Epidemiology MidTerm

# of new cases in a time period/# ppl at risk in the time period

# new cases over a specified time period /# ppl at risk at the beginning of the interval (example: all new undergraduate cases of flu from Sep-Aug/# undergraduates enrolled in Sep)

Uses "people time"; # new cases of disease over a specified time/the sum of time periods of observation of each person observed for all or part of the time period specified

Prevalence = incidence X durationPrevalence = # disease cases present at a specified time/ # persons in pop'n at specified time

Snapshot at one point in time"Do you currently have cancer?"

Snapshot of a time periodAll must have had the disease during defined period (existing + new cases)"Have you had cancer in the past 5 years?"

Water going in the tub = incidenceWater in the tub = prevalence

- More ppl get the disease- Detection methods become more sensitive- Increase screening- Reduced death (cure) of disease- Improve tx to lengthen duration before death

- Fewer ppl get the disease- Death rates increase- Cure rates increase- Less sensitive method for detection applied- Coding changes

Prevent develop of disease - immunizations, environmental exposure decrease/eliminated

Finding the disease early to reduce effects - Screening

After disease has occurred, reduce impact - PT after severe burning

Special kind of incidence rateRisk of death in a given time period

# deaths from all causes in one year/# ppl in population at midyear

# deaths from all causes in 1 year at a specific age/# ppl in pop'n at that age at midyear