Ppe Epidemiology--Common Calculations

Front 1

Define Prevalence

Back 1

The number of people affected by a disease in a given population at a specific time. It includes both old and new cases.

Front 2

Prevalence equation per 1000 ppl

Back 2

(# cases in populace at a point in time/#of people in population) x 1000

Front 3

Point Prevalence

Back 3

Prevalence of a disease at a given point in time. Often referred to as "prevelance".

Front 4

Period Prevalence

Back 4

Prevalence of a disease in a given period of time

Front 5

Incidence

Back 5

# of new cases of a disease that occur in a given period of time in a given population. This is a measure of risk

Front 6

Incidence per 1000 ppl

Back 6

(# new cases in an at risk population /#of people in at risk population) x 1000

Front 7

What is another way to calculate prevalence

Back 7

Prevalence = Incidence x Duration
Only if rates are not changing and in-migration equals out-migration.

Front 8

In age restricted mortality, where is age accounted for in the equation?

Back 8

In the numerator and denominator.

Front 9

Relative Risk Equation

Back 9

Relative Risk = Risk in exposed/Risk in unexposed

Front 10

What ratio can be used with either kind of observational study?

Back 10

Odds ratio= odds a case was exposed/odds a control was exposed (--case study)

Odds ratio = odds an exposed person develops disease/odds an unexposed person develops disease (--cohort study)

Front 11

Why can't relative risk be calculated in case-control studies?

Back 11

Because we don't have values for incidence in exposed and unexposed populations.