Epidemiology Flashcards
What is prevalence?
Number of disease cases in a population at a given time
What is incidence?
Number of new disease cases developing over a specific period of time in a defined population
What are ideal properties of an index?
Clear, unambiguous
Not subjective
Reproducible
Indicate treatment need
What is a null hypothesis?
No significant difference in variables
What are the 3 common indices of risk?
Absolute - incidence rate of disease
Relative - ratio of incidence rate in exposed group to incidence rate in non-exposed group
Attributable - difference between incidence rates in exposed and non-exposed groups, represents risk attributable to factor being investigated
What is an observational study and give 2 examples?
Not experimental
Investigator does not design study to expose one group on purpose
Involves comparing disease experience of two or more groups of people in relation to their possession of certain characteristics/ exposure to factor
Tests specific hypotheses
Cohort and case control
What is a cohort study?
Recruit group of people who have not manifest the disease at time of recruitment and assess risk factors.
Observe over period of time to measure frequency of occurrence of disease (some exposed to risk factor, some not)
What is a case control study?
Retrospective study comparing individuals with disease (cases) with those without disease (controls).
Trace back and assess risk factors
Good for initial investigation of hypothesis, followed by cohort
What is SIMD?
SIMD (Scottish Index of Multiple Deprivation) is a measure of relative deprivation across small areas of Scotland. The data used to calculate SIMD is derived from a variety of sources, including administrative data and surveys.
The Scottish Government uses a statistical model to combine data from seven domains of deprivation, including income, employment, health, education, housing, crime, and access to services.
What is absolute risk difference and what would the value be if there is no benefit?
Difference in risk between groups
Value of no difference = 0
What is the risk ratio and its value of no difference?
Risk in variable group / risk in placebo group
Value of no difference = 1
What is odds ratio and its value of no difference?
Ratio of odds of outcome in both groups
Value of no difference = 1
What are confidence intervals?
Tells us the range of values that a true population treatment effect (eg. Risk ratio) is likely to lie.
If they overlap the value of no difference - insufficient evidence for difference between treatment group and control in population
What is a randomised control trial?
Gold standard study design - provides strongest evidence
Participants allocated by chance to different interventions and are followed up and outcomes assessed
What a re the 4 design elements of RCT?
Specification of participants
Control/ comparison groups
Randomisation
Blinding/ masking
