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Which study type is that? A guide to study types

Study and experiment types for Health Sciences and Medicine

Cohort study


A cohort study is a type of observational research where a group of people (the cohort) is followed over time to observe outcomes such as the development of diseases or the effect of certain exposures. Typically the cohort is divided into groups based on certain characteristics or exposures (such as behaviors, environmental factors, or medical treatments) and researchers track these groups to compare how different exposures might affect health outcomes (such as diseases, injuries, or other health-related events) over time.

cohort study

Useful for addressing:

Etiology questions,  Prognosis questions, Therapy questions

Types of Cohort Studies

Different types of cohort studies are available to study the associations between exposure of a group of participants and outcomes as a result of exposure. Understanding the types of cohort studies is helpful in determining which study is appropriate to answer research questions..

There are two more main types of cohort study:

  • Prospective Cohort Study
    • Observations of the participant group is measured and recorded from the beignning of the study and followed through forward in time through to the point of time of the outcome  This is ideal for studying rare exposures or diseases and can provide strong evidence of associations.
  • Retrospective Cohort Study
    • Researchers use existing data to identify the group of people exposed to past exposures and tracks their outcomes. Data is collected after the outcome being studies has already occurred. Groups are then followed to examine the development of the disease or outcome.

Further reading and resources

  • Critical Appraisal Skills Programme (CASP). What is a Cohort Study? casp-uk.net/what-is-a-cohort-study/  Link
     
  • Barría, R. M. (Ed.). (2018). Cohort studies in health sciences. IntechOpen. Catalogue Link
     
  • Wang, X., & Kattan, M. W. (2020). Cohort Studies: Design, Analysis, and Reporting. CHEST, 158(1), S72-S78 Link

Examples

  • Gerritsen, H., Samim, M., Peters, H., Schers, H., & van de Laar, F. (2018). Incidence, course and risk factors of head injury: a retrospective cohort study. BMJ open, 8(5), e020364. Full Text
     
  • Makizako, H., Shimada, H., Doi, T., Tsutsumimoto, K., & Suzuki, T. (2015). Impact of physical frailty on disability in community-dwelling older adults: a prospective cohort study. BMJ open, 5(9), e008462. Full Text
     
  • Rowlands, I. J., Abbott, J. A., Montgomery, G. W., Hockey, R., Rogers, P., & Mishra, G. D. (2021). Prevalence and incidence of endometriosis in Australian women: a data linkage cohort study. BJOG: An International Journal of Obstetrics & Gynaecology, 128(4), 657-665. Full Text

 

 


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