Cited by 948Statistical Methods in EpidemiologyAdvanced Causal Inference TechniquesMethodologies in Health Research and Practice

Observational studies: Cohort and case-control studies

Open access
Song, Jae W., Chung, Kevin C.·2010·Plastic and Reconstructive Surgery

Abstract

Observational studies constitute an important category of study designs. To address some investigative questions in plastic surgery, randomized controlled trials are not always indicated or ethical to conduct. Instead, observational studies may be the next best method of addressing these types of questions. Well-designed observational studies have been shown to provide results similar to those of randomized controlled trials, challenging the belief that observational studies are second rate. Cohort studies and case-control studies are two primary types of observational studies that aid in evaluating associations between diseases and exposures. In this review article, the authors describe these study designs and methodologic issues, and provide examples from the plastic surgery literature.

Integrity signals

Registry

Crossref · 10.1097/prs.0b013e3181f44abc

Cites

32 of 32 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 18 cited sources checked · 0 supported · 0 flagged

  • Premisecitation

    For some investigative questions in plastic surgery, randomized controlled trials are not always indicated or ethical to conduct.

    “To address some investigative questions in plastic surgery, randomized controlled trials are not always indicated or ethical to conduct.”
    • Also stated in: § Abstract · plain
      “However, RCT methodology, which was first developed for drug trials, can be difficult to conduct for surgical investigations.3”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [3] Chung KC Burns PB A guide to planning and executing a surgical randomized controlled trial J. Hand Surg. [Am] 2008 33 407 412 18343300 source

      Not checked in the free run.

  • Premisereasoning

    Cross-sectional studies cannot assess a cause-and-effect relationship because the temporal relationship between disease occurrence and exposure cannot be established.

    “Because the temporal relationship between disease occurrence and exposure cannot be established, cross-sectional studies cannot assess the cause and effect relationship.”
    Quote in the paperSubstantial claim
  • Premisecitation

    In a retrospective review of 224 pedicled TRAM flaps in 200 patients over 10 years, obese patients had a significantly higher incidence of donor site complications, multiple flap complications, and partial flap necrosis than normal or overweight patients.

    “The findings revealed that obese patients had a significantly higher incidence of donor site complications, multiple flap complications, and partial flap necrosis than normal or overweight patients.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [11] Spear SL Ducic I Cuoco F Effect of obesity on flap and donor-site complications in pedicled TRAM flap breast reconstruction Plast. Reconstr. Surg 2007 119 788 795 17312479

      Not checked in the free run.

  • Premisereasoning

    Case-control studies are well suited to investigate rare outcomes or outcomes with a long latency period because subjects are selected by their outcome status.

    “Case-control studies are well suited to investigate rare outcomes or outcomes with a long latency period because subjects are selected from the outset by their outcome status.”
    Quote in the paperSubstantial claim
  • Premisecitation

    Maternal cigarette smoking during pregnancy was significantly associated with cleft lip/palate in newborns (adjusted OR 1.34, 95% CI 1.36-1.76).

    “A significant relationship with maternal cigarette smoking and cleft lip/palate in the newborn was reported in this study (adjusted OR 1.34, 95% CI 1.36-1.76).18”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [18] Chung KC Kowalski CP Kim HM Maternal cigarette smoking during pregnancy and the risk of having a child with cleft lip/palate Plast. Reconstr. Surg 2000 105 485 491 10697150 source

      Not checked in the free run.

  • Classified as probably not a substantial claim. 5
  • May combine two claims. 10
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    A 22-item STROBE checklist was generated to enhance the reporting of observational studies across disciplines.

    “Thus a 22-item checklist was generated to enhance the reporting of observational studies across disciplines.25,26”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [25] von Elm E Altman DG Egger M The strengthening the reporting of observational studies in epidemiology (STROBE) statement: Guidelines for reporting observational studies J. Clin. Epidemiol 2008 61 344 349 18313558 source

      Not checked in the free run.

    • cites [26] von Elm E Altman DG Egger M The strengthening the reporting of observational studies in epidemiology (STROBE) statement: Guidelines for reporting observational studies Lancet 2007 370 1453 1457 18064739 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Case-series are descriptive studies following one small group of subjects and lack a control group.

    “Contrasting with epidemiological cohort studies, case-series are descriptive studies following one small group of subjects.”
    • Also stated in: § Study Design · plain
      “Usually the cases are obtained from the authors' experiences, generally involve a small number of patients, and more importantly, lack a control group.12”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [12] Jenicek M Foundations of Evidence-Based Medicine 2003 1 542 Parthenon Pub. Group Boca Raton

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Matching is used to ensure comparability between cases and controls and reduces variability and systematic differences due to background variables not of interest to the investigator.

    “Matching is a method used in an attempt to ensure comparability between cases and controls and reduces variability and systematic differences due to background variables that are not of interest to the investigator.8”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [8] Everitt BS Palmer CR Encyclopaedic Companion to Medical Statistics 2005 Hodder Arnold London

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Because exposure is identified before the outcome, cohort studies have a temporal framework that allows assessment of causality and gives them the potential to provide the strongest scientific evidence.

    “Because exposure is identified before the outcome, cohort studies have a temporal framework to assess causality and thus have the potential to provide the strongest scientific evidence.8”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [8] Everitt BS Palmer CR Encyclopaedic Companion to Medical Statistics 2005 Hodder Arnold London

      Not checked in the free run.

  • May combine two claims.

    Premisereasoning

    Recall bias, interviewer bias, or reliance on the completeness or accuracy of recorded information decrease the internal validity of a case-control investigation.

    “These biases decrease the internal validity of the investigation and should be carefully addressed and reduced in the study design.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Premisecitation

    In a case-control study of congenital microtia, adverse maternal health was among the main risk factors, specifically maternal disease during pregnancy (OR 5.89, 95% CI 2.36-14.72), maternal toxicity exposure during pregnancy (OR 4.76, 95% CI 1.66-13.68), and living near air-pollution industries (OR 7.00, 95% CI 2.09-23.47).

    “The authors concluded that adverse maternal health was among the main risk factors for congenital microtia, specifically maternal disease during pregnancy (OR 5.89, 95% CI 2.36-14.72), maternal toxicity exposure during pregnancy (OR 4.76, 95% CI 1.66-13.68), and resident area, such as living near industries associated with air pollution (OR 7.00, 95% CI 2.09-23.47).16”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [16] Zhang QG Zhang J Yu P Environmental and genetic factors associated with congenital microtia: A case-control study in Jiangsu, China, 2004 to 2007 Plast. Reconstr. Surg 2009 124 1157 1164 19935299 source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    In the plastic surgery literature, retrospective cohort studies are better indicated than prospective cohort studies because they are timelier and less expensive.

    “Instead, retrospective cohort studies are better indicated given the timeliness and inexpensive nature of the study design.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Premisereasoning

    In case-control studies, cases and controls should stem from the same source population, and the validity of the study depends on the comparability of the two groups.

    “An important principle is that the distribution of exposure should be the same among cases and controls; in other words, both cases and controls should stem from the same source population.”
    • Also stated in: § Methodological Issues · plain
      “Because the validity of the study depends upon the comparability of these two groups, cases and controls should otherwise meet the same inclusion criteria in the study.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Premisereasoning

    Disadvantages of cohort studies include the need for a large sample size and a potentially long follow-up duration, which make the design costly.

    “Disadvantages include the need for a large sample size and the potentially long follow-up duration of the study design resulting in a costly endeavor.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Premisecitation

    Compared with cohort studies, case-control studies are quick, relatively inexpensive, require fewer subjects, and allow multiple exposures or risk factors to be assessed for one outcome.

    “Thus in comparison to cohort studies, case-control studies are quick, relatively inexpensive to implement, require comparatively fewer subjects, and allow for multiple exposures or risk factors to be assessed for one outcome (Table 4).2,9”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [2] Hulley SB Cummings SR Browner WS Designing Clinical Research: An Epidemiologic Approach 2001 1 336 Lippincott Williams & Wilkins Philadelphia 2nd Ed

      Not checked in the free run.

    • cites [9] Elwood M Critical Appraisal of Epidemiological Studies and Clinical Trials 2007 1 570 Oxford University Press Oxford 3rd Ed

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Loss to follow-up should not exceed 20% of the sample.

    “A general rule of thumb requires that the loss to follow-up rate not exceed 20% of the sample.6”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [6] Merril RM Timmreck TC Introduction to Epidemiology 2006 1 342 Jones and Bartlett Publishers Mississauga, Ontario 4th Ed

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisereasoning

    Of the STROBE checklist items, 18 are common to all three types of observational studies and 4 are specific to each of the three study designs.

    “In fact, 18 of the checklist items are common to all three types of observational studies, and 4 items are specific to each of the 3 specific study designs.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Premisecitation

    Selecting multiple controls per case increases the statistical power of an investigation by increasing the sample size, and precision may improve with up to about three or four controls per case.

    “This method increases the “statistical power” of the investigation by increasing the sample size. The precision of the findings may improve by having up to about three or four controls per case.21-23”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [21] Ury HK Efficiency of case-control studies with multiple controls per case: Continuous or dichotomous data Biometrics 1975 31 643 649 1100136 source

      Not checked in the free run.

    • cites [22] Bruce N Pope D Stanistreet D Quantitative Methods for Health Research 2008 1 529 John Wiley & Sons, Ltd West Sussex, England

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [23] Woodward M Epidemiology: Study Design and Data Analysis 2005 1 849 Chapman & Hall/CRC London 2nd Ed

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

13 of 13

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • The influence of recall or information bias was thought to be minimal due to the prospective design.

    “The influence of recall or information bias was thought to be minimal due to the prospective design [49].”

    From The Modified A-DIVA Scale as a Predictive Tool for Prospective Identification of Adult Patients at Risk of a Difficult Intravenous Access: A Multicenter Validation Study (2019) · cites this paper as [49]

    The Cohort Study > Study Design section says prospective studies can use tailored data-collection methods and may collect more complete exposure data. The Case-Control Studies > Methodological Issues section describes recall and information-quality problems with retrospective exposure assessment. These passages support the rationale, but they do not establish that recall or information bias was minimal in the citing authors’ particular study. (LLM, conf=0.84)

    Experimental — accuracy not yet measured

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Adjusted odds ratio lies outside its reported confidence interval

    Minor

    The reported point estimate of 1.34 is below the lower bound of its reported 95% confidence interval, 1.36.

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Authors
Song, J. W., & Chung, K. C.
Affiliations
Michigan Medicine (US)
Venue
Plastic and Reconstructive Surgery
Published
2010-12
Volume
126
Issue
6
Pages
2234-2242
ISSN
0032-1052 (ISSN-L)
OpenAlex
W2033465810
Cited by
948
References
32
Citations by year
2026: 58 · 2025: 113 · 2024: 115 · 2023: 106 · 2022: 75 · 2021: 104 · 2020: 85 · 2019: 76 · 2018: 63 · 2017: 46 · 2016: 52 · 2015: 38 · 2014: 6 · 2013: 5 · 2012: 2
FWCI
2.18
Type
journal article
Language
en
Open access
Locations
  • Plastic & Reconstructive Surgery (publishedVersion)
  • PubMed (publishedVersion)
  • PubMed Central (acceptedVersion)
Funders
National Institute of Arthritis and Musculoskeletal and Skin Diseases (K24AR053120, F32AR058105)
Topics
  • Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Epidemiology
  • Physical Sciences › Mathematics › Statistics and Probability › Advanced Causal Inference Techniques
  • Health Sciences › Health Professions › Health Information Management › Methodologies in Health Research and Practice
Keywords
observational study design, cohort studies, case-control study, plastic surgery research, exposure-disease association
MeSH terms
Humans, Prospective Studies, Retrospective Studies, Cohort Studies, Bias, Case-Control Studies, Randomized Controlled Trials as Topic, Evidence-Based Medicine, Plastic Surgery Procedures

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