Question

Using direct adjustment with the total study population as your reference group, please calculate the age-standardized cumulative incidence rate for the association between hypertension and stroke.

You, as an investigator, are interested in the association between hypertension and stroke and collect the following data.

Hypertension: 368 (stroke), 752 (no stroke)

Non-Hypertensive   556 (stroke), 2,324(no stroke)

a) Calculate the crude appropriate measure of association for the relationship between hypertension and stroke and interpret your answer.

After completing the crude analysis, you are then interested whether age is a potential confounder or effect modifier in your study. You then stratify the data above.

Age less than 40:

Hypertension 72 (stroke), 228 (no stroke)

Non-Hypertensive 272 (stroke), 1,428 (no stroke)

Age greater than or equal to 40:

Hypertension 296 (stroke), 524 (no stroke)

Non-Hypertensive 284 (stroke), 896 (no stroke)

g) Using direct adjustment with the total study population as your reference group, please calculate the age-standardized cumulative incidence rate for the association between hypertension and stroke.

Answer 1

Ans. 1(a).For finding crude rate appropriate we will calculated by dividing the total number of cases in a given time period by the total number of persons in the population like ,

In Hypertension Population Crude Rate = Total stroke case   Total no. of Person,

  = 368   1120

= 0.33

In Non Hypertensive Population Crude Rate = 556   2790

= 0.20

From above both data we found that population of Hypertensive group are vulnerable then non hypertensive group. Now calculate rate as per age,

1. For less then 40,

Hypertensive = 72 __________ 300 = 0.24 Non Hypertensive = 272   1700

= 0.16

2. Age greater or equal to 40 Hypertensive = 296 820 = 0.36

Non Hypertensive =    284 1184 = 0.24

Now from above both age group we can easily understand that hypertensive group patient either they are in less then 40 or equal to 40 are more vulnerable for stroke then compare to those person which are non hypertensive so by these  data we can say that stroke are more common in hypertensive patient and as per calculation 40 or greater age group population are more prone to stroke then compare to less then 40 age group patients.