Study Designs

Question 1

Define epidemiology

Answer 1

Study of how often disease occurs in diff grps of ppl + y

Question 2

What’s another way to say:
-disease occurrence
-risk factors
-disease prognosis

Answer 2

-Disease prevalence
-protective factors
-disease outcomes

Question 3

Observational studies ?
What investigators do/don’t ?

Answer 3

-question , observe, measure diff factors, record results
-no change or intervention w participants’ lives

Question 4

Intervention studies?
Investigators do/don’t?
Another name?

Answer 4

-intervention in pre-planned way (e.g. new treatment) - result recorded
Aka experimental studies

Question 5

3 types of observational studies ?

Answer 5

Cross-sectional
Case-control
Cohort

Question 6

2 types of intervention ?

Answer 6

-non-randomised
-randomised controlled trial (RCT)

Question 7

2 things that strength of evidence depend on?

Answer 7

Study design + quality

Question 8

Define exposure

Answer 8

Risk / protective factor

Question 9

Cross-sectional study ?
2 types of samples?
2 uses?

Answer 9

Sample from defines pop is surveyed - ‘snapshot’ - all factors (exposure/outcome) measures at one point in time.

-representative or random ?

-asses association between exposure and outcome / asses prevalence of disease

Question 10

Pros(2) and cons(2) of cross-sectional study ?

Answer 10

-cause and effect relationship hard to determine so not strong evidence
-evidence distorted by confounding factors
-quick
-inexpensive

Question 11

Cohort study is what? Used to do what?

Answer 11

-group selected - exposure status measures - follow up to see who develops disease outcome

-occurrence in exposed vs unexposed

• assess to association between exposure vs outcome

Question 12

Cohort studies are 1) longitudinal and 2) prospective … this means what?

Answer 12

1) tracking people over time
2) Following people forward into the future

Question 13

What are confounding factors?

Answer 13

factors that affect both disease exposure and outcome, and can distort results.

Question 14

Pros (1) and cons(4) of cohort studies.

Answer 14

• we know exposure comes before disease , so stronger evidence for cause/effect relationship vs cross-sectional
  -large numbers needed
  -not feasible for very rare diseases
  -time consuming + expensive due to large no.s + follow up
  -association distorted by confounding factors (same w all observational studies)

Question 15

What’s a case-control study ? Why is it used ?
How is it carried out?

Which group is ‘case’ or ‘control’

Answer 15

• select group of ppl w/ or w/out outcome disease , then previous exposure status found - compared between 2 groups

-used to find association between exposure and outcome

Case = w disease outcome
Control = w/out disease outcome

Question 16

Pros(2) and cons (4) of case control study?

Answer 16

-can’t measure risk or prevalence of disease , and we decide no. In each group
- have to use ‘odds’ ration to assess association
-ideal for rare disease
-less expensive and quicker than cohort - smaller no.s and no follow ups
-potential recall error or bias
-association may be distorted w confounding factors

Question 17

Pros(2) and cons (4) of case control study?

Answer 17

-can’t measure risk or prevalence of disease , and we decide no. In each group
- have to use ‘odds’ ration to assess association
-ideal for rare disease
-less expensive and quicker than cohort - smaller no.s and no follow ups
-potential recall error or bias
-association may be distorted w confounding factors

Question 18

Does systematic review of observational studies eliminate the issue w confounders?

Answer 18

No

Question 19

When and how can we deal w confounders

Answer 19

At analysis stage
-use adjusted analysis
-statistical model ( tells us to what extent confounding factors affected results)

Question 20

What’s an RCT? Used for what ?

Answer 20

-used to find impact of intervention on outcome
-participants recruited - fit criteria - give informed consent
-participants randomised to either intervention or control
-follow up - RCT longitudinal and prospective
-incidence compared in both groups

Question 21

Disadvantage of RCT ethically

Answer 21

Everyone wants/ needs intervention .
Ensure that everyone eventually get intervention , but control get it after study so it doesn’t affect outcome.

Question 22

What’s good about randomisation

Answer 22

Ensures similar baseline characteristics of men in both groups

Question 23

RCT’s have high or low confounders? Why?

Answer 23

Low- due to randomisation

Question 24

1 pro of RCT and 3 cons

Answer 24

• Strongest evidence for cause and effect relationship
• large number sneezed- time and money consuming
  -can’t be used to study exposures that can’t be changed

Question 25

What’s a systematic review of RCTs

Answer 25

All RCTs in topic identified - evaluated and results summarised - like meta analysis

Question 26

Is it better than systematic review for observational studies ? Why?

Answer 26

Yes - confounders minimised w randomisation.