Question

Assume that the horizontal lines in the diagram represent follow up of 800 different people during the 8 years period. Each horizon line represents 100 different people. Red ovals represent hypertension, blue ovals represent lost to follow up; green ovals represent death. All patients with hypertension survived through the 8 years.

8 7 6 5 4 3 2

1) Please calculate the point prevalence of hypertension at the end of 2nd year (1 point)?

2) Please calculate the point prevalence of hypertension at the end of 8th year (1 point)?

3) Please calculate the period prevalence of hypertension for the total 8 years(1 point)?

4) Please calculate the cumulative incidence of hypertension at the end of 5th year(1 point)

5)Please calculate the incidence density of hypertension for the 8 years period(1 point)?

Answer 1

1) Point prevalence of hypertension at the end of 2nd year = number of cases of hyper tension at the end of 2nd year / total number of people

= 100/ 800 = 0.125

2) Point prevalence of hypertension at the end of 8th year = number of cases of hyper tension at the end of 2nd year / total number of people at the end of 8th year

= 300/500 = 0.6

3) Period prevalence of hypertension for 8 years = Total number of Hyper tension cases in 8 years / Total number of people

= 300/800 = 0.375

4) Cumulative incidence at the end of 5th year = new events or cases of disease divided by the total number of individuals in the population at risk for 5-years

= 200/800 = 0.25