High prevalence of masked uncontrolled hypertension in people with treated hypertension.

AIM There are limited data on the quality of treated blood pressure (BP) control during normal daily life, and in particular, the prevalence of 'masked uncontrolled hypertension' (MUCH) in people with treated and seemingly well-controlled BP is unknown. This is important because masked hypertension in 'treatment naïve' patients is associated with a high risk of cardiovascular events. We therefore conducted the first study to define the prevalence and characteristics of MUCH among a large sample of hypertensive patients in routine clinical practice in whom BP was treated and controlled to recommended clinic BP goals. METHODS AND RESULTS We analysed data from the Spanish Society of Hypertension ambulatory blood pressure monitoring (ABPM) Registry and identified patients with treated and controlled BP according to current international guidelines (clinic BP <140/90 mmHg). Masked uncontrolled hypertension was diagnosed in these patients if despite controlled clinic BP, the mean 24-h ABPM average remained elevated (24-h systolic BP ≥130 mmHg and/or 24-h diastolic BP ≥80 mmHg). From 62 788 patients with treated BP in the Spanish registry, we identified 14 840 with treated and controlled clinic BP, of whom 4608 patients (31.1%) had MUCH according to 24-h ABPM criteria (mean age 59.4 years, 59.7% men). The prevalence of MUCH was significantly higher in males, patients with borderline clinic BP (130-9/80-9 mmHg), and patients at high cardiovascular risk (smokers, diabetes, obesity). Masked uncontrolled hypertension was most often because of poor control of nocturnal BP, with the proportion of patients in whom MUCH was solely attributable to an elevated nocturnal BP almost double that solely attributable to daytime BP elevation (24.3 vs. 12.9%, P < 0.001). CONCLUSION The prevalence of masked suboptimal BP control in patients with treated and well-controlled clinic BP is high. Clinic BP monitoring alone is thus inadequate to optimize BP control because many patients have an elevated nocturnal BP. These findings suggest that ABPM should become more routine to confirm BP control, especially in higher risk groups and/or those with borderline control of clinic BP.