Sympathovagal Imbalance in Young Prehypertensives: Importance of Male-Female Difference

Introduction: Although the prevalence of prehypertension is high, the pathophysiological mechanisms and the effects of gender in its causation have not yet been fully understood. Methods: Body mass index, waist-to-hip ratio, basal heart rate, blood pressure, rate pressure product and spectral indices of heart rate variability were reordered and analyzed in young normotensive (n = 344) and prehypertensive (n = 69) subjects. Each group was categorized into male and female subgroups. Results: Ratio of low-frequency to high-frequency powers (LF-HF ratio) of heart rate variability spectrum, the sensitive marker of sympathovagal imbalance (SVI), was significantly more increased (P < 0.001) in male prehypertensives compared with female prehypertensives. Although SVI in prehypertensives was found to be due to both sympathetic activation in the form of increased low-frequency power normalized (increased LFnu) and vagal inhibition in the form of decreased high-frequency power normalized (decreased HFnu), contribution of vagal withdrawal was more in males. LF-HF ratio was significantly correlated with body mass index, waist-to-hip ratio, basal heart rate, blood pressure and rate pressure product by Pearson correlation analysis. Furthermore, multiple regression analysis demonstrated an independent relationship between LF-HF ratio and gender (P = 0.000) and prehypertension status (P = 0.000) in both normotensives and prehypertensives. Conclusions: Vagal inhibition plays an important role in addition to sympathetic activation in alteration of SVI in the genesis of prehypertension, especially in males. Gender and prehypertension status play important role in the causation of SVI. It was suggested that vagal tone of prehypertensives should be maintained at a higher level to prevent their further rise in blood pressure.