Orthostatic hypertension as a predisposing factor for masked hypertension: the J-SHIPP study.

Masked hypertension (HT) is a known risk factor for cardiovascular outcomes. Postural blood pressure (BP) dysregulation is another BP phenomenon representing cardiovascular frailty. Given their several shared risk factors, we suspected an inter-relationship between these two BP phenomena. Here we investigated a possible relationship between masked HT and postural BP dysregulation in a general population. Study subjects were 884 apparently healthy individuals (aged 66.3±8.9 years). Masked HT was assessed on the basis of the ambulatory monitored average awake BP and office-measured BP values. Orthostatic BP change was measured at our office after a subject was asked to actively stand up. A strong inverse relationship was noted for orthostatic systolic BP (SBP) change and office-to-awake SBP differences (office-awake BP) (r=-0.422, P<0.001), and these relationships were replicated in the second-visit measurements (n=101, r=-0.326, P=0.001). Multivariate analysis revealed that the inverse association was independent (β=-0.23, P<0.001) of possible covariates, including baseline office BP and antihypertensive treatment. Orthostatic HT (OHT), which is defined as postural increases in SBP >10 mm Hg, 3 min after standing (P=0.001), but not transient HT at only 1 min (P=0.767), was associated with greater office-to-awake SBP differences than in orthostatic normotensive subjects. Among apparently normotensive subjects, the frequency of masked HT was therefore significantly greater in subjects who showed OHT 3 min after standing (52.1%) compared with controls (27.5%) (odds ratio=3.01, P=0.001). We observed an intra-individual relationship between the postural BP change and the office-to-awake BP differences, and subjects who showed OHT were likely to have masked HT irrespective of antihypertensive treatment.