RESEARCH SERIES

Observational research methods. Research design II: cohort, cross sectional, and case-control studies

C J Mann

Department of Accident and Emergency Medicine, Taunton and Somerset Hospital, Taunton, Somerset, UK

Correspondence to:
Correspondence to:
Dr C J Mann;
tonygood{at}doctors.org.uk

Cohort, cross sectional, and case-control studies are collectively referred to as observational studies. Often these studies are the only practicable method of studying various problems, for example, studies of aetiology, instances where a randomised controlled trial might be unethical, or if the condition to be studied is rare. Cohort studies are used to study incidence, causes, and prognosis. Because they measure events in chronological order they can be used to distinguish between cause and effect. Cross sectional studies are used to determine prevalence. They are relatively quick and easy but do not permit distinction between cause and effect. Case controlled studies compare groups retrospectively. They seek to identify possible predictors of outcome and are useful for studying rare diseases or outcomes. They are often used to generate hypotheses that can then be studied via prospective cohort or other studies.

Keywords: research methods; cohort study; case-control study; cross sectional study

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

• Jones, G, Asghar, A, Llewellyn, D J (2008). The epidemiology of rock-climbing injuries. Br. J. Sports. Med. 42: 773-778 [Abstract] [Full Text]  
• Garnacho-Montero, J., Ortiz-Leyba, C., Herrera-Melero, I., Aldabo-Pallas, T., Cayuela-Dominguez, A., Marquez-Vacaro, J. A., Carbajal-Guerrero, J., Garcia-Garmendia, J. L. (2008). Mortality and morbidity attributable to inadequate empirical antimicrobial therapy in patients admitted to the ICU with sepsis: a matched cohort study. J Antimicrob Chemother 61: 436-441 [Abstract] [Full Text]  
• Beattie, P. F, Nelson, R. M (2007). Evaluating Research Studies That Address Prognosis for Patients Receiving Physical Therapy Care: A Clinical Update. ptjournal 87: 1527-1535 [Abstract] [Full Text]