Exam 2 : Lecture Cohorts

Question 1

What type of study is a cohort, interventional or observational?

Answer 1

Observational

Question 2

Groups are put together in two ways:

Answer 2

Allocation based on exposure status

Membership (something in common)

Question 3

Allocation via membership means?

Answer 3

Everybody that uses blue cross blue shield or other such groups

Question 4

When is it useful to study using a cohort?

Answer 4

Rare exposure

Question 5

What are cohort studies termed?

Answer 5

Incidence studies/follow-up/ longitudinal studies

Question 6

Reasons to select a cohort design

Answer 6

Unable to force group allocation
Limited resources
Exposure is rare
More interested in incidence rate

Question 7

How can a cohort study be conducted?

Answer 7

Prospective
Retrospective
Ambidirectional

Question 8

Exposure group is selected on basis of a past or current exposure and both groups followed into future to assess for outcome of interest, then compared

Answer 8

Prospective

Question 9

Group allocation is based on exposure status not disease status

Answer 9

Retrospective

Question 10

Individuals assembled at a given point based on some common factor
Ex: where they live, work,

Answer 10

Inception cohort

Question 11

Types of cohort

Answer 11

Birth
Inception
Exposure

Question 12

Cohort size

Answer 12

Fixed
Closed
Open

Question 13

A cohort which can’t gain members but can have loss-to follow ups

Answer 13

Fixed

Question 14

A cohort with no loss-to-follow ups

Answer 14

Closed

Question 15

A cohort with new additions and some loss-to follow ups

Answer 15

Open

Question 16

Unexposed can come from 3 places

Answer 16

Internal 
-patients from same cohort
General population
-2nd choice
Comparison cohort
-least acceptable

Question 17

Strengths of cohort study

Answer 17

Good for assessing multiple outcomes of ONE exposure
Useful when exposure are rare
Useful in calculating risk and RR
Less expensive than inter
Good when ethical issues limit use of interventional
Good for long induction/later periods (retro)
Able to represent Temporality (prospective)

Question 18

Advantages of prosepective cohort

Answer 18

Obtain greater amount of study info
Follow up easier
Better at giving answer to temporality
May look at multiple outcomes form a single exposure
Can calculate incidence and incidence rate

Question 19

Disadvantages of prospective cohort

Answer 19

Time,expense, lost to follow up
Not efficient for rare disease
Not suited for long induction
Exposure may change over time

Question 20

What are two things found in cohort studies during loss to follow up?

Answer 20

Type II error

Loss to follow up may not be equal between groups

Question 21

How is a cohort retrospective study better than a cohort prospective study?

Answer 21

Saves time and money

Able to study rare exposures

Question 22

Disadvantages of retrospective cohort

Answer 22

Requires access to charts, databases, employment records

Question 23

Key biases with cohort studies

Answer 23

Healthy worker

Selection bias