Lecture 1 Flashcards
Module 1
What is a population?
A group of people who share one or more common features
What is the narrow definition of health?
The absence of death, disease or disability
What is the broad definition of health?
The capacity to do what matters most to you
What are the 5 parts of the Gate frame?
P-opulation E-xposure C-omparison O-utcomes T-ime
What are the formulae for occurence?
O/EG & O/CG
EGO & CGO
What is a Cohort study?
A cohort of people who are allocated into groups by measuring exposures and followed over time.
What is ‘incidence measuring’?
When disease events are counted as they occur over a period of time.
What is ‘prevalence measuring’?
When people with a disease are counted at one point in time.
What are the strengths and weaknesses of incidence?
+ Determined only by the disease risk in a population (clean)
+ Measures include event, population and time
- Can be difficult to measure
What are the strengths and weaknesses of prevalence?
+ Relatively easy to count
- Do not include time as a measure
- Determined by incidence AND cure/death rate
What is an epidemic?
When an occurrence of disease is clearly in excess of normal and spreading quickly.
When is it better to measure period prevalence rather than point prevalence?
When the disease events occur regularly but not continuously. e.g. asthma attacks
Why can period prevalence be better than incidence measurement?
Because it can take account of things that are hard to measure over time due to practicality, cost and interpretation of disease event. i.e. asthma
What is an example of a disease where prevalence is a better measure than incidence?
Obesity
Asthma
What is a RCT?
Following a group of participants over time when they have been allocated into groups randomly
What is Risk Difference?
Comparing disease frequencies to measure the ASSOCIATION between EG and CG.
Absolute Risk
(EGO - CGO)
What is Risk Ratio?
Comparing the disease occurrence of EG relative to CG
Relative Risk
(EGO / CGO)
What are the differences between RR and RD?
Risk difference has units
Risk ratio doesn’t have units
What is a Relative Risk Reduction?
The change in relative risk, when RR is
What is Relative Risk Increase?
The change in relative risk, when RR is > 1.
Why can Risk Ratio be misleading?
Because the benefit of treatment is very dependent on the risk of disease before the treatment has started.
What provides more information RR or RD?
Risk differences because they take into account the number of people.
.67 of nothing is nothing!
What is considered a valid study?
A study with little random or non-random error.
What does RAMboMAN stand for?
Recruitment Allocation - (Adjustment) Maintenance blind objective Measurement ANalyses
What is a non-random error in recruitment?
The participants studied are not representative of the population in question.
e.g. self-report bias, selection bias, response rates, population/setting defined
What is a non-random error in allocation/adjustment?
When allocation puts participants into incorrect groups.
e.g. dishonesty, poor questionnaire, non-random allocation in RCT, confounding factors not addressed.
How do you adjust for confounding variables?
Stratify the study into sub-studies.
What is a non-random error in maintenance?
When participants leave the comparison group for the exposure group during the study.
When participants are lost-to-follow-up.
What is a non-random error in blind or objective measurement?
Subjective measurements.
What is ‘regression to the mean’?
Studies with extreme results will usually give less extreme results with repetition.
What is random error?
The unavoidable error in measurement due to the complexity, movement and random nature of biology.
What reduces random error?
Increasing the sample size
What is a 95% confidence interval?
In 100 identical studies using samples from the same population, 95 of the 95%CIs will include the true value of the population.
