Podcast
Questions and Answers
What distinguishes cumulative incidence from incidence rate?
What distinguishes cumulative incidence from incidence rate?
- Incidence rate is used for fixed populations, while cumulative incidence is used for dynamic populations.
- Incidence rate is expressed as a proportion, while cumulative incidence is expressed per person-time.
- Cumulative incidence accounts for loss to follow-up, while incidence rate does not.
- Cumulative incidence is a measure of risk, while incidence rate is a measure of speed. (correct)
Why is person-time used in calculating incidence rate?
Why is person-time used in calculating incidence rate?
- To simplify the calculation of prevalence.
- To exclude individuals who develop the disease early in the study.
- To account for varying lengths of observation for individuals in the study. (correct)
- To standardize cumulative incidence across different populations.
In epidemiology, which scenario would indicate that cumulative incidence might be less accurate than incidence rate?
In epidemiology, which scenario would indicate that cumulative incidence might be less accurate than incidence rate?
- A study where the disease develops rapidly and uniformly across the population.
- A study where the population is dynamic, with individuals entering and leaving over time. (correct)
- A study focusing on a disease with a long latency period.
- A study with a complete follow-up of all participants over a short period.
What is the key difference between point prevalence and period prevalence?
What is the key difference between point prevalence and period prevalence?
What does a high prevalence of a disease indicate, and how does it relate to incidence?
What does a high prevalence of a disease indicate, and how does it relate to incidence?
If a new treatment dramatically increases the survival time of individuals with a disease without preventing new cases, what would be the expected impact on prevalence and incidence?
If a new treatment dramatically increases the survival time of individuals with a disease without preventing new cases, what would be the expected impact on prevalence and incidence?
Which measure is most useful for assessing the potential impact of an infectious disease outbreak in a narrowly defined population over a limited time?
Which measure is most useful for assessing the potential impact of an infectious disease outbreak in a narrowly defined population over a limited time?
Why might the cumulative incidence be misleading when studying a disease with a long incubation period and significant in-migration to the study area?
Why might the cumulative incidence be misleading when studying a disease with a long incubation period and significant in-migration to the study area?
How does calculating Years of Potential Life Lost (YPLL) contribute to understanding the impact of different diseases on public health?
How does calculating Years of Potential Life Lost (YPLL) contribute to understanding the impact of different diseases on public health?
What is the primary limitation of using proportionate mortality to compare the health status of different populations?
What is the primary limitation of using proportionate mortality to compare the health status of different populations?
What is the critical assumption when calculating incidence rate?
What is the critical assumption when calculating incidence rate?
How does case-fatality rate (CFR) differ from mortality rate?
How does case-fatality rate (CFR) differ from mortality rate?
What do Years of Potential Life Lost (YPLL) measure, and what does it reflect?
What do Years of Potential Life Lost (YPLL) measure, and what does it reflect?
If the crude mortality rate in two populations are the same, but one population is significantly older, what can be inferred about the age-specific mortality rates?
If the crude mortality rate in two populations are the same, but one population is significantly older, what can be inferred about the age-specific mortality rates?
When analyzing mortality trends, what does a disease-specific mortality rate provide that a crude mortality rate does not?
When analyzing mortality trends, what does a disease-specific mortality rate provide that a crude mortality rate does not?
What is the primary use of factor-specific mortality rates in epidemiological studies?
What is the primary use of factor-specific mortality rates in epidemiological studies?
How might a public health agency use infant mortality rate (IMR) data to improve community health?
How might a public health agency use infant mortality rate (IMR) data to improve community health?
When is using cumulative incidence most appropriate?
When is using cumulative incidence most appropriate?
During an epidemic, 200 people in a village of 1,000 got sick with a new illness. What is the attack rate?
During an epidemic, 200 people in a village of 1,000 got sick with a new illness. What is the attack rate?
In a town of 50,000, there are 500 existing cases of diabetes at the start of the year. Over the year, 50 new cases are diagnosed. What is the prevalence of diabetes at the start of the year?
In a town of 50,000, there are 500 existing cases of diabetes at the start of the year. Over the year, 50 new cases are diagnosed. What is the prevalence of diabetes at the start of the year?
A study follows 1000 people for 5 years. 20 people develop a disease. What is the cummulative incidence for the study period?
A study follows 1000 people for 5 years. 20 people develop a disease. What is the cummulative incidence for the study period?
Which measure is useful for assessing the burden of mortality?
Which measure is useful for assessing the burden of mortality?
If better roads lead to an increased incidence of accidents but lower case fatality due to rapid access to better medical help, how will proportionate mortality due to accidents change?
If better roads lead to an increased incidence of accidents but lower case fatality due to rapid access to better medical help, how will proportionate mortality due to accidents change?
A study measures the number of new cases of influenza reported in a city each week over a year. Which epidemiologic measure is being used?
A study measures the number of new cases of influenza reported in a city each week over a year. Which epidemiologic measure is being used?
Flashcards
Incidence
Incidence
The number of new cases of a disease in a population at risk over a period of time.
Cumulative Incidence
Cumulative Incidence
A measure of risk; the probability an individual will develop a disease during a specific time period.
Cumulative Incidence (Incidence Proportion)
Cumulative Incidence (Incidence Proportion)
The proportion of a population that becomes diseased over a specified period of time.
Incidence Rate (Incidence Density)
Incidence Rate (Incidence Density)
Signup and view all the flashcards
Person-Time
Person-Time
Signup and view all the flashcards
Attack Rate
Attack Rate
Signup and view all the flashcards
Prevalence
Prevalence
Signup and view all the flashcards
Point Prevalence
Point Prevalence
Signup and view all the flashcards
Period Prevalence
Period Prevalence
Signup and view all the flashcards
Mortality Rate
Mortality Rate
Signup and view all the flashcards
Crude Mortality Rate
Crude Mortality Rate
Signup and view all the flashcards
Disease-Specific Mortality Rate
Disease-Specific Mortality Rate
Signup and view all the flashcards
Factor-Specific Mortality Rate
Factor-Specific Mortality Rate
Signup and view all the flashcards
Infant Mortality Rate
Infant Mortality Rate
Signup and view all the flashcards
Case-Fatality Rate (CFR)
Case-Fatality Rate (CFR)
Signup and view all the flashcards
Proportionate Mortality
Proportionate Mortality
Signup and view all the flashcards
Years of Potential Life Lost (YPLL)
Years of Potential Life Lost (YPLL)
Signup and view all the flashcards
Study Notes
- Morbidity and Mortality are the focus of the lecture.
- The goal is to compare rates of incidence, cumulative incidence, and prevalence.
- Calculating incidence rate and explaining person time is covered.
- Calculating prevalence and attack rate are key points.
- Comparing and calculating measures of mortality is a key focus.
- Analyzing the measures of morbidity and mortality on epidemiology reports is taught.
Measures of Morbidity
- Incidence is the number of new cases of disease in a population at risk over a period of time.
- Cumulative incidence is a type of incidence.
- Incidence rate is a type of incidence.
- Prevalence is the measure of persons in a population who have a particular disease at a specified point in time or over a specified period of time.
- Point prevalence is an example of prevalence.
- Period prevalence is an example of prevalence.
Incidence
- Incidence is the number of new cases of disease in a population at risk over a period of time.
- Two types of incidence measures exist.
- Calculating cumulative Incidence is: No. of new cases of disease occurring during a specified time period/ No. of persons at risk of developing the disease during that time period
- Cumulative incidence is a measure of risk; how probable is it that an individual will develop a disease during a period of time?
- Population at risk is calculated using the size of the population at the start, average, or middle of the time period.
- A critical assumption is that the population at risk is a "fixed population" where all individuals are followed for the entire time period.
- Problems include: competing risks, loss to follow-up, and in/out migration.
Incidence Rate
- Incidence rate is the number of new cases of a disease that occur in a population at risk per person-time of observation.
- Incidence rate = # of new cases of diseases/ person-time of observation in the population at risk of developing the disease
- Person-time units is a more exact expression of the population at risk during the period of time when the change from non-disease to disease is being measured.
- An estimate of the actual time-at-risk in years, months, or days that persons at risk contributed.
- A critical assumption concerning the incidence rate is that it is constant over different periods of time.
- The following are equivalent: 1 person at risk observed for 1 year = 1 person-year, 1 person at risk observed for 5 years = 5 person-years, 5 persons at risk observed for 1 year = 5 person-years
Attack Rate
- An attack rate is a variant of incidence, applied to a narrowly defined population observed for a limited time, such as during an epidemic.
- Calculating the attack rate is : No. of new cases among the the population during the time period/ population at risk at the beginning of the time period × 100%
Summary of Incidence
- Cumulative incidence is easy to calculate and understand.
- Cumulative incidence is usually reserved for fixed populations.
- Less accurate when "fixed population" assumption is not met.
- Incidence rate is more accurate compared to cumulative incidence.
- Person-time denominator is difficult to calculate.
- Incidence rate is most useful for dynamic populations.
- Less accurate when “constant incidence rate" assumption is not met.
Prevalence
- Prevalence is the measure of persons in a population who have a particular disease at a specified point in time or over a specified period of time.
- Prevalence = number of cases of a disease present in the population during a specific time period/ Total no. of persons in the population during the specific time × 10n
- Point prevalence is the number of people who have a disease at a point in time.
- Period prevalence is the number of people who have a disease at any time during a certain period of time.
- Prevalence = Incidence × Duration of Disease expressed as P = I × D
Measures of Mortality
- Mortality rate expresses the incidence of death in a population during a specific period of time.
- Case-fatality rate represents the proportion of deaths among people with the disease.
- Proportionate mortality rate may be ascribed to a specific cause.
- Years of Potential Life Lost is based on the life lost through premature death, before some arbitrarily determined age.
Mortality Rate types.
- Crude mortality rate is also referred to as the overall or all-cause mortality rate.
- Disease- or cause-specific mortality rate measures deaths from a certain disease in a population during a specific period.
- Factor-specific mortality rate measures deaths in a population restricted by a factor during a specific time period.
- Calculating mortality rate is : No. of deaths occurring in a population during a period of time/ Total population at risk during that period of time × 10n.
- Calculating Crude mortality rate is: No. of all deaths occurring in a population during a period of time/ Total population at risk during that period of time × 10n.
- Disease-special mortality rate=Total no. of deaths from Disease X occurring in /a population during a period of time/ Total population at risk during that period of time * 10^n
- Factor rate = Total no. of deaths occurring in a population with Factor X during a period of time/ Total population with Factor/ During that period of time * 10^n
- Infant Mortality Rate measures mortality rate in children during the first year of life.
- Total no. of deaths of infants <1 year during a period of time / Number of live births during that period of time * 10^n
- A case-fatality rate represents the proportion of deaths among people with the disease and is expressed as a percent.
- Total no. of deaths due to a disease during a period of time after disease onset or diagnosis/ No.of persons with the diseases * 100
- Proportionate mortality is the proportion of the overall mortality that may be ascribed to a specific cause. No. of deaths due to a specific disease during a period of time / Total no.of deaths during that period of time * 100
- Years of Potential Life Lost (YPLL) is based on the life lost through premature death, before some arbitrarily determined age.
- Reflects both the number of individuals who die of a particular cause and the age at which death occurred.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
