Measures of Impact

Question 1

What are 2 ways to describe the frequency of disease in a population?

Answer 1

• incidence: rate, risk, CI

- prevalence: proportion

Question 2

Frequency numerically describes ______

Answer 2

The movement of well to ill/force of disease (incidence)

Question 3

Prevalence

Answer 3

The commonness of disease at a time point/window

Question 4

________ describes those factors/exposures related to disease

Answer 4

Measures of association

Question 5

Cohort study - summary

Answer 5

Monitor a cohort exposed to a factor, and another unexposed

• risk of disease in each cohort is calculated
• RR: numerical multiplier of risk in exposed, compared to unexposed

Question 6

Case-control study - summary

Answer 6

One group of cases, the other non-cases

• odds of exposure to punitiive risk factors is calculated for cases and non-cases
• OR: numerical multiplier of odds that expressed association between cases and exposure

Question 7

_____ is an estimate of RR

Answer 7

OR

- interpreted the same, represent the same exposure, disease relationships

Question 8

Measures of impact

Answer 8

Describe the impact of exposures/disease at the population level

Question 9

RR is reflective of the _____

Answer 9

Whole population

Question 10

If you contain exposure, then you will _______

Answer 10

Reduce the amount of disease

- there will still be some incidence of disease without exposure

Question 11

What happens if you decrease the % exposure?

Answer 11

Many fewer exposed

• much less D+
• changed number of cases and distribution of cases
• occurs even if relative risk remains the same!!

Question 12

If you have a high number of unexposed, then decreasing the %exposed would ______

Answer 12

Not reduce the incidence of disease!

- there may be another exposure that is causing disease

Question 13

How is RR misleading at the population level?

Answer 13

• most disease is not related to exposure
• there is “baseline” disease occurence in E-, and disease is not reliant on a single type of exposure (multifactorial disease)
• still, those who are exposed carry a much higher risk of disease

Question 14

Why do we still use RR?

Answer 14

The relative exposure: disease relationship tends to hold at this level, regardless of baseline risk variation
- no matter what the disease incidence in the E- group is, the RR does not change!!

Question 15

What are 4 measures that compliment the RR and describe disease at the population level?

Answer 15

• attributable risk (exposed, aka risk difference)
• population attributable risk
• attributable fraction (exposed)
• population attributable fraction

Question 16

Attributable risk

Answer 16

Difference in risk (incidence) between exposed and unexposed groups

• ____ cases per 100 animals
• a/(a+b) - c/(c+d)
• expresses increased incidence of disease, over the baseline, in exposed animals

Question 17

AR directly applies to _____

Answer 17

Exposed animals only

• for every 100 animals exposed, expect an additional ____ cases
• over baseline

Question 18

Population attributable risk

Answer 18

Difference in risk (incidence) between the total population and unexposed group

• (D+/N) / (D+/E-) minus D+/E-
• ___ cases per 100 animals in the population
• expresses amount of disease in the total population attributable to exposure —> if exposure were eliminated, ___% of population would not be affected with D+

Question 19

PAR applies directly to _____

Answer 19

Population

• in ______ animals, ___ cases could be eliminated if you eliminate exposure
• if you eliminate exposure, everybody is at the same risk of disease as the E-

Question 20

Attributable proportion

Answer 20

Proportion of incidence in exposed that is attributed to the exposure

• what fraction (%) of disease in the exposed is really due to exposure?
• (RR-1)/RR
• among exposed, ___% of D+ is due to exposure

Question 21

Disease in E+ =

Answer 21

Baseline + disease associated with exposure

Question 22

Population attributable proportion

Answer 22

Proportion of incidence in population attributed to exposure

• what fraction (%) of disease in the population is due to exposure?
• the disease incidence that would be eliminated if the E+ group had incidence equal to the E- group
• (incidence in population - incidence in E-)/incidence in population
• ____% of disease in the population can be eliminated if you eliminate E+

Question 23

AR - summary

Answer 23

Expresses the increased incidence of disease, over the baseline, in exposed animals
- exposed

Question 24

PAR - summary

Answer 24

Expresses the amount of disease in the total population attributable to exposure
- total population

Question 25

AP - summary

Answer 25

Proportion of disease in exposed attributed to exposure

- exposed

Question 26

PAF - summary

Answer 26

Fraction (10%) of disease in the population due to exposure

- population