Question

What measure of disease frequency is each of the following? (Incidence density, cumulative incidence, period prevalence, point prevalence).

a. The percentage of 70-year-old men living in Harris County who develop pneumonia between January 1, 2011 and December 31, 2011.

b. The percentage of women who delivered babies on December 31, 2010.

c. The percentage of fifth graders who meet the criteria for obesity during the 2011-2012 school year.

d. The number of live-born babies who die of sudden infant death syndrome during the first year of life per 100,000 baby-years of follow-up.

Answer 1

Period prevalance is much similar to point prevalence except the point of time is broader.Example of this measurement is option c)The percentage of fifth graders who meet the criteris for obesity during 2011-2012 school year..

Point prevalence is the number of persons with the disease in a time interval divided by no of persons in the population ex:thepercentage of women who delivered babies on december 31,2010

Incidence density refers to the number of new cases per unit of time.ex :the number of live born babies who die of sudden death during the first year of life per 100,000 baby years of follw up.

Cumulative incidence which measures the number of cases per person in the population over a period of time.ex:a)The percentage of 70 year old men in harris country who develop pneumonia between jan 1 ,2011 and dec 31 2011.In this the time period is clearly mentioned with existence of disease.