Analytical epidemiology – Flashcards

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What is analytic epidemiology?
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- Testing the hypothesis - Addressing the question of "why" - Seeks to explain already observed patterns - Usually more rigorous study design, so more expensive "Why are certain groups at higher or lower risk of disease than others"
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What are some key concepts in analytic epidemiology?
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- Exposure and outcome - Exposure (E) independent variable (Risk factor, determinant, treatment, intervention) - Outcome (D) dependent variable (Health state, disease, death, survival, cure)
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Exposure leads to what?
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Outcome
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If exposure occurs & then we look for outcome it is a what?
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Prospective study
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What are some key features of study designs?
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- Artificial manipulation of exposure (E) (experimental/observational)? - Information on exposure (E) and outcome (D) collected concurrently or in separate time period? - Direction of study from E>>D (forward) or D>>E (backward)? - Timing between study and occurrence of E and D (retrospective/prospective)?
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What are different types of analytical studies?
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Experimental: Randomized control trials (RCT) Observational: Cross-sectional, longitudinal (case control, cohort)
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What are randomized control trials (AKA cohort) ?
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- Most rigorous of the studies - Random allocation of population into 2 groups (experimental or control) - Blinding (double blinded? Placebo?) - Results observed at some future time (ALWAYS prospective) - Ethical/logistical problems - Direction always E>D
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Describe cohort (prospective) studies
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- Tracks groups of individuals over time - Selection based on exposure (E) - Forward directionality E>D (PROSPECTIVE) - Study one exposure, many outcomes - Not suitable for studying rare disease - Prospective VS. retrospective - Measure: RELATIVE RISK(RR)
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Describe control studies
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- Selection based on outcome/disease - Backward directionality E<D (RETROSPECTIVE) - Study one disease many exposures - Persons with rare disease of interest (cases) are compared to another group without the disease (controls) - Purpose: Do 2 groups differ in proportion of exposure to specific risk factors? - Measure: ODDS RATIO (OR)
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What are advantages to case control studies?
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- Inexpensive - First step in hypothesis testing - Good for rare conditions/chronic diseases - Can look for multiple risk factors/exposures
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What are some disadvantages to case control studies?
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- Past information may not be available or recall bias - Selection of control subjects may be difficult - Temporal relationship may be unclear
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What is measures of association?
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- Relative risk (RR) or odds ratio (OR) - Depends on type of study - RR for cohort studies - OR for case-control studies - Either can be used for cross-sectional studies
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What does relative risk (cohort studies) look at?
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The ratio of the incidence of a health outcome (disease) among the exposed to that among the unexposed
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If result of Relative risk (RR) is 1 it means what?
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Risk is equal
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If result of Relative risk (RR) is > 1 it means what?
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Risk is greater in exposed group
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If result of Relative risk (RR) is < 1 it means what?
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Risk is less in exposed group
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What does odds ratio (case control studies, retrospective) look at?
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The ratio of the odds in favor of having a specific health condition when the suspected factor is present, (exposure among diseased) to the odd in favor of having the condition when the factor is absent (exposure among non-diseased)
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If the result of Odds ratio (OR) is 1 it means what?
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The odds are equal
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If the results of Odds ratio (OR) is > 1 it means what?
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The odds are greater in the exposed group
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If the results of Odds ratio (OR) is < 1 it means what?
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The odds are less in the exposed group
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