Epidemiology Flashcards
(35 cards)
What is the definition of epidemiology?
The study of the frequency, distribution and determinants of diseases and health-related states in populations in order toe prevent and control disease
What is the incidence?
Number of new cases; the denominator is the number of disease free people at the start of the study; it is over time
What is the prevalence?
Number of existing cases; it is at a point in time
What is person-time?
Person-time is a measure of time at risk. i.e. time from entry to a study to (i) disease onset, (ii) loss to follow-up. (iii) end of study
What is person-time used for?
It is used to calculate incidence rate which uses person-time as the denominator. (cumulative incidence uses the number of disease free people at the beginning of the study)
What is incidence rate used for?
It is useful when study participants are followed up for varying lengths of time
What is the incidence rate?
Number of persons who have become cases in a given time period / Total person-time risk during that period
What are the usual headings when describing the epidemiology of a disease?
Time; Place; Person (age, gender, class, ethnicity)
What is absolute risk?
It has actual numbers and units, so per number of people
What is relative risk?
Risk in one category relative to another
What is the attributable risk?
The rate of disease in the exposed that is due to the exposure
What does the relative risk tell us about?
About the strength of association between a risk factor and a disease
What does the attributable risk tell us about?
About the size of effect in absolute terms
What is bias?
A systematic deviation from the true estimation of the association between exposure and outcome
What are the two main types of bias?
Selection bias and information bias
What is a systematic bias?
An error in the selection of study participants or the allocation of participants into different study groups
What is an information bias?
A systematic error in the measurement or classification of exposure or outcome.
What are the sources of information bias?
Observer (observer bias); participant (recall bias); instrument (wrongly calibrated instrument)
What is confounding?
The situation where a factor is associated with the exposure of interest and independently influences the outcome (but does not lie on the causal pathway)
What should you consider when looking at association and causation?
Bias, chance, con-founders, criteria
What are the factors when assessing causality?
Strength of association; Dose-response; Consistency; Temporality (does exposure come before outcome); Reversibility (if you take away the exposure the outcome goes away); Biological plausability
How can you classify prevention?
Primary, secondary and tertiary
What is primary, secondary ad tertiary prevention?
Primary - no disease
Secondary - pre-clinical disease
Tertiary - clinical disease
What is the population approach to disease prevention?
A preventative measure delivered on a population wide basis and seeks to shift the risk factor distribution curve