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Advanced Epi > Cohort and Case Control Studies > Flashcards

Cohort and Case Control Studies Flashcards

1
Q

What are the steps in creating a retrospective cohort study?

A
  1. ID cohort (ex: CRC)
  2. Collect predictor (age, sex, BMI, etc.)
  3. Measure the outcome? (Diagnosis date, path exam)
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2
Q

Name one strength of a retrospective cohort study

A
  • Not expensive and/or time consuming

- Can study rare outcomes

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3
Q

Name one weakness of a retrospective cohort study

A
  • Can’t go back to investigate something interesting
  • Can’t ask for more information
  • High chance for confounders and bias
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4
Q

Name 3 strengths of a prospective cohort study

A
  • Risk and rate disease estimate over time
  • Rare exposures
  • Temporal relationship between exposure and outcome
  • Natural history of disease
  • Lower potential for bias vs case-control
  • Avoid recall and selection bias
  • Results more conclusive than case-control
  • Longer is stronger
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5
Q

What are the steps of creating a prospective cohort study?

A
  1. Assemble the cohort
  2. Measure predictor variables and potential confounders for all participants
  3. Follow-up the cohort and measure outcomes
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6
Q

Name 3 types of cohort studies.

A
  • Occupational
  • Convenience
  • Geographic
  • Disease/Procedure
  • Prepresentative (NHANES)
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7
Q

What are 3 challenges of large cohort studies?

A
  • Requirements of resources and manpower
  • Huge database mgmt
  • Followup op problems
  • Exposure information
  • Data quality?
  • Collection of biological samples?
  • Expensive and time-consuming, especially prospective
  • Cannot directly infer causal relation
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8
Q

What are the two types of descriptive observational studies?

A
  1. Case reports/Case series (Clinical)

2. Cross-sectional (Epi)

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9
Q

What are the 3 types of analytical observational studies?

A
  1. Cohort
  2. Case-control
  3. Ecological
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10
Q

What is information bias?

A

AKA observation or measurement bias, when key information/outcomes are measured, collected, or interpreted inaccurately.

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11
Q

For which type of study is incidence the best report of risk?

A

Cohort studies

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12
Q

What is the formula for incidence (risk)?

A 
# ppl get disease/
#ppl at riskxtime at risk
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13
Q

What are the outcome variable types of a cohort study?

A 
Cumulative incidence
Incidence rate (per person time)
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14
Q

What are the adjusted measures of association for cumulative incidence?

A 
Relative risk (direct), Standardized incidence ratio (indirect)
Hazard ratio (Cox model)
Rate ratio (Poisson regression)
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15
Q

How are participants selected in a retrospective case/control study?

A
  • Same underlying population
  • Represent people who would have had the same chance of being selected as cases if they had the outcome
  • Standard diagnostic criteria
  • Eligibility criteria
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16
Q

What are the 5 essential features of retrospective case-control study design?

A
  1. Directionality (outcome-exposure)
  2. Timing (case ascertainment can be retro or prospective)
  3. Rare or new disease
  4. Challenging
  5. Population- vs. hospital-based (more common)
17
Q

A nested case-control study is a _ study within a _ study.

A

A case-control study within a prospective cohort study.

18
Q

How can a nested case-control study be prospective?

A

Using incidence density sampling, within a prospective cohort, with specimens and exposures collected prospectively prior to disease (no recall bias). RR can be estimated without the need for rare disease assumption.

19
Q

How are case-cohort study cases and non-cases selected?

A

From within parent cohort, no matching, either at baseline or length of followup

20
Q

What statistics can be calculated in a case-cohort study?

A

odds ratio, risk ratio, logistic regression

must weight the probabilities when stratifying

21
Q

What are advantages of the case-cohort study?

A

efficient (only if more than one endpoint), relatively inexpensive, flexible, reduces selection bias (same population), multiple outcomes within the subcohort, can calculate person-time risk

22
Q

What are disadvantages of the case-cohort study?

A

Often complex analysis, increased info bias if subcohort established after baseline, may have too many censoring to be robust, not for longitudinal exposure changes

23
Q

When is a case-crossover study most appropriate (what exposure/outcome)?

A

When investigating an intermittent exposure with immediate and transient effect on risk related to an abrupt outcome.

24
Q

How are case-crossover study cases and non-cases selected?

A

Cases serve as their own controls at another time point

Advanced Epi (8 decks)

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