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Epidemology > Risk, Causation, etc. > Flashcards

Risk, Causation, etc. Flashcards

1
Q

What is absoltue risk reduction? (ARR)

A

The DIFFERENCE in risk between patients who have undergone therapy and those who have not; is (a/a+b)-(c/c+d)

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2
Q

What is relative risk reduction? (RRR)

A

The estimate of % of baseline risk that is removed as a result of therapy. Is calculated ARR/R unexposed

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3
Q

What is the number needed to treat? (NNT)

A

Number needed to treat to prevent an event. It can be positive or negative. Is calculated as 1/ARR.

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4
Q

What is baseline risk?

A

The risk of an adverse effect among the placebo/control group.

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5
Q

What is the odds ratio? (OR)

A

Occurrence of event/event not occurring; it is the odds of exposure in cases/odds of exposure in control. (a/c / b/d)

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6
Q

What is a confound?

A

A third variable that distorts the observed RR/OR/HR between exposure and outcome. It over/underestimates the association and can change direction of effect. It must be related to both the exposure and the outcome.

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7
Q

What is effect modification?

A

A third variable that modifies the magnitude of an effect of association by varying it in different LEVELS of a third variable. It should be described and reported.

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8
Q

How is confounding assessed?

A

Calculate crude OR/RR, Recalculate adjusted OR/RR (this controls effects of a confounder), and compare the two to see if different by 20%.

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9
Q

When do researchers attempt to control confounding?

A

During a design study and during data analysis.

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10
Q

What does randomization do?

A

Randomizes data so that an equal number of subjects and confounders are in each group.

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11
Q

What does restriction do?

A

Only allows participation of particular subjects.

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12
Q

What does matching do?

A

Study subjects are selected in match-pairs related to the confounding variable in order to distribute confounds.

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13
Q

What is bias?

A

A systematic (non-random error) in study design leading to erroneous results. It distorts the relationship between exposure and outcome.

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14
Q

What are the two main types of bias?

A

information/observation/measurement and selection.

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15
Q

What are the types of selection bias?

A

healthy worker bias, self selection/participant bias, control selection bias.

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16
Q

Is bias more likely to account for weak or strong associations?

A

Weak

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17
Q

What are the measurement biases?

A

recall/reporting bias, hawthorne effect, contamination bias, compliance/adherence, lost to follow-up bias, interviewer (proficiency) bias, diagnosis/surveillance (expectations) bias

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18
Q

What is a measurement (information/observation) bias?

A

A bias related to any aspect of collecting/measuring information; creates a difference between the two groups.

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19
Q

What is recall/reporting bias?

A

Differential level of accuracy/detail in reports; e.g. those with symptoms may have a better memory of the event.

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20
Q

What is the Hawthorne effect?

A

individuals can report “effects” of exposure, disease and treatment differently because they are part of a study.

21
Q

What is contamination bias?

A

members of the control group accidently, outside of a study, receive treatment.

22
Q

What is compliance/adherence bias?

A

Bias in which groups interventionally studied have different compliances.

23
Q

What is lost to follow-up bias?

A

Groups studied have different withdrawal or lost to follow-up rates OR there are other differences of those that say in the study and are lost.

24
Q

What is interviewer (proficiency) bias?

A

Systematic difference in soliciting, recording or interpreting on part of the researcher (e.g. skills/training or how questions are worded).

25
Q

What is diagnosis surveillance (expecations) bias?

A

Systematic difference in soliciting, recording or interpeting on part of the researcher.

26
Q

What are the types of selection biases?

A

healthy worker bias, self-selection/participant bias, neyman bias, lead time bias, length-time bias

27
Q

What is self selection/participatn responders bias?

A

A bias in which those that participate are different from those who do not.

28
Q

What is neyman bias?

A

incidence/prevalence bias; arises when there is a gap between exposure and selection of participants (e.g. heart attack and snow shovelling - some may have died before study, but were not included; OR lowered).

29
Q

What is lead time bias?

A

An apparent benefit for an intervention due to early detection of disease despit unchanged clinical outcome; e.g. detection of early cancer, but it does not reduce age-specific mortality.

30
Q

Length-time bias?

A

Preferential detection of conditions with long, indolent causes that do not impact survival. e.g. prostate screening detects slow glowing tumors, but not fast ones.

31
Q

What are examples of how researchers control for misclassification?

A

selecting most appropriate methods, blinding/masking, using multiple sources to gather information, randomly allocate observers/interviewers for data collection

32
Q

What are the two types of misclassification?

A

non-differential (error in both groups), and differential (error in one group that is different than the other).

33
Q

What is differential misclassification?

A

Misclassification of disease/exposure related to the other disease/eposure, depending on the study. It can move (RR/OR) in either direction.

34
Q

What is non-differential misclassification?

A

Misclassification of exposure/disease that is unrelated to the other disease/exposure; moves measure of association to 1.0 (RR/OR)

35
Q

What are the 3 main types of associaton?

A

Artifactual (AKA false), non-causal and causal

36
Q

What is artifactual association?

A

Association that rises from significant bias or extensive confounding.

37
Q

What is non-causal association?

A

Association in which the disease may cause exposure rather than the exposure causing disease OR the disease and exposure are both associated with a third factor (confounding).

38
Q

What is sufficient cause?

A

Minimum conditions needed to produce a disease; it is a cause that precedes a disease (can have multiple components)

39
Q

What is a necessary cause?

A

Necessary Cause which pecedes a disease and cause must be present for disease to occur, yet the cause may be present without the disease occuring (e.g. mononucleosis).

40
Q

What is a component cause?

A

A characteristic that, if present and active, increases the probability of a particular disease.

41
Q

What is a proximate cause?

A

A short term event; it is an event sufficiently related to legally recognizable injuries to be held to be the cause of injury.

42
Q

What is a distant cause?

A

higher level, ultimate cause (e.g. real reason of occurrance); long term induction or latent.

43
Q

What are Hill’s criteria?

A

the 5 primary criteria for establishing causation; they include strength, consistency, temporality, biologic gradient and plausibility.

44
Q

What does strength refer to (Hill’s Criteria)?

A

the size of an association (RR/OR/HR)

45
Q

What does consistency refer to?

A

Repeated observation of association in different populations under different studies.

46
Q

What does temporarilty refer to?

A

The necessity that the cause preceds the outcome.

47
Q

What does biologic gradient refer to (Hill’s criteria)?

A

Observation of a griadient of risk (dose-response) associated with degree of exposure.

48
Q

What does plausibility (Hill’s criteria) refer to?

A

biological feasibility that the asssociated can be understood and explained.

49
Q

What is relative risk? (RR)

A

The risk of an event after treatment; it is the ratio of the exposed group to the unexposed group (a/a+b)/(c/c+d)

Epidemology (5 decks)

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