The International Children's Continence Society defines nocturnal enuresis as incontinence while sleeping. The enuresis is classed as Primary Nocturnal Enuresis if the child has never achieved a period of at least six months dry at night (1).

Most children are able to remain dry at night by the time they reach five years old; however if left untreated it can persist so that even at 7.5 years 16 out of every hundred children wet the bed. This means that in a class of 30 pupils 4 or 5 of them could be affected. It is generally more common in boys than in girls. The severity of the bedwetting varies for children 7.5 years of age (2):

• 12 children in every hundred wets less than once a week
• 1 child in every hundred wets once per week
• 3 children in every hundred wets twice or more per week

References:

1. Neveus T et al. The standardisation of terminology of lower urinary tract function in children and adolescents: Report from the Standardisation Committee of the International Children's Continence Society (ICCS)

2. Alspac, Butler et al 2005, BJU; 96: 404-410