Professor Chung K Yeung from the Chinese University of Hong Kong teamed up with colleagues from the Prince of Wales Hospital to analyse the results of more than 16,500 questionnaires surveying children aged from five to 19.
He hopes that his findings will reassure parents of children with mild bed wetting problems, but stress the importance of seeking advice in severe cases, which can often be caused by underlying medical problems and continue into adulthood.
512 children - just over three per cent of those surveyed - reported night-time bedwetting and one in five of those also had daytime incontinence. 302 were boys and 210 were girls.
The researchers found that although bed wetting was less common as children got older, the percentage reporting severe problems increased with age.
Children and adolescents who wet the bed at night also showed a similar pattern when it came to daytime incontinence, with a higher percentage of problems reported in older age groups.
When the researchers looked in detail at the 512 children with bed wetting problems they found that:
"Bed wetting showed a general reduction as children got older" says Professor Yeung, who is also President of the International Children's Continence Society. "However, this reduction was much greater in those with mild symptoms who wet the bed three or less times a week, compared to those with severe problems who were wetting the bed every night.
"Just over 14 per cent of five year-olds who wet the bed did so seven nights a week. By the age of 19, severe bed wetting accounted for over 48 per cent of teenagers who were still wetting the bed."
21,000 questionnaires were distributed to 67 schools, with a greater emphasis on children over ten, and just under 79 per cent were returned by parents and children.
The average age of respondents was just under 14 and the largest number of responses were from teenagers aged 16-18. 24 per cent of the questionnaires concerned children under ten.
"Our findings challenge the myth that bedwetting will always get better and disappear as the child gets older" says Professor Yeung.
"In 2004 we published findings of a previous study in BJU International that showed that adults showed no significant decrease in bed wetting problems from the age of 10 to 40.
"These latest findings underline the importance of seeking help for children with severe bed wetting problems, especially if they continue into adolescence. If these individuals are left untreated, the evidence suggests that they will continue to experience ongoing problems when they become adults."
Notes to editors
Differences in characteristics of nocturnal enuresis between children and adolescents: a critical appraisal from a large epidemiological study. Yeung et al. Chinese University of Hong Kong and Prince of Wales Hospital, Hong Kong. BJU International. Volume 97, pages 1069 to 1073 (May 2006).
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