Age-related hypotensive effect of placebo and active treatment in patients older than 60 years. European Working Party on High Blood Pressure in the Elderly. Elderly hypertensive patients were randomly assigned to active treatment (n = 365) or placebo (n = 377). The effects of treatment on blood pressure were calculated by subtracting pretreatment blood pressure from the blood pressure at 3 months. In the two treatment groups, the decrease in systolic and diastolic pressures was more pronounced in older patients. However, the slopes of blood pressure change with age were not significantly different in the two treatment groups: systolic, -0.47 and -0.37 mm Hg/year in the active-treated and placebo patients, respectively; diastolic, -0.26 and -0.15 mm Hg/year, respectively. Thus, proving that an observed age-related hypotensive effect is caused by a particular drug requires comparison with a control group on placebo. 