Abstract
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.
Full Text
The Full Text of this article is available as a PDF (149.1 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Alberman E. D., Butler N. R., Sheridan M. D. Visual acuity of a national sample (1958 Cohort) at 7 years. Dev Med Child Neurol. 1971 Feb;13(1):9–14. doi: 10.1111/j.1469-8749.1971.tb03026.x. [DOI] [PubMed] [Google Scholar]
- Fowkes F. G., Fulton P. M. Critical appraisal of published research: introductory guidelines. BMJ. 1991 May 11;302(6785):1136–1140. doi: 10.1136/bmj.302.6785.1136. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Goyder E. C., Goodacre S. W., Botha J. L., Bodiwala G. G. How do individuals with diabetes use the accident and emergency department? J Accid Emerg Med. 1997 Nov;14(6):371–374. doi: 10.1136/emj.14.6.371. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Jaffe H. W., Bregman D. J., Selik R. M. Acquired immune deficiency syndrome in the United States: the first 1,000 cases. J Infect Dis. 1983 Aug;148(2):339–345. doi: 10.1093/infdis/148.2.339. [DOI] [PubMed] [Google Scholar]
- Karjalainen J., Kujala U. M., Kaprio J., Sarna S., Viitasalo M. Lone atrial fibrillation in vigorously exercising middle aged men: case-control study. BMJ. 1998 Jun 13;316(7147):1784–1785. doi: 10.1136/bmj.316.7147.1784. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kunst A. E., Groenhof F., Mackenbach J. P., Health E. W. Occupational class and cause specific mortality in middle aged men in 11 European countries: comparison of population based studies. EU Working Group on Socioeconomic Inequalities in Health. BMJ. 1998 May 30;316(7145):1636–1642. doi: 10.1136/bmj.316.7145.1636. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lerner D. J., Kannel W. B. Patterns of coronary heart disease morbidity and mortality in the sexes: a 26-year follow-up of the Framingham population. Am Heart J. 1986 Feb;111(2):383–390. doi: 10.1016/0002-8703(86)90155-9. [DOI] [PubMed] [Google Scholar]
- Reidy A., Minassian D. C., Vafidis G., Joseph J., Farrow S., Wu J., Desai P., Connolly A. Prevalence of serious eye disease and visual impairment in a north London population: population based, cross sectional study. BMJ. 1998 May 30;316(7145):1643–1646. doi: 10.1136/bmj.316.7145.1643. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Smith G. D., Hart C., Blane D., Hole D. Adverse socioeconomic conditions in childhood and cause specific adult mortality: prospective observational study. BMJ. 1998 May 30;316(7145):1631–1635. doi: 10.1136/bmj.316.7145.1631. [DOI] [PMC free article] [PubMed] [Google Scholar]