Detection of masked hypertension and the 'Mask Effect' in patients with well-controlled office blood pressure

Background: Masked hypertension (MH) is characterized by its hidden nature and poor prognosis. However, it is not practical to routinely recommend home or ambulatory blood pressure monitoring (HBP or AMBP) to all patients with apparently well-controlled BP. The purpose of this study is to present, within the group of patients with well-controlled office BP (OBP), the clinical predictors of MH and to evaluate the gap (ie, the 'mask effect' (ME)) between OBP and HBP. Methods and Results: BP was measured at the outpatient clinic and at home in 1,019 treated hypertensive patients. Candidate predictors for MH were analyzed within 511 patients with well-controlled OBP (45.6% men, 57.1±9.0 years). Among them, the prevalence of MH was 20.9% (n=107). In the multivariate-adjusted analysis, the risk of MH increased with high serum fasting blood glucose level (odds ratio (OR) 1.009, 95% confidence interval (CI): 1.001-1.018, P=0.020), higher systolic OBP (OR 1.075, 95%CI 1.045-1.106, P<0.001), higher diastolic OBP (OR 1.045, 95%CI 1.007-1.084, P=0.019) and the number of antihypertensive medications (OR 1.320, 95%CI 1.113-1.804, P=0.021). Furthermore, systolic HBP correlated well with systolic OBP (r=0.351, P<0.001) and with the degree of systolic ME (r=-0.672, P<0.001). Conclusions: To recognize MH, it is practical to investigate those patients who are taking multiple antihypertensive drugs and have a high OBP with a high FBG level. The term "ME" identifies MH more appropriately than the term "negative white-coat effect".