the reviews by strictly following the pre-determined eligibility criteria (Systematic and narrative reviews that focused on the management of diseases). We conducted regression analyses to investigate the associations among review type, number of citations, and IF. We also descriptively reported narrative reviews containing some methodology that might be reproducible. RESULTS: Two hundred seventy-five reviews were included: 75 (27%) systematic; 126 (46%) narrative with some methodology reported, and 74 (27%) narrative reviews. In comparison to systematic reviews, narrative reviews were more frequently published in journals with higher IF (risk ratio [RR] = 1.114 (95% CI 1.080 to 1.149). Systematic reviews received more citations than narrative reviews (group formed by narrative and narrative with some methodology reported (RR = 0.985 95% CI 0.978 to 0.991). CONCLUSIONS: Non-systematic evidence is the most prevalent type of evidence in reviews published in the five highest-ranked general medical journals. Narrative reviews were more frequently published in journals with higher IF. We recommend that journals limit their space for narrative information, and to address clinical research questions, these journals consider publishing systematic evidence exclusively.