60 Questions
What does prevalence measure in a population?
The number of people with a disease at a specific time
Why is prevalence NOT useful for determining what caused a disease?
Prevalence only tells us how many are affected but not why or how
What is point prevalence?
The proportion of persons with a particular disease on a specific date/time
Which of the following is a characteristic of period prevalence?
is the proportion of a population that has the disease during a given time period of interest
What information does prevalence provide for planning health services?
Burden of diseases in a population
Which group should be excluded from the denominator when calculating incidence?
People who already have the disease and People who are immune to the disease
What is the key focus when assessing incidence in a population?
Measuring the probability of developing the disease over time
Why are individuals with immunity or those who lack susceptibility not included in incidence calculations?
To avoid underestimating the risk in the population
What distinguishes Incidence Rate from Cumulative Risk in measuring new disease cases?
How they account for different time periods
Why is Cumulative Risk not valid when a large number of people leave your study?
It distorts the actual incidence proportion
What is the main issue with loss to follow-up in a study?
Different dropout rates between study groups
In which scenario is risk a more valid measure of disease frequency?
When the follow-up period is short and loss to follow-up is low
What is the incidence rate?
The rate at which people come down with a disease
How is incidence rate calculated?
Number of cases divided by the total person-time at risk
What does incidence rate help address in studies where incidence proportion may be limited?
Both A and c
When is risk considered less valid as a measure of disease frequency?
With longer follow-up periods and high loss to follow-up
What is the concept behind person-time in calculating incidence rates?
The total amount of time each person spends in the study
In practice, why do different people contribute different amounts of person-time in calculating incidence rates?
As a result of different times they are enrolled and develop the disease
What does the incidence rate measure?
The rate at which new cases occur per unit of person-time
What does hazard rate refer to in epidemiology?
The likelihood of developing a disease after exposure to a risk factor
Why are individuals who have already contracted the illness often not considered at risk for developing it again in incidence calculations?
To avoid counting them multiple times and inflating incidence rates
What is a key difference between Cumulative Risk (CR) and Incidence Rate (IR) in measuring new disease cases?
CR is easier to calculate, while IR is more accurate.
When comparing Cumulative Risk (CR) and Incidence Rate (IR), which statement is true?
CR is more useful for fixed populations, while IR is more useful for dynamic populations.
Which of the following accurately describes the calculation of Incidence Rate (IR)?
It involves a complex person-time denominator calculation to determine new cases.
When considering the distinction between Cumulative Risk (CR) and Incidence Rate (IR), which characteristic makes CR less accurate?
It becomes less accurate when its assumptions are not met.
What does Mortality Rate measure?
Number of deaths divided by the total population during a specified time period
Which of the following defines Morbidity Rate?
Incidence of non-fatal cases of a disease in a population during a specified time period
Which term refers to the proportion of those exposed that develop the disease?
Attack Rate
What characterizes the concept of causation in relation to a disease?
An event, condition, or characteristic that precedes the disease and is necessary for its occurrence
When considering the concept of causation in epidemiology, what does it mean when we say cause is viewed probabilistically?
Everyone exposed has a higher risk of developing the disease
Which of the following is NOT one of Hill’s criteria for establishing causality?
Mortality rate measurement
Why is it important for exposure to precede the disease when considering temporality in epidemiology?
To establish a causal relationship between exposure and disease
Which of the following is NOT a component of Hill’s criteria for establishing causality?
Temporal consistency
What is the significance of a stronger association in epidemiology?
It suggests a causal relationship
In epidemiology, what does the dose-response relationship suggest?
Higher exposure amounts are linked to higher disease risk
Why is replicating findings in multiple studies important in epidemiology?
To demonstrate consistency and increase the likelihood of causality
What role does biologic plausibility play in epidemiological studies?
It ensures that proposed mechanisms align with current biological knowledge
How does the strength of association relate to the explanation of weaker associations?
They are typically explained by bias or confounding
What does a measure of association quantify in epidemiology?
The relationship between exposure and disease
Which scale tells us the relative increase or decrease in effect comparing one quantity to another?
Relative scale
Which measure is not commonly used in epidemiology but is important to understand conceptually?
Prevalence ratio
What does Prevalence Ratio calculate for each exposure group?
Prevalence
Which measure tells us the absolute increase or decrease in effect?
Absolute scale
What does the Risk Ratio (RR) measure?
Disease risk in exposed and unexposed groups
What does the Incidence Rate Ratio (IRR) compare?
Risk of disease in exposed vs unexposed groups
What is the range of values for the Risk Ratio (RR)?
0 to +∞
How are populations divided when calculating Risk Ratio (RR)?
Exposed and unexposed to a particular factor
What is the key characteristic of the Incidence Rate Ratio (IRR)?
It compares the incidence rates for two groups
What is the key difference between Risk Difference (RD) and Incidence Rate Difference (IRD)?
RD refers to the additional risk among those exposed, while IRD refers to the difference in incidence rates
Which measure of association has a range from -∞ to +∞?
Incidence Rate Difference (IRD)
Why is it not possible to calculate rate and prevalence measures from the given 2x2 table data?
No person-time information available
What does the Incidence Rate Difference (IRD) measure?
Additional risk among those exposed compared to those unexposed
What does the Absolute Scale Risk Difference (RD) quantify?
Additional risk among those exposed compared to those unexposed
What does a Relative Risk (RR) of 1 indicate?
There is no effect or association between exposure and disease
If the Risk Difference (RD) is 0, what does it imply?
There is no effect or association between exposure and disease
When the Odds Ratio (OR) is greater than 1, what does it suggest?
There is a higher risk in the exposed group
If the Incidence Rate Difference (IRD) is negative, what does it indicate?
There is a decrease in disease incidence among the exposed
What conclusion can be drawn when the Relative Risk (RR) is less than 1?
There is a lower risk in the exposed group
What does the Risk Ratio provide information on?
Strength of association
How does the Risk Difference differ from the Risk Ratio?
One measures strength of association, the other measures public health impact
Learn about the concept of prevalence in epidemiology, which represents the number of people affected by a disease in a population. Understand how prevalence helps in assessing the burden of diseases in a population and planning health services.
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