Cohort, case-control, cross-sectional, and randomized controlled trial study designs with their key strengths and limitations.
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- What is the defining feature of a cohort study's direction of investigation?
- It follows exposed and unexposed groups forward in time to see who develops the outcome.
- In a cohort study, is exposure or outcome status known at the start?
- Exposure status is known at the start; outcome is observed over time.
- What is the key difference between a prospective and a retrospective cohort study?
- Prospective follows subjects forward from now; retrospective uses existing records to look back from a past exposure to an outcome that already occurred.
- What measure of disease frequency can cohort studies calculate directly?
- Incidence (the rate of new cases).
- What association measure is typically calculated from a cohort study?
- Relative risk (risk ratio).
- What is one strength of cohort studies regarding outcomes?
- They can examine multiple outcomes from a single exposure.
- Why are cohort studies well suited to studying rare exposures?
- Subjects are selected based on exposure status, ensuring enough exposed people are included.
- What is a major limitation of prospective cohort studies related to cost and time?
- They are often expensive and take a long time, especially for diseases with a long latency period.
- Why are cohort studies poorly suited to studying rare diseases?
- A very large sample size and long follow-up would be needed to observe enough cases.
- What bias can result when many cohort study participants drop out before the outcome is assessed?
- Loss to follow-up bias (attrition bias).
- What is the defining feature of a case-control study's direction of investigation?
- It starts with people who already have the outcome (cases) and those who do not (controls), then looks backward for exposure.
- What association measure is calculated from a case-control study?
- The odds ratio.
- Why are case-control studies well suited to studying rare diseases?
- Subjects are selected based on disease status, ensuring enough cases are included even if the disease is rare.
- What is one strength of case-control studies regarding exposures?
- They can examine multiple exposures for a single outcome.
- Why are case-control studies generally faster and cheaper than cohort studies?
- They do not require long-term follow-up since the outcome has already occurred.