Epidemiology Flashcards
What is epidemiology?
‘the study of that which Is upon people’
What does endemic mean?
Diseases that reside within a population
What does epidemic mean?
Diseases that befall a population
How is epidemiology defined?
The study of the distribution and determinants of health-relates states or events in specified populations, and the application of this study to the control of health problems
Give a more succinct definition of epidemiology
How often disease in different groups of people and WHY
What are the three types of prevention?
Primary
Secondary
Tertiary
What is primary prevention?
The prevention of disease through the control of exposure to risk factors
before onset of disease
What is secondary prevention?
The application of available measures to detect early departures from health and to introduce appropriate treatment and interventions
slows progression
What is tertiary prevention?
The application of measures to reduce or eliminate long-term impairments and disabilities, minimising suffering caused by existing departures from good health and to promote the patient’s adjustments to their condition.
e.g. rehabilitation of someone who has had a stroke
enabling return to normal function
What does being good at epidemiology involve?
Curiosity Problem-solving Numerical ability Critical thinking Communication Creativity
What are the three dimension of epidemiology?
Time
People
Place
What two things are often studied in epidemiology?
Exposures and Outcomes
What does the demographic transition model consist of?
5 stages of progression looking at birth rate, death rate and total population
What are the four stages of epidemiological transition?
Pestilence and famine
Receding pandemics
Degenerative man-made diseases
Delayed degenerative diseases and emerging infections
When was the era of pestilence of famine occurring the UK?
Pre-industrial revolution (up to 1800s)
What was associated with this period of pestilence and famine?
Urbanisation
Constraints on food supply
High birth rate and high mortality
Life expectancy low at birth
When was the era of receding pandemics occurring the UK
1800s - 1950
What was associated with this receding pandemics and famine?
Agricultural development improves nutrition
Life expectancy increases
Water, sanitation, hygiene
Vaccination emerges
High birth rate and decreasing deaths
When was the era of degenerative diseases occurring the UK?
1950 -2010s
What was associated with this degenerative and man-made disease period?
Lifestyle factors and NCDs predominate: Cancer and CVD
Environmental and global determinants drive obesity and other risk factors
Technology reduces need for physical labour
Addiction, violence and other issues emerge
When was the era of delayed degenerative diseases and emerging infections occurring the UK?
2010s onwards
What was associated with this degenerative and man-made disease period?
Health technology defer morbidity, albeit at increasing financial cost
Emerging zoonotic disease presents new threats
Inequalities within and between countries come to the fore
What determines which stage a country falls under?
Access to food, water, healthcare and sanitation
What are the levels of evidence?
The pyramid
Systematic reviews and meta-analysis
Randomised control trials
Cohort Studies
Case-control studies
Case series, case reports
Editorial, Expert opinion
What are the two types of research?
Quantitative research
Qualitative research
What are the different types of epidemiological approach?
Descriptive
Analytic
What does qualitative research often explore?
Underlying ideas and themes to inform research questions and possible future hypotheses
How to does qualtitative research express findings?
In words
What are the main pros and cons of qualitative research?
Relies on small numbers participants
Goes into substantial details
When is qualitative research often used?
Earlier in the research process
What are the three groups of conditions that affect DALYs?
Communicable disease
Non-communicable disease
Injuries
Give 4 measures of frequency
Odds
Prevalence
Cumulative incidence
Incidence rate
What are odds?
Ratio of a probability of an event to its complement
Number of people who have the disease divided by the number of people who don’t have the disease
What is prevalence?
Proportion of individuals in a population who have the disease or attribute of interest at a specific timepoint
Number of people with the disease divided by the population
Always need to specify timepoint
Prevalence is measure with a percentage
Provides no information on new cases of a disease
What is cumulative incidence?
Proportion of the population with a new event during a given time period
Number of new cases during the period of interest
divided by the number of disease-free individuals at the start of this time period
Need to be explicit about time period
What does a cumulative incidence value of 0 mean?
There were no new cases during the study period
What does a cumulative incidence value of 1 mean?
All individuals developed the disease during the time period
What are other names for cumulative incidence?
Incidence proportion
Risk
What must happen to calculate cumulative incidence?
Follow up from participants in study
At the same time
No new participants can join
No participants should leave
What is incidence rate?
Number on new cases per unit of person time
The number of new cases during the follow up period divided by the total person-time by disease-free individuals
Can take values from 0 to infinity
Must mention unit of person time
Suitable for studies when people enter/leave study at different times
What is person-time?
The total time a participant spends in the study
Can be expressed in various units hours-years
Ends when person acquires disease, dies or is lost to follow up
What does standardisation allow us to do?
Make comparison
Adjusting for factors
What are the two types of standardisation?
Direct Standardisation
Indirect Standardisation
What does direct standardisation give you?
Comparable incidence e.g. 120 stroked per 100,000 a year
What does indirect standardisation give you?
Gives a ration out of 100
What does direct standardisation allow us to do?
Compare like-for-like between populations
E.g. look ate age-specific incidence in a standard population
How would you conduct direct standardisation?
Step one: Calculate rate for each age bin
Step two: Add standard population to table
Step three: Rate x standard population divided by 100k to obtain expected count
Step 4: Take expected and divided by total population to get age-standardised incidence
What is important to note about every stat?
Potentially hiding another fact
A hospital has a seemingly high post-elective surgery 30 day mortality. What are the three possible explanations?
Unwanted variation - Hospital A is dangerous
Explained variation - e.g. the hospital does more high risk procedures
Statistical artefact - hospital is better at recording deaths (can be difficult to explain deaths outside of a hospital)
How do you conduct indirect standardisation?
Use national statistics to calculate expected values
Calculate SMR
What is the SMR?
Standard mortality ration
How do you calculate SMR?
Dividing the observed count by the expected count
What is SIR?
Standardised incidence ratio
What is SHMI data?
Summary hospital mortality indicator data
When is indirect standardisation useful?
When we only have high-level data about outcomes
We cannot make direct comparison
First step on a journey of enquiry
What does the SHMI do?
indirect standardisation to produce ‘expected’ number of deaths by a series of adjustments taking into account the
volume of cases
blend of diagnoses
casemix adjustments for underling demography and health status variation of patients
What doe SHMI values range from?
0.6 - 1.2
