SYSTEMATIC REVIEW
Quality of Systematic Reviews of Observational Nontherapeutic Studies

Tatyana Shamliyan, MD, MS; Robert L. Kane, MD; Stacy Jansen, MPH

Suggested citation for this article: Shamliyan T, Kane RL, Jansen S. Quality of systematic reviews of observational nontherapeutic studies. Prev Chronic Dis 2010;7(6):A133. http://www.cdc.gov/pcd/issues/2010/nov/09_0195.htm. Accessed [date].

PEER REVIEWED

Abstract

Introduction
High-quality epidemiologic research is essential in reducing chronic diseases. We analyzed the quality of systematic reviews of observational nontherapeutic studies.

Methods
We searched several databases for systematic reviews of observational nontherapeutic studies that examined the prevalence of or risk factors for chronic diseases and were published in core clinical journals from 1966 through June 2008. We analyzed the quality of such reviews by using prespecified criteria and internal quality evaluation of the included studies.

Results
Of the 145 systematic reviews we found, fewer than half met each quality criterion; 49% reported study flow, 27% assessed gray literature, 2% abstracted sponsorship of individual studies, and none abstracted the disclosure of conflict of interest by the authors of individual studies. Planned, formal internal quality evaluation of included studies was reported in 37% of systematic reviews. The journal of publication, topic of review, sponsorship, and conflict of interest were not associated with better quality. Odds of formal internal quality evaluation (odds ratio [OR], 1.10 per year; 95% confidence interval [CI], 1.02-1.19) and either planned, formal internal quality evaluation or abstraction of quality criteria of included studies (OR, 1.17 per year; 95% CI, 1.08-1.26) increased over time, without positive trends in other quality criteria from 1990 through June 2008. Systematic reviews with internal quality evaluation did not meet other quality criteria more often than those that ignored the quality of included studies.

Conclusion
Collaborative efforts from investigators and journal editors are needed to improve the quality of systematic reviews.

Back to top

Introduction

Valid epidemiologic research is essential in preventing chronic diseases (1-3). Assessing the quality of observational studies is an important part of evidence synthesis (4). Systematic reviews have become key tools in evidence synthesis from a growing number of epidemiologic studies (5). Producing high-quality systematic reviews is essential to developing generalizable and actionable conclusions (6,7). Quality criteria for systematic reviews have been proposed by working groups that developed the Meta-analysis of Observational Studies in Epidemiology (MOOSE), Strengthening the Reporting of Observational Studies in Epidemiology (STROBE), and a measurement tool for assessment of multiple systematic reviews (AMSTAR) (8-12). The working groups and the Cochrane handbook (13) addressed those criteria for systematic reviews that more likely result in biased results, including bias in selection of the studies or the information within studies by the reviewers (14-18) or bias in the publication of positive significant results (6,15,19,20).

Previous research and guidelines (13,21-23) focus on systematic reviews of interventional therapeutic studies. Validity of observational nontherapeutic studies of prevalence of chronic diseases or risk factors for diseases is essential for effective preventive public health actions (24,25). Our aim was to evaluate the quality of systematic reviews of observational nontherapeutic studies that examined the incidence and prevalence of chronic conditions and risk factors for diseases. The criteria we used to determine the reporting and methodologic quality in systematic reviews were from published standards (8-12). We hypothesized that the quality of systematic reviews differs by the time when the study was published, the country in which the study was conducted, the journal of publication, the sponsorship of the study, and whether a conflict of interest was disclosed. We hypothesized also that systematic reviews with internal quality evaluation of the included studies would have better quality, demonstrating commitment to quality of evidence.

Back to top

Methods

Data sources

We searched MEDLINE via PubMed and via Ovid MEDLINE, the Cochrane Library (26) and working groups, WorldCat (27), and Scirus (28) to find systematic reviews of observational nontherapeutic studies published in English from 1966 through June 2008 in core clinical journals (exact search string is listed in Appendix Table 1). We used the definitions of core clinical journals from the Abridged Index Medicus (119 indexed titles). We defined observational nontherapeutic studies as observations of patient outcomes that did not examine procedures concerned with the remedial treatment or prevention of diseases (29).

Study selection

Three investigators independently decided on the eligibility of the studies according to recommendations from the Cochrane Handbook for Systematic Reviews of Interventions (13). We reviewed abstracts to exclude comments, expert opinions, letters, case reports, systematic reviews of interventional studies, and systematic reviews of studies of diagnostic accuracy of tests.

Data extraction

Evaluations of the studies and data extraction were performed independently by 2 researchers. Predefined categorical responses to the checklist items were abstracted into our spreadsheet. Errors in data extraction were assessed by a comparison of the data charts with the original articles (13,30). Any discrepancies were discussed and resolved. The quality criteria that we abstracted were based on guidelines for determining the reporting and methodologic quality of systematic reviews (8-12).

To evaluate selection bias, we abstracted whether the authors of systematic reviews described the search strategy (yes, no, or partially); yes indicated that the authors reported time periods of searches, searched databases, and exact search string. We abstracted whether the authors of systematic reviews described study flow (yes, no, or partially); yes indicated that the authors reported the list of retrieved citations, the list of excluded studies, and justification for exclusion.

We abstracted as dichotomous variables whether the authors of systematic reviews did any of the following:

• Stated the aim of the review and the primary and secondary hypotheses of the review.
• Included or justified exclusion of articles published in languages other than English.
• Searched for gray literature, including abstracts and unpublished studies, to evaluate publication bias (21).
• Described any contact with authors of the included studies.
• Analyzed sponsorship of and conflict of interest in the included studies.

We abstracted how the authors of systematic reviews described obtained statistical methods with justification and models for pooling with fixed or random effects models in sufficient detail to be replicated (no pooling, random, or fixed). We abstracted whether the authors of pooling analyses reported statistical tests for heterogeneity and whether heterogeneity was statistically significant (not reported, not significant, or significant).

We used 3 categories to classify whether the authors of systematic reviews had evaluated the quality of included studies by using developed or previously published checklists or scales (31): 1) the authors stated planned, formal internal quality evaluations; 2) the authors abstracted selected criteria of external or internal validity without using a planned, formal, and comprehensive internal quality evaluation; and 3) the authors did not conduct internal quality evaluations. We further categorized the studies that evaluated quality criteria to compare studies with no mention of internal quality evaluation of the included studies. We also compared studies with and without planned formal internal quality evaluation. We abstracted with dichotomous responses blinding and reliability testing (reported or not reported) of internal quality evaluations.

We abstracted several explanatory variables that could be related to the quality of systematic reviews:

• The year of publication, defined as a continuous variable. We created categories of 4- or 5-year periods: 1990 to 1994, 1995 to 1999, 2000 to 2004, and 2005 through June 2008.
• The journals of publication.
• The country where the systematic reviews were performed.
• The sponsorship of the reviews. Those that had either governmental or foundational support or were fellowships were defined as having nonprofit support.
• The disclosure of conflict of interest by authors of reviews (either not disclosed, disclosed as no conflict of interest, or disclosed conflict of interest).
• The number of disclosed relationships with industry, defined as a continuous variable.
• The sponsor’s participation in data collection, analysis, and interpretation of the results of the review.
• The review outcomes as risk factors for prevalence or incidence of chronic conditions or diseases.

Data synthesis

We summarized the results in evidence tables. We used prespecified categories of dependent and independent variables and did not force the data into binary categories for definitive tests of significance. We used univariate logistic regression to examine the association between internal quality evaluation and the year of the publication by using the Wald test. Odds ratios (ORs) were calculated with binary logit models and Fisher’s scoring method technique. We computed the fractions of systematic reviews meeting various quality criteria in each of the 4 time periods considered. The proportions of systematic reviews that met different levels of each quality criterion were evaluated by using χ² tests and Fisher’s exact tests in cases of small numbers. All calculations were performed at 95% confidence intervals (CIs) by using 2-sided P values with SAS version 9.1.3 (SAS Institute Inc, Cary, North Carolina).

Back to top

Results

We found 145 eligible systematic reviews of observational nontherapeutic studies (study flow in the Appendix Figure) (32-176). The number of published systematic reviews increased from 17 during 1990-1994 to 56 during 2005-2008. Most of the studies were conducted in the United States (55 publications) or in the United Kingdom (28 publications) (Appendix Table 2). Half of the systematic reviews (73 publications) were funded by nonprofit organizations; 56 (39%) reviews did not publish their funding sources, 4 reviews received industry support, and 10 were sponsored jointly by industry and nonprofit organizations. Almost three-fourths (106) of the authors of systematic reviews did not disclose conflict of interest; 35 publications stated that the authors do not have any conflict of interest; and 4 studies were conducted by authors who reported conflict of interest. The studies were published in 49 journals. Most systematic reviews (122 studies) assessed risk factors for chronic diseases, 19 summarized estimates of prevalence or incidence, 2 studies reported prevalence and associations with risk factors, and 2 studies examined levels of risk factors. Most studies reported incidence and risk factors for cardiovascular diseases (46 studies) or cancer (26 studies).

Quality of systematic reviews

Less than half of the studies reported study flow (49%), assessed gray literature (27%), or addressed language bias (29%) (Table 1). Only 2% of reviews abstracted sponsorship of individual studies and none abstracted the disclosure of conflict of interest by the authors of individual studies that were eligible for the reviews. Pooling was performed in 137 studies; of these, 62% used a random effects model; 57% reported detecting significant heterogeneity across the studies; and 19% did not provide any information about statistical heterogeneity in pooled estimates. The proportion of systematic reviews that met quality criteria including study flow, assessment of gray literature, or the abstraction of funding sources of included studies did not show significant trends from 1990 through 2008. The proportion of systematic reviews that assessed language bias increased from 8% during 1995-1999 to 41% during 2005-2008. In later years, more studies reported using random effects models (79% during 2005-2008 vs 39% during 1995-1999) and tests for statistical heterogeneity (89% during 2005-2008 vs 65% during 1995-1999).

Internal quality evaluation

Planned and detailed quality assessment of included studies was reported in 37% of systematic reviews, and 18% abstracted more than 1 criterion of external or internal quality; significant positive trends were reported during the evaluated time (Table 1). Quality assessment was masked in 3 studies. Development of the appraisals, including references to previously published tools, was reported in 32 studies, but only 6 tested interobserver agreement for quality assessment.

Quality of systematic review by explanatory factors

The quality of systematic reviews did not differ much by study location or by the journal of publication. Systematic reviews of prevalence or incidence or risk factors of the diseases did not differ in their quality measures. Sponsorship was not associated with quality of the reviews. The role of conflict of interest was impossible to establish because the authors of 56 reviews did not disclose funding and authors of 106 reviews did not disclose conflict of interest.

Explanatory factors of internal quality evaluation of included studies

The journal of publication, topic of the review, and continent where the review was conducted were not associated with the likelihood of internal quality evaluation. Systematic reviews of risk factors tended to conduct internal quality evaluation of the included studies more often than reviews of incidence or prevalence or of levels of risk factors. Systematic reviews sponsored by nonprofit organizations conducted internal quality evaluations of individual studies more often than reviews that received corporate funding. Systematic reviews that disclosed conflict of interest conducted internal quality evaluation of individual studies less frequently (10 of 39 studies; 26%) than reviews with no disclosure (44 of 106 studies; 42%). Odds of formal internal quality evaluation (OR, 1.10 per year; 95% CI, 1.02-1.19) and either planned, formal internal quality evaluation or abstraction of quality criteria (OR, 1.17 per year; 95% CI, 1.08-1.26) increased over time. Disclosure of conflict of interest by the authors of systematic reviews was not associated with greater odds of internal quality evaluation.

Quality of systematic reviews by internal quality evaluation

Complete documentation of the literature search including time period, databases searched, and exact literature search strings was less common among reviews with planned, formal internal quality evaluation (48 studies, 35%) than among reviews without it (90 studies, 65%) (Table 2). However, reviews that either abstracted selected quality criteria or planned, formal internal quality evaluation reported partial (6 studies) or complete (74 studies) information about the literature search more often than studies that did not evaluate quality of included studies (64 studies). Reviews that did not justify exclusion of non-English studies ignored quality of individual studies more often (72 studies) than reviews with planned, formal internal quality evaluation (31 studies). The same pattern was present for publication bias: the reviews that did not mention gray literature also ignored the quality of individual studies. The reviews reporting attempts to contact the authors of included studies either performed planned, formal internal quality evaluation or abstracted selected quality criteria more often than reviews without such attempts (OR, 2.3; 95% CI, 1.1-4.7). Reviews with complete reporting of study flow performed planned, formal internal quality evaluation or abstracted quality criteria more often (51 studies) than reviews without study flows (20 studies). More than half of systematic reviews without planned, formal internal quality evaluation (44 studies) also did not report study flow.

The association between quality of systematic reviews and sponsor participation in the data collection, analyses, and interpretation was difficult to analyze because this information was either omitted or reported in various ways. Less than 10% of systematic reviews contained a clear statement that the sponsors did not play any role in gathering the studies or analyzing or interpreting the results and did not influence the content of the manuscript. Other reviews omitted mention of the role of the sponsor in approval of the manuscript or provided a general statement that sponsors did not influence the conclusions or the content of the paper. Two reviews included statements of unconditional or unrestricted sponsorship of the meta-analyses.

Back to top

Discussion

Our analyses showed that less than half of the systematic reviews of nontherapeutic observational studies that were published in core clinical journals met each quality criterion. Quality of systematic reviews did not improve over time. Planned, formal internal quality evaluations of the included studies was reported in less than half of systematic reviews, but the prevalence of internal quality evaluations has increased during the last decade. Our findings are in concordance with previously published methodologic analyses of systematic reviews that also found inconsistent quality and incomplete internal quality evaluation of individual studies (6). Methodologic analyses of systematic reviews that focused on particular diseases or conditions demonstrated that half of the publications had major flaws in design and reporting. For instance, systematic reviews of therapies for renal diseases failed to assess the methodologic quality of included studies (177). Methodologic analyses of systematic reviews of interventions showed that 69% of those randomly selected in MEDLINE meta-analyses did not analyze quality of trials (22). Most (68%) systematic reviews of diagnostic tests for cancer did not provide formal assessments of study quality (178). We also found that the quality of reviews did not differ among types of studies (incidence or risk factors for diseases), types of diseases, or journal of publication.

Journal commitment to high-quality research, however, was associated with improved reporting quality of the publications. For example, adoption by journals of the Consolidated Standards of Reporting Trials (CONSORT) improved the quality of the publications of interventional studies (179,180). An endorsement of the developed standards for observational studies including MOOSE and STROBE checklists may also improve quality of the publications. We did not analyze how many core clinical journals adopted these standards and how quality of the publications changed depending on this adaptation. Peer review of submitted manuscripts should include quality assessment using validated tools (12).

We could not identify the factors that can explain differences in quality of systematic reviews. The role of sponsorship and conflict of interest could not be estimated because of poor reporting of this information. The quality and reliability of quality evaluation of the included studies is unclear because development of the appraisals was described in a small proportion of systematic reviews (32 of 80 studies), and only 6 of 80 studies tested interobserver agreement for quality assessment. We did not evaluate all reviews of observational studies that were published in epidemiologic journals. However, it is unlikely that the quality of reviews published in other journals would be better than those in core clinical journals. Future research should investigate the factors that can explain differences in the quality of systematic reviews.

Peer reviewed publications of high-quality systematic reviews can provide the best available research evidence for evidence-based public health (24). Evidence-based decisions can improve public health practice in preventing incidence and progression of chronic diseases (25). In our analysis, less than half of the systematic reviews of observational nontherapeutic studies met quality criteria established in the MOOSE, STROBE, and AMSTAR statements. Internal quality evaluation of included studies should be an essential part of evidence synthesis, but only half of the reviews reported such evaluation. Collaborative efforts from investigators and journal editors are needed to improve quality of systematic reviews.

Back to top

Acknowledgments

This article is based on research conducted by the Minnesota Evidence-based Practice Center under contract to the Agency for Healthcare Research and Quality (AHRQ), Rockville, Maryland (contract no. 290-02-0009).

We thank our reviewers David Atkins, MD, John Hoey, MD, and Christine Laine, MD, for reviewing and commenting on the draft; our collaborating experts, Mohammed Ansari, MBBS, Ethan Balk, MD, Nancy Berkman, PhD, Chantelle Garritty, Mark Grant, MD, Gail Janes, PhD, Margaret Maglione, MPP, David Moher, PhD, Mona Nasser, DDS, Gowri Raman, MD, Karen Robinson, MD, Jodi Segal, MD, and Thomas Trikalinos, PhD, for their scientific input throughout this project; and Carmen Kelly, PharmD, our task order officer, and Stephanie Chang, MD, medical officer, at AHRQ for their guidance throughout the project. We also thank librarian Judith Stanke for her contributions to the literature search; research assistants Emily Zabor, candidate for the master of science degree (MS) in biostatistics, and Akweley Ablorh, candidate for MS in biostatistics, for the data abstraction, quality control, and synthesis of evidence; Zhihua Bian, candidate for MS in biostatistics, for her statistical help; Zhiyuan Xu, candidate for MS in applied economics, for his work creating the ACCESS database; Dean McWilliams for his assistance in database development; Qi Wang, research fellow, for her statistical expertise in reliability testing; Susan Duval, PhD, for her help estimating sample size; Marilyn Eells for editing and formatting the report; and Nancy Russell, MLS, and Rebecca Schultz for their assistance gathering data from the experts and formatting the tables, and Christa Prodzinski for quality control of the data.

Back to top

Author Information

Corresponding Author: Tatyana Shamliyan, MD, MS, Minnesota Evidence-based Practice Center, University of Minnesota School of Public Health, D351 Mayo (MMC 197), 420 Delaware St SE, Minneapolis, MN 55455. Telephone: 612-624-1185. E-mail: shaml005@umn.edu.

Author Affiliations: Robert L. Kane, Stacy Jansen, University of Minnesota School of Public Health, Minneapolis, Minnesota.

Back to top

References

1. Bero LA, Jadad AR. How consumers and policymakers can use systematic reviews for decision making. Ann Intern Med 1997;127(1):37-42.
2. Chan KS, Morton SC, Shekelle PG. Systematic reviews for evidence-based management: how to find them and what to do with them. Am J Manag Care 2004;10(11 Pt 1):806-12.
3. Biss PA, Zaza S, Pappaioanou M, Fielding J, Wright-De Agüero L, Truman BI, et al. Developing an evidence-based Guide to Community Preventive Services — methods. The Task Force on Community Preventive Services. Am J Prev Med 2000;18(1 Suppl):35-43.
4. West S, King V, Carey TS, Lohr KN, McKoy N, Sutton SF, et al. Systems to rate the strength of scientific evidence. Evidence Report/Technology Assessment no. 47 (Prepared by the Research Triangle Institute — University of North Carolina Evidence-based Practice Center under Contract no. 290-97-0011). AHRQ Publication no. 02-E016. Rockville (MD): Agency for Healthcare Research and Quality; 2002.
5. US Preventive Services Task Force, Agency for Healthcare Research and Quality. The guide to clinical preventive services, 2008: recommendations of the US Preventive Services Task Force. Rockville (MD): Agency for Healthcare Research and Quality; 2008.
6. Moher D, Tetzlaff J, Tricco AC, Sampson M, Altman DG. Epidemiology and reporting characteristics of systematic reviews. PLoS Med 2007;4(3):e78.
7. Tricco AC, Tetzlaff J, Sampson M, Fergusson D, Cogo E, Horsley T, et al. Few systematic reviews exist documenting the extent of bias: a systematic review. J Clin Epidemiol 2008;61(5):422-34.
8. Stroup DF, Berlin JA, Morton SC, Olkin I, Williamson GD, Rennie D, et al. Meta-analysis of observational studies in epidemiology: a proposal for reporting. Meta-analysis of Observational Studies in Epidemiology (MOOSE) group. JAMA 2000;283(15):2008-12.
9. Tooth L, Ware R, Bain C, Purdie DM, Dobson A. Quality of reporting of observational longitudinal research. Am J Epidemiol 2005;161(3):280-8.
10. Vandenbroucke JP, von Elm E, Altman DG, Gøtzsche PC, Mulrow CD, Pocock SJ, et al. Strengthening the Reporting of Observational Studies in Epidemiology (STROBE): explanation and elaboration. Epidemiology 2007;18(6):805-35.
11. von Elm E, Altman DG, Egger M, Pocock SJ, Gotzsche PC, Vandenbroucke JP. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. Lancet 2007;370(9596):1453-7.
12. Shea BJ, Grimshaw JM, Wells GA, Boers M, Andersson N, Hamel C, et al. Development of AMSTAR: a measurement tool to assess the methodological quality of systematic reviews. BMC Med Res Methodol 2007;7:10.
13. Higgins JPT, Green S, editors. Cochrane handbook for systematic reviews of interventions. Chichester, West Sussex (GB): John Wiley and Sons Ltd; 2008.
14. Whitehead A. Meta-analysis of controlled clinical trials. Chichester, West Sussex (GB): John Wiley and Sons Ltd; 2002.
15. Egger M, Smith GD. Bias in location and selection of studies. BMJ 1998;316(7124):61-6.
16. Dickersin K. The existence of publication bias and risk factors for its occurrence. JAMA 1990;263(10):1385-9.
17. Dickersin K. How important is publication bias? A synthesis of available data. AIDS Educ Prev 1997;9(1 Suppl):15-21.
18. Dickersin K, Min YI. NIH clinical trials and publication bias. Online J Curr Clin Trials 1993;Doc No 50:[4,967 words; 53 paragraphs].
19. Ravnskov U. Cholesterol lowering trials in coronary heart disease: frequency of citation and outcome. BMJ 1992;305(6844):15-9.
20. Moher D, Soeken K, Sampson M, Ben-Porat L, Berman B. Assessing the quality of reports of systematic reviews in pediatric complementary and alternative medicine. BMC Pediatr 2002;2:3.
21. Methods guide for comparative effectiveness reviews. Agency for Healthcare Research and Quality. http://www.effectivehealthcare.ahrq.gov/repFiles/ 20090427IdenttifyingTopics.pdf. Accessed June 2010.
22. Jadad AR, Cook DJ, Jones A, Klassen TP, Tugwell P, Moher M, et al. Methodology and reports of systematic reviews and meta-analyses: a comparison of Cochrane reviews with articles published in paper-based journals. JAMA 1998;280(3):278-80.
23. Liberati A, Altman DG, Tetzlaff J, Mulrow C, Gøtzsche PC, Ioannidis JP, et al. The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate healthcare interventions: explanation and elaboration. BMJ 2009;339:b2700.
24. Brownson RC, Fielding JE, Maylahn CM. Evidence-based public health: a fundamental concept for public health practice. Annu Rev Public Health 2009;30:175-201.
25. Brownson RC, Gurney JG, Land GH. Evidence-based decision making in public health. J Public Health Manag Pract 1999;5(5):86-97.
26. Higgins J, Green S. The Cochrane handbook for systematic reviews of interventions 4.2.6, updated September 2006. http://www2.cochrane.org/resources/handbook/handbook.pdf. Accessed July 2010.
27. WorldCat. OCLC Online Computer Library Center. http://www.oclc.org/worldcat/. Accessed July 2010.
28. Scirus for scientific information only. Elsevier. http://www.scirus.com. Accessed July 2010.
29. Principles of epidemiology in public health practice: an introduction to applied epidemiology and biostatistics. 3rd edition. Atlanta (GA): US Department of Health and Human Services, Centers for Disease Control and Prevention, Office of Workforce and Career Development; 2006.
30. Higgins JPT, Green S, editors. Cochrane handbook for systematic reviews of interventions, version 5.0.2 [updated September 2009]. London (GB): Cochrane Collaboration; 2009. http://www.cochrane-handbook.org/. Accessed July 2010.
31. Lundh A, Gøtzsche PC. Recommendations by Cochrane Review Groups for assessment of the risk of bias in studies. BMC Med Res Methodol 2008;8:22.
32. Bracken MB. Oral contraception and congenital malformations in offspring: a review and meta-analysis of the prospective studies. Obstet Gynecol 1990;76(3 Pt 2):552-7.
33. Romieu I, Berlin JA, Colditz G. Oral contraceptives and breast cancer. Review and meta-analysis. Cancer 1990;66(11):2253-63.
34. Haughey BH, Gates GA, Arfken CL, Harvey J. Meta-analysis of second malignant tumors in head and neck cancer: the case for an endoscopic screening protocol. Ann Otol Rhinol Laryngol 1992;101(2 Pt 1):105-12.
35. Lemon HM, Heidel JW, Rodriguez-Sierra JF. Increased catechol estrogen metabolism as a risk factor for nonfamilial breast cancer. Cancer 1992;69(2):457-65.
36. McKenna MJ. Differences in vitamin D status between countries in young adults and the elderly. Am J Med 1992;93(1):69-77.
37. Morris RD, Audet AM, Angelillo IF, Chalmers TC, Mosteller F. Chlorination, chlorination by-products, and cancer: a meta-analysis. Am J Public Health 1992;82(7):955-63.
38. Myers MG, Basinski A. Coffee and coronary heart disease. Arch Intern Med 1992;152(9):1767-72.
39. Becker LB, Smith DW, Rhodes KV. Incidence of cardiac arrest: a neglected factor in evaluating survival rates. Ann Emerg Med 1993;22(1):86-91.
40. Brownson RC, Novotny TE, Perry MC. Cigarette smoking and adult leukemia. A meta-analysis. Arch Intern Med 1993;153(4):469-75.
41. Ernst E, Resch KL. Fibrinogen as a cardiovascular risk factor: a meta-analysis and review of the literature. Ann Intern Med 1993;118(12):956-63.
42. Katerndahl DA. Panic and prolapse. Meta-analysis. J Nerv Ment Dis 1993;181(9):539-44.
43. Harris EC, Barraclough BM. Suicide as an outcome for medical disorders. Medicine (Baltimore) 1994;73(6):281-96.
44. Kawachi I, Colditz GA, Stone CB. Does coffee drinking increase the risk of coronary heart disease? Results from a meta-analysis. Br Heart J 1994;72(3):269-75.
45. Law MR, Thompson SG, Wald NJ. Assessing possible hazards of reducing serum cholesterol. BMJ 1994;308(6925):373-9.
46. Law MR, Wald NJ, Thompson SG. By how much and how quickly does reduction in serum cholesterol concentration lower risk of ischaemic heart disease? BMJ 1994;308(6925):367-72.
47. Steffen R, Kane MA, Shapiro CN, Billo N, Schoellhorn KJ, van Damme P. Epidemiology and prevention of hepatitis A in travelers. JAMA 1994;272(11):885-9.
48. Zhang ZF, Begg CB. Is Trichomonas vaginalis a cause of cervical neoplasia? Results from a combined analysis of 24 studies. Int J Epidemiol 1994;23(4):682-90.
49. Everhart J, Wright D. Diabetes mellitus as a risk factor for pancreatic cancer. A meta-analysis. JAMA 1995;273(20):1605-9.
50. Feinberg WM, Blackshear JL, Laupacis A, Kronmal R, Hart RG. Prevalence, age distribution, and gender of patients with atrial fibrillation. Analysis and implications. Arch Intern Med 1995;155(5):469-73.
51. Ritchie K, Kildea D. Is senile dementia “age-related” or “ageing-related”? — evidence from meta-analysis of dementia prevalence in the oldest old. Lancet 1995;346(8980):931-4.
52. Raman-Wilms L, Tseng AL, Wighardt S, Einarson TR, Koren G. Fetal genital effects of first-trimester sex hormone exposure: a meta-analysis. Obstet Gynecol 1995;85(1):141-9.
53. Hatsukami DK, Fischman MW. Crack cocaine and cocaine hydrochloride. Are the differences myth or reality? JAMA 1996;276(19):1580-8.
54. Hill JC, Schoener EP. Age-dependent decline of attention deficit hyperactivity disorder. Am J Psychiatry 1996;153(9):1143-6.
55. Hackshaw AK, Law MR, Wald NJ. The accumulated evidence on lung cancer and environmental tobacco smoke. BMJ 1997;315(7114):980-8.
56. Kluijtmans LA, Kastelein JJ, Lindemans J, Boers GH, Heil SG, Bruschke AV, et al. Thermolabile methylenetetrahydrofolate reductase in coronary artery disease. Circulation 1997;96(8):2573-7.
57. Law MR, Hackshaw AK. A meta-analysis of cigarette smoking, bone mineral density and risk of hip fracture: recognition of a major effect. BMJ 1997;315(7112):841-6.
58. Law MR, Morris JK, Wald NJ. Environmental tobacco smoke exposure and ischaemic heart disease: an evaluation of the evidence. BMJ 1997;315(7114):973-80.
59. Danesh J, Collins R, Appleby P, Peto R. Association of fibrinogen, C-reactive protein, albumin, or leukocyte count with coronary heart disease: meta-analyses of prospective studies. JAMA 1998;279(18):1477-82.
60. French R, Brocklehurst P. The effect of pregnancy on survival in women infected with HIV: a systematic review of the literature and meta-analysis. Br J Obstet Gynaecol 1998;105(8):827-35.
61. Forgie MA, Wells PS, Laupacis A, Fergusson D. Preoperative autologous donation decreases allogeneic transfusion but increases exposure to all red blood cell transfusion: results of a meta-analysis. International Study of Perioperative Transfusion (ISPOT) Investigators. Arch Intern Med 1998;158(6):610-6.
62. Huang JQ, Sridhar S, Chen Y, Hunt RH. Meta-analysis of the relationship between Helicobacter pylori seropositivity and gastric cancer. Gastroenterology 1998;114(6):1169-79.
63. Johnston SC, Colford JM Jr, Gress DR. Oral contraceptives and the risk of subarachnoid hemorrhage: a meta-analysis. Neurology 1998;51(2):411-8.
64. Lazarou J, Pomeranz BH, Corey PN. Incidence of adverse drug reactions in hospitalized patients: a meta-analysis of prospective studies. JAMA 1998;279(15):1200-5.
65. Ray JG. Meta-analysis of hyperhomocysteinemia as a risk factor for venous thromboembolic disease. Arch Intern Med 1998;158(19):2101-6.
66. Spencer-Green G. Outcomes in primary Raynaud phenomenon: a meta-analysis of the frequency, rates, and predictors of transition to secondary diseases. Arch Intern Med 1998;158(6):595-600.
67. Stratton JF, Pharoah P, Smith SK, Easton D, Ponder BA. A systematic review and meta-analysis of family history and risk of ovarian cancer. Br J Obstet Gynaecol 1998;105(5):493-9.
68. Zock PL, Katan MB. Linoleic acid intake and cancer risk: a review and meta-analysis. Am J Clin Nutr 1998;68(1):142-53.
69. Zondervan KT, Yudkin PL, Vessey MP, Dawes MG, Barlow DH, Kennedy SH. The prevalence of chronic pelvic pain in women in the United Kingdom: a systematic review. Br J Obstet Gynaecol 1998;105(1):93-9.
70. Angelillo IF, Villari P. Residential exposure to electromagnetic fields and childhood leukaemia: a meta-analysis. Bull World Health Organ 1999;77(11):906-15.
71. He J, Vupputuri S, Allen K, Prerost MR, Hughes J, Whelton PK. Passive smoking and the risk of coronary heart disease — a meta-analysis of epidemiologic studies. N Engl J Med 1999;340(12):920-6.
72. Shaffer HJ, Hall MN, Vander Bilt J. Estimating the prevalence of disordered gambling behavior in the United States and Canada: a research synthesis. Am J Public Health 1999;89(9):1369-76.
73. Wittrup HH, Tybjaerg-Hansen A, Nordestgaard BG. Lipoprotein lipase mutations, plasma lipids and lipoproteins, and risk of ischemic heart disease. A meta-analysis. Circulation 1999;99(22):2901-7.
74. Yoder PR, Sabbagha RE, Gross SJ, Zelop CM. The second-trimester fetus with isolated choroid plexus cysts: a meta-analysis of risk of trisomies 18 and 21. Obstet Gynecol 1999;93(5 Pt 2):869-72.
75. Christen WG, Ajani UA, Glynn RJ, Hennekens CH. Blood levels of homocysteine and increased risks of cardiovascular disease: causal or casual? Arch Intern Med 2000;160(4):422-34.
76. Cleophas TJ, Hornstra N, van Hoogstraten B, van der Meulen J. Homocysteine, a risk factor for coronary artery disease or not? A meta-analysis. Am J Cardiol 2000;86(9):1005-9, A8.
77. DiMatteo MR, Lepper HS, Croghan TW. Depression is a risk factor for noncompliance with medical treatment: meta-analysis of the effects of anxiety and depression on patient adherence. Arch Intern Med 2000;160(14):2101-7.
78. Effect of breastfeeding on infant and child mortality due to infectious diseases in less developed countries: a pooled analysis. WHO Collaborative Study Team on the Role of Breastfeeding on the Prevention of Infant Mortality. Lancet 2000;355(9202):451-5.
79. Wilson K, Gibson N, Willan A, Cook D. Effect of smoking cessation on mortality after myocardial infarction: meta-analysis of cohort studies. Arch Intern Med 2000;160(7):939-44.
80. Zeegers MP, Tan FE, Dorant E, van Den Brandt PA. The impact of characteristics of cigarette smoking on urinary tract cancer risk: a meta-analysis of epidemiologic studies. Cancer 2000;89(3):630-9.
81. Danesh J, Whincup P, Walker M, Lennon L, Thomson A, Appleby P, et al. Fibrin D-dimer and coronary heart disease: prospective study and meta-analysis. Circulation 2001;103(19):2323-7.
82. Eaden JA, Abrams KR, Mayberry JF. The risk of colorectal cancer in ulcerative colitis: a meta-analysis. Gut 2001;48(4):526-35.
83. Faraone SV, Doyle AE, Mick E, Biederman J. Meta-analysis of the association between the 7-repeat allele of the dopamine D(4) receptor gene and attention deficit hyperactivity disorder. Am J Psychiatry 2001;158(7):1052-7.
84. Horta BL, Kramer MS, Platt RW. Maternal smoking and the risk of early weaning: a meta-analysis. Am J Public Health 2001;91(2):304-7.
85. Rebora A. Baldness and coronary artery disease: the dermatologic point of view of a controversial issue. Arch Dermatol 2001;137(7):943-7.
86. Cannon M, Jones PB, Murray RM. Obstetric complications and schizophrenia: historical and meta-analytic review. Am J Psychiatry 2002;159(7):1080-92.
87. Hellermann JP, Jacobsen SJ, Gersh BJ, Rodeheffer RJ, Reeder GS, Roger VL. Heart failure after myocardial infarction: a review. Am J Med 2002;113(4):324-30.
88. Huang JQ, Sridhar S, Hunt RH. Role of Helicobacter pylori infection and non-steroidal anti-inflammatory drugs in peptic-ulcer disease: a meta-analysis. Lancet 2002;359(9300):14-22.
89. Huncharek M, Kupelnick B. Use of topical sunscreens and the risk of malignant melanoma: a meta-analysis of 9067 patients from 11 case-control studies. Am J Public Health 2002;92(7):1173-7.
90. Juul K, Tybjaerg-Hansen A, Steffensen R, Kofoed S, Jensen G, Nordestgaard BG. Factor V Leiden: The Copenhagen City Heart Study and 2 meta-analyses. Blood 2002;100(1):3-10.
91. Kelly PJ, Rosand J, Kistler JP, Shih VE, Silveira S, Plomaritoglou A, et al. Homocysteine, MTHFR 677C-->T polymorphism, and risk of ischemic stroke: results of a meta-analysis. Neurology 2002;59(4):529-36.
92. Klerk M, Verhoef P, Clarke R, Blom HJ, Kok FJ, Schouten EG. MTHFR 677C-->T polymorphism and risk of coronary heart disease: a meta-analysis. JAMA 2002;288(16):2023-31.
93. Kozer E, Nikfar S, Costei A, Boskovic R, Nulman I, Koren G. Aspirin consumption during the first trimester of pregnancy and congenital anomalies: a meta-analysis. Am J Obstet Gynecol 2002;187(6):1623-30.
94. Law MR, Watt HC, Wald NJ. The underlying risk of death after myocardial infarction in the absence of treatment. Arch Intern Med 2002;162(21):2405-10.
95. Wald DS, Law M, Morris JK. Homocysteine and cardiovascular disease: evidence on causality from a meta-analysis. BMJ 2002;325(7374):1202.
96. Wald A, Link K. Risk of human immunodeficiency virus infection in herpes simplex virus type 2-seropositive persons: a meta-analysis. J Infect Dis 2002;185(1):45-52.
97. Benjamin DK Jr, Poole C, Steinbach WJ, Rowen JL, Walsh TJ. Neonatal candidemia and end-organ damage: a critical appraisal of the literature using meta-analytic techniques. Pediatrics 2003;112(3 Pt 1):634-40.
98. Clarfield AM. The decreasing prevalence of reversible dementias: an updated meta-analysis. Arch Intern Med 2003;163(18):2219-29.
99. Cole MG, Dendukuri N. Risk factors for depression among elderly community subjects: a systematic review and meta-analysis. Am J Psychiatry 2003;160(6):1147-56.
100. Gisbert JP, Garcia-Buey L, Pajares JM, Moreno-Otero R. Prevalence of hepatitis C virus infection in B-cell non-Hodgkin’s lymphoma: systematic review and meta-analysis. Gastroenterology 2003;125(6):1723-32.
101. Glatt SJ, Faraone SV, Tsuang MT. Association between a functional catechol O-methyltransferase gene polymorphism and schizophrenia: meta-analysis of case-control and family-based studies. Am J Psychiatry 2003;160(3):469-76.
102. Halbert RJ, Isonaka S, George D, Iqbal A. Interpreting COPD prevalence estimates: what is the true burden of disease? Chest 2003;123(5):1684-92.
103. Huang JQ, Zheng GF, Sumanac K, Irvine EJ, Hunt RH. Meta-analysis of the relationship between cagA seropositivity and gastric cancer. Gastroenterology 2003;125(6):1636-44.
104. Rey E, Kahn SR, David M, Shrier I. Thrombophilic disorders and fetal loss: a meta-analysis. Lancet 2003;361(9361):901-8.
105. Riboli E, Norat T. Epidemiologic evidence of the protective effect of fruit and vegetables on cancer risk. Am J Clin Nutr 2003;78(3 Suppl):559S-569S.
106. Scholten-Peeters GGM, Verhagen AP, Bekkering GE, van der Windt DA, Barnsley L, Oostendorp RA, et al. Prognostic factors of whiplash-associated disorders: a systematic review of prospective cohort studies. Pain 2003;104(1):303-22.
107. Thurnham DI, McCabe GP, Northrop-Clewes CA, Nestel P. Effects of subclinical infection on plasma retinol concentrations and assessment of prevalence of vitamin A deficiency: meta-analysis. Lancet 2003;362(9401):2052-8.
108. Zeegers MP, Jellema A, Ostrer H. Empiric risk of prostate carcinoma for relatives of patients with prostate carcinoma: a meta-analysis. Cancer 2003;97(8):1894-903.
109. Burzotta F, Paciaroni K, De Stefano V, Crea F, Maseri A, Leone G, et al. G20210A prothrombin gene polymorphism and coronary ischaemic syndromes: a phenotype-specific meta-analysis of 12,034 subjects. Heart 2004;90(1):82-6.
110. Casas JP, Bautista LE, Humphries SE, Hingorani AD. Endothelial nitric oxide synthase genotype and ischemic heart disease: meta-analysis of 26 studies involving 23,028 subjects. Circulation 2004;109(11):1359-65.
111. Casas JP, Hingorani AD, Bautista LE, Sharma P. Meta-analysis of genetic studies in ischemic stroke: thirty-two genes involving approximately 18,000 cases and 58,000 controls. Arch Neurol 2004;61(11):1652-61.
112. He K, Song Y, Daviglus ML, Liu K, Van Horn L, Dyer AR, et al. Accumulated evidence on fish consumption and coronary heart disease mortality: a meta-analysis of cohort studies. Circulation 2004;109(22):2705-11.
113. Huang X, Chen PC, Poole C. APOE-[epsilon]2 allele associated with higher prevalence of sporadic Parkinson disease. Neurology 2004;62(12):2198-202.
114. Klement E, Cohen RV, Boxman J, Joseph A, Reif S. Breastfeeding and risk of inflammatory bowel disease: a systematic review with meta-analysis. Am J Clin Nutr 2004;80(5):1342-52.
115. Kovalevsky G, Gracia CR, Berlin JA, Sammel MD, Barnhart KT. Evaluation of the association between hereditary thrombophilias and recurrent pregnancy loss: a meta-analysis. Arch Intern Med 2004;164(5):558-63.
116. Levitan EB, Song Y, Ford ES, Liu S. Is nondiabetic hyperglycemia a risk factor for cardiovascular disease? A meta-analysis of prospective studies. Arch Intern Med 2004;164(19):2147-55.
117. Lovett JK, Coull AJ, Rothwell PM. Early risk of recurrence by subtype of ischemic stroke in population-based incidence studies. Neurology 2004;62(4):569-73.
118. Mitsikostas DD, Sfikakis PP, Goadsby PJ. A meta-analysis for headache in systemic lupus erythematosus: the evidence and the myth. Brain 2004;127(Pt 5):1200-9.
119. Montanez A, Ruskin JN, Hebert PR, Lamas GA, Hennekens CH. Prolonged QTc interval and risks of total and cardiovascular mortality and sudden death in the general population: a review and qualitative overview of the prospective cohort studies. Arch Intern Med 2004;164(9):943-8.
120. Woodbury MG, Houghton PE. Prevalence of pressure ulcers in Canadian healthcare settings. Ostomy Wound Manage 2004;50(10):22-4, 26, 28 passim.
121. Bolland MJ, Grey AB, Gamble GD, Reid IR. Association between primary hyperparathyroidism and increased body weight: a meta-analysis. J Clin Endocrinol Metab 2005;90(3):1525-30.
122. Contopoulos-Ioannidis DG, Manoli EN, Ioannidis JP. Meta-analysis of the association of beta2-adrenergic receptor polymorphisms with asthma phenotypes. J Allergy Clin Immunol 2005;115(5):963-72.
123. Dauchet L, Amouyel P, Dallongeville J. Fruit and vegetable consumption and risk of stroke: a meta-analysis of cohort studies. Neurology 2005;65(8):1193-7.
124. Etminan M, Takkouche B, Isorna FC, Samii A. Risk of ischaemic stroke in people with migraine: systematic review and meta-analysis of observational studies. [Errata published in: BMJ 2005;330(7491):596. BMJ 2005;330(7487):345.] BMJ 2005;330(7482):63.
125. Fazel M, Wheeler J, Danesh J. Prevalence of serious mental disorder in 7000 refugees resettled in western countries: a systematic review. Lancet 2005;365(9467):1309-14.
126. García-Closas M, Malats N, Silverman D, Dosemeci M, Kogevinas M, Hein DW, et al. NAT2 slow acetylation, GSTM1 null genotype, and risk of bladder cancer: results from the Spanish Bladder Cancer Study and meta-analyses. Lancet 2005;366(9486):649-59.
127. Lee YH, Witte T, Momot T, Schmidt RE, Kaufman KM, Harley JB, et al. The mannose-binding lectin gene polymorphisms and systemic lupus erythematosus: two case-control studies and a meta-analysis. Arthritis Rheum 2005;52(12):3966-74.
128. Lin J, August P. Genetic thrombophilias and preeclampsia: a meta-analysis. Obstet Gynecol 2005;105(1):182-92.
129. McDonald S, Murphy K, Beyene J, Ohlsson A. Perinatal outcomes of in vitro fertilization twins: a systematic review and meta-analyses. Am J Obstet Gynecol 2005;193(1):141-52.
130. Palmer BA, Pankratz VS, Bostwick JM. The lifetime risk of suicide in schizophrenia: a reexamination. Arch Gen Psychiatry 2005;62(3):247-53.
131. Sin DD, Wu L, Man SF. The relationship between reduced lung function and cardiovascular mortality: a population-based study and a systematic review of the literature. Chest 2005;127(6):1952-9.
132. Boudville N, Prasad GV, Knoll G, Muirhead N, Thiessen-Philbrook H, Yang RC, et al. Meta-analysis: risk for hypertension in living kidney donors. Ann Intern Med 2006;145(3):185-96.
133. Clark EM, Tobias JH, Ness AR. Association between bone density and fractures in children: a systematic review and meta-analysis. Pediatrics 2006;117(2):e291-7.
134. de Boer AG, Verbeek JH, van Dijk FJ. Adult survivors of childhood cancer and unemployment: a metaanalysis. Cancer 2006;107(1):1-11.
135. Di Castelnuovo A, Costanzo S, Bagnardi V, Donati MB, Iacoviello L, de Gaetano G. Alcohol dosing and total mortality in men and women: an updated meta-analysis of 34 prospective studies. Arch Intern Med 2006;166(22):2437-45.
136. Flores-Mateo G, Navas-Acien A, Pastor-Barriuso R, Guallar E. Selenium and coronary heart disease: a meta-analysis. Am J Clin Nutr 2006;84(4):762-73.
137. Galassi A, Reynolds K, He J. Metabolic syndrome and risk of cardiovascular disease: a meta-analysis. Am J Med 2006;119(10):812-9.
138. Huxley R, Barzi F, Woodward M. Excess risk of fatal coronary heart disease associated with diabetes in men and women: meta-analysis of 37 prospective cohort studies. BMJ 2006;332(7533):73-8.
139. Kahlenborn C, Modugno F, Potter DM, Severs WB. Oral contraceptive use as a risk factor for premenopausal breast cancer: a meta-analysis. Mayo Clin Proc 2006;81(10):1290-302.
140. Larsson SC, Giovannucci E, Wolk A. Folate intake, MTHFR polymorphisms, and risk of esophageal, gastric, and pancreatic cancer: a meta-analysis. Gastroenterology 2006;131(4):1271-83.
141. Mahid SS, Minor KS, Soto RE, Hornung CA, Galandiuk S. Smoking and inflammatory bowel disease: a meta-analysis. Mayo Clin Proc 2006;81(11):1462-71.
142. Owen CG, Martin RM, Whincup PH, Smith GD, Cook DG. Does breastfeeding influence risk of type 2 diabetes in later life? A quantitative analysis of published evidence. Am J Clin Nutr 2006;84(5):1043-54.
143. Ownby RL, Crocco E, Acevedo A, John V, Loewenstein D. Depression and risk for Alzheimer disease: systematic review, meta-analysis, and metaregression analysis. Arch Gen Psychiatry 2006;63(5):530-8.
144. Pavia M, Pileggi C, Nobile CG, Angelillo IF. Association between fruit and vegetable consumption and oral cancer: a meta-analysis of observational studies. Am J Clin Nutr 2006;83(5):1126-34.
145. Riddle MS, Sanders JW, Putnam SD, Tribble DR. Incidence, etiology, and impact of diarrhea among long-term travelers (US military and similar populations): a systematic review. Am J Trop Med Hyg 2006;74(5):891-900.
146. Rutledge T, Reis VA, Linke SE, Greenberg BH, Mills PJ. Depression in heart failure: a meta-analytic review of prevalence, intervention effects, and associations with clinical outcomes. J Am Coll Cardiol 2006;48(8):1527-37.
147. Smith GL, Lichtman JH, Bracken MB, Shlipak MG, Phillips CO, DiCapua P, et al. Renal impairment and outcomes in heart failure: systematic review and meta-analysis. J Am Coll Cardiol 2006;47(10):1987-96.
148. Weis E, Shah CP, Lajous M, Shields JA, Shields CL. The association between host susceptibility factors and uveal melanoma: a meta-analysis. Arch Ophthalmol 2006;124(1):54-60.
149. Williams JG, Higgins JP, Brayne CE. Systematic review of prevalence studies of autism spectrum disorders. Arch Dis Child 2006;91(1):8-15.
150. Bahekar AA, Singh S, Saha S, Molnar J, Arora R. The prevalence and incidence of coronary heart disease is significantly increased in periodontitis: a meta-analysis. Am Heart J 2007;154(5):830-7.
151. Baurecht H, Irvine AD, Novak N, Illig T, Bühler B, Ring J, et al. Toward a major risk factor for atopic eczema: meta-analysis of filaggrin polymorphism data. J Allergy Clin Immunol 2007;120(6):1406-12.
152. Bellamy L, Casas JP, Hingorani AD, Williams DJ. Pre-eclampsia and risk of cardiovascular disease and cancer in later life: systematic review and meta-analysis. BMJ 2007;335(7627):974.
153. Conde-Agudelo A, Rosas-Bermudez A, Kafury-Goeta AC. Effects of birth spacing on maternal health: a systematic review. Am J Obstet Gynecol 2007;196(4):297-308.
154. Dehghan A, Kardys I, de Maat MP, Uitterlinden AG, Sijbrands EJ, Bootsma AH, et al. Genetic variation, C-reactive protein levels, and incidence of diabetes. Diabetes 2007;56(3):872-8.
155. Eichler K, Puhan MA, Steurer J, Bachmann LM. Prediction of first coronary events with the Framingham score: a systematic review. Am Heart J 2007;153(5):722-31, 731.e1-8.
156. Gami AS, Witt BJ, Howard DE, Erwin PJ, Gami LA, Somers VK, et al. Metabolic syndrome and risk of incident cardiovascular events and death: a systematic review and meta-analysis of longitudinal studies. J Am Coll Cardiol 2007;49(4):403-14.
157. Grulich AE, van Leeuwen MT, Falster MO, Vajdic CM. Incidence of cancers in people with HIV/AIDS compared with immunosuppressed transplant recipients: a meta-analysis. Lancet 2007;370(9581):59-67.
158. Havemann BD, Henderson CA, El-Serag HB. The association between gastro-oesophageal reflux disease and asthma: a systematic review. Gut 2007;56(12):1654-64.
159. Hirtz D, Thurman DJ, Gwinn-Hardy K, Mohamed M, Chaudhuri AR, Zalutsky R. How common are the “common” neurologic disorders? Neurology 2007;68(5):326-37.
160. Huxley R, Owen CG, Whincup PH, Cook DG, Rich-Edwards J, Smith GD, et al. Is birth weight a risk factor for ischemic heart disease in later life? Am J Clin Nutr 2007;85(5):1244-50.
161. Krishna V, Kim DH. Ethnic differences in risk factors for subarachnoid hemorrhage. J Neurosurg 2007;107(3):522-9.
162. Langan SM, Flohr C, Williams HC. The role of furry pets in eczema: a systematic review. Arch Dermatol 2007;143(12):1570-7.
163. Larsson SC, Wolk A. Obesity and colon and rectal cancer risk: a meta-analysis of prospective studies. Am J Clin Nutr 2007;86(3):556-65.
164. Larsson SC, Wolk A. Coffee consumption and risk of liver cancer: a meta-analysis. Gastroenterology 2007;132(5):1740-5.
165. Liu T, Li G, Li L, Korantzopoulos P. Association between C-reactive protein and recurrence of atrial fibrillation after successful electrical cardioversion: a meta-analysis. J Am Coll Cardiol 2007;49(15):1642-8.
166. Loza MJ, Chang BL. Association between Q551R IL4R genetic variants and atopic asthma risk demonstrated by meta-analysis. J Allergy Clin Immunol 2007;120(3):578-85.
167. Pittas AG, Lau J, Hu FB, Dawson-Hughes B. The role of vitamin D and calcium in type 2 diabetes. A systematic review and meta-analysis. J Clin Endocrinol Metab 2007;92(6):2017-29.
168. Polanczyk G, de Lima MS, Horta BL, Biederman J, Rohde LA. The worldwide prevalence of ADHD: a systematic review and metaregression analysis. Am J Psychiatry 2007;164(6):942-8.
169. Rona RJ, Keil T, Summers C, Gislason D, Zuidmeer L, Sodergren E, et al. The prevalence of food allergy: a meta-analysis. J Allergy Clin Immunol 2007;120(3):638-46.
170. Sarwar N, Danesh J, Eiriksdottir G, Sigurdsson G, Wareham N, Bingham S, et al. Triglycerides and the risk of coronary heart disease: 10,158 incident cases among 262,525 participants in 29 Western prospective studies. Circulation 2007;115(4):450-8.
171. Snoep JD, Hovens MM, Eikenboom JC, van der Bom JG, Jukema JW, Huisman MV. Clopidogrel nonresponsiveness in patients undergoing percutaneous coronary intervention with stenting: a systematic review and meta-analysis. Am Heart J 2007;154(2):221-31.
172. Zintzaras E, Kaditis AG. Sleep-disordered breathing and blood pressure in children: a meta-analysis. Arch Pediatr Adolesc Med 2007;161(2):172-8.
173. Ageno W, Becattini C, Brighton T, Selby R, Kamphuisen PW. Cardiovascular risk factors and venous thromboembolism: a meta-analysis. Circulation 2008;117(1):93-102.
174. Barclay AW, Petocz P, McMillan-Price J, Flood VM, Prvan T, Mitchell P, et al. Glycemic index, glycemic load, and chronic disease risk — a meta-analysis of observational studies. Am J Clin Nutr 2008;87(3):627-37.
175. Conde-Agudelo A, Villar J, Lindheimer M. Maternal infection and risk of preeclampsia: systematic review and metaanalysis. Am J Obstet Gynecol 2008;198(1):7-22.
176. Schunkert H, Gotz A, Braund P, McGinnis R, Tregouet DA, Mangino M, et al. Repeated replication and a prospective meta-analysis of the association between chromosome 9p21.3 and coronary artery disease. Circulation 2008;117(13):1675-84.
177. Mrkobrada M, Thiessen-Philbrook H, Haynes RB, Iansavichus AV, Rehman F, Garg AX. Need for quality improvement in renal systematic reviews. Clin J Am Soc Nephrol 2008;3(4):1102-14.
178. Mallett S, Deeks JJ, Halligan S, Hopewell S, Cornelius V, Altman DG. Systematic reviews of diagnostic tests in cancer: review of methods and reporting. BMJ 2006;333(7565):413.
179. Needleman I, Worthington H, Moher D, Schulz K, Altman DG. Improving the completeness and transparency of reports of randomized trials in oral health: the CONSORT statement. Am J Dent 2008;21(1):7-12.
180. Plint AC, Moher D, Morrison A, Schulz K, Altman DG, Hill C, et al. Does the CONSORT checklist improve the quality of reports of randomised controlled trials? A systematic review. Med J Aust 2006;185(5):263-7.

Back to top