Measures of Disease Occurrence Flashcards
Study Population
Subjects in the study
Usually a ‘sample’ from a source population
Source Population
Population from which the subjects were drawn
Target Population
Population to which we may want to generalize our results
What are the most common types of measures in epidemiology?
Counts
Proportions
Ratios
Rates
Proportion
The count of animals with the disease as a fraction of the total animals that could be diseased
Prevalence
the most commonly-used proportion in epidemiology
Ratios
A measure of the frequency with which an event occurs in a defined population over a specified period of time
A fraction in which the numerator is not part of the denominator
What are the commonly used rates in epidemiology?
Cumulative incidence
Incidence rate/density
What are the types of Prevalence?
Point prevalence
Period prevalence
What are the types of incidence?
Cumulative incidence
Incidence rate
Attack rate
a specific type of cumulative incidence
Prevalence
the proportion of the study population that is diseased at any one time
Point Prevalence definition
The proportion of the study population that is diseased at a single point in time
What is the most common measure of prevalence?
Point Prevalence
Period Prevalence definition
the proportion of the study population that is disease during specified period of time
Incidence
the number of new cases of disease that occur in the study population over time
The rate of occurrence of new diseases in that study population
Cumulative incidence
the proportion of disease free (susceptible) individuals in the study population who became diseased during a specified period of time
Assumption with cumulative incidence
all individuals in that study population are at risk of getting the disease (or other outcome) of interest
Every individual in the study population is assessed at the start study, to identify and remove existing cases
The entire population at risk must be followed from the start of the study until the end
Attack Rate
a specific type of cumulative incidence
cumulative incidence during an outbreak
Incidence rate
instantaneous rate of occurrence of new cases of disease among non-diseased animals in the population
Expressed as the number of cases per animal-time at risk
Disease risk
the probability of becoming diseased
at risk
an individual is not diseased and is capable of becoming diseased
Risk Factors
factors that increase the probability of becoming diseased
Exposure to a risk factor
an individual has come in contact with a risk factor or has the risk factor (while not diseased)
Mortality rate
the incidence of death in a given time period
Case Fatality rate
The number of cases of a specific disease that are fatal, within a specified time following disease onset or diagnosis
