We spend a third of our lives asleep, but scientists still don’t know why. It is thought this unconscious state serves some physiological or neural function that can’t be accomplished while fully conscious.

One such theory involves brain housekeeping – filtering memories from the day, filing the useful ones, and binning the rest – while the body relaxes. Without this opportunity to re-organise memories, dreams intrude into our waking lives, causing difficulty distinguishing our inner lives from reality. While we sleep the body also uses cellular energy to repair torn muscle tissue and remove free radicals, while our immune system recharges after a day of fighting toxins, bacteria, viruses and infections.

So a lot happens in our bodies while we dream, and it is no wonder we feel great after a good night’s sleep! But what is the damage when we are sleep-deprived? The need for sleep gets so strong, people have been known to fall asleep standing up, or while having intolerably loud music played at them. Within days of no sleep, people report confusion, forgetfulness and hallucinations.

Unfortunately, sleep deprivation can become the norm for some people, plus a vicious cycle is created when increased daytime stress makes sleep elusive at night, while lack of quality sleep contributes to stress during the day. Over time, it can seriously damage physical and mental health.

Sleep is especially important for the developing brain. Late nights and erratic bedtime routines blunt children’s brainpower, according to last year’s University College London study of more than 11,000 seven-year-olds.

The study found that children who went to bed later than 11pm had lower reading and maths scores, and spatial awareness, compared to children who went to bed 7.30pm-8.30pm. There is, however, no evidence to suggest that putting children to bed earlier than 7.30pm adds to brainpower!