Epidemiology: Key concepts

Question 1

Meaningful mortality rate statistics need what?

Answer 1

A denominator population (how many people) and a time frame

Question 2

What is a denominator and name some examples?

Answer 2

• It is where the deaths have happened. Examples include:
• Health board,
• City,
• Hospital,
• Disease register,
• Recruited to a study

Question 3

Name some examples of observational studys

Answer 3

Case series, cross sectional study, cohort study and case controlled study.

Question 4

What is a case series?

Answer 4

A series pf cases with the same disease

Question 5

What is a population case-series (ecological studies)

Answer 5

Unit of study is a whole population, and these are useful to study signs and symptoms and look for causal hypotheses.

Question 6

What is standardisation?

Answer 6

A set of techniques based on weighted averaging used to remove the effects of differences in age or other confounding variables when comparing two populations.

Question 7

What are some of the limitations of ‘crude’ rates?

Answer 7

They are of limited value when comparing two populations with different structures because of confounding variables.

Question 8

What are the methods of direct and indirect standardisation?

Answer 8

Direct - Using known age-specific mortality rates to standardise.
Indirect - Using a reference population when the age-specific mortality rates are unknown to standardise

Question 9

What is the SMR?

Answer 9

The standard mortality rate. Compares the number of deaths to the number of expected deaths.

Question 10

What is a confounding variable?

Answer 10

A third variable that also has an effect on your dependent variable.

Question 11

What are two methods of dealing with a confounding?

Answer 11

Study design and data analysis (standardisation)

Question 12

What is mean’t by confounding?

Answer 12

Confounding is the distortion of the association between an exposure and health outcome by an extraneous, third variable called a confounder.

Question 13

What is bias?

Answer 13

An error in the conception and design of a study leading to results or conclusions that are systematically different from the truth.

Question 14

Describe how systematic errors can occur

Answer 14

In what data is collected, how the data is collected, analysed, interpreted or reported.

Question 15

Bias can lead to wrong conclusions about?

Answer 15

Disease causation and treatment effectiveness

Question 16

What is at the bottom and the top of the evidence hierarchy?

Answer 16

Bottoms - editorials and expert opinions.

Top - Systematic review.

Question 17

What is Bradford Hill criteria for Causality?

Answer 17

Strength of association, consistency, specificity, temporality, biological gradient, plausibility, coherence, experiment and anaolgy.

Question 18

Why is consistancy a criteria?

Answer 18

A causal link is more likely if the association is observed in different studies and different sub-groups (reporducibility)

Question 19

Why is specificity a criteria?

Answer 19

Causal link is more likely when a disease is associated with ONE specific factor

Question 20

Why is biological gradient a criteria?

Answer 20

A causal link is more likely if different levels of exposure to the factor leads to different risks of acquiring the outcome.

Question 21

Why is plausibility a criteria?

Answer 21

A causal ink is more likely if a biologically plausible mechanism is likely or demonstrated

Question 22

Why is coherance a criteria?

Answer 22

A causal link is more likely if the observed association conforms with current knowledge.

Question 23

Why is experiment a criteria?

Answer 23

A causal link is very likely if removal or prevention of factor leads to reduced or non-existent risk of outcome.

Question 24

Why is analogy a criteria?

Answer 24

A causal link is more likely is analogy exits with other diseases, species or settings.

Question 25

Why is temporality a criteria?

Answer 25

Causal link is more likely if exposure to assumed causes has been shown to come before the outcome