The midnight sheet-and-pyjama change is a routine familiar to many Hong Kong families. Nocturnal enuresis, the medical term for bed-wetting, affects up to 10 per cent of children aged between six and eight.
The good news is that most of these children will outgrow the problem and by the time they are teenagers only 2 per cent will still wet the bed at night.
Bed-wetting was traditionally thought to be caused by an immature bladder, but the latest research contradicts this theory, according to Professor C.K. Yeung, head of the Primary Nocturnal Enuresis Clinic at the Prince of Wales Hospital in Sha Tin.
'In the past, treatments were oversimplified because it was seen as one homogenous problem. Nocturnal enuresis is a complex issue and there can be many reasons behind the condition,' Yeung said.
Simple things such as drinking too much, drinking carbonated soft drinks that act as a diuretic, or not putting the child on the toilet before bed, can lead to bed-wetting. Some children do not have a mechanism in the brain to wake them when the bladder is full, and for a small percentage the problem is more serious, where diabetes or kidney dysfunction is the underlying cause.
Age is also a factor. There was once a rule of thumb that by the age of five children should be dry at night, but Yeung says this is unrealistic. 'You can't use a simple cut-off; it depends on how severe the condition is,' he says. 'If bed-wetting is infrequent, say once every couple of weeks, then even at age eight the chances are the condition will get better on its own. But if it is frequent, that is, at least four nights a week, then as early as age five it should be considered abnormal.'