Chapter 3: Chapter 3: Epidemiologic Measurements Used to Describe Disease Occurrence

Prevelance

all existing cases, determine how bad disease is (burden of disease and frequency of exposure)

Point prevalence

proportion of the pop. that is diseased (with a specific characteristic) at a single point in time, snapshot at given point in time

Period prevalence

proportion of pop that is diseased (with a characteristic) during a specified period of time

Incidence

number of new cases of a disease that develop in a population at risk over a specified time period

Incidence rate

Number of new cases over a period of time

total population at risk during same time period

Cumulative incidence

use for a FIXED POPULATION (number of people at risk/denominator is unchanging)

Number of new cases over a period of time

total population at risk during same period

Incidence density

use for a DYNAMIC POPULATION (population at risk is varied over time)

Number of new cases over a period of time

total person time of observation

Person time

the amount of time each individual at risk is observed over the course of the study

Specific rates of mortality

focus on specific sub group of population (ex. race/age/cause of death or illness)

crude mortality

total number of deaths from all causes in a population

prevalence is proportional to…

incidence rate x duration

attack rate

large proportion of population contracts disease rapidly - often used for food borne illnesses