Unit 07: Disease Frequency and Measures of Association (Part 2) Flashcards
Which of the following are measures of association in epidemiology?
A) Prevalence ratio, mortality rate, and relative risk
B) Relative risk, odds ratio, and incidence rate ratio
C) Incidence rate, mean difference, and odds ratio
B
What is the relative risk (RR) in epidemiology?
The ratio of the risk of disease in exposed individuals to the risk in unexposed individuals.
True/False): Relative risk can be calculated directly in cohort studies.
True
How do you interpret a relative risk of 1, greater than 1, and less than 1?
A) 1: No association; >1: Negative association; <1: Positive association
B) 1: No association; >1: Positive association; <1: Negative association
C) 1: Protective effect; >1: No association; <1: Increased risk
B
Why can’t relative risk be calculated directly in case-control studies?
Because case-control studies start with diseased and non-diseased individuals rather than exposed and unexposed populations, making incidence rates unavailable.
In case-control studies, the ____ is used instead of relative risk.
odds ratio
What is absolute risk?
A) The difference in risk between exposed and unexposed individuals
B) The risk of disease in a population
C) The ratio of risks in exposed vs. unexposed individuals
B
In a matched case-control study, a ____ pair occurs when the case and control have the same exposure history.
concordant
A ____ pair occurs when the case and control have different exposure histories.
discordant
In a matched case-control study, which pairs are ignored when calculating the odds ratio?
A) Concordant pairs
B) Discordant pairs
C) Both are used
A
Why are concordant pairs ignored when calculating the odds ratio in matched studies?
Because concordant pairs do not contribute information about differences in exposure between cases and controls.
What does a relative risk of 2 mean?
It means the risk of disease in the exposed group is twice the risk of disease in the non-exposed group.
In case-control studies, the OR is interpreted as the odds of ____ in the ____ group relative to the non-outcome group.
A) disease; exposed
B) exposure; outcome
C) exposure; exposed
B
(True/False): For rare diseases (prevalence <5%), the odds ratio closely approximates the relative risk.
True
(True/False): ORs < 1 are often associated with protective factors such as vaccination or wearing masks.
True
(True/False): IRR measures the ratio of incidence rates between exposed and non-exposed groups.
True
If IRR = 1, it indicates ____ between exposure and the outcome.
no association
Which component is essential for calculating IRR?
A) Relative risk
B) Time at risk
C) Odds ratio
B
(True/False): An exposure with a high measure of association will always have a large impact on disease occurrence in the population
False (if the exposure is rare, its impact on the absolute level of the outcome may be small).
Why might public health practitioners be more interested in risk difference or attributable proportion than relative risk?
Because these measures indicate how much of the disease occurrence could be eliminated by removing a specific exposure, which is more actionable for program planning and priority setting
The ____ measures how much of the total risk of an outcome in the exposed group is due to the exposure of interest.
risk difference (RD)
What does attributable proportion exposed (APe) measure?
A) The ratio of the risk in exposed versus unexposed groups
B) The proportion of disease occurrence in the exposed group attributable to the exposure
C) The incidence rate difference between exposed and unexposed groups
B
(True/False): Risk difference (RD) is calculated for the entire population, not just the exposed group
False (RD is calculated within exposed groups).
____ quantifies how much of the disease risk or incidence can be attributed to a specific exposure.
Attributable risk
What is the primary purpose of calculating attributable risk?
A) To establish causal relationships between exposure and disease
B) To determine how much of the disease risk could be reduced by eliminating the exposure
C) To calculate relative risk
B
What is background risk, and how does it affect disease risk in both exposed and unexposed individuals?
Background risk is the risk of disease that exists regardless of exposure, and it is shared by all individuals, exposed or unexposed.
____ quantifies the proportion of disease incidence in the total population (both exposed and unexposed) that can be attributed to a specific exposure.
Population attributable risk (PAR)
The null value for Risk Difference (RD) is ____ because it measures ____ differences, not ratios.
0, absolute
How is RD interpreted if RD = 0?
If RD = 0, it means the exposure has no differential effect on the outcome, and the risk or rate of the outcome is the same in both exposed and unexposed groups.
What is the difference between RD and measures like Relative Risk (RR) or Odds Ratio (OR)?
A) RD measures ratios, while RR and OR measure absolute differences.
B) RD measures absolute differences, while RR and OR measure ratios.
C) RD uses time at risk, while RR and OR do not.
B
(True/False): RD can be used to calculate both risks and rates depending on the data available.
True
Attributable Proportion (Exposed) expresses the proportion of the ____ (or ____) in the exposed group that is caused by a specific exposure.
risk, rate
How do you interpret an APe of 88.2%?
It means that 88.2% of the outcome in the exposed group is caused by the exposure and could be eliminated if the exposure were removed.
(True/False): Attributable Proportion (Exposed) can be used for both risk and rate data.
True
What is the key difference between RD and APe?
A) RD is a ratio, while APe is an absolute difference.
B) RD measures an absolute difference, while APe measures the proportion of the outcome due to exposure.
C) RD measures the rate, while APe measures risk.
B
Population Attributable Risk (PAR) is analogous to ____ but uses risk or incidence of the outcome in the ____ population.
RD, total
What does Population Attributable Fraction (PAF) measure?
A) The proportion of the population exposed to a risk factor.
B) The proportion of the total population’s outcome that is due to a specific exposure.
C) The rate difference between exposed and non-exposed groups.
B
What is the null value for PAR, and what does it signify?
A) Null value = 1; exposure has no effect.
B) Null value = 0; exposure has no effect.
C) Null value = -1; exposure has a protective effect.
B
PAR expresses the ____ difference in outcome levels between the entire population and the ____ group.
absolute, non-exposed
How does PAR differ from Attributable Proportion (Exposed)?
PAR measures the impact of exposure on the entire population, while APe focuses only on the exposed group.
PAF helps quantify the potential ____ in disease occurrence in the ____ population if an exposure is eliminated.
reduction, total
Measures of ____ (e.g., RR, OR, IRR) express the magnitude or ____ of the relationship between an exposure and an outcome.
association, strength
Measures of ____ (e.g., RD, APe, PAR, PAF) determine the amount of ____ in exposed groups or the total population caused by the exposure of interest.
effect, outcome
Which measure would you use to determine the proportion of disease in an exposed group that is caused by the exposure?
A) Population Attributable Risk (PAR)
B) Attributable Proportion (Exposed) (APe)
C) Relative Risk (RR)
B
(True/False): Measures of association, like RR and OR, are important for determining causation, while measures of effect are more practical for public health and clinical decision-making.
True
