Assignment:
Prevalence and Incidence Calculation Measures This assignment comprises two tasks.
Task 1 Read the scenario below and complete the questions that follow.
A cohort study is conducted to assess the association between clinical characteristics of hypertension and the risk of stroke. The study involves 1,250 (n) participants who are free of stroke at the start of the study. Each participant is assessed at the study start (baseline) and every year thereafter for five years. The data on hypertension status measured at baseline and at two years is as follows:
|
|
2 Years: Not Hypertensive
|
2 Years: Hypertensive
|
| Baseline: Not Hypertensive |
850 |
148 |
|
Baseline: Hypertensive
|
45
|
207
|
i. Compute the prevalence of hypertension at baseline.
ii. Compute the prevalence of hypertension at two years.
iii. Compute the incidence of hypertension over two years.
Task 2 The data on hypertension status measured at baseline and five years is as follows:
|
Table Hypertension at Baseline and Stroke Five Years Later
|
|
Free of Stroke at Five Years
|
Stroke
|
Total
|
|
Baseline: Not
Hypertensive
|
952
|
46
|
998
|
|
Baseline: Hypertensive
|
234
|
18
|
252
|
|
Total
|
1186
|
64
|
1250
|
Complete the following:
i. Compute the cumulative incidence of stroke in the study.
ii. Compute the cumulative incidence of stroke in patients classified as hypertensive at baseline.
iii. Compute the cumulative incidence of stroke in patients free of hypertension at baseline.
iv. Compute the risk difference of stroke for patients with hypertension as compared to patients free of hypertension.
v. Compute the relative risk of stroke for patients with hypertension as compared to patients free of hypertension.
vi. Compute the population-attributable risk of stroke due to hypertension.
In your answers, show the formulae you use and the steps of the calculation. Analyze the measures you calculate to draw conclusions. Present the calculations and answers in an Excel spreadsheet and Word document.
Write the interpretation of results in a Word document.
Complete the calculations below
Method for calculating prevalence of disease
(All new and pre-existing cases during a given time period / Population during the same time period) × 10n
The value of 10n is usually 1 or 100 for common attributes. The value of 10n might be 1,000, 100,000, or even 1,000,000 for rare attributes and for most diseases.
Method for calculating incidence rate
(Number of new cases of disease or injury during specified period / Time each person was observed, totaled for all persons)