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Epidemiology Exam 2 > Cohort Studies > Flashcards

Cohort Studies Flashcards

1
Q

relate cohort studies to strength in evidence of all observational studies

A

has the most evidence

only observational that can be a controlled prospective study

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2
Q

cohort studies are _______ studies that allow the researcher to be …..

A

observational

a passive observer of natural events occurring in naturally exposed or unexposed groups

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3
Q

group allocation is based upon?

A

exposure status
or
group membership—simply something in common

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4
Q

cohort studies are useful when studying ?

A

a rare exposure

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5
Q

other terms for cohort studies

A

incidence studies

longitudinal studies

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6
Q

what measures of association do cohort studies calculate?

A
  1. risk of disease/outcome

2. RR/relative risk

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7
Q

define cohort

A

a group of people who simply have something in common

and then you can further allocate them into groups based upon exposure or not/ or disease/ not diseased

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8
Q

reasons to choose a cohort design

A
  1. unable to randomize
  2. limited resources
  3. exposure of interest is rare
  4. more interested in incidence rate or risk of outcome than an intervention
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9
Q

exposure of interest is rare

A
  • -rarely occurs

- -little is known about its associations or outcomes

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10
Q

time line direction of cohort studies

A

can be prospective, retrospective, or ambidirectional fashion

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11
Q

prospective cohort studies

A
  1. exposure groups is selected based on past or present exposure
  2. both groups are followed into future to assess for outcomes
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12
Q

historical cohort study = ?

A

retrospective design

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13
Q

retrospective cohort studies

A
  1. at start of study exposure and outcome has already occurred
  2. but groups are still allocated based on past history of exposure
  3. not disease status
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14
Q

ambidirectional design

A
  • -uses past exposure for group allocation
  • -adds present data and
  • –keeps going in a prospective fashion
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15
Q

birth cohort

A

–individuals assembled into a cohort based upon being born in same region/in same time period

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16
Q

inception cohort

A

–individuals assembled in a cohort at a specific time based upon a common factor

–ex. cob class– all in this grad program

17
Q

exposure cohort

A
  • -brought together based upon some common exposure

ex. 9/11 responders – exposed to carcinogens

18
Q

cohort sizes may ______ over time

A

not change

19
Q

cohort size control

A
  1. fixed cohort
  2. closed cohort
  3. open/dynamic cohort
20
Q

fixed cohort

A

a cohort which cannot gain members but can have lost to follow-up

21
Q

closed cohort

A

a fixed cohort but no loss to follow-up

22
Q

open cohort

A
  • -dynamic cohort
  • –a cohort w/ new additions and some loss to follow-up
  • ex. nurse health

moving, death, etc.

23
Q

sources of the unexposed group

A
  1. internal
  2. general population
  3. comparison cohort
24
Q

internal source

A
  1. best option
  2. patients from same cohort yet unexposed
  3. use lowest exposure group when levels of exposure exist
25
Q

describe levels of exposure

A

–when exposure intensity increases/decreases over time

  • -in some events there are no unexposed subjects
  • -comparison group may just have to be the lowest exposure people
26
Q

general population

A
  1. a second choice when an internal group is not available
27
Q

comparison cohort

A
  1. the least favorable group

2. simply match groups as close as possible on personal characteristics

28
Q

strengths of cohort design

A
  1. good for multiple outcomes of one exposure
  2. rare exposures
  3. calculate risk and RR
  4. less expensive
  5. less ethical limits
  6. good for retrospective
  7. can be prospective
29
Q

matching in cohort studies

A

–a way to strive to make groups as equal as possible for known confounders

30
Q

key biases in cohort studies

A

healthy worker effect

selection bias

31
Q

weaknesses of cohort studies

A
  1. can’t show causality
  2. can’t control variables in retro
  3. retro can’t control for other exposures
  4. prospec not good for long induction periods
  5. impacted by unknown confounders
  6. effected by biases
  7. limited by available data when retro
32
Q

advantages of prospective cohort studies

A
  1. obtain greater amount of specific data
  2. tracking subjects easier
  3. can assess temporality
  4. can eval multiple outcomes of one exposure
  5. calc incidence risk and rate
33
Q

disadvantages of prospective cohort studies

A
  1. time, money, lost to follow up
  2. not great for rare diseases
  3. not suited for long induction or latent periods
  4. exposure can change – levels of exposure
34
Q

lost to follow up in prospective designs

A
  • -a problem just like in interventional designs

- -increases risk of type 2 error

35
Q

advantages of retrospective cohort designs

A
  1. best for long induction/latent periods
  2. study rare exposures
  3. useful when data already exists
  4. saves time and money compared to prospec
36
Q

disadvantages of retrospective cohort designs

A
  1. requires access to data
  2. cannot control for variables or other exposures
  3. patients might not be available for contact
  4. exposure can change over time – levels

Epidemiology Exam 2 (6 decks)

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