How many hours of sleep does a five-year-old need? Does the time at which a child sleeps matter? What hormones are produced only during sleep? If, as a parent, you don’t know the answers, you are not alone. According to a new survey by the Sleep Council, most parents cannot answer these or even more basic questions about children’s sleep. Neither can most GPs, health visitors or teachers — and children are paying the price in health problems.

Mandy Gurney, an expert on children’s sleep, says that an increasing number of children spend their formative years “chronically sleep-deprived”. As a result they are not only tired, ratty and inattentive but are more prone to a spectrum of health problems including obesity, hypertension and clinical depression.

Gurney has been asked to set up a sleep clinic by a North London health authority because it recognises that simply getting children to sleep better will produce huge cost savings in health treatments over their lifetimes.

Why is the problem not more widely recognised? Because sleep is seen as something that we “just do”, says Gurney. “It is seen as organic rather than a medical issue, and people looking after children don’t connect the chronic and often serious symptoms with simple lack of sleep. Children are even less likely to see the connection.”

Which is why the Sleep Council is calling for sleep to be taught in schools.

Kathleen McGrath, a paediatric nurse who has written the council’s new Good-night Guide for Children booklet, says that attention, memory and learning are some of the first casualties of sleep shortage, so schools have a vested interest in getting children to take their sleep more seriously.

“Sleep deficiency impacts strongly on the prefrontal cortex of the brain,” she says. “This is the area engaged in what you might call higher-order thinking, involving creative and conceptual processes, as well as short-term memory.”

The recent changing of the clocks produced its annual reminder of just how sensitive our minds are to even a little sleep deprivation. According to the Royal Society for the Prevention of Accidents, the accident rate on the road and at work rose again significantly, if briefly, after our loss of that one autumnal hour.

Children are more susceptible to minor changes than adults, says McGrath: “They get clumsier, slower and less responsive.” The effect is more noticeable nowadays because they are already drawing on a low “sleep tank” as 24-hour television and social media cut into night-time routines.

The problem is insidious because, as children have started sleeping less, parents have shifted their expectations and many do not appreciate how much sleep children need. A five-year-old, for example, needs 11 hours but many children of that age get far less. The effect becomes apparent in the classroom and beyond — but not always in obvious ways.

Amara Willis was 5 when her sleep started to become disrupted. She had been sleeping through the night since she was 2, then stopped. Her daytime behaviour became aggressive and troubled and she started complaining about a catalogue of problems, from a blocked nose at night to blotches in front of her eyes that she said “turned into monsters”. The family GP referred her to the mental health services, who diagnosed an anxiety disorder and sent her mother on a positive parenting course. She was also sent to an ear, nose and throat specialist for the nocturnal catarrh, and her school was informed of her “psychiatric problem”.

She was then referred to Millpond Sleep Clinic, which Gurney runs. Within weeks her sleep pattern settled and all the diagnosed problems disappeared.

Amara, who turns 7 next month, now sleeps for the requisite 10 hours a night and is “confident, happy, sociable and doing well at school”, says Susan, her mother. “Learning to sleep has transformed her, but I don’t think it ever occurred to the mental health team that a few sessions in a sleep clinic could achieve that.”

Susan Willis, a 40-year-old bookkeeper, strongly supports the idea of teaching children about sleep. “After all,” she says, “schools now teach them about diet and sex but not about something that they spend a third of their lives doing.”

Older children are probably in even more need of sleep education, says Russell Foster, professor of circadian neuroscience at Brasenose College, Oxford, because they are subject to fewer parental controls and inclined to go to bed only when they have to. Add to that ever-present screens and mobile phones in their lives and sleep time is cut brutally short.

“In the Sixties and Seventies teenagers were getting what they need — nine to nine-and-a-half hours of sleep a night,” says Professor Foster. “That is now more like seven to seven-and-a-half.”

It is not only the duration of sleep that matters but the timing and type. Teenagers, like babies and toddlers, need a lot of “slow-wave” sleep, and tend to need more morning sleep for optimal functioning.

After hearing about experiments with later school start times in the US, Monkseaton High School in Whitley Bay, Tyneside, has instituted a 10am start to the day for its older pupils. Paul Kelley, the head teacher, became interested when he learnt about the “two-hour shift” in teenagers which means that their biological sleep cues, from melatonin levels to body temperature, come a couple of hours after those of young children and adults.

Although it is too early to predict results, Kelley says that the omens are good. “The children say that they prefer it — and they do seem brighter when they arrive.” Alertness peaks in the early afternoon for the average teenager (though unfortunately not for teachers) and in the late evening (in contrast to parents).

Lack of awareness of the distinct sleep patterns and needs of teenagers can lead to them being not only misjudged but misdiagnosed. Anthony Pantello was almost 13 when his mother decided that his sleep problem needed tackling. His GP said that he couldn’t help. Anthony’s problem was compounded slightly by the fact that he has suffered from mild Tourette’s, ADHD and anxiety since his father and two other close relatives died in quick succession.

“He had difficulty in settling into school, problems with concentrating and his behaviour was often loud and impatient,” says his mother Caroline, a legal secretary. She was “surprised and relieved” to find a sleep clinic that dealt with older children.

Children and teenagers with special needs often suffer from sleep problems that make their underlying troubles worse, and sleep therapy can often help.

“Anthony now sleeps really well and has completely changed,” says Caroline. “He is doing much better at school and any perception of him as a ‘special case’ has gone.”

With 30 per cent of children suffering from sleep problems and the evidence on associated medical conditions accruing, the prospects do not look favourable, says Professor Foster. “The good news is that if emerging problems are treated in childhood they invariably resolve.” If, conversely, they are not addressed, there is every chance that they will continue for life. That is something for parents to sleep on.

Teach Your Child to Sleep by Mandy Gurney and Tracey Marshall (Hamlyn) www.mill-pond.co.uk

Getting them to sleep

1 Have a set sleep time Set a regular sleep-wake schedule with no more than one hour deviation from day to day, including weekends.

2 Check out the bedroom Keep the room below 18C. Too much heat disturbs sleep. Constant noise can have the same effect, as can too much light: try using blackout blinds.

3 Relaxation time Get your child or teenager to do something relaxing in the half hour before bed — reading or listening to an audio book.

4 Remove distractions Make bedtime mean sleep time. This may mean removing toys, TV and computer from the bedroom. No eating, drinking or talking.

5 Enforce boundaries When you say two stories, mean two stories. Lack of limits can lead to long bedtime battles.

6 Focus the routine Aim to do the same things each night, about 30 minutes before bed — for example: a quick bath; straight into the bedroom; dim lights; read stories; say goodnight and leave. Expect your child to be asleep 15 minutes later.

7 Prevent “worry time” If your child is awake after 30 minutes because of worries, he or she should go to another room and read or listen to a tape for a while. A warm milky drink may help.

8 Diet Avoid caffeine close to bedtime (tea, Coke). For a snack, try a banana, warm milk, an oat biscuit or wholegrain cereal.

9 Regular exercise Encourage exercise for 20-30 minutes three or four times a week (but not within three hours of bedtime).

10 Praise Praise children if they keep to “the rules”.