Introduction to Epidemiology

Question 1

What is the definition of epidemiology?

Answer 1

Epi= about
Demos= people of districts
Logos= study of
A study of the distribution and determinants of disease in population

Question 2

40,000 BC population?

Answer 2

2 million

10 species of human

Question 3

Describe the epidemiological method

Answer 3

1. Defining the disease
2. Counting the frequency of disease in the population (e.g. incidence, prevalence)- can be sample
3. Describing the occurrence of disease in a population (e.g. in time, space, age, sex)
4. Comparing the disease occurrence between two different sub-populations

Question 4

What are the types of study designs?

Answer 4

• Cohort Study (Prospective, Longitudinal)
• Controlled Trial- sub type of cohort study (randomised, double blind)
• Case Control Study (Retrospective), explorative purpose initially as cheap and quick
• Cross-Sectional Study (Prevalence)- poorest design to see relationships, useful to measure burden

Question 5

Describe a cohort study

Answer 5

Prospective, longitudinal
Present to extend into future
Need to prove relative risk >1
Establish if risk factors have effect on disease
-Sample those with and without risk factor, follow for a long time
Calculate absolute risk (incidence) or relative risk (divide absolute in exposed by not exposed)

Question 6

Describe Randomised Controlled Trial

Answer 6

Better than cohort
Randomise sample e.g. in smokers group some quit smoking and some dont
-Same distribution of other risk factors
-Makes the only variable the risk factor of interest

Question 7

Describe case-control study

Answer 7

Retrospective
Start now, look back
Disease and people who do not have disease
Look at history of exposure
Hospital= biased, all have some disease
No period of time
Can only estimate absolute risk through odds ratio

Question 8

Describe cross-sectional study

Answer 8

Prevalence
Dangerous
-Death, reverse causality (changed behaviour)
No inferences
Present time

Question 9

What is statistics?

Answer 9

Plural= tabulated numerical information
Singular= a discipline- the art/ science of handling uncertainty

Question 10

How is hypothesis used in statistics?

Answer 10

Incorrect until proven correct beyond reasonable doubt

Proven by rejecting the null-hypothesis (rejected only when it becomes too implausible)

Question 11

Why are stringent P-values and large samples required?

Answer 11

It is more dangerous to take science down the incorrect
path and waste resources, than it is to reject the correct
path until there is more conclusive (and better quality)
evidence

Question 12

What is hypothesis-free science?

Answer 12

Measure so precisely so that it can be computed

• DNA Genome
• e.g. uric acid= which gene controls this? Screen, read

Question 13

What makes technology-driven, hypothesis-free research so appealing?

Answer 13

• Free of human bias/ opinion
• Human errors minimised
• Does not depend on previous human knowledge
• Results not false positive/ questionable
• Extremely accurate measurements