30. Epidemiology

Question 1

Define ‘epidemiology’

Answer 1

• scientific method of studying disease in populations
• study of distribution and determinants of disease frequency in human populations
• in dentistry, includes measurement of dental disease in populations, evaluates effectiveness of treatment and assess needs/demands

Question 2

3 components of epidemiology

Answer 2

• distribution
• frequency
• determinants

Question 3

What is distribution in epidemiology?

Answer 3

• who is getting a disease?
• where/when is it occurring?
• are there patterns of disease?

Question 4

What is frequency in epidemiology?

Answer 4

• quantification of existence and occurance of disease

Question 5

What is determinants in in epidemiology?

Answer 5

• derived from data obtained from distribution and frequency
• necessary to test an epidemiologic hypothesis

Question 6

Process of epidemiology

Answer 6

• a suspicion exists that a particular factor may be influencing occurrence of a disease (your suspicion may arise from clinical practice, observation, research)
• formulation of a specific hypothesis
• hypothesis is tested in epidemiological studies with comparison group
• collect and analyse data to determine whether a statistical association exists
• assess validity of any observed association by excluding alternative explanations like chance, bias, confounding etc
• does statistical association suggest a causal relationship?

Question 7

What is looked at to see if statistical association suggests a causal relationship?

Answer 7

• magnitude of association
• other studies
• consistency of findings against other studies
• biological credibility

Question 8

Ways to measure disease

Answer 8

• indices
• standardisation
• quantify it
• indirectly - evaluation of effectiveness

Question 9

A ‘gold standard’ measure of dental disease would be …

Answer 9

• valid
• reliable
• objective
• simple
• reproducible
• quantifiable
• sensitive
• accceptable

Question 10

List descriptive study designs

Answer 10

• observational
• case-reports
• case-series
• cross-sectional

Question 11

Give analytic study design

Answer 11

• observational - case-control, cross-sectional
• experimental - clinical trials

Question 12

Give study designs from bottom to strongest methodology

Answer 12

• animal and lab research
• case reports/case series
• case control studies
• cohort studies
• randomized controlled trials
• systematic reviews
• meta-analysis

Question 13

Case-studies/case-series are used for …

Answer 13

• highlighting interesting or novel cases/treatment
• recognition of new disease/outcome
• formulation of new hypotheses

Question 14

Disadvantages of case studies/case series

Answer 14

• cannot demonstrate valid statistical association
• lack of appropriate comparison group can obscure a relationship or suggest an association where none exists

Question 15

Define ‘case-report/case-series’

Answer 15

a report on a single patient or series of patients with an outcome of interest
- no control group required

Question 16

What is a cross sectional study?

Answer 16

• observation of a defined population at a single point in time (or time-interval)
• exposure and outcome are determined simultaneously

Question 17

Cross sectional surveys are used for …

Answer 17

• measuring prevalence of disease
• look at potential risk factors or cause

Question 18

Disadvantages of cross sectional surveys

Answer 18

• may establish association, NOT causality
• confounders may be unequally distributed
• group sizes may be unequal
• recall bias

Question 19

What’s a cohort studies?

Answer 19

• involves identification of two groups (cohorts) of patients
• one which received the exposure of interest
• one which did not
• and following these cohorts forward to assess the outcome of interest

Question 20

Cohort studies are used for …

Answer 20

• measures the incidence of disease
• looking at causes of disease
• determining prognosis
• establishing timing and directionality of events

Question 21

Disadvantages of cohort studies

Answer 21

• controls may be difficult to identify
• exposure may be linked to hidden confounder
• blinding is difficult
• for rare diseases, large sample size is often necessary or a long follow up

Question 22

What is a case-control study?

Answer 22

• a study which involves identifying patients who have the outcome of interest (case)
• and patients without same outcome (controls)
• looking back in time to see if they had the exposure of interest

Question 23

Case-control studies are used for …

Answer 23

• looking at potential causes of disease
• suitable for rare diseases

Question 24

Disadvantages of case-control studies

Answer 24

• confounders
• selection of controls may be difficult
• recall and selection bias
• difficult to establish time relationships between exposure to risk factor and development of disease

Question 25

Randomised Controlled Trials are used for ...

Answer 25

evaluating the effectiveness of an intervention

Question 26

Disadvantages of randomised controlled trials

Answer 26

- high costs - ethical issues - participant compliance

Question 27

How are randomised controlled trials random?

Answer 27

- exposure status assigned by researcher preferably by random allocation - best way to reduce selection bias between 2 groups of participants

Question 28

Define 'systematic reviews'

Answer 28

- the evidence from a number of studies can be gathered together in one report - which pools and analyses all available data to assess the strength of evidence

Question 29

Why do a systematic review?

Answer 29

- can end confusion - highlight where there isn't enough evidence - yield new insights by combining findings from different studies

Question 30

Key features of a systematic review

Answer 30

- needs to be an analysis of evidence not just a review - question needs to be defined precisely defining population and outcomes so studies included are appropriate and comparable - complete methods available detailing comprehensive searching for all evidence and author quality guidelines