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14 Cards in this Set
- Front
- Back
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What does a Cohort study do?
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Enrolls participants AT RISK FOR DISEASE on the basis of ABSENCE OR PRESENCE OF AN EXPOSURE OF INTEREST and follows them over time to assess their clinical outcome
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What are 4 types of exposures?
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1. Biological or clinical attriubutes (BP, cholesterol)
2. Health Behaviors (smoking, sex) 3. Environmental Exposures (location, radiation) 4. Medication exposures |
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What are the 2 types of cohort studies?
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1. Prospective (concurrent) - going forward
2. Retrospective (nonconcurrent) - getting from past |
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What are 2 applications of cohort research?
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1. Studies of natural history of disease
2. Studies of disease etiology |
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What is a limit of cohort studies?
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Limited by bias and confounding compared to experimental studies
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What are 3 benefits of a cohort study?
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1. Study exposures not amenable to experimental allocation
2. Study "real world" conditions 3. Study representative population groups |
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What are 2 limitations of cohort studies?
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1. Potentially biased imbalance of exposure groups for prognostic factors
2. Dependent on statistical tools to achieve valid inference |
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What are benefits of cohort studies in terms of outcomes?
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Many outcomes can be studied
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What does relative risk equal?
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Incidence in Exposed
-------------------------------------- Incidence in Unexposed In chart: A / (A+B) ------------------- C / (C+D) |
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What are the possible mathematical values for the risk ratio?
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0 to infinity
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What are 2 types of information that can be gleaned from cohort?
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1. Risk of disease
2. Rate of disease |
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What must be considered when clinically interpreting relative risk?
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- Must consider the level of absolute risk in the comparison group
- Even large relative risks may not be clinically significant if "baseline" risk is low |
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What is attributable risk in words?
in formula? |
Measure of the absolute risk of the exposure
= Incidence in Exposed - Incidence in Unexposed Ex: .001287 over 6 years -Means 1287 excess cases among 1,000,000 who drank heavily over 6 years |
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What does the number needed to treat (or harm)?
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- Simple measure of the absolute benefit (or harm) resulting from a treatment (or exposure)
- Calculated as the reciprocal of the attributable risk Ex: 1/0.001287 = 770 For every 770 who drink a lot, there will be 1 additional case of breast cancer |
