Objective: To assess risk factors for different type of urinary incontinence-stress, urge or mixed-and overactive bladder without urinary incontinence.
Design: Case-control study.
Setting: Gynaecology clinics.
Population: Women attending first level gynaecological centres.
Methods: Cases were 1062 women with urinary incontinence or overactive bladder aged 40 years or more (mean age 62.3 years, range 40-88) consecutively observed in first level gynaecological centres. Controls were 1143 women (mean age 58 years, range 40-86) observed in the same centre after the identification of the cases, without any symptoms related to urinary incontinence or overactive bladder.
Main outcome measures: Determinants of different types of urinary incontinence and overactive bladder.
Results: The risk of urinary incontinence was lower in more educated patients and increased with body mass index (BMI). The number of vaginal births was associated with the risk of stress and mixed urinary incontinence, but not urge urinary incontinence and overactive bladder. In comparison with nulliparae, the odds ratios (OR) for stress and mixed urinary incontinence were 5.4 (95% confidence interval [CI] 1.9-15.0) and 1.6 (95% CI 1.0-2.6), respectively, for women reporting one or two vaginal birth and 5.1 (95% CI 1.8-14.5) and 2.2 (95% CI 1.3-3.7), respectively, for three or more. A history of operative vaginal delivery was directly associated with the risk of stress and mixed urinary incontinence and increased the risk of urge urinary incontinence and of overactive bladder, but the latter ORs were not statistically significant. When compared with women with no birth, a history of caesarean section increased the risk of stress urinary incontinence. A history of hysterectomy, recurrent urinary infection and perineal trauma increased the risk of all types of urinary incontinence.
Conclusions: Vaginal births increased the risk of stress and mixed urinary incontinence, but not of urge urinary incontinence and overactive bladder. The risk of all types of urinary incontinence was increased in women with higher BMI, with a history of hysterectomy, urinary infection and perineal traumas. These factors were not related to the risk of overactive bladder.