Aetiology and Risk Factors for CVD Flashcards
What is a descriptive research question?
A question which will give a descriptive answer e.g. how common is CHD?
What is an analytical research question?
A question which looks at cause and effect e.g. do lipid-lowering meds decrease the risk of CHD?
What are observational studies?
case series, ecological, cross sectional, case control, cohort
What are interventional studies?
clinical trials
Which study designs are descriptive?
Case series, ecological, cross sectional
Which study designs are analytical?
Case control, cohort, clinical trial
What is a longitudinal study?
involves follow up - information progressively collected over multiple encounters
Which study designs are longitudinal?
Cohort and clinical trials
What is prevalence?
The number of existing cases of a disease or a risk factor at one point in time - it is expressed as a proportion or a percentage
What is incidence?
The number of new cases of a disease or a risk factor over a period of time - can only be drawn from a longitudinal study - expressed as a rate (involves time)
What is risk?
The number of new cases over a defined period divided by the population at risk ???
What is rate?
The number of people who develop a new case divide by total person-time of follow up
What is person-time?
The total number of time of all the people who followed up - e.g. if there were 10 people in a study for 12 months the person-time would be 120 months if everyone was there for the whole time but due to staggered recruitments and drop outs it would be something more like 88 months
What is hazard?
A rate that is updated as the longitudinal study progresses - it is an instantaneous rate
What is an absolute risk/rate?
An isolated measure of risk/rate that does not indicate association with exposure e.g. 5 strokes/10000 men per year
What is a relative risk?
A ratio of risk/rate among the exposed (Re) compared to the risk/rate among the unexposed (Ru). Indicates the relative magnitude of change. Also called risk/rate ratio.
How is relative risk calculated?
RR = Re/Ru. e.g. 10/1000p-yr over 5/1000p-yr = 2
What does a relative risk of 2 indicate?
That exposure means you are twice as likely to get the disease
What is attributable risk?
A measure which indicates the absolute magnitude of change of the risk/rate between the exposed and the unexposed. Also called risk/rate difference
How is attributable risk calculated?
AR = Re - Ru e.g. 10/1000p-yr minus 5/1000p-yr = 5/1000p-yr
What is attributable risk percent?
Proportion of incident disease among exposed people that is due to exposure
How is attributable risk percent calculated?
Divide attributable risk by the number of exposed and multiply by 100
What does an attributable risk percent of 50% mean?
That 50% of the disease in the exposed is due to exposure
What is population attributable risk?
The excess risk/rate of the outcome in the population due to exposure
How is population attributable risk calculated?
PAR = Rt - Ru (where Rt is the risk/rate in the whole population and Ru is the risk/rate in the unexposed e.g. 8/100p-yr minus 5/100p-yr is a PAR of 3/100p-yr
What is population attributable risk percent?
The proportion of incidence of disease in the whole population that is actually due to exposure
What does a PAR% of 40% mean?
That 40% of the incident disease in the population is due to exposure - and if exposure was removed there would be 40% less incidence of that disease in the population
What are the Bradford Hill Criteria for Causality?
- temporal relationship
- strength
- dose-response relationship
- consistency
- plausibility
- exclude alternatives
- experimental evidence
- specificity
- coherence