Interpreting Epidemiological Findings

Question 1

Bradford Hill Criteria

helps infer what?

Answer 1

STRENGTH
CONSISTENCY
SPECIFICITY
TEMPORALITY
BIOLOGICAL GRADIENT
PLAUSIBILITY
COHERENCE
EXPERIMENT
ANALOGY

causation

Question 2

strength?

Answer 2

strong association increases confidence that an exposure causes an outcome

but the 9 or 10-fold increase in risk was suggestive of causality

Question 3

CONSISTENCY

Answer 3

repeatable findings by time, person, place is suggestive

as rules out errors/fallacies that befall one/2 studies§

Question 4

most criticised criteria?

Answer 4

specificity as unusual for an effect to be related to only 1 cause

specificity can be informative but it’s absence doesn’t say much

Question 5

temporality

Answer 5

exposure must precede outcome

cross-sectional approach determines presence of exposure and outcome

Question 6

reverse causality?

Answer 6

He also asks whether in chronic diseases where diet X co-exists with disease Y, does diet precede disease, or do those with the disease begin to prefer a specific diet? This is reverse causality

Question 7

BIOLOGICAL GRADIENT

Answer 7

we talk about deterministic effects where there is a continuous outcome (such as cataract or infertility) and stochastic effects where the outcome is discrete (cancer).

Quantification is often difficult! Like specificity, when present the biological gradient is suggestive, but it’s absence may be of no value.

Question 8

coherance

Answer 8

does association keep up with existing science?

relationship may be deemed stronger where several elements of scientific understanding point in the same direction.
but if existing science is wrong?

however when most scientists are wrong, this criterion may support the status quo.

Question 9

analogous findings

Answer 9

rubella is a viral illness- what rubella does other viral illness contracted during pregnancy may also do; deafness, eye and heart problem

thalidomide caused fetal abnormalities ; rational to suspect other antenatal drugs of doing the same

but reliant on exisiting knowledge

Question 10

causation is not the same as association

T/F?

Answer 10

T

Correlation is a linear relationship between two variables

Question 11

internal validity

Answer 11

The extent to which findings accurately describe the relationship between exposure and outcome in the context of the study

Question 12

external validity is synonymous with?

Answer 12

generalisability

Question 13

types of selection bias?

Answer 13

Healthy worker effect

non-response bias: is the process through which people who do not respond are systematically different to the people who do respond. This is a type of selection bias.

Question 14

Lake Wobegon effect

Answer 14

illusory superiority

believe to be better than you are, when self reporting : information bias

Question 15

Hawthorne effects

Answer 15

The precise definition is controversial, but is usually described as the consequence of participants realising they are being observed and therefore acting differently. For example, if you knew you were being studied, you might behave in a slightly different way to normal!

Question 16

types of information bias

Answer 16

• recall bias
• response bias
• interviewer bias
• diagnostic bias

Question 17

non-differential misclassification

Answer 17

Where cases and controls equally mis-report their exposures, this would more likely be described as

Question 18

differential misclassification

Answer 18

if cases or controls were likely to report exposures differentially then it would be differential misclassification. But in this case, the statement says they are equally likely to mis-report their exposures

Question 19

Where cases and controls unequally mis-report their exposures AND in such a way that the overall consequence is an association that tends away from the null, this is best described as:

Answer 19

information bias

Question 20

differential diagnosis is always biased towards the null?

T/F?

Answer 20

false

can be biased towards/ away from null

Question 21

non-differential misclassification always results in bias __ null

Answer 21

non-differential misclassification always results in bias towards null

Question 22

selection bias

Answer 22

systematic difference in study
= systematic error in association / outcome

if participation in study sample is associated with both outcome and exposure then there is selection bias

Question 23

Berkson’s bias

Answer 23

type of selection bias

hospital-based case control study and controls are selected amongst the hospital’s patients

Question 24

healthy worker effect

Answer 24

Healthy worker effect: occupational studies where active workers are more likely to be healthy compared to those who have retired or stopped working

Question 25

how to minimise selection bias?

Answer 25

Controls representative of target population

Minimise non-response

Compare respondents with non respondents

Question 26

information bias

Answer 26

misclassification
y variables are not properly defined
Flaws in data collection