Abstract-Baroreceptor reflex sensitivity (BRS) has been found lower and heart rate variability (HRV) parasympathetic markers have been found higher in healthy women than in healthy men. Thus, in the present study we hypothesized gender differences in the autonomic function among hypertensive subjects. Forty-one hypertensive patients and 34 normotensive subjects, age 53Ϯ1 years, were examined. Four weeks after cessation of antihypertensive therapy, HRV was assessed in 24-hour Holter ECGs, and BRS was calculated with the transfer technique. A t test was performed after log transformation of spectral values. Resting blood pressure and heart rate in the hypertensive and the normotensive groups were 150Ϯ2/100Ϯ1 (meanϮSEM) and 121Ϯ2/81Ϯ1 mm Hg, respectively, and 68Ϯ1 and 60Ϯ1 bpm, respectively (PϽ0.0005). Compared with normotensive controls, hypertensive patients had lower total power (1224Ϯ116 versus 1797Ϯ241 ms 2 ; Pϭ0.03), lower low frequency power (550Ϯ57 versus 813Ϯ115 ms 2 ; Pϭ0.04), lower high frequency power (141Ϯ23 versus 215Ϯ38 ms 2 ; Pϭ0.06), lower root mean square successive difference (28.7Ϯ2.7 versus 35.7Ϯ3.0 ms; Pϭ0.03), and PNN50 (4.9Ϯ0.6% versus 9.8Ϯ1.5%; Pϭ0.003). BRS was also lower in the hypertensive subjects (7.6Ϯ0.6 versus 10.4Ϯ0.8 ms/mm Hg; Pϭ0.005). When comparing the same parameters between normotensive subjects and hypertensive subjects within the same gender group, we found significant reduction (PϽ0.05) only within the female group. The difference in BRS within the female group was twice that within the male group. Stepwise multiple regression analysis revealed gender, age, HDL cholesterol, and blood pressure as independent explanatory variables of BRS and HRV. Our results suggest that gender is an important determinant of BRS and HRV. Autonomic function parameters were especially impaired in hypertensive women compared with hypertensive men. Key Words: hypertension Ⅲ gender Ⅲ baroreflex Ⅲ catecholamines Ⅲ heart rate T he autonomic nervous system plays a crucial role in blood pressure (BP) and heart rate (HR) control and may thus be an important pathophysiological factor in the development of hypertension. There have been numerous studies on plasma catecholamines in essential hypertension, 1 most of which have shown increased levels in hypertensive subjects. Moreover, disturbed autonomic HR and BP control has been demonstrated in several studies by means of HR variability (HRV) and baroreceptor reflex sensitivity (BRS). [2][3][4][5][6][7][8][9][10] HRV, which estimates the tonic HR control, 11-13 is generally reduced (standard deviation of all R-R intervals [SDNN] and total power [energy in the heart period spectrum between 0.0033 and 0.40 Hz] [TP]) in hypertensive patients. 2,4 -6 Markers of sympathetic predominance are increased in some 3 but not all studies. 4 -6 BRS, which estimates the reflex vagal HR control, 11-13 is reduced in hypertensive subjects. 6 -10 Both BRS and HRV parameters (except low frequency power [energy in the heart period spectrum between 0.04 and 0.15 Hz] [LF]/h...
Several studies have shown increased sympathetic activity during acute exposure to hypobaric hypoxia. In a recent field study we found reduced plasma catecholamines during the first days after a stepwise ascent to high altitude. In the present study 14 subjects were exposed to a simulated ascent in a hypobaric chamber to test the hypothesis of a temporary reduction in autonomic activity. The altitude was increased stepwise to 4500 m over 3 days. Heart rate variability (HRV) was assessed continuously in seven subjects. Baroreceptor reflex sensitivity (BRS) was determined in eight subjects with the 'Transfer Function' method at baseline, at 4500 m and after returning to baseline. Resting plasma catecholamines and cardiovascular- and plasma catecholamine- responses to cold pressor- (CPT) and mental stress-test (MST) were assessed daily in all and 12 subjects, respectively. Data are mean +/- SEM. Compared with baseline at 4500 m there were lower total power (TP) (35 457 +/- 26 302 vs. 15 001 +/- 11 176 ms2), low frequency (LF) power (3112 +/- 809 vs. 1741 +/- 604 ms2), high frequency (HF) power (1466 +/- 520 vs. 459 +/- 189 ms2) and HF normalized units (46 +/- 0.007 vs. 44 +/- 0.006%), P < or = 0.001. Baroreceptor reflex sensitivity decreased (15.6 +/- 2.1 vs. 9.5 +/- 2.6 ms mmHg(-1), P = 0.015). Resting noradrenaline (NA) decreased (522 +/- 98 vs. 357 +/- 60 pmol L(-1), P = 0.027). The increase in systolic blood pressure (SBP) and NA during mental stress was less pronounced (21 +/- 4 vs. 10 +/- 2% and 25 +/- 9 vs. -2 +/- 8%, respectively, P < 0.05). The increase in SBP during cold pressor test decreased (16 +/- 3 vs. 1 +/- 6%, P = 0.03). Diastolic blood pressure, HR and adrenaline displayed similar tendencies. We conclude that a transient reduction in parasympathetic and sympathetic activity was demonstrated during stepwise exposure to high altitude.
Heart rate variability (HRV) and baroreflex sensitivity (BRS) are indexes reflecting the ability to maintain cardiovascular homeostasis amidst changing conditions. Evidence primarily from small studies suggests that both HRV and BRS may be reduced in individuals with chronic pain (CP), with potential implications for cardiovascular risk. We compared HRV and BRS between individuals with CP (broadly defined) and pain-free controls in a large unselected population sample. Participants were 1143 individuals reporting clinically meaningful CP and 5640 pain-free controls who completed a 106-second cold pressor test (CPT). Participants self-reported hypertension status. Resting HRV and BRS were derived from continuous beat-to-beat blood pressure recordings obtained before and after the CPT. Hierarchical regressions for the pre-CPT period indicated that beyond effects of age, sex, and body mass index, the CP group displayed significantly lower HRV in both the time domain (SDNN and rMSSD) and frequency domain (high-frequency HRV power), as well as lower BRS. Results were somewhat weaker for the post-CPT period. Mediation analyses indicated that for 6 of 7 HRV and BRS measures tested, there were significant indirect (mediated) effects of CP status on the presence of comorbid hypertension via reduced HRV or BRS. Results confirm in the largest and broadest sample tested to date that the presence of CP is linked to impaired cardiovascular regulation and for the first time provide support for the hypothesis that links between CP and comorbid hypertension reported in previous population studies may be due in part to CP-related decrements in cardiovascular regulation.
There is an increased parasympathetic and reduced sympathetic nerve activity and increased overall HRV, while practising the technique. Hence, nondirective meditation by the middle aged may contribute towards a reduction of cardiovascular risk.
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