Epidemiology Flashcards
refers not only to the number of health events, but to the relationship of that number to the size of the population?
frequency
refers to the occurence of the health related events by time, place and person
pattern
- any factor, whether event, characteristic, or other definable entity, that brings about a change in a health condition or other defined characteristic
- illness does not occur randomly in a population
determinant
Types of questions epidemiology can answer?
- who is making them sick?
- who is or isn’t getting sick?
- where are they getting sick?
- when are they getting sick?
- how many are sick (frequency or count)
key feature of analytic epidemiology?
comparison group
when we find that persons with a particular characteristic are more likely than those without the characteristic to experience a certain health outcome, the characteristic is said to be associated with that health outcome
analytic epidemiology
Measure of the frequency with which an event occurs in a defined population over a specified period of time
Rate
what is needed to calculate the rate?
- the number of cases or illness or health outcome (i.e, disease or death)
- the size of the defined population
- the period of time during which an event occurs
- multiplier (usually 100,000)
- refers to only new cases of illness or disease in the population of interest occuring in specified time period
incidence
- refers to the existing or current (new+old) cases of illness or disease in the population of interst occuring in a specified time period
prevalence
what are considered non-experimental/ observational studies?
cohort studies (prospective and retrospective)
case-control studies
cross-sectional
what are considered experimental studies?
- clinical trials
- field trial
- community intervention
- refers to the act of randomly assigning subjects in a study to different treatment groups
- helps to control for confounding variables
- guards against bias
Randomized clinical trial
- a variable that is hidden or not included in an analysis, but impacts the relationship being analyzed
- some hide real relationships, while others make a false relationship appear to exist
- related to independent and dependent variable
Confounding variables
what are two conditions that must be met to be a confounder?
- It must be correlated with the independent variable. this may also be a casual relationship but it does not have to be
- it may be causally related to the dependent variable
- Anything that leads to a systematic difference between the true parameters of a population and the statistics used to estimate those parameters
Bias
occurs when there is a systematic difference between either:
- those who participate in the study and those who do not (affecting generalizability) or
- those in the treatment arm of a study and those in the control group (affecting comparability between groups)
selection bias
- occurs where the way in which outcome information is collected differs between groups
- can occur in trials when groups differ in the way outcome information is collected or the way outcomes are verified
- a test or treatment for a disease may perform differently according to some characteristic of the study participant, which itself may influence the likelihood of disease detection or the effectiveness of the treatment
Detection Bias
- Results from the systemic differences in the way data on exposure or outcome are obtained from the various study groups
- occurs when information is collected differently between tow groups, leading to an error in the conclusion of the association
information bias
- may be a result of the investigator’s prior knowledge of the hypothesis under investigation or knowledge of an individual’s exposure or disease status
observer bias
occurs where an interviewer asks leading questions that may systematically influence the response given by interviewees
interviewer bias
refers to the classification of an individual, a value or an attribute into a category other than that to which it should be assigned
misclassification
- a systemic error that occurs when participants do not remember previous events or experiences accurately or omit details
- a problem that usually occurs with the use of self reporting, such as case-control studies and retrospective cohort studies
Recall bias
- a sample of persons is enrolled- exposures and health outcomes are measured simultaneously
- assess the presence (prevalence) of the health outcome at that point in time without regard to duration
- “snapshot”
- not as powerful as a cohort study or case control studies because outcomes and exposure variables are measured at the same time
- suitable for generating hypotheses and informing other study designs
Cross-sectional
- enroll a group of people and groups them by disease status
- those with the disease, and then, as a comparison group, those without disease
- cares about disease status of participants and then compares previous exposures between the two groups
- the control group provides an estimate of the baseline or expected amount of exposure in that population
Case Control
- cares are about exposure status of participants, and then tracks the participants overtime to see if they develop the disease of interest
- after a period of time, compares the disease rate in the exposed group with the disease rate in the unexposed group
- the unexposed group is the comparison group- provides an estimate of the baseline or expected amount of disease occurance in the community
- can be retrospective or prospective
cohort
