Exam 1- Epidiemology Flashcards
Strength of association
association between exposure and outcome
Temporality
MOST IMPORTANT; an exposure must precede the occurence of a disease
Biological gradient
risk of disease being related to degree of exposure
Plausibilty
biological plausibility of hypothesis, biological mechanism to explain
Coherence
Should not conflict with what is known of natural history
analogy
one drug causes a defect, similar will to…
Specificity
LEAST IMPORTANT; exposure should lead to a single effect
Experimental Evidence
Reduction in exposure is associated with reduction in risk and vise versa
Prevalence
Number of EXISTING CASES at a specified time
Incidence
number of NEW CASES
Relative Risk
measure of association in cohort studies because incidence can be measured in them, how common disease is among the exposed
RR=1
null association, no difference in disease between the two groups
RR > 1
means exposure increases risk
RR<1
exposure decreases risk
Odds Ratio
measure of association in CASE CONTROL and CROSS-SECTIONAL studies; indirect estimate of RR as incidence cannot be measured in these studies; tells how common the exposure is among the diseased
Can measure incidence
cohort studies
cannot measure incidence
Case control and cross-sectional
OR=1
no difference in exposure history between cases and controls
OR<1
exposure history is less common
OR >1
exposure history is more common among cases
Attributable risk
absolute risk difference or the percentage of cases due to a given exposure
how much long cancer can actually be attributed to smoking
attributed risk
Attributable proportion
proportion of people who developed disease due to exposure
Bias
a systemic error in conduct of study based on selection of groups not being comparable, differences in information collected from study groups
Confounding
the observed relationship between the dependent and independent variables is due to a third varibale
gray hair associated to heart disease, really it is
age- confounding variable
counterfactual model
comparing the experience of a population exposed to a factor with the experience of the same population at the same time but without the exposure (can’t, so use substitute population)
ways to control confounding
- randomization, restriction
- matching; forces distribution of matching factors to be identical in various study groups
- analysis: look at the OR, multivariable analysis
descriptive studies
Case reports, case series, and cross-sectional;
you cannot assert causation; not a true experimental study
Case reports and case series
types of descriptive studies, with no controls so you cannot assert causation; not a true experimental study
Cross sectional
a type of descriptive study; made at ONE POINT in time so temporality is NOT known and hence causation cannot be ascertained (think snapshot view)
Cohort studies
follow exposed and unexposed people around, expensive, based on independent predictor variable; include prospective and Retro
Prospective Cohort study
follow subjects without disease (see if they get it)
Retrospective cohort study
both exposure and disease have happened in the past
Case Control Studies
ID people with disease and suitable non disease individuals as controls (Retrospective design, must have controls with similar chance of exposure, Incidence CANNOT be measured)
Experimental studies/clinical trials
researcher assigns exposure; these people provide highest level of epidemiological evidence; Blinding and randomization; includes validity (ext and int) and reliability
Internal validity
study is done without methodological problems
external validity
study accurately reflecting events that would occur in real situation
Meta Analysis and Systemic Reviews
studies of studies; PROVIDE the HIGHEST level of confidence
Provide the highest level of evidence
systemic reviews
Co-relational/ecological
individual exposure level not available (study populations)-type of descriptive study
