Lecture 5 - Measuring Disease Frequency: Prevalence and Incidence Flashcards
Define prevalence
The proportion of the group of people who have the disease in question at this point in time
*existing cases…they are existing cases (present in the population at a specific point in time)
What are the ideal study design for measuring prevalence?
- Cross sectional study
- Random sample (w/ descriptive analysis)
Define incidence
The proportion of the group, initially free of the disease, that develops it over the year
What does incidence measure?
The rate at which news cases develop over a period of time
What does incidence also measure?
Absolute Risk
What are the best study designs to measure incidence?
- RCT
- Cohort studies
What is prevalence proportional to?
Incidence x Duration
What are factors that influence prevalence?
- Change in incidence (primary prevention strategies)
- Change in disease duration (secondary prevention strategies)
- Selective migration
What does mortality rate express?
Incidence of death in a specific population during a specific period of time
What is crude rate?
[Number of deaths in a specific year] / [number of individuals in the population at midyear]
What is cause-specific rate?
[Number of deaths by a specific cause in a specified year] / [number of individuals in the population at midyear]
What is attack rate?
[Number (No.) of new cases] / [Population ‘at risk’]
What is case-fatality?
[Number of deaths from specific disease] / [Number of cases of the disease during the same time period]
What is proportionate mortality rate (PMR)?
[Number of deaths from a specific cause] / [Total deaths in same period]
