Lecture 7 Flashcards
what are types of observational studies that seek to establish statistical association
- cohort studies
does association mean causation
- no
does statistical association imply clinical importance
- no
which study measures exposure at the start of the study and then follows research participants over time to see who develops disease
- prospective cohort studies
which study identifies cohorts based on measurements of exposure at some time in the past for some other purpose and then identifies which individuals developed or did not develop disease between the time of exposure and the start of the study
- retrospective cohort study
cohort studies estimate the association between an exposure and a disease by comparing the ______ of disease in those who are exposed to those who are not
- incidence (risk)
cohort studies have been used to study
- risk factors
- prognostic factors
- treatments
the research design that argues most convincingly for causality is the
- randomized control trials
the research design that argues most convincingly for causality is the
- RCT
the findings that argue most convincingly are
- strong relationship
- dose response relationship
what is a dose-response
- larger exposure associated with higher rates of disease
what is temporality
- cause precedes effect
what is strength
- large relative risk
what is reversibility
- reduction in exposure followed by lower rates of disease
what is consistency
- repeatedly observed in different situations
what is biologic plausibility
- makes sense according to biologic knowledge of the time
what is specificity
- one cause leads to one effect
what is analogy
- cause and effect relationships already established for a similar exposure or disease
what is the only criterion absolutely required to establish causality
- temporality
temporality is ________ evidence, in itself, in favor of causality
- weak
what is an observational study in which a group of people who do not have a condition but who could possibility develop it in the future is assembled
- cohort study
information about the characteristics of people in the cohort is gathered when
- beginning and end of study
advantage of retrospective study
- less costly and time consuming
disadvantage of retrospective study
- past records may not be as accurate
how to select participants for cohort studies
- select cohort from gen pop then measure exposure to factors of interest
- select exposed and unexposed groups separately on the basis of their levels of exposure
when a person in a cohort study develops the outcome of interest, what happens
- that person’s time in the study is complete
when a person considered to be censored in a cohort study
- develops outcome of interest
- followed and don’t develop outcome
- lost to follow-up
how to calculate hazard
number who develop outcome/total person time
how to calculate hazard ratio
- exposed group/unexposed group
what is meant by the hazard ratio being higher than the risk ratio
- participants in the exposed group develop the outcome prior to the end of the 5 year period.
advantages of hazard ratios over risk ratio as outcome measures in cohort studies
- allow subjects to contribute different amounts to the denominator
- represents odds of exposed group developing a disease EARLIER in time than unexposed group
what does it mean if hazard ratio is greater than 1.0
- exposed group developing outcome more rapidly than unexposed group
how to use cohort studies
- identify exposures that increase or decrease risk of disease
- used to study natural history of a disease
- investigate the effect of a treatment on a disease or condition
what studies are used when patients are unlikely to participate in in a study because they or their doctors believe one of the treatments is not effective
- cohort studies
criteria for critical appraisal of research studies
- research question and study design
- sample
- measures defined
- statistical analysis
- effect size (results)
- internal validity - due to bias?
- reasonable conclusion
- relevance
QSD MAE ICR
SAME DI QCR (same di quicker)
we use _______ to evaluate the strength of a study’s evidence towards establishing a causal relationship
- reason and evidence
the most widely used criteria to evaluate causality on the basis of epidemiological evidence are known as
- Bradford Hill criteria
what is the evaluation of the validity, importance, and generalizability of original research articles called
- critical appraisal
