Masked hypertension: evaluation, prognosis, and treatment.

Blood pressure (BP) may be high during usual daily life in one out of 7-8 individuals with normal BP in the clinic or doctor's office. This condition is usually defined as masked hypertension (MH). Prevalence of MH varied across different studies depending on patient characteristics, populations studied, and different definitions of MH. Self-measured BP and ambulatory BP (ABP) have been widely used to identify subjects with MH. Various factors have been identified as possible determinants of MH. Cigarette smoking, alcohol, physical activity, job, and psychological stress may increase BP out of the clinical environment in otherwise normotensive individuals, leading to MH. In most studies, target organ damage was comparable in subjects with MH and those with sustained hypertension, and greater than in those with true normotension. Subjects with MH showed a 1.5- to 3-fold higher risk of major cardiovascular (CV) disease than those with normotension, and their risk was not different from that of patients with sustained hypertension. In an overview of literature, we found that the risk of major CV disease was higher in subjects with MH than in the normotensive subjects regardless of the definition of MH based on self-measured BP (hazard ratio (HR) 2.13; 95\% confidence interval (CI): 1.35-3.35; P = 0.001) or 24-h ABP (HR 2.00; 95\% CI: 1.54-2.60; P < 0.001). MH is an insidious and prognostically adverse condition that can be reliably diagnosed by self-measured BP and ABP. MH should be searched for in subjects who appear to be more likely to have this condition. Antihypertensive treatment is envisaged in these subjects, although the associated outcome benefits are still undetermined.