2.4 Cohort Studies

Question 1

What type of study are cohort studies?

Answer 1

Observational

Question 2

What are cohort studies?

Answer 2

Researchers is a passive observer of natural events occurring in naturally-exposed and unexposed groups.

Question 3

How is group allocation based or not based on ?

Answer 3

Group allocation based on EXPOSURE status or not based on Group membership.

Question 4

What are cohort studies useful for?

Answer 4

Studying rare exposures.

Question 5

Based on the epi table, what are the cohort studies focused on?

Answer 5

A+B and C+D.

Question 6

What are 4 reasons to choose a cohort study?

Answer 6

1. Unable to force group allocation (randomize). 2. Limited resources. 3. exposure is rare. 4. interesting in IR and risk outcomes

Question 7

How can cohort studys be conducted?

Answer 7

Prospective, retrospective or ambidirectional fashion

Question 8

What does the term cohort mean?

Answer 8

Refers to a group with something in common

Question 9

What 3 terms describe the size of cohorts over time?

Answer 9

Fixed, closed and open (dynamic)

Question 10

What is a fixed cohort?

Answer 10

Doesnt gain members but can lose members

Question 11

What is a closed cohort?

Answer 11

No gain or loss of pts

Question 12

What is an open or dynamic cohort?

Answer 12

Can gain and loss pts.

Question 13

How does one select exposed study population in cohort studies?

Answer 13

Based on pre-defined criteria of exposure

Question 14

How does one select unexposed study population in cohort studies?

Answer 14

Make groups as close as possible.

Question 15

What 3 sources can the unexposed group come from?

Answer 15

Internal, general population, and comparison cohort.

Question 16

Where does the internal come from?

Answer 16

Pts from the same cohort, Best option

Question 17

How good is general population source option?

Answer 17

2nd best choice.

Question 18

Which of the 3 sources is least acceptable. why?

Answer 18

Comparison cohort. Simply attempt to match groups as close as possible on numerous personal characteristics

Question 19

What are the 7 strengths to Cohort studies?

Answer 19

1. Good for assessing multiple outcomes of one exposure. 2. Useful with rare exposures. 3. Good in calc Risk and RRs. 4. Less expensive. 5. Good with ethical issues. 6. Good for long induction/latent periods. 7. Able to represent temporality (prospective).

Question 20

What are 7 weaknesses to cohort studies?

Answer 20

1. Cant demonstrate causation. 2. Hard to control for other exposures.3. Restrospective cant control for other exposures. 4. Not good for long induction/latent periods. 5. Confounders. 6. Biases. 7. Limited by available data

Question 21

What are 5 advantages of prospective cohort studies?

Answer 21

1. can obtain a greater amount of study important info from pts. 2. Follow up/tracking pts easier. 3. Better temporality. 4. Look at multiple outcomes from a single exposure. 5. Calculate incidence and incidence rates.

Question 22

What are 4 disadvantages of prospective cohort studies?

Answer 22

1. Time, expense. lost to follow up. 2. Not good with rare diseases. 3. Not good for long induction/latency conditions. 4. Exposure may change over time.

Question 23

What are 4 advantages of retrospective cohort studies?

Answer 23

1. Best for long induction/latency conditions. 2. good for rare exposures. 3.Useful if data exists. 4. Saves time and money

Question 24

What are disadvantages of retrospective cohort studies?

Answer 24

1. Requires charts, databases,employement records. 2. Cant control for other exposures. 3.Pts may not be available for interview. 4. exposure may change over time

Question 25

What are 2 key biases with cohort studies?

Answer 25

Healthy worker effect and selection bias

Question 26

What is healthy worker effect?

Answer 26

The really sick are not in the study, only the healthy are

Question 27

What is selection bias?

Answer 27

How exposure status is defines/determines.