By the age of two, children have spent 13 months of their lives asleep. Sleep, as every parent knows, is central to kids' wellbeing. But as parents know equally well, bedtime can be the biggest battleground of family life.
There are three main sleep difficulties in children: falling asleep, staying asleep and being too sleepy in the daytime. Every parent experiences at least one of them at some point or other. Perhaps because of this, and because disturbed nights have become regarded as almost normal, we fail to appreciate just how important sleep is for our children's health. In fact, sleep has a major impact on their physical development and growth: when your mum told you you wouldn't grow up big and strong if you didn't go to bed, she was spot on. Research has shown that children who do not sleep as much as they should are smaller than they ought to be.
But the impact of sleep is not just physical. Sleep also has a profound influence on children's behaviour, emotions and ability to learn. Remember how gran told us to "sleep on it"? Children (and adults) need sleep to consolidate new learning, be it French vocab or bike riding. In one study, cutting children's sleep from 10 to nine hours a night had a marked effect on working memory and verbal task ability, in addition to making children irritable and "oppositional" - a marvellous medical turn of phrase that encompasses everything we dread as parents, from truculent defiance to constant picking of fights with siblings. And that's with just one hour less sleep a night, a time period that many of us would consider insignificant.
"The problem with children and sleep is that while we all know what a sleep-deprived adult looks like, we can't say the same of a sleep-deprived child." So says Paul Gringras, consultant in paediatric neurodisability at Guy's and St Thomas's NHS Foundation Trust and director of the trust's paediatric sleep disorder clinic. Such kids, he says, may not even appear sleepy: in fact, they may appear the reverse.
What all this means is that children's sleep disorders are not often recognised as such, although they may well be referred to hospitals for treatment of the behavioural or learning problems that occur because of their sleep deprivation. For instance, children with narcolepsy, a classic sleep disorder, may initially be referred for specialist assessment because of concern about "underachievement".
The situation is compounded by a lack of paediatric sleep disorder clinics. While Chicago alone has three, Britain has fewer than 10 for the whole country; most are adjuncts to adult sleep clinics.
Gringras sees plenty of children who have neurodisabilities such as autism and attention deficit hyperactivity disorder (ADHD) - and, he says, about 50% of them also have sleep problems. For children with ADHD, popularly perceived to be on the go all the time, this is not a surprise. Yet what is completely counterintuitive is that many of those with ADHD also experience daytime sleepiness, revealed by something called a multiple sleep latency test. It involves repeatedly bringing a child into a very dull room and asking them to lie down and go to sleep. "No normal child ever falls asleep in these circumstances," says Gringras, "whereas children with narcolepsy reliably fall asleep every time. The real surprise is that children with ADHD often fall asleep, too."
Some paediatric sleep specialists, such as Stephen Sheldon, director of the Sleep Medicine Centre at Chicago's Children's Memorial Hospital, go so far as to say that as many as 30% of children with ADHD have been wrongly diagnosed. "There's a proportion of youngsters that have sleep pathology causing their daytime symptoms that appear virtually identical to ADHD." Gringras does not go this far, but does say that sorting out underlying sleep problems can make a real difference to behaviour in those diagnosed with ADHD, so much so that in many cases drug treatments, such as Ritalin, are no longer necessary.
There is an increasing body of evidence pointing to a link between sleep problems and attention deficit disorders. For instance, work from the University of Michigan in 2002 by Dr Ronald Chervin showed that children who snored faced double the risk of being inattentive and hyperactive. "If there is indeed a cause-and-effect link, sleep problems could represent a major public health issue," says Chervin. But many paediatricians feel that disordered sleep is a consequence of ADHD, not a cause of it.
No one sleep disorder is linked to ADHD. Just as in adults, there are many different types of sleep problem, some of which can be revealed simply by careful history taking. Nor are overnight stays in a sleep lab always required as for adults. Children may be given an "Actiwatch" to wear at home, which records movement detection to a computer chip over a two-week period before the information is downloaded on to a PC for analysis.
"Basically, it tells us how much napping is going on," says Gringras. He points out that when parents think their darling is asleep, he may actually be reading under the bedclothes with a torch or, more likely, texting his equally wide-awake mates.
Even for those children reaching a tertiary referral centre such as the one at St Thomas's, the Little Angel-style behavioural approach is still of value, especially if the parents are supported by professionals. So-called "sleep hygiene" measures such as a bedroom that is dark and only for sleeping, consistent bedtimes and daytime exercise can make a big difference on their own.
A forgotten aspect is that sleep needs the right prompts, such as darkness. Light-emitting computer screens wake the brain up, not put it to sleep, so it makes sense to ban the PC from the bedroom.
Treatments for paediatric sleep disorders vary depending on the type identified. Sleep phase disturbances, for instance, are treated with light. Adult body rhythms, which naturally run to near 25-hour cycles, are reset every day by time cues, such as morning light, ensuring that we adhere to a 24-hour cycle. Circadian rhythm disorders are common in babies and toddlers, who may be wide awake when everyone else in the house is fast asleep, and vice versa. Somewhere between 18 months and four years old, children develop adult rhythms. But about one in 15 children between the ages of five and 13 continues to march to the beat of their own personal time drum. Essentially, what these children have is jet lag without having moved through any time zones. And like us after a red-eye overnight flight from New York, they are irritable, "oppositional" and sleepy, and can't concentrate or learn properly.
The answer for these children is not a fixed bedtime, but a firmly anchored morning wake-up time. Although letting them sleep an hour later is OK, a three-hour lie-in at weekends is disastrous because their bodies will reset their clocks every day to this rhythm. The most effective treatment is a simulated dawn at a fixed time each morning using light therapy.
Needless to say, most kids can't or won't sit still for long enough, so sleep physiologists (specialist healthcare scientists who collect sleep data) have to be endlessly inventive. Visors that look like something out of Nasa are one option. These have a light source under the brim, which, being near the eye, does not have to be too bright. Also effective in some cases are carefully scheduled doses of melatonin, the hormone that is slave to the body clock and which carries its messages.
Another common problem is obstructive sleep apnoea. In adults, this is accompanied by heavy snoring. Children with this respiratory condition may not snore, but still wake up up to 12 times an hour, making them severely sleep deprived. Because their breathing seems normal during the day and even for much of the night, except in REM (dreaming) sleep, the real cause of poor daytime performance often goes unrecognised.
Here it is measurements obtained in a sleep lab that are the clincher for diagnosis. These rely on healthcare scientists whose job it is to wire up, cajole and comfort children, and then stay up all night to take the necessary measurements, showing extraordinary dedication. These children's respiratory difficulties are very often bound up with enlarged adenoids and tonsils. Shrinking them with steroid sprays or removing them surgically may provide a complete cure.
In adults, the link between sleep disorders and health disorders such as high blood pressure and coronary heart disease has long been recognised. Poor sleep in children is already linked with obesity, and it is known that children with sleep disorders are more likely to become adults with sleep disorders; but there may be a lot more to unravel about the dangers of doing without sleep when you're a kid. It's definitely not something to shut our eyes to.
