Study design, materials and methods
A cross-sectional study was carried out in 19 kindergartens and 18 primary schools in 12 cities distributed throughout the four main regions of mainland China with an anonymous, self-administered questionnaire that addressed non-neuropathic paediatric BBD. A total of 10166 children with ages ranging from 4 to 10 years old were included in the nationally representative sample.
A total of 10166 valid questionnaires were collected, and 409 children were diagnosed with BBD. ①The overall prevalence was 4.02% (409/10166) and decreased with age, from 6.19% at age 4 to 1.96% at 10. ②With the prolonged use of DDs, the onset time of EC was significantly delayed and the prevalence of BBD increased (P <0.001). The prevalence of BBD in children who stopped using DDs within the first 12 months and at more than 24 months was 2.79% and 4.38%, respectively, which were higher than that in those who had never used DDs (1.05%). ③The prevalence of BBD in children who started EC within 12 months after birth and those who never engaged in EC was 1.36% and 15.71%, respectively.④ In addition, the all-day use of DDs increased the risk of BBD (P<0.001). ⑤Logistic regression and the multi-factor analysis showed that the prolonged use of DDs for years and continuous use for the whole day increased the prevalence of BBD (OR>1). Starting EC before 2 years old (especially within one year) was an obvious protective factor for BBD (OR<1).
Interpretation of results
Bladder and bowel dysfunction (BBD) is highly prevalent worldwide and is thought to result from the interplay of multiple factors that vary regionally. The coexistence of voiding dysfunction symptoms and functional constipation and/or faecal incontinence (FI) in children was previously termed ‘dysfunctional elimination syndrome’ (DES). However, there was no standardized definition of DES for children until 2013 when the International Children’s Continence Society (ICCS) suggested the term ‘bladder and bowel dysfunction’ (BBD) instead of DES to describe children with a combination of functional bladder and bowel incoordination or disease, including bladder overactivity (urge), voiding frequency, bladder underactivity, constipation, etc. 
The prevalence of BBD gradually decreases with age, however,the time to initiate EC or toilet training is delayed with the popular use of DD, resulting in the actual practice of missing children’s early learning self-controlled urination and feces as soon as possible, as well as an increase in the prevalence of BBD.
EC, also known as natural infant hygiene, is the practice of using the infant s natural timing and cues to recognize when they need to defecate or urinate. By identifying the cues, caregivers can coordinate elimination in the toilet rather than in DDs. Contrary to the notion that infants relieve themselves randomly and constantly throughout the day, infants naturally eliminate at predictable times, such as on waking or after feeding. Caregivers can incorporate audio cues (soft whistle or hum) to associate with the act of eliminating. With practice, many children learn to eliminate when they are in proper position and hear the cue EC is not a new concept. Humans have been doing this for millennia and still do in most resource-limited regions like being absent from DDs. However,in the recent decades,DDs are widely used in most countries worldwide due to their strong water absorption capacity, which has become a necessity for solving voiding and defecation problems during childcare.