Dr. Greene's Answer
Children who can control their bladders during the day, but who have never been dry at night for at least a six month period, have what is known medically as primary nocturnal enuresis (PNE), the most common form of bed-wetting. Over five million school-age children in the US alone have PNE. What are common bed wetting causes?
Sadly, most children with PNE feel that there is something wrong with who they are that causes their problem. Many of them feel that it’s the result of either bad thoughts or bad actions. They feel that somehow bed-wetting is a punishment.
Similarly, many parents feel that their children’s bed-wetting is a result of a defect in their parenting. This feeling is heightened by well-meaning friends and relatives who bring up questions of emotional instability as the cause of bed-wetting.
In a recent survey of 9,000 parents of kids ages 6 – 17, 22% stated that they thought the reason their child wet the bed was laziness (survey conducted by ICR Survey Group from July 10, 1996, through August 6, 1996). I am happy to tell you that this could not be further from the truth! Primary nocturnal enuresis is a common developmental phenomenon related to physical and physiologic factors. It does not come from emotional stress, poor self-esteem, or emotional immaturity.
Bed Wetting Causes
Children with PNE have two things in common. First, they need to urinate at night. Not all children do. During the first months of life, babies urinate around-the-clock. Most adults, however, don’t need to urinate at night (although a small percentage of the population will need to urinate at night throughout life). Sometime in middle childhood, most individuals make the transition from urinating around-the-clock to only urinating during waking hours. There are three reasons why individuals continue to need to urinate at night:
- There is an imbalance of the bladder muscles. For example, the muscle that contracts to squeeze the urine out is stronger, at moments, than the sphincter muscle that holds the urine in.
- They have bladders that are a little too small to hold the normal amount of urine.
- They make more urine than their normal-size bladders can hold, for several reasons:
- They may drink too much. Drinking in the two hours before bed increases nighttime urine production.
- They may be consuming a diuretic medication, a substance that directly increases urine output. Usually these are not prescribed medications, but caffeinated cola drinks or chocolate.
- They may make more urine in response to a chronic disease such as diabetes or a chronic urinary tract infection.
- They may make more urine than average because of their hormonal regulatory systems. Babies make about the same amount of urine around-the-clock. Most adults make less urine while they sleep. The reason for this is thought to be a nighttime surge of a hormone called Antidiuretic Hormone (ADH). The levels of ADH found in the blood are higher beginning in the evening. One study looking at ADH levels in bed wetters, compared to controls, found that there was a constant low level of ADH in the bed wetters. The nighttime surge did not happen. Perhaps this is a reason bed wetters tend to make more urine at night.
If an individual consistently has to urinate at night, one or more of the above three reasons is the cause. The second thing children with PNE have in common is that they don’t wake up when they need to urinate. When infants need to urinate, there is no signal that goes from the bladder to the brain to wake them up. This is wonderful, since they are not yet able to walk to the bathroom and use the toilet! On the other hand, when an adult’s bladder is full at night, there is a signal that goes from the bladder, through the nervous system, up to the brain. This initiates a dream about water, or more specifically, about going to the bathroom. The dream alerts our reticular activating system, which awakens us. We can then get out of bed, walk to the bathroom, and use the toilet. This signaling mechanism comes into play sometime in middle childhood.
For many years, parents of bed-wetting children have claimed that their children were deep sleepers. Physicians have usually disagreed with this, citing evidence from sleep EEGs showing that bed-wetting children went through the same stages of sleep as other children, at the same frequency, and that bed-wetting can occur at any stage of sleep.
I have never heard a parent come in and say, “My child spends too much time in stage four sleep.” They just say that their children are deep sleepers and are difficult to wake up. About a decade ago, researchers in Canada performed a simple, but powerful, study where they put headphones on children in a sleep lab. They began the study by allowing the children to get used to sleeping with the headphones on. Then they began introducing tones through the headphones. They measured the minimum volume it took to wake each child. The study showed that the children in the bed-wetting group were dramatically more difficult to wake up than normal controls — confirming what parents have known for years!
Children who wet the bed at night both need to urinate at night and do not wake up when their bladders are full. These are the only children who wet the bed.
Understanding the causes of bed-wetting can help remove its stigma. You are also now better equipped to evaluate the suggestions people make to you. Effective therapy is aimed at the underlying causes. Most children can be completely dry within 12 weeks.
N.B. As I stated in my earlier answer titled, “Is bed-wetting genetic?”, there is help for children who wet the bed! The biggest hindrances to getting help are the absence of a skilled, empathetic physician, and shame — parents and children are ashamed to bring the subject up with someone who can help. It is up to you to take the first step! Talk with your doctor. If you find that for some reason she or he is not able to get your child dry quickly and effectively, I would call the closest Children’s Hospital to find out who treats bed-wetting issues.