Sex differences in short-term heart rate variability in patients with newly diagnosed essential hypertension.

The authors report the results of the analysis of heart rate variability (HRV) indices during 5 minutes of supine rest and 5 minutes of standing and conventional indices of autonomic function in 69 men and 51 women with untreated newly diagnosed hypertension matched for body mass index and resting blood pressure. Mean RR interval, standard deviation of normal-to-normal RR intervals, low-frequency RR spectral power, HRV during deep breathing at 6 breaths per minute, and the 30:15 ratio (maximum RR interval 30th beat/minimum RR interval 15th beat) were significantly lower in women (P=.01, .02, .001, .04, .01, respectively) compared with men. Low frequency RR in normalized units was lower in women in the supine position alone (P=.03). HRV was significantly lower in women with untreated newly diagnosed hypertension compared with men. The authors interpret these results as indicating an increase in baseline cardiac sympathovagal balance in female hypertensive patients.