Sex differences in hypertension development strategy: A role of LF HRV power
Authors: Shekh Vera Evgenievna 
Published: November 2023

The aim of this study was to investigate sex differences in autonomic regulation of heart rate and blood pressure in normotensive and prehypertensive subjects by means analysis of LF and HF HRV power expressed in absolute units. HF power was considered as a measure of cardiovagal outflow, LF power, we hypothesized, represents baroreflex‐mediated inhibition of tonically active medullary presympathetic neurons.

A total of 152 men and 138 women were enrolled in the study from V.N. Karazin Kharkiv National University multiethnic student population. All participants gave written informed consent. The subjects were classified into normotensive and prehypertensive groups according to JNC‐7 classification. GLM two‐way MANOVA with sex and prehypertension as independent variables was used to test for possible effects of sex, prehypertension and their interaction. The stepwise multiple linear regression analysis was carried out to assess the relative importance of LnLF and LnHF power in HR, SBP, and DBP, adjusted for sex, prehypertension, BMI, height, and two‐way interactions.

There were significant sex differences in heart rate and systolic blood pressure between normotensive subjects and between prehypertensives (Table 1). At the same time, there was a significant sex difference in LnHF power between normotensives only. However, diastolic blood pressure was higher and LnLF power was lower in prehypertensive women compared with prehypertensive men (Table 1).

The significant effect of prehypertension on heart rate and LnLF power was observed only between women: heart rate was lower and LnLF power was higher in normotensive than in prehypertensive women (Table 1). The effects of sex and prehypertension were significant after controlling for BMI and age with the exception of the effect of sex on the systolic blood pressure between prehypertensives.

The stepwise multiple regression analysis revealed that in both genders heart rate was negatively associated with LnHF power (p<0.001) and LnLF by BMI interaction (p=0.038), systolic blood pressure was negatively associated with LnLF by BMI interaction (p=0.008) and LnLF by height interaction (p=0.025), and diastolic blood pressure was negatively associated with LnLF by BMI interaction (p=0.021) (not shown). The current findings indicate that (1) in congruence with well documented in literature fact heart rate in supine rest is mainly under control of the parasympathetic nervous system; (2) LnLF power decreases heart rate, systolic blood pressure and diastolic blood pressure, and the higher BMI the greater the effect of LnLF power decreasing heart rate, systolic and diastolic blood pressure, counterbalancing pressor effect of BMI; (3) the taller subject the greater LnLF power decreases systolic blood pressure, counterbalancing influence of the height on heart parameters and stroke volume. On the base of our data and literature we hypothesize that LF HRV power represents baroreflex‐mediated inhibition of the tonically active medullary presympathetic neurons.

In consistence with our hypothesis it is suggested that (1) higher heart rate, systolic and diastolic blood pressure in prehypertensive than in normotensive women, and (2) higher diastolic blood pressure in prehypertensive women than in men may be explained partially by lower LF power, indicating lack of baroreflex‐mediated inhibition of the tonically active medullary presympathetic neurons.

Hemodynamic characteristics, LnLF and LnHF power by sex and presence of prehypertension (HT) (unadjusted means)

Men
Women

Normotensive
Prehypertensive
Normotensive
Prehypertensive

n
53
99
91
47

HR, bpm
65.56±1.23
67.07±0.90
68.97±0.94*
72.69±1.31***†

SBP, mm Hg
115.60±0.64***
127.75±0.47*†††
112.57±0.49
125.98±0.68†††

DBP, mm Hg
67.14±0.66
74.32±0.48†††
68.47±0.50
77.52±0.70***†††

LnLF power, ms2§§
6.84±0.11
7.07±0.08**
6.90±0.08†
6.61±0.12

LnHF power, ms2
7.13±0.10
7.24±0.07
7.46±0.08*
7.32±0.11

Data are expressed as means±SE; n, number of participants;

P<0.05, vs. sex counterparts;

P<0.01, vs. sex counterparts;

P<0.001, vs. sex counterparts;

P<0.05 vs. prehypertensive counterparts;

P<0.001, vs. normotensive counterparts;

P<0.01, significant sex by HT interaction were found from general linear model (GLM) two‐way MANOVA