Amboss Epidemiology Flashcards
what is classical epidemiology
the study of distribution and determinants of disease in populations
what is clinical epidemiology
this is applying classical epidemiology to the prevention, detection, and treatment of disease in a clinical setting
what are the two main types of epidemiological studies?
observational and experimental
what is the latency period
period of inactivity between stimulation (infection with the pathogen) and response (symptomatic)
what is a random error
an error that occurs by chance and or limitations of precision
how can we reduce random error
repeated measurements and a large number of observations
what is systematic error
aka bias
an error in the way in which a study is conducted that causes a systematic deviation of findings from the true value
what is selection bias
bias when people in a sample group are not representative of the population from which the sample is drawn from (not random selection)
types of selection bias
sampling bias - nonresponse bias
attrition bias (loss of participation to follow up)
Berkson (all patients are selected from a hospital)
attrition bias is most commonly seen in what type of studies
attrition
solution for selection bias
control for unknown and known confounders
what is information bias
when data is collected incorrectly, measurements or interpretations leads to misclassification of groups or exposure
types of information bias
measurement
performance
recall
what is measurement bias
a systematic error that occurs when you measure the exposure or outcome
what is performance bias
there are differences between the study groups that are related to group assignments
hawthorn; subjects change their behavior when they are aware that they are being observed
recall bias
awareness of a condition by the patients changes how much they recall the related risk factors (common in retrospective studies and is reduced by decreasing time to follow up with them)
misclassification bias
research subjects are classified into the wrong exposure or outcome group which then distorts the observed association
cognitive bias
personal beliefs of the participants or investigators influences the results of the study
observer bias (type of cognitive bias)
aka pygmalion effect
the outcome or measurements of the study is influenced by the researches knowledge or beliefs
(avoided using placebo and blinding)
what is a confounder?
a third variable that is associated with the exposure and the outcome
can be responsible for an observed relationship between the dependent and independent variables
how can you minimize confounding variables during study design?
randomization, crossover study design
how can matching be done in studies
participants are matched individually to other participants with similar attributes
done in case-control studies to avoid confounders
Hazard Ratios
a measure of relative risk in statistical analyses
a HR greater than 1 is an increased risk
a HR less than 1 indicated a decreased risk
