Epidemiology

Question 1

Define epidemiology

Answer 1

The study of the distribution and determinants of health related states or events in specified populations and the application of this study to control health problems

Question 2

What is a case series?

Answer 2

A series, often consecutive, of cases with the same disease

Question 3

Describe ecological studies (population case-series)

Answer 3

• The unit of study is a population (not and individual)
• Useful to study signs and symptoms, look at characteristics of cases for causal hypotheses
• Create disease definitions, foundation for other studies
• Descriptive, retrospective, observational

Question 4

What are the limitations of crude rates?

Answer 4

• Of limited value when comparing two populations with different structures
• Two populations with the same crude rates for a particular outcome will have different overall rates if the distribution of a confounder within the populations are different

Question 5

Define standardisation

Answer 5

A set of techniques, based on weighted averaging, used to remove, as much as possible, the effects of differences in age or other confounding variables in comparing two or more populations

Question 6

Describe confounding

Answer 6

• True relationship confused by a third factor

- Can deal with confounding by: study design, data analysis

Question 7

Define confounding

Answer 7

The distortion of a measure of the effect of an exposure on an outcome due to the association of the exposure with other factors that influence occurrence of the outcome

Question 8

Define bias

Answer 8

An error in the conception and design of a study - or in the collection, analysis, interpretation, reporting, publication or review of data - leading to results or conclusions that are systematically different from truth

Question 9

What is the bradford hill criteria for causality?

Answer 9

• Consistency (reproducibility) - a causal link is more likely if the association is observed in different studies and different sub-groups
• Specificity - a casual link is more likely when a disease is associated with one specific factor
• Temporality - a causal link is more likely if exposure to the putative cause has been shown to precede the outcome
• Biological gradient - a causal link is more likely if different levels of exposure to the putative factor lead to different risk of acquiring the outcome
• Plausibility - a causal link is more likely if a biologically plausible mechanism is likely or demonstrated
• Coherence - a causal link is more likely if the observed association conforms with current knowledge
• Experiment - a causal link is very likely if removal or prevention of the putative factor leads to a reduced or non-existent risk of acquiring the outcome
• Analogy - a causal link is more likely if an analogy exists with other diseases species or settings