35 - Aetiology and Risk Factors for CVD

Question 1

Two broad types of research questions

Answer 1

1) Descriptive (EG: how common is coronary heart disease?)

2) Analytical (EG: does dyslipidaemia increase risk of CHD?)

Question 2

Examples of descriptive studies
1)
2)
3)

Answer 2

1) Case studies, reports
2) Ecological studies
3) Cross-sectional

Question 3

Examples of analytical studies
1)
2)
3)

Answer 3

1) Case-control studies
2) Cohort studies
3) Clinical trials (interventional)

Question 4

Longitudinal vs non-longitudinal studies

Answer 4

Longitudinal studies involve following subjects over time. Non-longitudinal studies only give data on one point in time

Question 5

Examples of non-longitudinal studies 
1)
2)
3)
4)

Answer 5

1) Case-studies
2) Ecological reports
3) Cross-sectional studies
4) Case-control studies

Question 6

Examples of longitudinal studies
1)
2)

Answer 6

1) Cohort studies

2) Clinical trials

Question 7

Prevalence

Answer 7

Number of existing cases of outcome of interest at a point in time in a defined population

Question 8

How is prevalence expressed?

Answer 8

As a proportion or percentage

Question 9

Examples of prevalence
1)
2)
3)

Answer 9

1) Percentage of Australians who smoke
2) Percentage of 65 year-old Australians with coronary heart disease
3) Percentage of these who smoke

Question 10

Incidence

Answer 10

Number of new cases of outcome of interest in a defined population, observed over a defined period

Question 11

How is incidence expressed?

Answer 11

As a proportion

Question 12

Only source of data for calculating incidence

Answer 12

Longitudinal studies

Question 13

Examples of incidence
1)
2)

Answer 13

1) Number of Australians who started smoking in 2014

2) Number of 65 year old males who began smoking in 2014

Question 14

Common measurement of incidence

Answer 14

Number of outcomes of interest/1000 people per year

Question 15

Risk

Answer 15

Probability of disease occurring in a disease-free population during a specified time period

Question 16

How is risk calculated?

Answer 16

N/P
N = number of new cases in a defined period
P = population at risk

Question 17

Issue with risk

Answer 17

P = population at risk assumes that all subjects were measured for equal periods of time.
EG: in 1995, 3 cases of lung cancer developed out of 1000
men; risk = 3/1000 per year.
This assumes that all 1000 men were followed for the entire year, which is not necessarily the case.

Question 18

Rate

Answer 18

Probability of disease occurring in a disease-free population during the sum of the individual follow-up periods

Question 19

Benefits of rate
1)
2)

Answer 19

1) Takes into account different measurement times for subjects.
2) Recruitment of subjects can be staggered. Each subject can have a different baseline time.

Question 20

Hazard
1)
2)
3)

Answer 20

1) Special kind of rate that is continuously updated as a longitudinal study progresses.
2) Is an instantaneous rate - applies to one particular point in time.
3) Derived from longitudinal studies

Question 21

Absolute risk/rate

Answer 21

Isolated measurement of risk/rate.
Says nothing about association with exposure.
EG: 3/1000 myocardial infarcts/year

Question 22

Ways to indicate association

Answer 22

Relative risk and attributable risk

Question 23

Which absolute risk-rate measurements of relative and attributable risks rely on?
1)
2)

Answer 23

1) Risk/rate among exposed

2) Risk/rate among unexposed

Question 24

Synonyms of relative risk

Answer 24

Risk ratio, rate ratio

Question 25

What does relative risk describe?

Answer 25

Relative change in magnitude of risk/rate outcome, associated with exposure

Question 26

How is relative risk calculated?

Answer 26

Rate exposed/Rate unexposed

Question 27

Attributable risk synonyms

Answer 27

Risk difference, rate difference

Question 28

What does attributable risk describe?

Answer 28

Absolute magnitude of change in risk/rate outcome, associated with exposure

Question 29

How is attributable risk calculated?

Answer 29

Rate exposed - rate unexposed

Question 30

Attributable risk percent

Answer 30

(Rate exposed - rate unexposed / rate exposed) x 100

Gives percentage of incident disease among exposed that can be attributed to exposure.

Question 31

Rt

Answer 31

Incidence in total population

Question 32

Population attributable risk

Answer 32

Rt (incidence in whole population) - Ru (unexposed)

Gives excess risk of the outcome in the population due to exposure

Question 33

Population attributable risk percent

Answer 33

(Rt-Ru/Ru)x100

Proportion of incident disease among whole population that is due to exposure.

Question 34

Synonym of population attributable risk

Answer 34

Preventable fraction