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Epidemiology > Lecture 5 - Observational Studies II > Flashcards

Lecture 5 - Observational Studies II Flashcards

1
Q

In cohort studies _________ is assessed at baseline

A

exposure

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2
Q

In cohort studies, participants are ______ at baseline

A

disease-free

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3
Q

What are two other terms for prospective

A

longitudinal, concurrent

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4
Q

What are two other terms for retrospective

A

historical, nonconcurrent

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5
Q

for cohort studies, _______ is measured before ____

A

exposure is measured before outcome

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6
Q

When are prospective studies used?

A

time btw exposure and disease is short, LTFU is low, adequate funding

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7
Q

When are retrospective studies used?

A

long follow up time required, temporality preserved

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8
Q

when are cohort studies used

A

for rare exposures, multiple exposures for same disease, long follow up time btw exposure and disease, RCT is unethical, medium-long term follow up of drug performance

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9
Q

What are the cons of cohort

A

high drop out rate, residual confounding, long wait for rare diseases, lil evidence to justify long study examining exposure-disease relationship, data quality might be poor, historical effect

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10
Q

Define historical effect

A

advance in medicine may render old data obsolete for answering today’s questions

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11
Q

Cohort participants are selected on

A

exposure

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12
Q

Case participants are selected on

A

outcome

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13
Q

Define selection bias

A

participants LTFU (drop out associated with outcome or unique exposure pattern)

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14
Q

what are three examples of information biase?

A

observational/misclassfication bias, ascertainment bias, analytic bias

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15
Q

define information bias

A

quality of info is diff btw groups

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16
Q

define observational bias

A

quality and extent of info is diff btw exposed and unexposed

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17
Q

define misclassification bias

A

quality and extent of info is diff btw exposed and unexposed

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18
Q

define ascertainment bias

A

disease assessor knows exposure status

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19
Q

define analytic bias

A

belief of investiggators influence data analysis and interpretation

20
Q

define relative risk

A

ratio of risk of disease in exposed to risk of disease in unexposed

21
Q

interpret relative risk

A

the risk of outcome in exposed is ___% higher/lower than risk of outcome in unexposed

22
Q

RR = 1

A

null value, risk in exposed = risk in unexposed

23
Q

RR>1

A

positive association

24
Q

RR<1

A

negative association

25
Q

When can OR approx RR?

A

when disease is rare

26
Q

When does ability of OR to estimate RR become worse

A

as disease prevalence increases

27
Q

Why cant we do RR for case control

A

bc we fix # of cases and controls

28
Q

What measure indicates the potential for prevention if exposure is eliminated?

A

attributable risk

29
Q

Equation for attributable risk?

A

incidence in exposed group - incidence in non-exposed group

30
Q

Attributable risk as proportion?

A

AR/ incidence in exposed group

31
Q

Incidence in total pop?

A

incidence in exposedproportion of popEXPOSED + incidence in unexposedproportion of popUNEXPOSED

32
Q

Population attributable risk?

A

incidence in total pop - incidence in unexposed group

33
Q

Population attributable risk %?

A

PAR/ incidence in total population

34
Q

Equation for incidence density?

A

of cases/# of PY

35
Q

Equation for incidence density ratio?

A

ID exposed/ ID unexposed

36
Q

Interpretation of ID ratio?

A

incidence of disease in exposed group is ___xx the incidence of disease in unexposed group

37
Q

What is a cross sectional study

A

identify exposure and disease status at same time and there is no follow up

38
Q

Cross sectional studies identify what

A

prevalent cases of disease in exposed and unexposed

39
Q

What are the pros of cross sectional studies

A

quick, cheap, useful for hypothesis generation, suggest need for CC or cohort

40
Q

What are the cons of cross sectional studies?

A

reverse causality bias, prevalent may not be representative of all cases

41
Q

Why doesnt RR apply to cross sectional studies?

A

bc subjects arent at risk or follows up

42
Q

What is causality bias

A

cant be sure exposure proceeded disease

43
Q

What is prevalence ratio

A

prevalence of disease in exposed/prevalence of disease in uexposed

44
Q

What is the interpretation of prevalence ratio

A

prevalence of disease in exposed is ____% higher/lower than prevalence of disease in unexposed

45
Q

What observational study does prevalence ratio apply to

A

cross sectional study

Epidemiology (8 decks)

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