Abstract
INTRODUCTION: Individuals with erectile dysfunction (ED) have been shown to display lower heart rate variability (HRV), suggesting dysregulation of cardiac autonomic function. No studies have explored whether HRV is predictive of erectile response among men with clinically normal erectile function. AIM: The study aims to examine associations between resting HRV and objective measures of genital response (i.e., resting penile circumference; erectile tumescence) and self-reported sexual function. METHODS: The sample comprised 59 male community volunteers (mean age = 20.15 years; SD = 2.52) selected from the control conditions of two previously published studies. Participants reported erectile function in the normal range (scoring ≥ 26 on the International Index of Erectile Function [IIEF]) and had no history of cardiovascular disease or myocardial infarct. During a laboratory visit, self-report, anthropometric, cardiovascular, and electrocardiographic data were assessed, as well as resting penile circumference and erectile tumescence in response to viewing an erotic film. MAIN OUTCOME MEASURES: Resting penile responses, erectile tumescence (circumferential change via penile plethysmography), self-reported sexual function per the IIEF, and both time-domain (standard deviation of beat-to-beat [NN] intervals, square root of the mean squared difference of successive NN intervals, and percent of NN intervals for which successive heartbeat intervals differed by at least 50 msec [pNN50]) and frequency-domain (low frequency [LF], high frequency [HF], LF/HF ratio) parameters of HRV were assessed. RESULTS: Higher-resting HF power and lower-resting LF/HF ratio were associated with greater erectile tumescence. There were marginally significant positive associations between mean NN interval and pNN50 and penile tumescence. HRV was not associated with self-reported sexual function or with resting penile circumference. CONCLUSIONS: Results suggested that, among men without ED, relatively elevated parasympathetic tone was predictive of larger erectile tumescence. Limited variance in sexual function scores may have accounted for the lack of association between HRV and IIEF scores.