Chapter 2 Flashcards
(16 cards)
What are the descriptive epidemiological measures used to determine the frequency of outcomes?
Prevalence, risk (including attack rate), odds, and incidence rate
These measures help describe the distribution of an outcome in a population.
How is frequency defined in epidemiology?
The number of occurrences in a defined population over a defined period
This quantification is necessary to study the distribution of a health outcome.
What is a ‘case’ in epidemiological studies?
Individuals with the outcome of interest
A case may occur once, more than once, or frequently depending on the condition.
What methods do epidemiologists use to count cases?
Clinical assessments, diagnostic tests, registry or facility record entries, observation, or self-reporting in population surveys
Accurate case counting is essential for epidemiological research.
Why is knowing the number of cases alone insufficient for comparison?
Without knowing the population size, comparisons between cases in different populations cannot be made
Enumeration of the population at risk is necessary.
Define ‘Population at Risk’.
Individuals who could develop the outcome
For example, if the outcome is pregnancy, only women of child-bearing age are included.
What is the difference between prevalence and incidence?
Prevalence measures existing cases at a defined time point, while incidence measures new cases over a defined period
Both are crucial for understanding health outcomes.
How is prevalence calculated?
Number of existing cases divided by the total number of people at risk at the same time
Prevalence is typically presented as a percentage.
What is cumulative incidence?
Total number of new cases in a defined population at risk during a specified period
It is essential to specify the time period considered.
What does the term ‘odds’ represent?
The probability of becoming a case compared to not becoming a case
Odds can be used to represent incidence in epidemiological studies.
How is the odds ratio calculated?
Odds among cases divided by odds among controls
It provides insight into the likelihood of exposure between cases and controls.
True or False: Odds and risk are interchangeable when an outcome is very common.
False
They tend to be used interchangeably when an outcome is rare.
What is the incidence rate?
Number of new cases divided by the total person-time at risk
It accounts for variation in the time individuals are at risk.
What is person-time at risk?
The time each individual is at risk
It is crucial for calculating incidence rates accurately.
How can person-time at risk be estimated in large studies?
By using the population at risk at the period mid-point multiplied by the total period under consideration
This method is used when exact person-time data is not available.
What relationship exists between prevalence and incidence?
Prevalence indicates how widespread an outcome is and is dependent on both incidence and duration of the outcome
As incidence increases, prevalence also increases.
