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Epidemiology > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

What are the kinds of descriptive studies

A

Cross-sectional, single case report, case series, and some ecologic studies

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2
Q

What are the 2 types of analytic studies

A

Observational and experimental

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3
Q

What are the kinds of observational studies

A

Case-control, cohort, and some ecologic studies

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4
Q

What are the kinds of experimental studies

A

Clinical trial and community trial

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5
Q

What are the 3 purposes of descriptive epidemiology

A

Identify possible health problems, characterize the amount and distribution of health/disease within a population, and generate an etiologic hypothesis

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6
Q

What are the 2 purposes of analytic epidemiology

A

Identify causes or determinants of health problems and test the etiologic hypothesis

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7
Q

What are the characteristics of experimental design

A

Controls who is exposed to a factor of interest (Manipulation/M) and assigns subjects randomly to study groups (Randomization/R)

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8
Q

What are the 4 characteristics of clinical trials

A

Experimental (M and R), tests efficacy of preventative/therapeutic measures, focuses on the individual, and prospective

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9
Q

What are the 4 characteristics of community trials

A

Quasi-experimental (M only), designed to produce health/behavioral changes in a target population (usually tests health programs, etc.), focuses on community (compares one to another, hard to randomize), and prospective

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10
Q

What kind of calculation can be done for clinical trials

A

Incidence rates, relative risk, incidence rate ratios, and odds ratio

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11
Q

What is another term for clinical trial

A

Randomized control trial (RCT)

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12
Q

What are the two types of clinical trials

A

Prophylactic (prevent disease) and therapeutic (improve health)

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13
Q

What is the timeline of clinical trials

A

Start with subjects who lack positive history of outcome of interest but are at risk, then include at least 2 time points to determine eligibility/treatment allocation as well as the number of new cases

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14
Q

What is the clinical end point

A

The outcome of interest in both the intervention and control groups (e.g. rates of disease, death, or recovery)

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15
Q

What is blinding/masking

A

Single-blind = participants don’t know if they’re intervention or placebo
Double-blind = participants and researchers don’t know if subjects are intervention or control (involves 3rd party)

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16
Q

What are 2 reasons for having phases in clinical trials

A

To protect public from a potentially deleterious intervention and satisfy the urgent needs for new interventions

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17
Q

What happens in Phase I Clinical Trials

A

New intervention tested in adult volunteers (usually less < 100 people) –> Must show successful demonstration of response on a small-scale)

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18
Q

What happens in Phase II Clinical Trials

A

100-200 subjects are selected from the target population for the intervention –> Antibody responses and clinical reactions are examined

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19
Q

What happens in Phase III Clinical Trials

A

Assesses protective efficacy in target population (at least 1000 people) –> License to manufacture can be granted after this phase

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20
Q

What is efficacy

A

How does an intervention perform under tightly controlled, ideal situations (compares incident rate of disease in intervention population with control population)

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21
Q

What is effectiveness

A

How does an intervention perform in the real world

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22
Q

What happens in Phase IV Clinical Trials

A

Post-marketing research to gather more information about risks and benefits from a drug (effectiveness and safety)

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23
Q

What can community trials help determine

A

The potential benefit of new policies and programs

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24
Q

What is the timeline for community trials

A

Determine eligible communities willing to participate, collect baseline measures, use a variety of measures (e.g. disease rates, knowledge, attitudes, and practices), communities randomized and followed over time, and measure outcomes of interest

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25
Q

What is temporality

A

The timing of information about cause and effect (e.g. did we ask about exposure at the same time, before, or after disease)

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26
Q

What is a cohort

A

A population group or subset that is followed over a period of time

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27
Q

What are other terms for cohort studies

A

Prospective or longitudinal studies

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28
Q

What are the basic timelines for cohort studies

A

Start with patients not positive for outcome of interest but at risk, include at least 2 observation points to determine exposure status/eligibility and number of new cases

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29
Q

What kinds of calculations can be done with cohort studies

A

Incidence rates, relative risk, incidence rate ratios

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30
Q

What are outcome measures of cohort studies

A

Discrete events (single events with multiple occurrences), levels of disease markers, and changes in disease markers (rate of change, change in level within time)

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31
Q

What are the 2 kinds of cohort studies

A

Population-based (exposures unknown until first period of observation when info is collected) or exposure-based (look at exposure first, usually 1:1 ratio)

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32
Q

What is a limitation of population-based cohort vs. exposure-based cohort

A

They aren’t efficient for rare exposures

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33
Q

What are temporal differences in cohort designs

A

Prospective vs. retrospective

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34
Q

What are the 3 applications of cohort studies

A

Studies chronic disease etiology, risk estimation, and hypothesis testing

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35
Q

What is attrition

A

Subjects lost to follow-up

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36
Q

What are relative measures of effect

A

Divide disease frequencies from one another (e.g. relative risk, incidence rate ratio, and odds ratio)

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37
Q

What are absolute measures of effect

A

Subtract disease frequencies from one another (e.g risk difference)

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38
Q

What information is garnered from relative measures of effect

A

The strength of the relationship between exposure and disease

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39
Q

What information is garnered from absolute measures of effect

A

The public health impact of an exposure

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40
Q

What are effect measures

A

A quantity that measures the effect of a factor on the frequency or risk of a health outcome

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41
Q

What is relative risk (risk ratio) and when can it be used

A

Ratio of risk of disease or death among exposed to risk among the unexposed

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42
Q

What does relative risk tell you

A

If the risk of disease is different among the exposed as compared to the nonexposed

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43
Q

What is relative risk interpretation

A

Exposed have X times the risk of disease compared to non-exposed

The risk of disease is X% higher/lower among exposed compared to nonexposed

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44
Q

What is an Incidence Rate Ratio (IRR) and when can it be used

A

The ratio of incidence rate (uses person time) among the exposed to the incidence rate among the nonexposed

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45
Q

What does Incidence Rate Ratio tell you

A

If the rate of disease is different among exposed compared to nonexposed

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46
Q

What is interpretation for Incidence Rate Ratios

A

Exposed have X times rate of disease compared to nonexposed

The rate of disease is X% higher/lower among exposed compared to nonexposed

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47
Q

What is Risk Difference

A

Difference between incidence of disease in the exposed group and the incidence of disease in the nonexposed group

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48
Q

What is another term for Risk Difference

A

Attributable Risk

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49
Q

What does Risk Difference tell you

A

The number of cases of disease that would be eliminated in the exposed group if the exposure was eliminated

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50
Q

What are the 2 measures of potential impact

A

Etiologic Fraction (Impact of exposure removal on exposed) and Population Risk Difference (Impact of exposure removal on population)

51
Q

What is etiologic fraction

A

Proportion of the rate of disease in the exposed that is actually due to exposure

52
Q

What does etiologic fraction tell you

A

How much the particular exposure accounts for disease etiology in exposed group

53
Q

What is population risk difference

A

Difference between incidence rate of disease in nonexposed part of population and the overall incidence rate in the total population

54
Q

What does population risk difference tell you

A

Identifies number of cases of disease that would be eliminated in total pop. if exposure was eliminated (helps see which exposures are most impactful to certain populations to prioritize prevention)

55
Q

What is “cause”

A

An event, characteristic, or condition that the disease wouldn’t occur without

56
Q

What are the 2 types of causality

A

Deterministic and probabilistic

57
Q

What is deterministic causality

A

A cause is always followed by an effect (necessary and sufficient)

58
Q

What is probabilistic causality

A

An cause is associated with increased probability of an effect happening (stochastic process)

59
Q

What are the 4 types of associations

A

Noncausal, causal, direct, and indirect

60
Q

What is a noncausal association

A

A secondary association (B causes D and C causes D, so B and C are not causally associated)

61
Q

What are the types of causal associations

A

Direct and indirect

62
Q

What is an example of a direct association

A

B directly causes C

63
Q

What is an example of an indirect association

A

A causes B which causes C (causal pathway)

64
Q

What is a case control study

A

Compares people with disease to people who don’t have disease (cases vs. controls)

65
Q

What is the purpose of a case-control study design

A

Looks at whether differences between cases and controls result from exposures to risk factors

66
Q

What is the timeline of a case-control study

A

Exposure determined retrospectively, involves just one point of observation

67
Q

What are the 4 advantages of case-control studies

A

Smaller sample sizes than surveys or prospective studies, quick and easy to complete, cost effective, and good for rare disease studies

68
Q

What are the 4 limitations of case-control studies

A

Unclear the timeline of exposures and diseases (because exposure info was collected retrospectively), indirect estimate of risk, not useful for rare exposures, recall bias

69
Q

What is a nested case-control studies

A

Case-control study where both cases and controls are drawn from an existing cohort study

70
Q

What are the 2 advantages of nested case-control studies

A

Provide control over confounding factors and reduce cost (because we’re just looking at old data in a new way)

71
Q

What are odds

A

The ratio of the probability of an event occurring to that of it not occurring

72
Q

What is an Odds Ratio

A

Measure of association between an exposure and an outcome

73
Q

What does an odds ratio tell you

A

If the odds of disease are different among exposed as compared to nonexposed

74
Q

What types of studies can odds ratios be used for

A

Case-control and RCTs

75
Q

When are the 3 times when an OR provides a good approximation of risk

A

When controls are representative of target population, cases are representative of all cases, and frequency of disease in population is small

76
Q

What are cross-sectional studies

A

Estimate prevalence of disease within population

77
Q

What can cross-section studies be used for

A

To describe magnitude and distribution of a health problem and (with repetition) examine trends in disease or risk factors that vary over time

78
Q

What are 3 advantages of cross-sectional studies

A

Generalizability, conducted in relatively short period of time, and low cost

79
Q

What are 4 disadvantages of cross-sectional studies

A

Not that useful to infer disease etiology, don’t provide incidence data, can’t study diseases with low prevalence, and can’t determine temporality of exposure or disease (because disease and exposure info collected at same time)

80
Q

What are ecologic studies

A

Group analysis usually using secondary data (like census tract) where level of exposure for each individual is unknown

81
Q

What is the ecologic fallacy

A

Observations at group level don’t represent exposure-disease relationship at individual level because incorrect inferences are applied to individuals from group data

82
Q

What is Simpson’s Paradox

A

Associations observed in subgroups of a population may be reversed in entire population (illustrates confounding)

83
Q

What are the 4 applications of ecologic studies

A

Test specific etiologic hypotheses, develop new etiologic hypotheses, suggest mechanisms of causation, and identify new methods for disease prevention

84
Q

What are 4 advantages to ecologic studies

A

Quick, simple, inexpensive, and a good approach to generate hypothesis when the etiology of a disease is unknown

85
Q

What are 2 disadvantages to ecologic studies

A

Ecological fallacy and imprecise measurement of exposure and disease

86
Q

What are 4 advantages of cohort studies

A

Permit direct determination of risk, time sequencing of exposure and outcome, can study multiple outcomes, and can study rare exposures

87
Q

What are 5 disadvantages of cohort studies

A

Take a long time, costly, subjects lost to follow up (attrition), selection bias, and difficult to use with rare diseases

88
Q

What are 2 advantages of RCTs

A

Provide best control over amount of exposure, timing and frequency of exposure, period of observation, and the ability to randomize reduces the likelihood that groups will differ significantly

89
Q

What are 4 disadvantages of RCTs

A

Artificial setting, limited scope of potential impact, adherence to protocol is difficult to enforce, and ethical dilemmas

90
Q

What is the advantage of community trials

A

Only way to estimate directly the impact that change in behavior or modifiable exposure has on incidence of disease

91
Q

What are 3 disadvantages of community trials

A

Don’t control entrance to study, delivery of intervention, or monitoring of outcomes as well as RCTs, fewer study units can be randomized (not as comparable), and affected by population dynamics, secular trends, and nonintervention influences

92
Q

What is external validity

A

For small samples, it implies the ability to generalize beyond a set of observations (study) to some universal statement

93
Q

What is internal validity

A

Proper selection of study groups and lack of error in measurement of exposure, outcome, and association between exposure and disease

94
Q

What is random error

A

Fluctuations around a true value of a parameter

95
Q

What 3 factors contribute to random error

A

Poor precision, sampling error, and variability in measurement

96
Q

What is poor precision

A

When factor being measured isn’t measured sharply

97
Q

What is sampling error

A

When obtained sample values (statistics) differ from values (parameters) of parent population

98
Q

What is variability in measurement

A

Lack of agreement in results due to type of measurement procedure used

99
Q

How can random error be reduced

A

Increase sample size and/or number of measurements

100
Q

What is bias

A

A systematic error resulting in incorrect (invalid) estimate of measure of association due to error in design, data collection/analysis, interpretation, reporting, and publication

101
Q

What 4 factors contribute to bias

A

Observer bias, selection bias, information bias, and confounding

102
Q

What is Hawthorne (Observer) Effect

A

Subject’s behavior changes because they know they’re being observed

103
Q

What is selection/survival bias

A

When relationship between exposure and disease is different for those who participate and those who theoretically would be eligible but don’t participate

104
Q

What is an example of survival bias

A

Fighter pilot plane coming back doesn’t show where armor should be because it made it back

105
Q

What is the healthy worker effect

A

Type of selection bias where employed populations tend to have lower mortality than general population

106
Q

What are 4 techniques to reduce selection bias

A

Develop an explicit (objective) case definition, enroll all cases in a defined time and region, strive for high participation rates, and take precautions to ensure representativeness

107
Q

What is information bias

A

Result of measurement error in assessment of exposure and disease

108
Q

What are the 3 kinds of information bias

A

Recall bias, interviewer bias, and prevarication (lying) bias

109
Q

What is recall bias

A

Better recall among cases than controls (often people can’t remember the things they did that might have exposed them when they didn’t get sick)

110
Q

What is interviewer bias

A

When interviewers probe more thoroughly for an exposure in a case than a control

111
Q

What is prevarication bias

A

When subjects have ulterior motives for answering a question so they understate or exaggerate an exposure

112
Q

What are 6 ways to reduce information bias

A

Use memory aids to validate exposures, blind interviewers to subject’s status, standardize training sessions and protocols, use standardized data collection, blind participants to study goals, and ensure questions are clearly understood

113
Q

What is a confounder

A

An alternate explanation for observed association between an exposure and disease –> Can be controlled for in data analysis

114
Q

What are the 3 criteria for confounders

A

Be a risk factor for disease, be associated with exposure, and not be in causal pathway between exposure and disease

115
Q

What are 3 ways to control confounding

A

Randomization, restriction, and matching

116
Q

What are advantages and disadvantages to randomization

A

+: Convenient, inexpensive, and allows straightforward data analysis

-: Need control over exposure, ability to assign subjects to groups, and large sample sizes

117
Q

What is the purpose of restriction

A

To prohibit variation of the confounder within groups

118
Q

What are the advantages and disadvantages of restriction

A

+: Gives complete control of known confounders

-: Cannot control for unknown confounders

119
Q

What are the advantages and disadvantages of matching

A

+: Fewer subjects needed than in unmatched studies with same hypothesis

-: Costly because requires searching and record keeping to find matches

120
Q

How can you control confounding through analysis

A

Stratification and multivariate techniques

121
Q

What are 3 advantages of stratification

A

Direct and logical, minimum assumptions need to be satisfied for appropriate analysis, and computational procedure is straightforward

122
Q

What are 4 disadvantages of stratification

A

Small numbers of observations in some strata, many ways to form strata with continuous variables, hard to interpret when several confounders, and categorization can result in loss of information

123
Q

What are advantages and disadvantages of multivariate techniques

A

+: Allows for simultaneous adjustment of several confounding variables in a single analysis

-: Needs more advanced training in statistics

Epidemiology (2 decks)

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