Background: White-coat response, defined as higher office blood pressure readings than ambulatory readings, is common. Few studies have estimated its prevalence among subjects with treated hypertension, and almost none have defined its determinants. The objective of this study was to estimate the prevalence of white-coat response among subjects with treated hypertension and to determine whether the phenomenon could be predicted using clinical and psychometric data.
Methods: A total of 103 treated patients (55 men and 48 women) with uncontrolled hypertension who attended a hypertension outpatient clinic in Saskatoon between September 1993 and December 1995 were entered into the study. Patients had at least 2 clinic blood pressure readings of 140/90 mm Hg or higher, had no target organ damage or left ventricular hypertrophy, and had been prescribed 2 or more classes of antihypertensive drugs. Patients had blood pressure measured in the supine position in the clinic, were placed on 24-hour ambulatory blood pressure monitoring and then completed questionnaires before returning to the clinic. Patients were classified as exhibiting a white-coat response if their mean daytime ambulatory systolic/diastolic blood pressure was 139/89 mm Hg (both) or less, or if the systolic/diastolic pressure was at least 20/15 mm Hg (both) lower than the clinic reading.
Results: Eleven men (20%, 95% confidence interval [CI] 10%-33%) and 26 women (54%, 95% CI 39%-69%) showed white-coat response. Logistic regression modelling showed that determinants such as stress had significantly different effects among men and women. Separate models were therefore created for men and women. For women, perceived level of stress was the most important predictor of white-coat response (odds ratio [OR] per unit 7.0, 95% CI 1.3-36.0), followed by time since diagnosis. For men, depression was a weak predictor, with higher depression scores predicting sustained hypertension (OR per unit 1.2, 95% CI 1.01-1.5).
Interpretation: Sex is an important factor in white-coat response. Attempts to predict white-coat response from psychometric variables should take sex differences into account. Clinical variables were not effective as predictors of white-coat response.