WEEK 3: EPIDEMIOLOGY

counts

absolute number of events; numerator only

retrospective

both the exposure and the outcome have already occured

odds ratio

compares odds of exposure among those with a health outcome to the odds of exposure among those without the health outcome

relative risk, risk ratio

compares the risk among the exposed with the risk among non-exposed by means of a ratio

experimental epidemiology

perform interventions and/or assign treatments or interventions to study participants/outcomes

proportion

persons with the outcome of interest divided by the denominator of all persons (with and without the outcome)

outcome

potential result

rate

ratio in which time is contained in the denominator

ratio

reported as a fraction; no specified relationship between numerator and denominator

absolute risk reduction

simplest measure of therapeutic effect; aka "risk difference" or "attributable risk"

observational epidemiology

study behaviors, characteristics and outcomes of populations

referral bias

subjects are differentially referred to a study based on knowledge of their exposure

recall bias

subjects formed recall of their exposure or outcome differently

relative risk reduction

the extent to which therapy or exposure reduces a risk in comparison with individuals in the exposed groups not receiving therapy

epidemiology

the study of what comes upon people

causality

to make a judgment on whether the exposure casually affected the health outcome of interest consider factors such as: biological plausibility, consistency of findings, strength of association, temporal sequence of association

exposure

determinants of health related outcomes; factors that increase or decrease risk of a specific health outcome; may be personal characteristics or interventions

prospective

exposed and nonexposed are followed over time to compare outcome of interest

interviewer bias

individuals collecting data record or probe for information in a differential manner

chance

likelihood of observing an apparent exposure/health outcome relationship when one does not truly exist

prevalence

measure of the number of existing cases (old and new) in the population; the proportion of the population who has the disease of interest at the time of assessment

number needed to treat

number of individuals who would have to receive the treatment for 1 of them to benefit from the treatment over a specified period of time

incidence

number of new cases of disease occurring in the population during a specified period of time in previously disease or condition free individuals; estimates probability that a person will get ill (risk) or how rapid new cases occur

confounding

occurs when an exposure-outcome pathway is distorted by a third factor; a nuisance effect that distorts a study; related to both and is not in the causal pathway

selection bias

occurs when dissimilar procedures are used to select study subjects