Type and severity of new-onset urinary incontinence in middle-aged women: the Hordaland Women's Cohort.

AIMS: To determine the natural history of new-onset urinary incontinence by type and severity in middle-aged women.
METHODS: In 1997-1999 2229 randomly selected women aged 41-45 agreed to participate in the Hordaland Women's' Cohort, and six identical postal questionnaires were sent them during the following ten years. Response rate was 95.7% at inclusion and has remained 87% to 93% in subsequent waves. A total of 1274 women were continent at baseline and used as source population for this paper. Distribution of type and severity of new-onset urinary incontinence and changes in these variables during four years follow-up (two checkpoints) were measured.
RESULTS: Among 1274 continent women, 514 (40.3%) reported new-onset urinary incontinence during 10 years. Type distribution was 49.8%, 18.3% and 20.3% for stress, urgency and mixed incontinence, respectively. A majority of women (89.3%) started with slight urinary incontinence and none reported severe new-onset urinary incontinence. During four years follow-up of 337 women, 212 (62.9%) reported transient and 125 (37.1%) women reported persistent urinary incontinence. In the latter group 74.6% had the same type of urinary incontinence and 62.4% reported slight grade of incontinence in all reports.
CONCLUSIONS: Our study demonstrates that in middle-aged women new-onset urinary incontinence is mainly of stress type and of slight severity. One third of the women developed persistent incontinence, with low tendency of shifting type and severity over several years. Mixed urinary incontinence is not a final stage of incontinence in this age group.