title: Resting sympathetic outflow does not predict the morning blood pressure surge in hypertension.
abstract: OBJECTIVE
  The blood pressure (BP) rise on awakening (morning surge) might be a predictor of hypertension-related cardiovascular complications. Previous studies suggest that the autonomic nervous system may contribute to the early morning BP increase. We tested the hypothesis that resting sympathetic outflow [assessed by direct measures of intraneural sympathetic nerve activity (SNA)] may help predict the morning BP surge in hypertension.
  
  
  METHODS
  We measured muscle SNA (MSNA), heart rate (HR) and BP during undisturbed supine rest in 68 newly diagnosed untreated hypertensive patients (53 men and 15 women, age 40 ± 3 years, BMI 27 ± 1 kg/m(2), mean ± SEM). The morning BP surge was defined as the difference between the morning BP and the pre-awake BP.
  
  
  RESULTS
  SBP averaged 143 ± 3 mmHg for daytime and 126 ± 2 mmHg for night-time. Mean HR was 81 ± 2 beats/min for daytime and 69 ± 2 beats/min for night-time. Average MSNA was 32 ± 2 bursts/min., SBP morning surge 19 ± 2 mmHg and HR morning surge 14 ± 2 beats/min. In univariate analysis, MSNA correlated with daytime SBP (r = 0.28, P = 0.02); night-time SBP (r = 0.26, P = 0.03); daytime HR (r = 0.28, P = 0.02); and night-time HR (r = 0.26, P = 0.03). Multivariate analysis, taking into consideration age, BMI and sex, revealed that MSNA was independently related to both daytime (P = 0.006) and night-time HR (P = 0.02), but not to ambulatory SBP. The morning surge of SBP and HR was not related to MSNA (r = 0.01 and r = 0.07, respectively, P = NS).
  
  
  CONCLUSIONS
  In patients with essential hypertension, MSNA is related to both daytime and night-time HR, but not to the morning BP surge.
authors: Department of Hypertension and Diabetology, Medical University of Gdansk, Gdansk, Poland.
authors: Dagmara
authors: D
authors: Hering
authors: Wieslawa
authors: W
authors: Kucharska
authors: Tomas
authors: T
authors: Kara
authors: Virend K
authors: VK
authors: Somers
authors: Krzysztof
authors: K
authors: Narkiewicz
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology*; D018660:Blood Pressure Monitoring, Ambulatory; D002940:Circadian Rhythm / Q000502:physiology*; D019963:Clinical Chemistry Tests; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D010507:Periodicity; D012146:Rest; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D014666:Vasomotor System / Q000502:physiology