Term
| confounding (definition and impact) |
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Definition
- mixing of effects; association between exposure and disease is distorted because it is mixed with the effect of another factor that is associated with the diseases
- impact- results of confounding is to distort the true association toward the null (negative confounding)or away from the null (positive confounding)
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Term
| criteria for confounding variables |
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Definition
- must be more or less common in the exposed than unexposed group
- must be an independent cause or predictor of the disease
- must not be an intermediate step in the causal pathway between disease and exposure
- can be risk factor, preventative, or correlate for a cause of disease
- must be associated with disease independently of exposure
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Term
| assessing for presence of confounding |
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Definition
- is variable related to both exposure and outcome
- does the association seen in the crude analysis have the same direction and similar magnitude to associations seen within strata of confounding variable
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Term
| how to control for confounding in general |
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Definition
- design and analysis phase
- control for confounding, you must have info on variables that are potential confounders
- this is true for all methods controlling confounding except randomization
Usually, confounders are risk factors for disease
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Term
| Name ways to control for confounding in design phase |
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Definition
- randomization
- with large enough sample size, likely to control for known and unknown sample size
- restriction
- restrict admissibility criteria for study subjects and limit entrance to individuals who fall within a specified category of the confounder
- advantage- straightforward, convenient, inexpensive
- disadvantage- limit generalizability
- matching
- select study subjects so that potential for confounding is distributed in an identical manner among exposed and unexposed groups (cohort) or among cases and controls (case control study)
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Term
| goals of controlling for confounding in design phase |
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Definition
- goal- eliminate or reduce variation in the level of confounding factor between compared group
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Term
| methods for controlling for confounding in analysis |
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Definition
- multivariate analysis
- simultaneously adjusts for several variables
- involves construction of math model that describes association between exposure, disease, and confounders
- stratification
- evaluate the association within homogeneous categories of the confounding variable
- if stratum specific estimates differ appreciably from each other = presence of effect modification
- purpose- control for confounding and to assess effect modification
- limits- difficult to multiple variables simultaneously due to large number of strata that will be generated relative to number of study subjects
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