Blood pressure, 'white-coat' pressor responses and cardiovascular risk in placebo-group patients of the MRC Mild Hypertension trial.
OBJECTIVE
To study the relationship between blood pressure and cardiovascular risk in 8654 patients randomly assigned to receive placebo in the Medical Research Council Mild Hypertension trial; 339 patients had a cardiovascular event during 5 years of follow-up.


RESULTS
Tracking of blood pressure and regression of blood pressure to and from the mean were demonstrated. Cardiovascular risk was related independently and positively to blood pressure, smoking and cholesterol, and inversely to low-normal plasma sodium. The relationship with blood pressure was stronger when measurements were made at entry to the trial by nurses and weaker when measurements were made by doctors.


CONCLUSIONS
One reason for this finding was that blood pressure increased at entry and, because the rise was greater in females, in whom the risk was lower than in males, a low-risk group predominated in the upper part of the blood pressure distribution. Another reason was that the rise itself conferred little or no cardiovascular risk. This rise might be a 'white-coat' response, because the increase in blood pressure in individuals correlated with the subsequent decrease after entry.


CONCLUSIONS
If the rise is a 'white-coat' effect and if, as the present study suggests, it is common and relatively free from risk, then changes are needed in the design of placebo-controlled trials and in the management of hypertension.
Millar
J A
JA
Department of Pharmacology, University of Otago Medical School, Dunedin, New Zealand.
Isles
C G
CG
Lever
A F
AF
D000368:Aged; D001794:Blood Pressure; D002318:Cardiovascular Diseases / Q000209:etiology* / Q000378:metabolism / Q000523:psychology; D002784:Cholesterol / Q000097:blood; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010919:Placebos / Q000008:administration & dosage*; D012307:Risk Factors; D012907:Smoking
D010919:Placebos; D002784:Cholesterol