BLOOD PRESSURE RESPONSE TO STANDING IS A STRONG PREDICTOR OF MASKED HYPERTENSION

Abstract

Objective: The pathophysiologic mechanisms of masked hypertension are still debated. The aim of this study was to clarify the role of the blood pressure (BP) response to the upright posture as a potential mechanism for the development of masked hypertension in young subjects screened for stage 1 hypertension. Design and method: We studied 1078 young-to-middle-age (mean age 33.2 ± 8.5 years) subjects with stage I untreated hypertension at baseline. The response to standing was defined as the difference between 6 systolic BP measurements in the orthostatic and supine posture (OrthoResp). People with OrthoResp > 6.5 mmHg (upper decile) were defined as Hyperreactors. After 3 months of follow-up, 24-hour ambulatory BP was measured and the participants were classified as Normotensives (N = 120), White-coat hypertensives (N = 168), Masked hypertensives (N = 166), and Sustained hypertensives (N = 624) using the 140/90 and 130/80 mmHg cutoffs for office BP and 24-hour BP, respectively. In 591 participants, 24 h urinary epinephrine was also measured and patients were divided into four groups according to BP reactivity (>6.5 mmHg or < = 6.5 mmHg) and 24-hour urinary epinephrine/creatinine median level (>10.5 mcg/g or < = 10.5 mcg/g). The risk of developing masked hypertension was explored in a logistic regression model adjusting for confounders. Results: Mean ± SEM age-and-sex-adjusted OrthoResp was -3.8 ± 0.7 mmHg in the Normotensives, -3.1 ± 0.6 mmHg in the White-coat hypertensives, -0.9 ± 0.6 mmHg in the Masked hypertensives, and -2.6 ± 0.3 mmHg in the Sustained hypertensives. OrthoResp was an independent predictor of masked hypertension after 3 months (p = 0.001). The Odds ratio for the Hyperreactors was 2.5 (95%CI,1.5–4.0, p < 0.001). In the participants stratified by OrthoResp and urinary epinephrine, the risk of masked hypertension was 4.2 (95%CI,1.8–9.9, p = 0.001) in the hyperreactors with epinephrine above the median and was 2.6 (95%CI,0.9–7.3, p = 0.069) in those with epinephrine below the median. Conclusions: The present findings indicate that hyperreactivity to standing is a significant predictor of masked hypertension. The risk of masked hypertension was even quadrupled in people with an OrthoResp> 6.5 mmHg and high urinary epinephrine suggesting a role of sympathoadrenergic activity in the pathogenesis of masked hypertension which may be partly mediated by hyperreactivity to standing.