Female stress, urge, and mixed urinary incontinence are associated with a chronic and progressive pelvic floor/vaginal neuromuscular disorder: An investigation of 317 healthy and incontinent women using vaginal surface electromyography.

Reduction of the maximum vaginal surface electromyography (EMG) activity has previously been demonstrated in women with stress, urge, and mixed incontinence in comparison with healthy volunteers [Gunnarsson and Mattiasson, Scand J Urol Nephol 157:89-95, 1994]. The present study was performed to investigate if these EMG changes are age dependent and whether healthy parous women in general might show an age-related decrease of vaginal and pelvic neuromuscular activity. A total of 317 women, 144 with urinary incontinence and 173 healthy volunteers, 20 to 76 years of age, were investigated. The maximum EMG activity during repeated short contractions (2 s) was measured. We found that parous women who have maintained continence through the years had a normal pelvic floor function as estimated with vaginal surface EMG. In contrast, all three groups of incontinent women showed a successive decrease of the EMG activity with increasing age. This difference was highly significant (P < 0.001) in women above the age of 50. No significant differences could be seen between groups when stress, urge, and mixed incontinent women were compared. Even though any convincing correlation between the amount of urinary leakage and the reduction of EMG activity was not found, we conclude that a chronic and progressive deterioration of the pelvic-vaginal neuromuscular function occurs in women who develop urinary incontinence. The results support the view that a common pathophysiological mechanism in patients with stress, urge, and mixed incontinence might exist. The findings might help to establish a new perspective for the understanding of the pathophysiology, diagnosis, treatment, and prevention of female incontinence. Neurourol. Urodynam. 18:613-621, 1999. Copyright 1999 Wiley-Liss, Inc.