Part 1: Epidemiology, GATE, Errors Flashcards
What is epidemiology?
Epidemiology is the study/science of dis-ease occurrence in a population/group over a period of time or at a point in time including the factors which determine the differences of the occurrence of dis-ease between groups.
What is occurrence?
Occurrence is the transition between being a non dis-eased state to being a dis-eased state.
Describe the hourglass analogy.
- Sand, being individuals in a population
- The middle of the hourglass being the (OCCURRENCE) transition from being non-dis-eased to the being in a state of dis-ease.
- The top glass is the non dis-eased state
- The bottom is the dis-eased state
Dis-ease occurrences is referring to the idea of….
Quantifying an event/or the outcome.
Why is important to measure the occurrence of an outcome?
It will help identify the causes of dis-eases and therefore help with fixing or preventing future case.
In what ways can measuring the outcome help? (3)
- Can inform health planning and promotion
- Prevention of dis-eases
- Treatment decisions (like which treatments actually work)
What does the term population mean?
It is a group of people who share similar/common characteristic(s) or factor(s)
What’s the things you say which helps you to find the common factors which could be included in a population?
“Men and women aged 18 and above who live on the North Shore who are non-smokers test a new drug to see if lung cancer can be reduced in 2018”
So what are the factors which can may be common in a population?
- Demographic
- Geographic
- Behavioural
- Same treatment/drug
- Time period
- Combo of the above
What is the difference of the focus target of clinical medicine and population health?
Clinical Medicine
- TREAT the INDIVIDUAL
(How can I fix the individual? What is wrong with them?)
THE AMBULANCE AT THE BOTTOM OF CLIFF
Poplhlth
- Look as population as a whole
(Looking at trends through epidemiological studies)
THE FENCE AT THE TOP OF THE CLIFF
What is the difference of the education background of clinical medicine and population health? What models do they use?
CM
- Cure rather than prevention $$$$$$$$$$$$
- Biomedical model
(Individual focused, may be victim blaming, what is the individual doing to make them injured like obese?)
Poplhlth
- Prevention before occurrence
- Social model
(If the individual is obese/injured, what is his living environment like? Are there lots of McD’s around his home? Is it safe to walk around at night?)
What is the difference of the rights of clinical medicine and population health?
CM
- Individual rights (Autonomy, patient’s rights)
Poplhlth
- Human rights
- Social and environmental justice
What are the two ways of data collection?
- Numerical
2. Categorical
What is numerical data collection?
Data collection when the data you are collecting are numerical values.
ONE POINT IN TIME collected but can be displayed in GATE frame as CATEGORICAL too.
What are some examples of numerical data collection?
BMI, BP, BGL, No, of hospital visits. No. of births
NOTE: Numerical measures can be classed as Categorical sometimes.
When taking pulses, you have have fast pulse (>70 bpm) or slow pulse (<70 bpm)
What is categorical collection?
It is for easier observable onsets, can be characterised by having it or not.
YES or NO
Can be prevalence or incidence
What are some examples of categorical data collection?
Male or Female
Smoker or Non-smoker
Lung cancer or No Lung cancer
Dead or Alive
What is the basic equation of epidemiology?
E = N / D / T
numerator/denominator/time
Describe the GATE frame.
Triangle - population
Circle - exposure and Comparison group
Square - outcome
Arrow - time
Describe the triangle in GATE frame w subtypes and add examples:
Population - Triangle gets smaller (you filter them out to the eventual participants,) three sub types:
- Study setting
The New Zealand Population
Eligibles - Secondary High School Students (Maori and Pakeha)
- Actual participants
9500 Yr 11, 12, and 13 Maori and Pakeha students.
What can be in the GATE frame sometimes for extra marks?
Allocation rectangle between the triangle and the circle
What can allocation be? (2)
- Measurement (inclu. surveys and questionnaires
- Randomised
Describe the circle in GATE frame w subtypes and add examples:
1/2 circle: Exposure - EG, these are the people exposed of the exposure, like smoking. So these would be the smokers.
THIS IS D for EXPOSURE GROUP.
1/2 circle: Comparison - CG, these are the comparison group. Who are not exposed to the exposure, this would be the non-smokers.
THIS IS D for COMPARISON GROUP.
Describe the square in GATE frame w subtypes and add examples:
Outcome - these are the numerators in respect of the EG and CG directly above it.
Outcomes can be numerical or categorical
How many compare groups can you have in a GATE frame?
There is ALWAYS ONE CG!!! If you have more than one, you wrong…
How do you do the maths in numerical outcomes?
You calculate the averages of the results and chuck em’ in the square
Give an example of numerical outcomes.
EG is walking
CG is not walking
Because you allocate through measurement, (BMI) you calculate the averages of the BMI of each group and put in the average in the square outcome.
What is the equation for averaging for EGO and CGO?
EGO = Σa/EG
CGO = Σb/CG.
Describe the arrow in GATE frame w subtypes and add examples:
Time - this is the time when or during the outcomes are measured.
- Horizontal
“CUT, NOW!” like a prevalence measure. - Vertical
“Down the line” like an incidence measure.
What are the epidemiological measures of dis-ease occurrence?
Incidence
Prevalence
What is incidence?
Over a period of time
Counting transition from non-dis-eased to dis-eased, easily observable characteristics
How do you remember incidence?
Imagine constantly working (overtime like 10yrs, you tired af!!!)
and imagine people popping up (you count one by one) over time and you mark a tally when they pop up,
you count FORWARDS (vertical arrow, down the line)
What is prevalence?
ONE POINT IN TIME, STATE
not easily observable characteristics like obesity when was the person obese?
Hard to pinpoint, GRADUAL.
What are the sub-types of prevalence?
Period prevalence
Point prevalence
How do you remember period prevalence?
“Tell me the answer now, but do you remember having lung cancer in the last 10 years?” Recalling the past. It is a mix of incidence and prevalence.
IT GIVES A TIME FRAME OF WHEN TO REMEMBER
How do you remember point prevalence?
“Tell me the answer now! But do you smoke? Do you have lung cancer?” GATE frame fill out is quick and easy.
So what is point prevalence?
Counting people in one point in time, measure OUTCOME and EXPOSURE same time.
So what is period prevalence?
Ask now, but asking them to recall back over the period.
Describe the population cloud analogy.
Population cloud
Incidence rain/drizzle
Prevalence pool
Death drips
Cure cloud
What is population cloud?
Population cloud is all the people (the population) which you will be trying to investigate.
What is incidence rain?
Calculated by the number of onsets (events) occurring in a period of time.
Raindrops falling illustrates the population of people which are changing state, falling into the prevalence pool.
This is when it is EASILY OBSERVABLE: CATEGORICAL
What is incidence drizzle?
NOT EASILY observable events which means that it is more difficult to count and therefore NUMERICAL and is better to count the prevalence pool rather than the incidence drizzle.
What is prevalence pool?
SNAPSHOT IN TIME
How many people are diseased? is the alternative of counting dis-ease occurrence to incidence and is counting the number of people who are now dis-eased,
AT ONE POINT IN TIME (Numerator) and then dividing by the number of people in the study at that point in time.
What are prevalence equations?
Prevalence in EG = a / EG at one point in time
Prevalence in CG = b / CG at one point in time
Population with high incidence of dis-ease could have a low prevalence if the death rate or cure rate is also high.
True or False?
True
A population with low prevalence if dis-ease could have a high prevalence of dis-ease, if almost no one dies of the the dis-ease in a population at a point in time.
True or False?
True
What did the two statements mean then?
Prevalence is a DIRTYYYY measure
Why is prevalence a dirty measure? (3)
Affected by cure cloud, death drips, and incidence rain.
This it is less useful than incidence because a high incidence of dis-ease could result in either a high or low prevalence depending on the death rate and the cure rate.
ALSO prevalence does not include the time. It is excluded so it takes away a factor.
What is epidemiology all about?
To compare EGO and CGO, comparing dis-ease occurrences in different populations
Why is measuring CG and EG important?
We need CG because if we only measure EG we are taking away all the other factors which could have affected the exposure.
CG will not always be dis-ease free. If we take the example of drive deaths non smokers (CG) other factors could have affected deaths not j the non smoking.
What is a factor of misinterpretation?
Side effects