Incidence and risk factors of female urinary incontinence: a 4-year longitudinal study among 24 985 adult women in China

Objective: To estimate the incidence of urinary incontinence (UI), including its subtypes stress UI (SUI), urgency UI (UUI) and mixed UI (MUI), and to examine risk factors for de novo SUI and UUI in Chinese women.

Design: Nationwide longitudinal study.

Setting: Six geographic regions of China.

Participants: Women aged ≥20 years old were included using a multistage, stratified, cluster sampling method.

Methods: This study was conducted between May 2014 and March 2016, with follow up in 2018. Data on demographics, medical history, lifestyle and physiological and anthropometric information were collected.

Main outcome measurements: Incidence, rate ratio (RR).

Results: Analyses included 24 985 women (mean age 41.9 years).The follow-up response rate was 55.5%, median follow-up time was 3.7 years. The standardised incidences of UI, SUI, UUI and MUI were 21.2, 13.1, 3.0 and 5.1 per 1000 person-years, respectively. Risk factors for de novo SUI included delivery pattern (vaginal spontaneous delivery RR 2.12, 95% CI 1.62-2.78 and instrumental delivery RR 3.30, 95% CI 1.99-5.45), high body mass index (BMI) (overweight RR 1.52, 95% CI 1.33-1.74 and obesity RR 1.67, 95% CI 1.32-2.11), cigarette smoking (RR 1.54, 95% CI 1.12-2.12), chronic cough (RR 1.44, 95% CI 1.17-1.76), diabetes (RR 1.33, 95% CI 1.10-1.60) and older age (50-59 years RR 1.49, 95% CI 1.16-1.90 and 60-69 years RR 1.61, 95% CI 1.22-2.13).The risk factors significantly associated with de novo UUI were age (RR increased from 1.21, 95% CI 0.74-1.99, at 30-39 years to 6.3, 95% CI 3.85-10.30, at >70 years) and diabetes (RR 1.48, 95% CI 1.05-2.09).

Conclusions: The incidence of female UI is 21.2 per 1000 person-years in China. Delivery (vaginal spontaneous delivery, instrumental delivery), high BMI, cigarette smoking, chronic cough, diabetes and older age were risk factors.

Tweetable abstract: The incidence of female urinary incontinence was 21.2 per 1000 person-years in China. Delivery, BMI, diabetes and old age are risk factors.