Into to Epidemiology Flashcards
denominators
data or facts about a population:
Person Time
the time period e.g. number of years a person is exposed to risk
X years of follow up
is the time period from which people have been followed up
incidence
the occurrence, rate, or frequency of a disease
incidence rate
Number of new people with outcome over a time period x 100000
/
total person-time for people in the group AT RISK
Prevalence
proportion of persons in a population who have a particular disease
point
at a specified time
period:
over a specified period
period prevalence rate
Number of people with outcome during a time period x 100
/
Average number of people in a group
Different types of exposures
non-modifiable: - age, sex, genotype modifiable; - smoking, weight, diet, alcohol consumption interventions - special kind - drug therapy - surgery - lifestyle advice
risk
number of outcomes in a group
/
number of people in the group
x 100
relative risk
risk in exposed / risk in unexposed
relative risk reduction
(1-relative risk) x 100
absolute risk reduction
risk in unexposed - risk in exposed
number needed to treat
1 / absolute risk reduction
confidence intervals
– “A confidence interval can be thought of as a range of plausible values”
– Values near the limits less plausible than those in the middle
– The wider the interval the greater the uncertainty
cross-sectional study - past
sample a popultion estimate the proportion: - different exposures - different signs/symptoms - different outcomes use data - to describe prevalence/burden - to explore associations
case-control study - past
- Select cases with an outcome
- Select controls without the outcome
- Explore EXPOSURES in cases and controls • Compare exposures in cases and controls
- Identifyassociation
cohort study - future and past
• Select people without an outcome • Classify according to an exposure • Follow-up – Prospective = during the time period – Retrospective past • Compare RISK of disease in exposed and unexposed
randomised controlled trial - future
Random allocation
– Intervention
– Control/comparator
• Compare RISK of outcome in intervention and control groups
