Lecture 10

Question 0

What are the reasons to use a cohort study?

Answer 0

Unable to randomize
Limited resources
More interested in incidence rates/predictors than effects of interventions

Question 1

Cohort Study Design

Answer 1

Observational & analytical studies allowing passive observance of natural events occurring in naturally-exposed and unexposed groups
*Always start knowing the exposure/disease

Question 2

T/F: A cohort is a group with something in common.

Answer 2

True

Question 3

Birth Cohort

Answer 3

People grouped based on being born in a certain region/time period (KC in 2000)

Question 4

Inception Cohort

Answer 4

People grouped at a given point based on some common factor (where they live, work, etc.)

Question 5

What is the most popular inception cohort in the U.S.?

Answer 5

Framingham Study…followed population of Framingham, MA starting in 1948 through today

Question 6

Exposure Cohort

Answer 6

People grouped based on some common exposure

Question 7

Fixed Cohort

Answer 7

Can’t gain members but can have loss-to-follow-ups

Question 8

Closed Cohort

Answer 8

Fixed cohort with no loss-to-follow-ups

Question 9

Open/Dynamic Cohort

Answer 9

Some new additions and loss-to-follow-ups

Question 10

What are the 2 primary purposes of cohort studies?

Answer 10

Descriptive: measure of frequency (incidence/incidence rate)
Analytic: measures of association (risk ratio & predictive risk-factors)

Question 11

Prospective Cohort Study

Answer 11

Exposure group selected on the basis of past or current exosure and both groups followed into future to assess outcome(s) of interest, then compare

Question 12

Retrospective Cohort Study

Answer 12

At the start of the study, both the exposure and the outcome of interest have occurred

Question 13

Ambidirectional Cohort Study

Answer 13

Uses retrospective design to assess past differences but ads all data collected on additional outcomes prospectively from start of study (looking for outcomes in both directions)

Question 14

Advantages of Prospective Cohort Studies…

Answer 14

Obtain greater amount of important information from patients
Follow-up may be easier
Better at giving answer to “temporality”
Look at multiple outcomes from single exposure
Calculate incidence/incidence rate

Question 15

Disadvantages of Prospective Cohort Studies…

Answer 15

Time/expense/loss-to-follow-up’s
Not efficient for rare diseases
Not suited for long induction/latency conditions
Exposure may change over time

Question 16

Advantages to Retrospective Cohort Studies…

Answer 16

Best for long induction/latency conditions
Able to study rare exposures
Useful if data already exists
Saves time and money

Question 17

Disadvantages of Retrospective Cohort Studies…

Answer 17

Requires access to private charts, databases, & employment records
Information may not factor in other exposures
Patients may not be available to interview
Exposure may have changed over time

Question 18

When selecting the unexposed group, where should they come from?

Answer 18

1) Internal
2) General Population
3) Comparison Cohort

Question 19

What are the 2 key biases with cohort studies?

Answer 19

Healthy-worker effect: Only healthy people work, unhealthy ones don’t work
Selection bias: How exposure status is defined/determined