Populations Over Time

Question 1

Incidence?

Answer 1

Measure of new cases of a condition in some given time perios

Question 2

Prevalence equation?

Answer 2

Incidence x disease duration

Question 3

Incidence risk/cumulative/crude incidence?

Answer 3

Number of new events in a population/ average number of person at risk during this period

Question 4

Strengths and weaknesses of cohort study?

Answer 4

Strengths:

1. More than one disease releated to single exposure
2. Rare exposure
3. Can calculate incidence and relative risk
4. Offer some evidence of cause-effect relationship

Weaknesses:

1. Loss to follow up
2. Require large sample
3. Data availability and quality may be poor
4. Long time to complete and expensive
5. Vulnerable to confounding

Question 5

Confounding?

Answer 5

A variable that influences both exposure and disease and so causes association

Question 6

Strength of association?

Answer 6

RR of 1.5- risk of outcome 50% higher in exposed than unexposed

RR of 3- x3 high than exposed

RR of 0.8 risk of outcome 20% lower in exposed than unexposed

Question 7

Relative risk?

Answer 7

Risk of developing disease in an exposed group compared to developing a disease in unexposed group

Question 8

Direction of association?

Answer 8

Under 1- protective

Over 1- risk factor

Question 9

How is a cohort study more protected from confounding?

Answer 9

Establishes temporal precedence (ie independent variable happens before outcome