Final answer:
To calculate relative risk in a cohort study, a 2 x 2 table is used to compare incidences between groups, and the ratio of these incidences provides the relative risk. Normal blood pressure is established as a reference point for the calculation.
Step-by-step explanation:
To calculate the relative risk of cognitive loss by blood pressure status in a cohort study, researchers would use a 2 x 2 table to compare the incidence of cognitive loss in those with hypertension to those with normal blood pressure. The relative risk is the ratio of the probability of cognitive loss occurring in the hypertensive group to the probability of cognitive loss occurring in the normal blood pressure cohort. Blood pressure status is a significant health indicator, with hypertension often leading to more severe health issues, including the risk of cognitive decline.
Normal blood pressure is defined by the American College of Cardiology and American Heart Association as less than 120/80 mm Hg. Building a 2 x 2 table will involve calculating the incidence rate of cognitive loss among those with normal blood pressure and comparing it to that of individuals with elevated blood pressure or hypertension. By dividing the incidence rate of cognitive loss in the hypertensive group by the incidence rate in the normal group, we obtain the relative risk.