Objective: To study whether the cardiovascular preventive effect of antihypertensive therapy can be explained solely by the reduction in office blood pressure, and to what extent the risk of stroke and cardiac events is associated with in-study diastolic blood pressure (DBP) and systolic blood pressure (SBP).
Design: The Swedish Trial in Old Patients with Hypertension (STOP-Hypertension) was a prospective, randomized, double-blind, multicentre trial comparing active antihypertensive treatment with placebo in patients aged 70-84 years. The study group comprised 1,627 elderly patients (mean blood pressure 195/102 mm Hg; mean age 75.7, SD 3.7; 63% females). The average follow-up was 25 months (range 6-65 months). No patient was lost to follow-up.
Method: We applied a Poisson model taking current age, sex, treatment, DBP and SBP into account for all patients in the study. The constants of the model were estimated by the maximum likelihood method.
Results: The risk of stroke was significantly lower (42%, p = 0.0402) for a patient on active therapy than for a patient on placebo having the same blood pressure level, age, and sex. There was a corresponding, non-significant, reduction in cardiac events of 21%. In the whole study group the risk of stroke increased by 3% per mmHg (p = 0.0247) with increasing diastolic blood pressure for a given systolic pressure. The corresponding value for cardiac events was 2% per mmHg (p = 0.0376).
Conclusion: In STOP-Hypertension we found a substantial risk reduction in stroke in actively treated patients, which was not solely explained by the blood pressure reduction obtained by treatment with beta-blockers and a potassium-sparing diuretic combination.