1. What are the types of cohort studies? Define each.
2. Advantages of prospective 4 vs. retrospective? 4
3. Disadvantages of prospective 5 vs. retrospective? 3
4. Define historical prospective
1. Prospective - subjects are identified by exposure status and are disease-free --> disease status becomes apparent during follow-up period.
Retrospective - subjects are selected & analyzed based on exposure status, but follow-up has already taken place and disease status is known.
2. Advantages: Prospective --> exposure to risk factor is assessed before disease occurs, can estimate all measures of incidence and effect, possible to study several outcomes to one cause, and recall bias is not a problem
Retrospective --> can study rare exposures, less expensive than prospective, can be quick.
Prospective --> large investiment of time, resources, and finances, requires large sample size, dropout is a huge problem for long-term nature of study, cannot use for rare diseases, not easy to reproduce findings (difficult to look at consistency of effect).
Retrospective --> not good for rare diseases
, problems in ascertaining disease outcome
(duration & intensity)
4. Combo of 2 designs - exposure is from past, objective records but may gather more info over time. Cohort is followed into future.