Relationship Between Muscle Sympathetic Nerve Activity and Diurnal Blood Pressure Profile

The physiological mechanisms mediating the variability and diurnal rhythm of blood pressure are unclear. We tested the hypothesis that resting sympathetic activity is linked to the variability characteristics and 24-hour profile of ambulatory blood pressure measurements. We evaluated the relationship between muscle sympathetic nerve activity (MSNA) and the level, variability, and nocturnal fall of ambulatory blood pressure in 69 normal men. Subjects were subdivided according to the tertiles of MSNA distributions. Mean 24-hour blood pressure was not significantly different across the 3 groups. Compared with subjects in the first tertile (lowest MSNA, 25 bursts/min) had significantly greater daytime blood pressure variability, whether expressed as absolute values (10.2±0.5 versus 8.1±0.4 mm Hg for systolic blood pressure and 9.4±0.4 versus 7.2±0.4 mm Hg for diastolic blood pressure;P