Incidence and Prevalence Flashcards
What are the 2 measures of dis-ease occurrence?
- incidence
- prevalence
What is incidence?
no. of dis-ease events that occur over period of time?
Incidence exposure equation
EGO = a / EG (/T)
Incidence comparison equation
CGO = b / CG (/T)
What is prevalence measure?
no. of people with dis-ease at one point in time
(T=1)
Prevalence exposure equation
EGO = (a / EG) / 1
Prevalence comparison equation
CGO = (b / CG) / 1
Is time a required factor for incidence or prevalence measures?
Incidence measures
no dis-ease > having dis-ease
occurence/event
Incidence or prevalence when easy to observe when dis-ease occurs
measure incidence
- (death, road crash)
Incidence or prevalence if hard to observe dis-ease occurrence
measure prevalence
- (obesity, diabetes, psych disease)
What incidence rain drops represent?
rain drop = person having dis-ease event during specified time period
When do you count how much is in the ‘prevalence pool’
incidence drizzle
- too difficult to measure individual data
What is numerical data described in?
numbers
- ie: heart rate
What is categorical data described in?
categories (yes/no)
- ie: death
What involves counting categorical (yes/no) dis-ease EVENTS?
Incidence
- ONLY categorical outcomes
What involves counting categorical dis-ease EVENTS or measuring numerical dis-ease STATES?
Prevalence
- both categorical or numerical
Cross-section study
Exposure(s) and outcome measured at one point in time
Is a cross-section study incidence or prevalence?
Prevalence
How to measure incidence/prevalence in cohort study?
- any point during study
- at beginning
Cohort vs cross-section study?
identical structure…
- Cohort = exposures measured longitudinally
- Cross = exposures/outcomes measured at same time
What determines dis-ease incidence?
numerator = no. of rain drops falling over period of time
Incidence depends only on no. of events that fall during specified time period.
What determines dis-ease prevalence?
numerator = amount of dis-ease in prevalence pool at point in time
prevalence = how much drizzle (incidence) in pool AND leakage (death) or evaporate (cured)
