Evaluation of the placebo effect and reproducibility of blood pressure measurement in hypertension

Pharmacologic studies in hypertension often describe blood pressure (BP) re ductions in placebo control groups. This placebo effect is currently debate d, as it seems to be related to BP measurement methods and as a regression to the mean phenomenon may lead to misinterpretation. Furthermore, data on pulse pressure are lacking. This study was designed to evaluate the placebo effect on BP and to differentiate it from regression to the mean. Accordin g to a crossover design, 26 mild-to-moderate hypertensive patients who were treated with placebo or given no treatment were followed-up for 1 month. C linic and ambulatory BP was assessed at baseline and at the end of each 1-m onth period. Placebo administration resulted in significant reductions in c linic systolic, diastolic, and mean BP (P < .01), ambulatory 24-h SEP (P < .05), and daytime systolic, diastolic, and mean BP (P < .01, P < .05, P < . 01, respectively). No significant differences were noted for pulse pressure and heart rate or between BP values measured at baseline and after 1 month without treatment, Despite a significant correlation between changes in cl inic and ambulatory BP, the scatter of individual data suggests that the pl acebo response observed with one method cannot be systematically extrapolat ed to the other method. This study conclusively shows the effect of placebo in mild-to-moderate hypertension on both clinic and ambulatory systolic, d iastolic, and mean BP, in which it has been shown to differ from the regres sion to the mean phenomenon. This effect was not observed for pulse pressur e or heart rate. (C) 2001 American Journal of Hypertension, Ltd.