Case Control Studies

Question 1

How are case control studies carried out

Answer 1

Identify cases -> identify similar individuals without disease /controls -> determine previous exposure -> relate exposure and disease info

Question 2

Where can cases for case control studies be found

Answer 2

Disease registry
Hospital recruitment

Question 3

Is there usually more cases or more controls in a case control study

Answer 3

Controls

Question 4

Why are patients and controls matched

Answer 4

Decr impact of confounders

Question 5

Why can overmatching effect results negatively

Answer 5

Case and control may not differ in exposure of interest, eg siblings both effected by parental smoking

Question 6

Types of bias in case control studies

Answer 6

Recall bias
Reverse causality
Selection of cases
Selection of controls

Question 7

Recall bias

Answer 7

differences in the accuracy or completeness of the recollections retrieved by study participants regarding events or experiences from the past.

Question 8

Reverse causality

Answer 8

direction of cause-and-effect contrary to a common presumption or to a two-way causal relationship
Disease causes changes in recent exposures

Question 9

Cohort study case control study difference

Answer 9

cohort study is concerned with frequency of disease in exposed and non-exposed individuals, the case-control study is concerned with the frequency and amount of exposure in subjects with a specific disease (cases) and people without the disease (controls)

Question 10

Are cohort studies or case control studies better for rare diseases

Answer 10

Case control

Question 11

How does a Nested case control study differ from a regular case control study

Answer 11

Cohort defined before identifying is individuals have disease or not in nested case control
Nested case controls require samples to be stored

Question 12

Is a cohort study or case control study better for a rare exposure

Answer 12

Cohort

Question 13

Are case control studies or cohort studies quicker

Answer 13

Case control

Question 14

Is recall bias more of a problem in cohort or case control studies

Answer 14

Case control

Question 15

Why can relative risk not be calculated in a case control study

Answer 15

Number with and without disease selected

Question 16

What type of disease is relative risk approximately equal to odds ratio in

Answer 16

Rare disease

Question 17

How is odds ratio calculated

Answer 17

Odds exposure in cases / odds exposure in controls

Question 18

How can confounding variables be adjusted for in cohort studies

Answer 18

Logistic regression

Question 19

Can risk be calculated in a case control study

Answer 19

No

Question 20

How is absolute excess risk calculated

Answer 20

Risk in exposed - risk in unexposed

Question 21

What does incidence in population attributable to exposure/ incidence in population calculate

Answer 21

Attributable proportion

Question 22

How are incidence in population and incidence in population attributable to exposure calculated

Answer 22

Attributable to exposure - proportion exposed (relative risk-1)
Total incidence - 1+proportion exposed (relative risk - 1)

Question 23

Cross sectional study

Answer 23

Measure existing disease and current exposure and 1 point in time

Question 24

What are cross sectional studies used to assess

Answer 24

Exposure that won’t change - eg sex
Prevalence rate
Exposure rate

Question 25

Disadvantages of cross sectional studies

Answer 25

Not useful for rare diseases Not useful for diseases with short duration Bias if responders and non responders differ Can’t assess causality

Question 26

Why can causality not be assessed in a cross sectional study

Answer 26

No follow up

Question 27

What is usually used to collect data in a cross sectional study

Answer 27

Questionnaire

Question 28

Which studies have the highest risk of bias and confounding out of clinical trials, cohort studies, case control studies, and cross sectional studies

Answer 28

Cross sectional -> case control -> cohort -> clinical trial Most to least likely to have bias and confounding

Question 29

Which studies give the strongest proof of causality out of clinical trial, cohort studies, case control studies, and cross sectional studies

Answer 29

Cross sectional -> case control -> cohort -> clinical Increasing strength of proof of causality

Question 30

What can cause incorrect associations between an exposure and a disease

Answer 30

Bias Reverse causality Confounding Incorrect analysis Chance

Question 31

What is used to assess whether there is a causal relationship between an exposure and a disease

Answer 31

Bradford hill criteria

Question 32

Aspects of Bradford hill criteria

Answer 32

Association strength Dose response Time sequence - exposure precedes outcome Consistency of findings in other population Biological plausibility Coherence of evidence w other study types Reversibility