A pilot survey shows that primary nocturnal enuresis (PNE) prevalence has increased significantly during the past decade in Mainland China. We hypothesis that it is related to delay of elimination communication (EC). The aims of this study is to investigate the influence of delayed EC on the PNE prevalence in children and adolescent retrospectively in mainland China.

A cross-sectional study of PNE prevalence was performed by distributing 19,500 anonymous self-administered questionnaires to parents in 5 provinces of mainland China from July 2017 to October 2017. The questionnaires included sociodemographic data, family caregivers’ information, and details about the disposable diapers (DD) usage, EC commencement date, psychological disorders, lower urinary tract symptoms and family history of PNE in children and adolescents. The 2017 PNE prevalence was compared with that of 2006 in Mainland China.

A total of 19,500 children and adolescent aged 5–18 years were included in the study,  and 18,631 questionnaires were returned: 92.39% (18,016/19,500) of them qualified（all questions were clearly answered) for statistical analysis. 

The PNE prevalence decreased with age from 11.83% and 15.13% in 5-year-olds to 1.05% and 1.13% in 18-year-olds, between 2006 and 2017, respectively. The overall PNE prevalence in 2017 was 7.30%, which is significantly higher than the prevalence found in 2016 (4.07%, p<0.001). Compared with the results from 2006, the PNE prevalence in the age group 5 to 9-year-olds was significantly higher in 2017. No significant difference was found in the age group 10 to 18 years (Table 1). 
	
A total of 82.42% (14,878/18,016) of all children began using DD immediately after birth. The PNE prevalence in infants with DD usage in D1, D2 and D3 was significantly lower than those of D3–D6, D4–D6, and D5–D6 (4.05% vs 8.57%, 5.80% vs 9.23%, 6.56% vs 10.03%, p<0.05), respectively. Children who began using DD immediately after birth began EC at 10.79±8.26 months of age. Those who never used DD began EC at 8.40±7.65 months. The difference between the two groups was significant (t = 12.630, p<0.05) . 

 A significantly different PNE prevalence was found between those who used DD only at night versus those who used DD all day (7.37% vs 8.61%, p<0.05). Only 17.42% (3138/18016) of children never used DD after birth. Their PNE prevalence was significantly lower than in those using DD only at night (3.54% vs 7.37%, p<0.05) , and those using  DD all day (3.54% vs 8.61, p<0.001) . 

Possible risk factors including gender, childhood caregiver, difficulty with arousal from sleep, and family history of PNE, DD usage, and EC starting time with multi-level logistic regression analysis assessing determinants of PNE are shown. Gender, age, type of care-giver, difficulty in awakening from sleep, family history of PNE, length of using DD, and late EC onset, were risk factors of PNE (p<0.001).

PNE is diagnosed when children over 5 years of age have at least one enuresis episode per month, lasting at least 3 months [1,2]. Based on these criteria, a cross-sectional study of PNE from 2006 estimated the overall PNE prevalence in Chinese children and adolescents aged 5 to 18 years to be 4.07%. Current studies showed PNE prevalence was significantly higher than previously reported in 2006 in mainland China before DD use and when early EC was common. 
A positive relationship was found between duration of DD usage, EC start time, and PNE prevalence. Children may become used to the feeling of wearing DD and may develop manifestations of dependence, making them resistant to toilet training. Thus, starting EC earlier seems to be important. Considering the higher frequency and lower volume of urination in newborns, and excess neck suppleness to maintain an EC position before 3 months, it would practical to begin EC after 3 month and before 6 months of age in infants. 
The reasons for increase NE prevalence in China might be multifactorial, as our present study shows that DD usage and delay EC are one set of the risk factor that contribute to this increase. The major socioeconomic changes during the last years in Mainland China include many factors, such as annual income, parents’ occupation, their educational background and dietary changes, all which could contribute to the increase of the prevalence However, data regarding annual income, occupation and educational background were not collected in this study due to potential for violation of privacy rules. This makes analyzing the socioeconomic differences or educational differences between the respondent’s parents impossible to gather. In order to guarantee the quality of our survey, we only chose to include public schools in the city, but this might have caused  a data bias by economic level and population mobility. So the relationship between other socioeconomic changes and the increase in NE prevalence as well as the prevalence of NMNE and bowel dysfunction needs to be investigated as well, in the future.

In summary, our study found a significantly higher PNE prevalence in 2017 than in 2006 in Mainland China, suggesting that the longer use of DD and later onset of EC may be risk factors for this increase. An international multi-center project is recommended to provide stronger evidence for update of present guidelines regarding  DD usage and time of EC, not only in Mainland China, but worldwide. The reasons for increase PNE prevalence in China might be multifactorial, as our present study shows that DD usage and delay EC are one set of the risk factor that contribute to this increase. The relationship between other socioeconomic changes and the increase in PNE prevalence as well as the prevalence of NMNE and bowel dysfunction needs to be investigated as well, in the future.