Lecture 51/52 - Epidemiology 3 & 4 (studies)

Question 1

what are the basics for case control studies

Answer 1

1. use source population as starting point
2. identify the group of cases with disease
3. identify the controls
4. compare proportion of exposed among cases and controls
5. no measures of disease frequency

Question 2

why is incidence not measured with case-control design

Answer 2

1. proportion of cases in entire population is unknown
   2 controls are representative of population at risk
2. # of cases and controls are chosen by investigator

Question 3

how are case-control studies structured

Answer 3

1. health outcome of cases
2. how controls are sampled

Question 4

advantages for case control designs

Answer 4

1. more efficient w// fewer participants
2. rapid results
3. optimal for rare disease
4. cost effective

Question 5

disadvantages for case control designs

Answer 5

1. temporality issues
2. information not collected for study purposes
3. susceptible to bias
4. cannot be used to estimate true risk

Question 6

cross-sectional study

Answer 6

measurement occurs on a single occasion or within short period of time

Question 7

what are the bascis of cross-sectional studies

Answer 7

1. exposure and outcome status ascerned at same point
2. individual-level data
3. exposure and outcome for same unit
4. first step in assessing clinical problem
5. used to estimate population parameters

Question 8

Descriptive cross-sectional study

Answer 8

characterize the prevalence of a disease in a specific population

Question 9

analytical cross-sectional study

Answer 9

compare disease differences between exposed and unexposed groups

Question 10

cross-sectional study advantages

Answer 10

1. faster and lower cost
2. easily leverage existing data
3. reasonably generalize broader population
4. can do repeatedly for estimation of time trends

Question 11

what are the potentials for bias in cross-sectional studies

Answer 11

1. over-representation of cases with long duration of illness
2. under-representation of cases with short duration of illness

Question 12

why might you use a cross-sectional design?

Answer 12

1. first step in assessing a clinical problem
2. to estimate population parameters

Question 13

ecologic studies

Answer 13

comparison of population-level estimates of exposure and outcomes

Question 14

ecologic fallacy

Answer 14

1. relationships or processes observed at group level are also present at individual level
2. attribution of effect to the population when a specific subgroup has the outcome

Question 15

ecologic study strengths

Answer 15

1. faster and lower cost
2. usually leverages existing data
3. can provide insight into ecological effects or population-level differences
4. hypothesis-generating

Question 16

ecologic study limitations

Answer 16

1. confounding factors difficult to control
2. cannot infer exposure-outcome association at individual level
3. cannot determine temporality of association

Question 17

association

Answer 17

statistical relationship between two or more events, characteristics, etc.

Question 18

causation

Answer 18

change in one variable is responsible, directly or indirectly, for an observed change in another

Question 19

“risk factor”

Answer 19

a factor that changes the risk of developing the disease

Question 20

what could association between exposure and outcome be due to

Answer 20

1. chance
2. bias
3. confounding
4. invetigator error
5. true

Question 21

Rothman’s Causal Pie

Answer 21

each pie is a theorhetical causal mechanism for a given disease

Question 22

sufficient cause

Answer 22

one or more factors that inevitably produce disease with a set of minimal conditions

Question 23

component cause

Answer 23

factor which contributes to disease

Question 24

necessary cause

Answer 24

factor that must be present for disease to occur

Question 25

Bradford Hill's Criteria for Causal Inference

Answer 25

1. temporality 2. strength of association 3 consistency 4. biological gradient 5. specificity 6. plausibility 7. coherence 8. experimental evidence 9. analogy 1-4 = strong 5-9 = weak

Question 26

temporality

Answer 26

- cause must precede an effect in time - criterion is inarguable - based on temporal sequence

Question 27

strength of association

Answer 27

stronger the relationship between the independent variable and the dependent variable, the less likely that the relationship is due to something else or by chance

Question 28

what are the two types of errors in epidemiologic studies

Answer 28

1. systematic error (validity) 2. random error (precision)

Question 29

what is internal validity

Answer 29

validity of the interferences drawn as they pertain to the members of the source population

Question 30

what is external validity

Answer 30

validity of the inferences as they pertain to individuals outside the source population

Question 31

what are the 3 general types of bias

Answer 31

1. selection 2. information 3. confounding

Question 32

selection bias

Answer 32

- stems from procedures used to select participants and factors that influence participation - occurs when the association between exposure and disease is different for participants compared to non

Question 33

what are common sources of selection bias

Answer 33

1. volunteers 2. healthy-worker effect 3. disproportionate loss to follow-up in cohort stuies

Question 34

information bias

Answer 34

occurs when information that an investigator collects about or from study participants is erroneous "misclassified"

Question 35

differential misclassification

Answer 35

misclassification of exposure related to disease status or vice versa

Question 36

nondifferential misclassification

Answer 36

misclassification of exposure is NOT related to disease staus or vice versa

Question 37

a cofounder must be

Answer 37

1. associated with disease as a cause of disease or proxy for a cause 2. associated with exposure but not an effect

Question 38

define cofounder

Answer 38

extraneous factors responsible for differences in the disease frequency between exposed and unexposed