Study Guide Exam 2 Flashcards
Rank the following types of research designs in terms of their respective strength in determining cause-effect relationships, from highest to lowest: cross-sectional, randomized control trial, cohort study, case-control study
- Randomized control trial
- Cohort study
- Case-control study
- Cross-sectional
Definition of descriptive epidemiology
The study of the amount and distribution of health states in the populations by characteristics of person, place, and time.
Used to ID the existence and extent of health problems in a defined pop. Are used to generate hypotheses for future study.
Definition of ecologic study
Study of the association between exposure and outcome on the group level
Ecologic fallacy definition
When incorrect inferences about the individual are made from group level data.
Distinguishing features of case-control studies
-Individuals with a particular dz or condition are selected for comparison with individuals in whom the dz or condition is absent.
-Looks for an association by comparing h/o exposure between a group of diseased individuals and a group of non-diseased individuals.
-Two separate samples
-Dz status is known at the beginning
-Retrospective
What is another characteristic of a case-control study?
The outcome is always identified prior to the exposure.
-Involves grouping people as cases and controls, and investigating whether the cases are more or less likely than controls to have had past experiences, lifestyle behaviors, or exposures.
From where can cases come?
Public health clinics
Physicians’ offices
Health maintenance organizations
Hospitals
Industrial and government sources (registries)
3 main sources of controls
Population-based (best): Can be a probability (representative) sample of those without the dz from the same source pop as the cases.
Downside: expensive
Same hospital as cases but different dz
Downside: no healthy controls
Family, friends, neighbors, coworkers, relatives of the cases
Downside: may be too similar to the cases
Double blind study definition
Neither the participants nor the investigators know who is receiving the active tx
Benefits of double blind study
Best way to avoid unconscious bias
-Physicians don’t know which pt is taking the placebo and which pt is taking the drug
-Assessors of outcome are not the treating doctors and are not told which tx was used
Problems with blinding
For non-drug studies such as those involving behavior changes or surgery, it may be impossible or unethical to blind
It may also be problematic to blind in drug studies where a tx has characteristic side effects
Ethical aspects of human experimentation
Informed and voluntary consent
Withholding beneficial tx from control group
-Crossover designs are used as a solution
Monitoring for harmful SEs in tx group
-Can be circumvented using animals
Deciding when to withdraw an individual pt
Deciding when to stop the entire study
-Depends on degree of uncertainty
Vulnerable groups
-Children
-Prisoners
-Intellectually challenged
-Poor, homeless
Definition of exposure-based cohort
Made up of participants with a common exposure. They are recruited because of this exposure
Advantages of cohort studies
Permit direct determination of incidence
Time sequencing of exposure and outcome
-The exposure occurred before the dz in time
-Best observational study for determining causality
Evidence about the length of the latency period or time lag btwn exposure and dz can be determined
Can study multiple outcomes
Can study rare exposures in exposure-based cohort studies
In pop-based cohort studies, generalizability is often good
