Compensatory mechanisms which prevent urinary incontinence in aging women.

The relationship between age and urodynamic parameters was studied cross-sectionally in a group of 28 women in whom clinically and urodynamically both stress incontinence and detrusor instability were excluded (no proven incontinence, NPI) and in a group, matched for age, with genuine stress incontinence (GSI). At all ages the maximal urethral closing pressure (MUCP) was higher in the NPI than in the GSI group; in both groups there was, however, a similar decrease in MUCP with age. The transmission rate increased significantly with age in the NPI group; this was not found in the women with GSI. These data indicate that in older women loss of MUCP is compensated by an increase in transmission rate (presumably because of active contraction of the pelvic floor muscles); this mechanism fails in women with GSI.