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Health science 2801 > Week 7 > Flashcards

Week 7 Flashcards

1
Q

What type of studys is an analytic study

A

Ecological
Cross-sectional
Case-Control
Cohort

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2
Q

Is case control and cohort studies observation or experimental

A

Observational

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3
Q

What are 4 determinants we should consider when creating a cohort study

A
  1. Those who enter the cohort study should be outcome-free
  2. Selecting exposed and comparison groups
  3. Following up participant
  4. Determining outcome status
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4
Q

Why is cohort study an observational study

A

There is no intervention you just follow up who gets a disease and who dosen’t

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5
Q

Is the exposure determined before the outcome happens

A

Yes

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6
Q

What are some disadvantages of cohort studies

A

More expensive
Time consuming
Not fesable for many disease

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7
Q

What are some advantages of cohort studies

A

Better exposure and confounder data
Less vulnerable to information bias (recall bias can still happen)

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8
Q

What is a prospective cohort study

A

You follow people for 10 years and compare incidence of disease

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9
Q

What is retrospective study

A

You start at outcome and look back in time to see what caused the disease

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10
Q

What are good ways to collect data for a retrospective study

A

Military data
Occupational study

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11
Q

What are some advantages of retrospective study

A

Cheaper
Faster
Efficent with disease with long latenet period

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12
Q

What are some disadvantages to a retrospective cohort study

A

Exposure and confounder data may be inadequate
More vulnerable to bias
Need an established recording system

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13
Q

What is the incidence rate ratio

A

a/(a+b)/c/(c+d)

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14
Q

if someone develops breast cancer but then latter dies what is there outcome

A

It is not death it is breast cancer

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15
Q

What is the concept of person-time

A

People are in the study for a varied durations
Different times under exposure
Contribute differentialy to the study /.p09

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16
Q

What are advantaged of Cohort studies

A

Valuable when exposure is rare
Can examine multiple effects of a single exposure
Easier to determine the temporal relationship between exposure and outcome
Allows measurement of incidence

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17
Q

What are some disadvantages of cohort studies

A

Validity affected by losses to follow-up (selection bias)
Other factors may not be distributed evenly between exposure groups
Inefficient for evaluation of rare disease
Can be expensive and tine consuming
If retrospective they require good records

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18
Q

What are limitations to cohort studies

A

May need large numbers of subjects to be followed for long periods
Loss to follow up to undermine validity
Not good for rare disease or those with long latency
Not good when exposure data are expensive to obtain

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19
Q

You classify participants according to their outcome status

A

Cases (+ disease)
Controls(no disease)
Then you need to ask for past exposures if the cases and controls were exposed or not exposed

20
Q

Is a case-control population real

A

No they are artifical

21
Q

If we have a lot of people in a study should we reduce the size of the study

A

Reducing the size of the study greatly reduces cost with a proper sampling we will get a correct value for the measure of association

22
Q

What do you calculate when it is case control

A

Odd provides provides the proper measure of association

23
Q

What is the odd of exposure

A

(A/C)/(B/D)

24
Q

What is the caculation for the not-exposed group

A

(A/B)/(C/D)

25
Q

What are some qualifications for selecting cases

A

Very clear case definition requried
Ideally case selection will invovle direct sampling of cases within a source population
All people in the source population who develop the disease of interest will be included as cases
If someone in the source population developed the disease of intrest would they

26
Q

What is the definition of controls

A

A sample of the source population that produced the cases

27
Q

What is the purpose of cases

A

To estimate the exposure distribution in source population that produced the cases

28
Q

What are the two things that matter when selecting controls

A
  1. Controls must come from the same source population as the cases
  2. Controls must be selected independently of exposure
29
Q

Where can you find controls

A
  1. Population based controls
  2. Nested controls from a cohort population/study
  3. Hospital or clinic based controls
  4. Family or friend control
30
Q

What is the definition of population based controls

A

Controls selected from the general population most suitable when cases are from well-defined geographic area

31
Q

What are sources of population-based control

A

Random digital dialing, cell phone or intrent subsurcibers residence lists, tax lists, voter registration, driver license holders

32
Q

What is the advantage and the disadvantage of population based control

A

Controls often come from well-defined source population
It is very time consuming harder to inspire participating may not recall past exposures as we as cases

33
Q

What is the definition of nested controls

A

Controls selected from an existing cohort population

34
Q

What is the advantage and disadvantage of nested controls

A

Controls come from clearly defined source population already enrolled willing participants
Restricted to memebrs of existing cohort may limit the hypothes

35
Q

What is the defention of Hospital or Clinic based controls

A

Controls selected from among patients at a hospital or clinic

36
Q

What is the requirement of a hospital or clinic based control

A

Same source population as cases must consider the would criterion and the referral pattern illness should be unrelated to that is independent of the exposure under study
1. Illness that have the same catchment area as the cases
2. Illnesses that have no relation to the risk factors under study

37
Q

What is the advantage of Hospital or clinic-based control

A

Easy to identify and access less time and money accuracy of exposure recall comparable to cases more willing to particpate
These controls are not randomly selected this mean that hopsital based controls must be carefully selected to accurately represent the exposure history in source population

38
Q

What is the defention of the matched design

A

The process of making a study group and a comparison group comparable with respect to extraneous factors

39
Q

How can you account for confounding in matched design

A

Randomization in experimental studies
Matching case to controls

40
Q

How does matching work

A

For each case a control with the same characteristics will be selected

41
Q

Whats the difference between individual matching and frequency matching

A

Indvidual matching is performed participant by participant and frequency matching providing similar distributions of confounder in groups

42
Q

What is matching like in cohort studies

A

Exposed matched to unexposed
Less common
Expensive
Sometimes unpractical
May require control

43
Q

What is matching in case control studies

A

After selection of a matching factor for each a case a control with the same characteristics will be selected
A unit is not a person but a pair
Paired anyalsis

44
Q

What is the measure of association for cross sectional

A

Prevalence rate ratio

45
Q

What is the measure of case control

A

Odds ratio

46
Q

What is the measure of (Cohort)

A

Incidence ratio

Health science 2801 (10 decks)

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