Epidemiology 1 Flashcards
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
What is an example of primary prevention?
Reducing salt in your diet reduces the. risk of developing hypertension
What is secondary prevention?
The application of available measures to detect early departures from health and to introduce appropriate treatment and interventions
What is an example of secondary prevention?
Controlling hypertension with antihypertensive drugs to 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
What is an example of tertiary prevention?
Rehabilitation for someone who’s had stroke so that they can return as close as possible to their pre-morbid activities
What are different types of exposure?
e.g. drug, behaviour (dietary sodium intake) or demographic characterise (ethnicity)
What is the exposure and outcome?
Exposure: independent variable
Outcome: dependent variable
What are the levels of evidence in research?
- Systematic reviews and meta analysis
- Randomised controlled trials
- Cohort studies
- Case-control studies
- Case series, case reports
- Editorials, expert opinion
What does qualitative research explore?
underlying ideas and themes to inform research questions and possible future hypothesis
What does qualitative research express?
Its findings and outputs of qualitative research in words
What does qualitative research rely on?
Smaller numbers of participants but goes in substantial detail
When is qualitative research used for?
used earlier in research process - gives you a place to start
What numbers and measures are used?
- Measures of frequency and associations
2. Comparisons and adjusting for differences
Where do these measures come from?
- Descriptive epidemiology
- Observational and interventional study design
- Systematic reviews and meta-analysis
How do we interpret epidemiological findings?
- Association, causation, validity and bias
2. Confounding and effect modification
What is the DALY?
measure of disease burden that combines years of life lost from ill-health, disability or premature death.
What are some measures of frequency?
- Odds
- Prevalence
- Cumulative incidence
- Incidence rate
How do you calculate odds?
number of people with the disease / number of people who don’t have the disease
What is the definition of odds?
The ratio of the probability (P) of an event to the probability of its complement (1-P)
What is prevalence?
the proportion of individuals in a population who have the disease or attribute of interest at a specific timepoint
How do you calculate prevalence?
number of people with the disease / total number of individuals in the population
What does prevalence not show?
no information on new cases of a disease
When is prevalence unhelpful?
- in short duration disease
- for causal inference
What is cumulative incidence?
proportion of the population with a new event during a given time period
How do you calculate cumulative incidence?
number of new cases during the period of interest / number of disease free individuals at the start of this time period
Are there units for cumulative incidence?
No units - 0-1
What does a cumulative incidence of 0 mean?
(0%) means there were no new cases during the study period
What does a cumulative incidence of 1 mean?
(100%) means that all individuals developed the disease during the time period
What do you have to be explicit with in cumulative incidence?
Timing
When is cumulative incidence not well defined?
- Need follow up period must be the same participants
- but not always possible lost participants, or someone get killed by car accident in follow up period despite about cancer diagnosis as no longer at risk of cancer diagnosis
What is person time?
measure the time participants spend in the study (at risk of developing disease) (sum up time observed for every person during study period) - until develop disease/die or lost to follow up
What is incidence rate?
the number of new case per unit of person time
How do you calculate incidence rate?
number of new cases during follow up period / total person-time by disease free individuals
What values can incidence rate take?
Take values of 0 to infinity
What are the units of incidence rate?
person time
What does incidence rate account for?
- time of follow ups and time for new event occurred
- Deal with lost follow up or enter and leave the study at different times and competing risks
When is incidence rate used?
When cumulative incidence cannot be properly defined
What does standardisation allow?
Want to understand whether the difference in incidence might be down to their different demography: sex and age
What does direct standardisation give?
gives comparable incidence - e.g. 120 strokes per 100K/year
What does indirect standardisation give?
Gives ratio out of 100 (sometimes 1.0)
When should you used indirect standardisation?
- When don’t know age specific data
- Only have high-level data about outcomes but can’t make direct comparison
How do you calculate the standardised mortality ratio (SMR)?
diving observed count by expected count
What would SMR of 1.65 mean?
65% more deaths than expected
What is SHMI data used?
For hospital performance identifying hospitals that report higher than expected mortality
What does standardisation not account for?
Change and confined intervals
How does the SHMI work?
- uses the process of indirect standardisation to produce ‘expected’ number of deaths by a series of adjustments taking into account the volume of cases, blend of diagnoses and casemix adjustments for underling demography and health status variation of patients
- A range of adjustments for casemix are undertaken and used to calculate an SHMI value (ranging from 0.6 to 1.2)
What is prevalence and incidence?
- Prevalence: all cases / total population
2. Incidence: new cases / population that can get disease
What does prevalence take into account?
incidence, recovery rate and death rate (no longer cases)
Why do you use person time?
- Incidence rate cannot be done at a specific moment
- Hard to follow up over study period
What happens in calculating cumulative incidence in Individuals who already had disease when period of interest started?
not be included in denominator or numerator
What are two different names for cumulative incidence?
- Incidence proportion
- Risk
What do you need for cumulative incidence?
Follow up
When can rates be used?
Can only be expressed as new cases per unit of person time
What does prevalence account for?
reflects both duration and occurrence
What can odds and prevalence be used for?
- Assess health of population
- To plan health services and allocate healthcare resources
- To monitor trends of diseases over time
