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1

what is association?

association is a link relationship or correlation

it is the statistical dependence between two variables
to the degree to which the rate of disease in persons with a specific exposure is either higher or lower than the rate of disease without exposure

2

what is the odds ratio

odds of exposure in cases / odds of exposure in controls

3

what things cause association?

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chance
bias
confounding
causation

4

what is chance?
how to check if it is chance?

coincidence
calculate confidence intervals
increase the sample size

5

what is bias?

systematic error leading to an incorrect estimate of the effect of an exposure on the development of a disease or outcome.

Defects in design cannot be overcome by increasing the sample size

6

what are the two types of bias?

measurement bias
systematic error with the measurement technique
increasing sample size makes no difference
selection bias
this is when the people chosen for the study are characteristically biased

7

what is confounding?

this is any factor which is believed to have a real effect on the risk of a disease
can include causal factors
or more direct unknown factors

8

what are the stages at which the control might be founded?

- design
restriction
randomisation
- analysis
stratification
standardisation
regression analysis

9

list the hierarchy of evidence in study design:

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systematic review
RCT
cohort studies
case control studies
ecological studies
descriptive studies
case reports

10

what is the bradford hill criteria?

a group of minimal conditions needed to provide adequate evidence of a causal relationship between incidence and possible consequences

11

what is the bradford hill criteria?

– a group of minimal conditions needed to provide adequate evidence of a causal relationship between incidence and possible consequence

12

what must the relationship be if it agrees with bradford hill criteria?

- must be temporal

13

what might the relationship be if it agrees with the bradford hill criteria?

- strength of effect
- consistent with other investigations
- specificity (one risk one disease)
- a biological gradient
- plausibility (means it is consistent with other knowledge)
- coherence with current thinking and previous experiments
- experimental evidence
- an analogy
- reversibility

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14

what is epidemiology?

the study of the distribution of health related states or events and the determinants of health relates states or events in specified populations

also the application of this study to control health problems

15

what is homeopathy?

- based on principle of like cures like
- uses toxin that causes similar symptoms to the disease
- only 50% of cures effective

16

what is a confidence interval?

- this is the range within which the value is expected to lie within given a degree of certainty - 95%

17

what is a P value?

- the probability that results are simply due to chance
. p < 0.05 = 95% certain results not due to chance

18

what is bias?

cannot be controlled by analysis/ sample size
- measurement bias
- selection bias

19

what is the MMR vaccine?

this combines measles mumps and rubella
- 2 stages
prevents deaths from mumps which causes meningitis
the rubella vaccine stops kids catching rubella from their mothers

20

why was the MMR vaccine taken away?

- studies based on the MMR vaccine made people believe that side effects like autism were caused by the vaccine
- there was no causal link
- the MMR vaccine was taken away
- deaths went up
- returned due to recognition of the flawed causality

21

what is human generation time?

- this is the time taken from our birth to a female producing a child
around 25+ years for humans

- much lower for viruses and bacteria

22

what are the origins of human infection?

- ancestors
- wildlife
- livestock

23

what are changes in the world leading to spread of infectious disease?

- increasing population
more dense faster transmission of disease
increase in rate of evolution

- movement of people by planes
influenza H1N1 spread like this
due to migration of people

24

what is epidemiology?

- based on ability to quantify the occurrence of disease in populations
- needs definition of word case:
- case = person with disease, heath disorder, or suffering from event of interest

25

what is prevalence

frequency of disease in a population at a point in time

number of cases / number of people in the population

measures the burden of a disease

26

what is incidence?

the number of new cases of a disease within a specified time interval

Incidence measures NEW CASES while prevalence measures ALL CASES

prevalence is dependent upon incidence

27

how to estimate incidence ?

- define the time period
- define the denominator (how many people are at risk)
- come up with a good test to define a true case
(eg. blood test for ebola)

28

how does incidence influence policy makers

- it affects if the country says there is an outbreak or not

29

what is mortality?

mortality is the number of deaths from a specify disease or condition

if mortality = incidence
then the epidemic is stable

30

what is the mortality equation

deaths from disease in time period / population at beginning of start of time period