1- Measures of frequency

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What does prevalence measure in a population?

The total number of people in the population

The number of people with a disease at a specific time (correct)

The specific cause of the disease

The burden of disease in a population

Why is prevalence NOT useful for determining what caused a disease?

Prevalence only tells us how many are affected but not why or how (correct)

Prevalence is directly linked to the total population size

Prevalence focuses on specific events like birth and death

Prevalence is calculated at a specific point in time

What is point prevalence?

The lifetime risk of having a certain disease

The proportion of persons with a particular disease on a specific date/time (correct)

The proportion of events like birth and death in a population

The total number of people in the population at any given 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 Signup and view all the answers

What information does prevalence provide for planning health services?

Burden of diseases in a population Signup and view all the answers

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 Signup and view all the answers

What is the key focus when assessing incidence in a population?

Measuring the probability of developing the disease over time Signup and view all the answers

Why are individuals with immunity or those who lack susceptibility not included in incidence calculations?

To avoid underestimating the risk in the population Signup and view all the answers

What distinguishes Incidence Rate from Cumulative Risk in measuring new disease cases?

How they account for different time periods Signup and view all the answers

Why is Cumulative Risk not valid when a large number of people leave your study?

It distorts the actual incidence proportion Signup and view all the answers

What is the main issue with loss to follow-up in a study?

Different dropout rates between study groups Signup and view all the answers

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 Signup and view all the answers

What is the incidence rate?

The rate at which people come down with a disease Signup and view all the answers

How is incidence rate calculated?

Number of cases divided by the total person-time at risk Signup and view all the answers

What does incidence rate help address in studies where incidence proportion may be limited?

Both A and c Signup and view all the answers

When is risk considered less valid as a measure of disease frequency?

With longer follow-up periods and high loss to follow-up Signup and view all the answers

What is the concept behind person-time in calculating incidence rates?

The total amount of time each person spends in the study Signup and view all the answers

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 Signup and view all the answers

What does the incidence rate measure?

The rate at which new cases occur per unit of person-time Signup and view all the answers

What does hazard rate refer to in epidemiology?

The likelihood of developing a disease after exposure to a risk factor Signup and view all the answers

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 Signup and view all the answers

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. Signup and view all the answers

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. Signup and view all the answers

Which of the following accurately describes the calculation of Incidence Rate (IR)?

It involves a complex person-time denominator calculation to determine new cases. Signup and view all the answers

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. Signup and view all the answers

What does Mortality Rate measure?

Number of deaths divided by the total population during a specified time period Signup and view all the answers

Which of the following defines Morbidity Rate?

Incidence of non-fatal cases of a disease in a population during a specified time period Signup and view all the answers

Which term refers to the proportion of those exposed that develop the disease?

Attack Rate Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

Which of the following is NOT one of Hill’s criteria for establishing causality?

Mortality rate measurement Signup and view all the answers

Why is it important for exposure to precede the disease when considering temporality in epidemiology?

To establish a causal relationship between exposure and disease Signup and view all the answers

Which of the following is NOT a component of Hill’s criteria for establishing causality?

Temporal consistency Signup and view all the answers

What is the significance of a stronger association in epidemiology?

It suggests a causal relationship Signup and view all the answers

In epidemiology, what does the dose-response relationship suggest?

Higher exposure amounts are linked to higher disease risk Signup and view all the answers

Why is replicating findings in multiple studies important in epidemiology?

To demonstrate consistency and increase the likelihood of causality Signup and view all the answers

What role does biologic plausibility play in epidemiological studies?

It ensures that proposed mechanisms align with current biological knowledge Signup and view all the answers

How does the strength of association relate to the explanation of weaker associations?

They are typically explained by bias or confounding Signup and view all the answers

What does a measure of association quantify in epidemiology?

The relationship between exposure and disease Signup and view all the answers

Which scale tells us the relative increase or decrease in effect comparing one quantity to another?

Relative scale Signup and view all the answers

Which measure is not commonly used in epidemiology but is important to understand conceptually?

Prevalence ratio Signup and view all the answers

What does Prevalence Ratio calculate for each exposure group?

Prevalence Signup and view all the answers

Which measure tells us the absolute increase or decrease in effect?

Absolute scale Signup and view all the answers

What does the Risk Ratio (RR) measure?

Disease risk in exposed and unexposed groups Signup and view all the answers

What does the Incidence Rate Ratio (IRR) compare?

Risk of disease in exposed vs unexposed groups Signup and view all the answers

What is the range of values for the Risk Ratio (RR)?

0 to +∞ Signup and view all the answers

How are populations divided when calculating Risk Ratio (RR)?

Exposed and unexposed to a particular factor Signup and view all the answers

What is the key characteristic of the Incidence Rate Ratio (IRR)?

It compares the incidence rates for two groups Signup and view all the answers

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 Signup and view all the answers

Which measure of association has a range from -∞ to +∞?

Incidence Rate Difference (IRD) Signup and view all the answers

Why is it not possible to calculate rate and prevalence measures from the given 2x2 table data?

No person-time information available Signup and view all the answers

What does the Incidence Rate Difference (IRD) measure?

Additional risk among those exposed compared to those unexposed Signup and view all the answers

What does the Absolute Scale Risk Difference (RD) quantify?