Chapter 12 and 13- Estimating risk- is there an association

Question 1

Risk

Answer 1

Risk represents the incidence of a disease/outcome. Prevalence cannot be used to estimate risk because it also reflects disease duration. Since we can never observe an individual’s potential outcomes – we use risks from a population as a proxy to estimate what outcomes would have been under a different exposure

Question 2

Absolute risk

Answer 2

The incidence of a disease in a population. It can indicate the magnitude of the risk in a group of people with a certain exposure, but does not take into account the risk of disease in unexposed individuals. It also does not indicate whether the exposure is associated with an increased risk of disease

Question 3

Relative risk

Answer 3

The ratio of the risk of disease in exposed individuals to the risk of disease in unexposed individuals, or the probability of the event occurring in exposed and unexposed people

Question 4

RR= 1

Answer 4

Risk in the exposed population is equal to risk in the unexposed population. There is no association

Question 5

RR is greater than 1

Answer 5

Risk in the exposed population is greater than the risk in the unexposed population

Question 6

RR is less than 1

Answer 6

Risk in the exposed population is less than risk in the unexposed

Question 7

Risk in cohort studies

Answer 7

Risk can be calculated directly

Question 8

What information does risk difference give us?

Answer 8

Tells us about impact in a population if we were able to prevent an exposure. More direct way to understand how many people in the population will benefit.

Question 9

What information does the risk ratio give us?

Answer 9

Tells us about the strength of the exposure on the outcome. More direct way to understand the likelihood of disease among exposed vs. unexposed. The RR is X times the risk

Question 10

Odds ratio

Answer 10

To calculate relative risk, we must have values for the incidence of the disease in the exposed and the incidence in the unexposed in a cohort study. However, in a case control study, we don’t know the incidence in the exposed population or the incidence in the unexposed population because we start with diseased people (cases) and controls. Therefore, RR can’t be calculated directly. The OR is the odds that the disease will develop in an exposed person

Question 11

Odds ratio in a cohort study

Answer 11

The ratio of the odds of developing disease in exposed people to the odds of developing disease in unexposed people

Question 12

When does the OR ≈ RR? (3)

Answer 12

1. When our cases are representative of the exposure odds of persons with disease,
2. When our controls are representative of the exposure odds of persons without disease, AND
3. When our disease is rare

Question 13

Expressing the odds ratio

Answer 13

The answer is X times the odds

Question 14

Attributable risk

Answer 14

Disease risk among exposed persons that is attributable to a specific exposure. How much disease can we prevent among exposed persons by eliminating the exposure?

Question 15

Population attributable risk

Answer 15

Disease risk among the total population that can be attributed to a specific exposure. How much disease can we prevent in the total population by eliminating the exposure?

Question 16

Population Attributable Risk Proportion

Answer 16

Proportion of disease risk among the total population that can be attributed to a specific exposure