Epidemiologic Measures of Association and Effect

Question 1

Absolute Risk

Answer 1

Incidence
– New disease events (or cases)
– Candidate population
• Population of people who are at risk of getting the
disease
– Specified time period

Question 2

name two types of incidence

Answer 2

cumulative incidence

incidence density

Question 3

cumulative incidence

Answer 3

– New cases (numerator)
– Population at risk (denominator)
– A.k.a. incidence proportion

Question 4

incidence density

Answer 4

New cases (numerator)
– Person-time at risk (denominator)
– A.k.a. incidence rate

Question 5

incidence ratio

Answer 5

-is a measure of association
• Risk ratio or relative risk
– Ratio of two cumulative incidences (CI)
•
𝐶𝐼𝑒/𝐶𝐼𝑛𝑒
• Rate ratio
– Ratio of two incidence rates (IR)
•
𝐼𝑅𝑒/𝐼𝑅𝑛E

Question 6

risk ratio

Answer 6

aka relative risk
– Ratio of two cumulative incidences (CI)
•
𝐶𝐼𝑒/𝐶𝐼𝑛E

Question 7

what is rate ratio?

Answer 7

– Ratio of two incidence rates (IR)
•
𝐼𝑅𝑒/𝐼𝑅𝑛E

Question 8

what is another name for incidence rate?

Answer 8

incidence density

Question 9

when would you use an Odds ratio for disease of exposed vs non-exposed?

Answer 9

– In a longitudinal study (cohort, clinical trials)
• Odds of disease among exposed
• Odds of disease among non-exposed
• A.k.a. disease-odds ratio

Question 10

describe the 2x2 table to calculate odds ratio

Answer 10

top (horizontal): Outcome (disease)

side (vertical): exposure

Question 11

formula to calculate Odds ratio?

Answer 11

(ad) / (bc)

Question 12

what does a RR or OR of 1 mean?

Answer 12

no association

Question 13

RR or OR > 1

Answer 13

positive association

Question 14

• RR or OR < 1

Answer 14

negative association. maybe a protective factor

Question 15

when is Odds Ratio a good estimate of RR?

Answer 15

the event (disease or outcome) is rare
• (a+c) is small
– a is small compared to b
– c is small compared to d