Name a few factors that can increase or
or decrease the prevalence
• Immigration and emigration
What does incidence measure?
incidence is a measures the risk of developing a disease
The number of new cases of a disease occurring in the population during a specific period of time divided by the number of persons at risk for developing the disease in the population
Name a few uses of Epidemiology
describe impact of disease on a population
describe natural history of disease
Causes of disease
Assess quality of diagnostic and screening tests
select an appropriate and effective intervention strategy
evaluate effectiveness of intervention and prevention programs
evaluate effectiveness of health services
evaluate disease screening programs
ormulation and evaluation of health policy
What element must be included when calculating incidence so that it will be a measure of risk
We must specify a period of time and have all of the individuals in the denominator followed up for that entire period
Define incidence rate
The rate at which new events occur in a population.The numerator is the number of new events that occur in a defined period or other physical span. The denominator is the population at risk of experiencing the event during this period, sometimes expressed as person-time; it may instead be in other units, such as passenger-miles.
When calculating incidence, what does the denominator represent?
The denominator represents the number of people who are at risk for developing the disease
Define incidence rate ratio
The incidence rate in the exposed group divided by the incidence rate in the unexposed group. Often referred to as the rate ratio.
Epidemiology is the study of how disease is distributed in
populations and of the factors that influence or determine this
Incidence per 1,000＝
# of new cases of a disease occurring in the
population during a specific period of time
I =-------------------------------------------------------------- *1000
# of persons at risk of developing the disease
during that period of time