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Statistical Modelling > Study Design > Flashcards

Study Design Flashcards

1
Q

What are two different types of epidemiological study designs?

A

Experimental

Observational

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2
Q

What are the different types of observational studies?

A

Cohort study

Case-control study

Cross sectional study

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3
Q

What is a cross sectional study?

A

Single timepoint study – measure exposures and outcomes simultaneously

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4
Q

What are the strengths of a cross sectional study?

A
  • Quick
  • Can answer descriptive questions

What is the prevalence of depression?

What proportion of people suffering from depression own smartphones?

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5
Q

What are the weakness of a cross sectional study?

A

Difficult to establish what happened first – reverse causality

Difficult to eliminate confounding when answering causal questions

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6
Q

What does a case control study involve?

A

Recruit people with outcome of interest (cases), recruit people without outcome (controls), trace histories to collect data on exposures.

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7
Q

What are the strengths of a case control study?

A

Relatively quick

Good for rare outcomes

Example: MMR and Autism:

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8
Q

What are the weaknesses of a case control study?

A

Recall bias

Cannot describe absolute risks

Difficult to eliminate confounding when answering causal questions

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9
Q

What entails a prospective cohort study?

A

Identify cohort (with exposure of interest), follow up over time and measure outcomes

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10
Q

What are the strengths of a prospective cohort study?

A

Study multiple outcomes

Choose what data is collected and how it is measured

Can link participants to electronic health records to collect outcomes

Data is often widely shared

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11
Q

What are the weaknesses of a prospective cohort study?

A

Can take decades

Can be difficult to maintain high follow up rates

Decisions about study are made a long time before analysis

Difficult to eliminate confounding when answering causal questions

e.g million women study

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12
Q

What entails a retrospective cohort study?

A

Identify cohort, use historical data collection e.g. health record

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13
Q

What are the strengths of a retrospective cohort study?

A

Strengths:

Much quicker than prospective studies

Less issues with loss to follow up

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14
Q

What are the weaknesses of a retrospective cohort study?

A

Challenges in selecting patients – data may only be available for people with more contact with health services

No control over historical data collection

Difficult to eliminate confounding when answering causal questions

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15
Q

What are the strengths of a registry based cohort study?

A

Study multiple outcomes and exposures

Potential for enormous sample sizes

Data can be improved over time

Can be prospective or retrospective

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16
Q

What are the weaknesses of a registry based cohort study?

A

Quality of registry data may not be as high as research data

There may be loss to follow up when people leave registry e.g. discharged from hospital

Ethical issues around using people’s data without explicit consent

Difficult to eliminate confounding when answering causal questions

17
Q

What are the different types of experimental study?

A

Randomised

Non- randomised trial

18
Q

What are the strengths of non-randomised intervention studies?

A

Can be good for assessing feasibility of intervention

Can collect important data on intervention uptake or adherence

19
Q

What are the weaknesses of non-randomised intervention studies?

A

Difficult to draw conclusions about effectiveness:

May not have control group

Natural trends limit before and after studies (regression to the mean).

Systematic differences will exist between those given the intervention and those not given the intervention

20
Q

What are the strengths of randomised trials?

A

Only study design that can draw causal conclusions with minimal assumptions

Control over data collection and measurement

21
Q

What are the weaknesses of randomised trials?

A

Challenges in recruitment

Can take a lot of time

Limited sample size limits questions that can be answered

Conditions in trial may not reflect those found in the real world

May not be ethical

22
Q

What are the different types of cohort studies?

A

Prospective, retrospective or registry based

23
Q

What problem affects all observational data?

A

eliminating confounders

24
Q

What type of cohort study offers the best data?

A

Large well conducted prospective cohort studies

25
Q

What design is best for causal questions?

A

Randomised as eliminates confounders

26
Q

What studies are prone to regression to the mean?

A

Before and after studies

27
Q

What do randomised trials involve?

A

Recruit patients, randomise to intervention or control, follow up

Statistical Modelling (11 decks)

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