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Letters to the Editor / Journal of Clinical Epidemiology 67 (2014) 830e842
Department of Community Medicine The Artic University of Norway Tromsø, Norway
Ilja C.W. Arts Department of Epidemiology CAPHRI School for Public Health and Primary Care Maastricht University PO Box 616, 6200 MD Maastricht, The Netherlands Department of Epidemiology CARIM School for Cardiovascular Diseases Maastricht University PO Box 616, 6200 MD Maastricht, The Netherlands
Rik Crutzen Department of Health Promotion CAPHRI School for Public Health and Primary Care Maastricht University PO Box 616, 6200 MD Maastricht, The Netherlands *Corresponding author. Tel.: þ31-43-38-84170; fax: þ31-43-38-84122. E-mail address:
[email protected]
References [1] Keriel-Gascou M, Buchet-Poyau K, Rabilloud M, Duclos A, Colin C. A stepped wedge cluster randomised trial is preferable for assessing complex health interventions. J Clin Epidemiol 2014;67:831e3 [In this issue]. [2] Kotz D, Spigt M, Arts IC, Crutzen R, Viechtbauer W. Use of the stepped wedge design cannot be recommended: a critical appraisal and comparison with the classic cluster randomized controlled trial design. J Clin Epidemiol 2012;65:1249e52. [3] Kotz D, Spigt M, Arts IC, Crutzen R, Viechtbauer W. Researchers should convince policy makers to perform a classic cluster randomized controlled trial instead of a stepped wedge design when an intervention is rolled out. J Clin Epidemiol 2012;65:1255e6. [4] Mdege ND, Man M, Taylor CA, Torgerson DJ. Systematic review of stepped wedge cluster randomized trials shows that design is particularly used to evaluate interventions during routine implementation. J Clin Epidemiol 2011;64:936e48. [5] Pearson D, Torgerson D, McDougall C, Bowles R. Parable of two agencies, one of which randomizes. Ann Am Acad Pol Soc Sci 2010;628:11e29. [6] Woertman W, de Hoop E, Moerbeek M, Zuidema SU, Gerritsen DL, Teerenstra S. Stepped wedge designs could reduce the required sample size in cluster randomized trials. J Clin Epidemiol 2013;66: 752e8. [7] Hemming K, Girling A, Martin J, Bond SJ. Stepped wedge cluster randomized trials are efficient and provide a method of evaluation without which some interventions would not be evaluated. J Clin Epidemiol 2013;66:1058e9. [8] Kotz D, Spigt M, Arts IC, Crutzen R, Viechtbauer W. The stepped wedge design does not inherently have more power than a cluster randomized controlled trial. J Clin Epidemiol 2013;66:1059e60. [9] Hemming K, Girling A. The efficiency of stepped wedge vs. cluster randomized trials: stepped wedge studies do not always require a smaller sample size. J Clin Epidemiol 2013;66:1427e8.
[10] de Hoop E, Woertman W, Teerenstra S. The stepped wedge cluster randomized trial always requires fewer clusters but not always fewer measurements, that is, participants than a parallel cluster randomized trial in a cross-sectional design. J Clin Epidemiol 2013;66:1428. [11] Brown CA, Lilford RJ. The stepped wedge trial design: a systematic review. BMC Med Res Methodol 2006;6:54. http://dx.doi.org/10.1016/j.jclinepi.2014.02.015
A call for revising the strengthening the reporting of observational studies in epidemiology statement to include ecologic studies The strengthening the reporting of observational studies in epidemiology (STROBE) statement that contains recommendations for accurate and complete reporting of 3 main observational study designs that is cohort, caseecontrol, and cross-sectional designs published in 2008 [1]. Two extensions of the STROBE statement soon after released to cover genetic association studies [2] and molecular epidemiology studies [3]. However, one important type of observational studies that is ecologic studies is overlooked in this statement and its extensions. Ecologic study is one of the oldest study designs that looks for the associations between disease incidence and variables of interest at aggregate, global, or environmental level. Missing individual data on the joint distribution of two or more variables within each group is the motive for focusing on the comparison on aggregate level rather than individual level [4]. Regardless of its numerous applications and advantages, ecologic design inherits a number of severe limitations, which may consist of ‘‘ecologic fallacy’’, ‘‘within-group misclassification’’, ‘‘insufficient data’’, ‘‘troubles in controlling the confounders’’, ‘‘collinearity’’, ‘‘migration across groups’’, and ‘‘temporal uncertainty’’ [5]. Therefore, it needs a robust design and a vigorous reporting. Unfortunately, the results of a rather new bibliometric review study revealed that substantial number of crosssectional ecologic studies apply untrustworthy methods or embrace statistical mistakes. For instance, 64% of studies under investigation improperly adjusted their outcomes for age or sex. Furthermore, 31% of studies failed to present important information when arguing the ecologic character of their design and so forth [6]. As a result, it is highly suggested that the STROBE statement should be revised or have another extension to provide an up-to-date set of guidelines that standardize reporting on ecologic studies. Mohsen Rezaeian Social Medicine Department Occupational Environmental Research Center Rafsanjan Medical School
Source of funding: NA.
Letters to the Editor / Journal of Clinical Epidemiology 67 (2014) 830e842
Rafsanjan University of Medical Sciences Rafsanjan, Iran Tel.: þ98-3915234003; fax: þ98-3915225209. E-mail address:
[email protected]
References [1] von Elm E, Altman DG, Egger M, Pocock SJ, Gøtzsche PC, Vandenbroucke JP, STROBE Initiative. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. J Clin Epidemiol 2008;61:344e9. [2] Little J, Higgins JP, Ioannidis JP, Moher D, Gagnon F, von Elm E, et al. STrengthening the REporting of Genetic Association Studies (STREGA)ean extension of the STROBE statement. J Clin Epidemiol 2009;62:597e608.e4. [3] Gallo V, Egger M, McCormack V, Farmer PB, Ioannidis JP, Kirsch-Volders M, et al. STrengthening the Reporting of OBservational studies in EpidemiologyeMolecular Epidemiology (STROBE-ME): an extension of the STROBE statement. J Clin Epidemiol 2011;64:1350e63. [4] Rezaeian M, Dunn G, St Leger S, Appleby L. Geographical epidemiology, spatial analysis and geographical information systems: a multidisciplinary glossary. J Epidemiol Community Health 2007;61:98e102. [5] Morgenstern H. Ecologic studies in epidemiology: concepts, principles, and methods. Annu Rev Public Health 1995;16:61e81. [6] Dufault B, Klar N. The quality of modern cross-sectional ecologic studies: a bibliometric review. Am J Epidemiol 2011;174:1101e7. http://dx.doi.org/10.1016/j.jclinepi.2014.02.010
Response to Rezaeian: Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) extension for ecological studies In reply: We thank Mohsen for his comments on the Strengthening the Reporting of Observational Studies in Epidemiology strengthening the reporting of observational studies in epidemiology (STROBE) Statement [1,2]. The decision to focus on the three main epidemiological study designs, cross-sectional studies, cohort studies, and caseecontrol studies was deliberately taken by the group when defining the scope of STROBE. As Rezaeian points out, several extensions to address the reporting issues that arise in specific studies and contexts have since been published [3,4] and other extensions are in preparation. We agree with Mohsen Rezaeian that an extension of STROBE to ecologic studies might be worth considering. In fact, the recent review of cross-sectional ecologic studies [5] mentioned by Rezaeian not only highlighted the methodological shortcomings of ecologic studies published in major
Conflict of interest: M.E., D.A., C.P., and E.v.E. are co-authors of the STROBE Statement and members of the STROBE group. M.C. coordinates the activities of the STROBE Initiative.
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epidemiology journals, but also proposed a draft extension to STROBE to improve the reporting of these studies. Dufault and Klar [5] suggested several items that should be reported in ecologic studies, including, for example, the intended level of inference or possible cross-level bias. Their list of items could serve as a useful point of departure for an extension of the STROBE statement to cross-sectional ecologic studies. Other types of ecologic studies exist, for example, studies based on longitudinal data; additional reporting issues might arise in these situations. We encourage Mohsen Rezaeian to assemble a working group of interested epidemiologists and editors who will build on the evidence on the reporting of ecologic studies and proposals to improve their reporting [5] to develop an extension of STROBE for ecologic studies. Detailed explanations on the rationale for the different recommendations, similar to the explanation and elaboration article written for STROBE [2], would strengthen such recommendations and provide a welcome service to the field. We are pleased to report that several members of the STROBE group have expressed an interest in contributing to this effort.
Myriam Cevallos* CTU Bern University of Bern Finkenhubelweg 11 3012 Bern, Switzerland
Charles Poole Department of Epidemiology UNC Gillings School of Global Public Health University of North Carolina 170 Rosenau Hall, CB #7400, 135 Dauer Drive Chapel Hill, NC 27599-7400, USA
Erik von Elm Centre d’epidemiologie clinique Codirector Cochrane, Switzerland Centre Hospitalier Universitaire Vaudois (CHUV) and University of Lausanne IUMSP - Institut universitaire de medecine sociale et preventive Biop^ ole 2, Route de la Corniche 10 CH-1010 Lausanne, Switzerland
Doug Altman Centre for Statistics in Medicine University of Oxford Botnar Research Centre Windmill Road OX3 7LD Oxford, UK
Matthias Egger for STROBE Institute of Social and Preventive Medicine University of Bern Finkenhubelweg 11 3012 Bern, Switzerland *Corresponding author. Tel.: þ41-31-631-35-28. E-mail address:
[email protected]
