Posted: September 7th, 2016
A prospective cohort study is run to estimate the incidence of stroke in persons 55 years of age and older. All participants are free of stroke at study start. Each participant is followed for a maximum of 5 years. The data are summarized in Table 3–14.
TABLE 3–14 Incidence of Stroke in Men and Women
Number of Strokes Number of Stroke- Free Person-Years
Men (n = 125) 9 478
Women (n = 200) 21 974
• a. What is the annual incidence rate of stroke in men?
• b. What is the annual incidence rate of stroke in women?
• c. What is the annual incidence rate of stroke (men and women combined)?
A clinical trial is run to assess the efficacy of a new drug to reduce high blood pressure. Patients with a diagnosis of hypertension (high blood pressure) are recruited to participate in the trial and randomized to receive either the new drug or placebo. Participants take the assigned drug for 12 weeks and their blood pressure status is recorded. At the end of the trial, participants are classified as still having hypertension or not. The data are shown in Table 3–15.
TABLE 3–15 Hypertension Status by Treatment
Group Number Randomized Number Free of Hypertension at 12 Weeks
Placebo 50 6
New drug 50 14
• a. What is the prevalence of hypertension at the start of the trial?
• b. What is the prevalence of hypertension at the end of the trial?
• c. Estimate the relative risk comparing the proportions of patients who are free of hypertension at 12 weeks between groups.
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