Study Designs - Lecture Twenty

Question 1

Cohort studies VS Case-control studies

Answer 1

Cohort - ascertain exposure status then find outcome(s)

Case-control - ascertain outcome status, then find out exposure(s)

Question 2

Case-control Studies Step One

Answer 2

Identify source population

Question 3

Case-control Studies Step Two

Answer 3

Identify people with outcome (cases)

Question 4

Case-control Studies Step Three

Answer 4

Sample people without outcome from same population (controls)

Question 5

Case-control Studies Step Four

Answer 5

Measure exposure prior to the outcome in cases and controls

Question 6

Case-control Studies Step Five

Answer 6

Compare odds of exposure to calculate measure of association (odds ratio)

Question 7

Transient exposures

Answer 7

Exposures that come and go

Question 8

Why use odds?

Answer 8

Cant calculate prevalence or incidence of outcome

Question 9

Measure of association for case-control studies

Answer 9

Ratio of odds instead of incidences

How many times as likely cases are to have the exposure compared to control

Question 10

What is the null value of the odds ratio?

Answer 10

1

Question 11

Relative risk

Answer 11

People with exposure are x times as likely to develop the outcome as people without the exposure

Question 12

Odds ratio

Answer 12

People with outcome are x times as likely to have the exposure than people without the outcome

Question 13

Index dates

Answer 13

The date that the case that the control is being recruited for had the event or developed the outcome

Question 14

Case-Selection: important points

Answer 14

Defined by outcome, so only one
Clear outcome definition and identification
Comprehensive case finding

Question 15

Exposure measurement: important points

Answer 15

Need to measure exposure period before outcome
Differential recall
Exposure measurement must be comparable

Question 16

Differential recall

Answer 16

Cases trying to work out what made them stick

Outcome may affect recall ability

Question 17

Exposure measurement must be comparable

Answer 17

Dead cases VS alive controls

Interviewers may act differently for cases and controls

Question 18

Case-Control strengths

Answer 18

Rare outcome, transient exposures
Multiple exposures
Temporal sequencing
Often comparatively quick and inexpensive

Question 19

Case-Control limitations

Answer 19

Usually can only study one outcome
Difficult to select appropriate control group
Can be susceptible to selection and recall bias