Overactive bladder: prevalence, risk factors and relation to stress incontinence in middle-aged women

To investigate the prevalence of and factors associated with overactive bladder in middle-aged women.

Cross sectional population-based study.

Southern Sweden and the Women's Health in the Lund Area study (WHILA 1995-2000) where 6917 (64% of the invited) women, 50-59 years old in 1995, participated.

From the WHILA study, 1500 women reporting troublesome urinary incontinence (INCONT-1) and 1500 without incontinence (CONT-1) were selected by computerised randomisation and received the Bristol Female Lower Urinary Tract Symptoms (BFLUTS) questionnaire in January 2001.

Overactive bladder was defined in two versions using the ICS definition of 2002 as either urgency alone (OAB-1) or urgency combined with frequency more than eight times per day and/or nocturia twice or more per night (OAB-2). Risk factors were analysed by multiple logistic regression analyses.

Prevalence figures and odds ratios with corresponding 95% confidence intervals.

The prevalence of OAB-1 was 46.9% in the INCONT-1 and 16.7% in the CONT-1 group, and that of OAB-2 was 21.6% and 8.1%, respectively. Most urgency occurred in combination with stress incontinence (i.e. as mixed incontinence). The overlap between stress and urge symptoms increased with the frequency of stress incontinence episodes (P < 0.001). Metabolic risk factors were body mass index (BMI) >/= 30 for OAB-1, OAB-2 and stress incontinence, positive metabolic screening for OAB-1, family history of diabetes for OAB-2 and elevation of BMI >/= 25% since the age of 25 for stress incontinence. Stress incontinence was associated with the current use of hormonal replacement therapy.

Overactive bladder and stress incontinence are intimately associated with each other. Both OAB and stress incontinence are associated with abnormal metabolic factors, mainly increased BMI.