The white coat phenomenon is benign in referred treated patients: a 14-year ambulatory blood pressure mortality study.

Objective: Previous reports on the prognosis of white coat hypertension are ambiguous. We aimed to determine the prognostic implications of the white coat phenomenon in treated patients.
Methods: Our 14-year hospital-based ambulatory blood pressure (BP) monitoring prospective database was analyzed for all-cause mortality. The relationships of the white coat and masking effects with mortality were assessed both categorically (controlled awake versus clinic BP) and in a continuous mode (clinic-awake BP difference).
Results: During the follow-up period, 2285 treated patients (aged 61 +/- 13 years, 57% women) were monitored (17621 patient-years, 286 deaths). Mean BMI was 27.8 +/- 4.5 kg/m2 and 13% were treated for diabetes. Controlled hypertension (normal clinic and awake BP) was found in 15.8%, high clinic BP (with controlled awake BP; namely, white coat uncontrolled hypertension) in 12.1%, awake hypertension (with controlled clinic BP; namely, masked uncontrolled hypertension) in 11.8%, and sustained hypertension (both clinic and awake) in 60.3%. Compared with white coat uncontrolled hypertension, age-adjusted Cox-proportional all-cause mortality hazard ratios were 1.42 (0.81-2.51) for controlled hypertension, 1.88 (1.08-3.27) for masked uncontrolled hypertension, and 2.02 (1.30-3.13) for sustained hypertension. Hazards ratios per 1% increase in the clinic-awake BP difference were 0.992 (0.983-1.002) for systolic BP and 0.981 (0.971-0.991) for diastolic BP, adjusted for age, sex, diabetes, and either systolic or diastolic awake BP, respectively.
Conclusion: In treated hypertensive patients referred for ambulatory BP monitoring, the white coat effect is benign compared with the reverse (masking) phenomenon, which has a poorer prognosis.