Aetiology and Risk Factors for CVD

Question 1

What is a descriptive research question?

Answer 1

A question which will give a descriptive answer e.g. how common is CHD?

Question 2

What is an analytical research question?

Answer 2

A question which looks at cause and effect e.g. do lipid-lowering meds decrease the risk of CHD?

Question 3

What are observational studies?

Answer 3

case series, ecological, cross sectional, case control, cohort

Question 4

What are interventional studies?

Answer 4

clinical trials

Question 5

Which study designs are descriptive?

Answer 5

Case series, ecological, cross sectional

Question 6

Which study designs are analytical?

Answer 6

Case control, cohort, clinical trial

Question 7

What is a longitudinal study?

Answer 7

involves follow up - information progressively collected over multiple encounters

Question 8

Which study designs are longitudinal?

Answer 8

Cohort and clinical trials

Question 9

What is prevalence?

Answer 9

The number of existing cases of a disease or a risk factor at one point in time - it is expressed as a proportion or a percentage

Question 10

What is incidence?

Answer 10

The number of new cases of a disease or a risk factor over a period of time - can only be drawn from a longitudinal study - expressed as a rate (involves time)

Question 11

What is risk?

Answer 11

The number of new cases over a defined period divided by the population at risk ???

Question 12

What is rate?

Answer 12

The number of people who develop a new case divide by total person-time of follow up

Question 13

What is person-time?

Answer 13

The total number of time of all the people who followed up - e.g. if there were 10 people in a study for 12 months the person-time would be 120 months if everyone was there for the whole time but due to staggered recruitments and drop outs it would be something more like 88 months

Question 14

What is hazard?

Answer 14

A rate that is updated as the longitudinal study progresses - it is an instantaneous rate

Question 15

What is an absolute risk/rate?

Answer 15

An isolated measure of risk/rate that does not indicate association with exposure e.g. 5 strokes/10000 men per year

Question 16

What is a relative risk?

Answer 16

A ratio of risk/rate among the exposed (Re) compared to the risk/rate among the unexposed (Ru). Indicates the relative magnitude of change. Also called risk/rate ratio.

Question 17

How is relative risk calculated?

Answer 17

RR = Re/Ru. e.g. 10/1000p-yr over 5/1000p-yr = 2

Question 18

What does a relative risk of 2 indicate?

Answer 18

That exposure means you are twice as likely to get the disease

Question 19

What is attributable risk?

Answer 19

A measure which indicates the absolute magnitude of change of the risk/rate between the exposed and the unexposed. Also called risk/rate difference

Question 20

How is attributable risk calculated?

Answer 20

AR = Re - Ru e.g. 10/1000p-yr minus 5/1000p-yr = 5/1000p-yr

Question 21

What is attributable risk percent?

Answer 21

Proportion of incident disease among exposed people that is due to exposure

Question 22

How is attributable risk percent calculated?

Answer 22

Divide attributable risk by the number of exposed and multiply by 100

Question 23

What does an attributable risk percent of 50% mean?

Answer 23

That 50% of the disease in the exposed is due to exposure

Question 24

What is population attributable risk?

Answer 24

The excess risk/rate of the outcome in the population due to exposure

Question 25

How is population attributable risk calculated?

Answer 25

PAR = Rt - Ru (where Rt is the risk/rate in the whole population and Ru is the risk/rate in the unexposed e.g. 8/100p-yr minus 5/100p-yr is a PAR of 3/100p-yr

Question 26

What is population attributable risk percent?

Answer 26

The proportion of incidence of disease in the whole population that is actually due to exposure

Question 27

What does a PAR% of 40% mean?

Answer 27

That 40% of the incident disease in the population is due to exposure - and if exposure was removed there would be 40% less incidence of that disease in the population

Question 28

What are the Bradford Hill Criteria for Causality?

Answer 28

• temporal relationship
  
  • strength
  • dose-response relationship
  • consistency
  • plausibility
  • exclude alternatives
  • experimental evidence
  • specificity
  • coherence