Epidemiology

Question 1

What are two models for the determinants of health?

Answer 1

Dahlgren and Whitehead

Evans and Stoddard

Question 2

What is the definition of epidemiology?

Answer 2

the study of the distribution and determinants of health related states or events in specified populations, and the application of this study to control of health problems
Last 2001
The science and practise which describes and explains disease patterns in populations
Bhopal

Question 3

What is meant by an exposure?

Answer 3

supposed cause of disease / health state of interest or possession of a characteristic that is a determinant of a health outcome

Question 4

What is meant by outcome?

Answer 4

all the possible results that may stem from an exposure to a causal factor, or from preventative or therapeutic interventions

Question 5

Describe cross-sectional studies

Answer 5

observational and descriptive / analytical
sample of a population
gather data once, simultaneously collecting information on exposure and outcome

Question 6

What are the uses of cross-sectional studies?

Answer 6

health service planning and resource allocation
generate and test hypotheses
using repeated studies to measure change over time
evaluate interventions

Question 7

What are the strengths of cross-sectional studies?

Answer 7

quick and easy
relatively cheap
multiple exposures / outcomes 
no loss to follow up
health service planning

Question 8

What are the weaknesses of cross-sectional studies?

Answer 8

need to standardise measurements of exposure and outcome
susceptible to bias - responder recall
associations can be difficult to interpret
prevalent cases = survival effect
not suitable for rare diseases, diseases with a short duration or emergent events
generalisability will depend on sampling population

Question 9

What is prevalence?

Answer 9

number of existing cases/ total population at risk (at a given time point)

Question 10

Describe a cohort study

Answer 10

enrol a group of people who are at risk of developing an outcome, measure their exposure status and then follow them up over time to observe whether they develop the outcome of interest

Question 11

What are the strengths of cohort studies?

Answer 11

useful for rare exposures
useful for more than one outcome
incidence of the outcome
temporal relationship between exposure and outcome is clear
if prospective, minimises bias in measurement of the exposure
sometimes the only ethical way to do a study
stratifications, nested case-controls and multivariate analyses can be applied

Question 12

What are the disadvantages of cohort studies?

Answer 12

not good for rare outcomes
if retrospective they rely on adequacy of records
exposed may be followed more closely than the unexposed
if prospective can be expensive
validity of results highly sensitive to loss to follow up

Question 13

Describe the incidence rate

Answer 13

useful in common / recurrent diseases
competing causes exist
high migration
complete follow up is available

Question 14

How is incidence calculated?

Answer 14

number of new cases/ population at risk over a certain time period

Question 15

Describe case-control studies

Answer 15

the exposure history of a group of individuals who have a disease or outcome is compared to a group who do not
starting point is the outcome, look back on exposures

Question 16

What are the advantages of case control studies?

Answer 16

cheap and quick
useful for rare diseases and outcomes
multiple exposures for a single outcome
study disease with long latent periods

Question 17

What are the disadvantages of case control studies?

Answer 17

selection of controls - similar population, over-matching 
information bias - recall of exposure 
cannot determine temporal relationship
Not good for rare exposures 
cannot usually estimate incidence rates

Question 18

What is bias?

Answer 18

a systematic error in collecting or interpreting data

Question 19

What is confounding?

Answer 19

additional factor responsible for association

Question 20

What are the Bradford Hill Criteria?

Answer 20

strength of association
biological plausibility 
consistency
coherence 
specificity 
temporality 
dose-response relationship 
analogy 
experimental evidence