To estimate the development of nocturnal urinary control (NUC) with age in Chinese children younger than 8 years of age using cross-sectional and retrospective surveys.

We used a cross-sectional survey of 4754 children (1 to 8 years old), a retrospective investigation of 2745 children younger than 9 years old, and an anonymous questionnaire of 8222 children 9 to 18 years old . The children without NUC were subdivided into infant (1 to 3 years old), preschool age (4 to 6 years old), and primary school (7 to 8 years old) groups.

The response rate to the cross-sectional and retrospective surveys was 90% and 89%, respectively. In the cross-sectional survey, the prevalence of children attaining NUC was 52% for those younger than 2 years of age, 76% for those aged 2 to 3 years, and 93% at age 8. Girls were more likely than boys to acquire NUC earlier. In the retrospective survey, the prevalence of children attaining NUC before age 2 was 17% and was 72% for those aged 2 to 3 years, and 98% by age 8. The proportion of nonmonosymptomatic bedwettings in children without NUC was 14%. Arousal difficulty and a positive family history were found in 67% and 11% of children with nocturnal wetting, respectively. The severity of bedwetting and arousal difficulty was significantly greater in infants than in preschool and school-age children.

The results from the cross-sectional and retrospective surveys showed that the most important period of attaining NUC is 2 to 3 years of age. Nearly 90% of children attained NUC by the age of 5.