Alteration of autonomic function in female urinary incontinence

Stress urinary incontinence (SUI) and urge urinary incontinence (UUI) have different mechanisms of action. We believe that alteration of autonomic nervous system (ANS) activity may contribute to UUI because the lower urinary tract is regulated through the sympathetic and parasympathetic nervous systems. Heart rate variability (HRV) allows measurement of autonomic nervous function, therefore we measured and compared HRV parameters in women with urinary incontinence.

From March 2008 to March 2010, we evaluated all patients who visited 2 university hospitals for treatment of urinary incontinence. Theywere performed 3-day voiding diary, urodynamic study, physical examination and routine laboratory examination. We excluded subjects who had diabetes, cardiovascular problems, or other condition that affect ANS. Patients with mixed urinary incontinence (MUI) were also excluded. Finally 47 women with SUI (group 1) and 29 women with UUI (group 2) were enrolled according to their symptoms and voiding diary. We compared their HRV parameters. And excluding 11 patients who had detrusor underactivity, we divided them again into group A, 53 women without detrusor overactivity (DO) and group B, 12 women with DO. We compared HRV parameters between DO and non-DO group.

Older women had a higher incidence of UUI and DO. In HRV parameters, only the ratio of low frequency (LF) and high frequency (HF) was significantly higher in group 2 than group 1 (3.5±3.6 vs. 1.6±1.1, P<0.05). Also group A had higher mean LF/HF ratio than group B (4.3±3.8 vs. 1.9±1.9, P<0.05).

Increased LF/HF values indicate relative sympathetic hyperactivity over parasympathetic activity. Changes in ANS activity could indicate the presence of UUI and potentially DO.