The average human will spend one third of his or her life asleep, so that a person who manages to live to 90 years will have spent at least 30 years of that life in the state of altered consciousness we call sleeping. Something we devote so much time to, as much as one third of our lives, must be very important. So why do we sleep? Modern neuroscience has begun to “unravel” the mystery of sleep and so to undo the many myths about this essential human activity. Perhaps the most interesting scientist working on sleep today is Professor Russell Foster, his TED talk “Why we sleep” is a must see for anyone interested in this area.
Sleep is very important to our mental and physical health. Obviously we sleep because we are tired. We need to rest to restore ourselves. The data show us that loss of sleep is definitely associated with decreased performance and increased hazards to general health. Sleep deprived people find problem solving more challenging and they have poor memory function compared to their somnolent fellow men and women. They have more road accidents, more accidents in general at work and more physical ill health in every way. Specifically increased trauma and increased cardiac illness are well established consequences of sleep deprivation.
Some say we sleep to conserve our energy, as animals do when they hibernate, or to avoid the jeopardy of the dark night, but these anthropological and sociological explanations do not bear close examination. In reality we use almost as much energy when we sleep as we do when we are awake and we now know that the brain sleeping is in an anabolic not a catabolic state. That is to say when we sleep the brain is growing, not breaking down. Brain processing increases during sleep; building memory, promoting learning and underpinning mental health. The key networks involved in these mental processes are active and amplified during sleep, and each of these circuits deteriorates in states of insomnia. It is sleeps brain-processing function that is probably its most important element explaining why it is of such necessity for us all.
Good sleep is essential for all health, both mental and physical, and all mental distress is associated with disturbance of restful sleep. The anxious often struggle to get to sleep and the depressed must struggle to stay there. In anxiety disorder it may take hours to get off to sleep, while the depressed ache for sleep to continue till morning, only to find they wake early with dread of the day ahead.
In manic states, sleep may be lost entirely since energy is increased, and in addiction, sleep is reduced since these substances, alcohol, marijuana, or benzodiazepine, alter the delicate architecture of sleep and ultimately break it down.
Sleep is divided by electrical brain rhythm analysis into Rapid Eye Movement (REM) sleep and Non-REM sleep. Sleep commences with Non REM and progresses uninterrupted through stages 1 to stage 3 (slow wave or deep sleep). REM sleep then commences for a phase and after this the whole cycle begins once more. In a normal eight hours this progression can happen more than three times with REM cycles becoming more frequent later on.
There are many myths about sleep which need to be recognised and countered.
Common myths about sleep
- “SLEEP IS A PASSIVE ACTIVITY”. It is an active process requiring energy.
- “OLDER PEOPLE NEED LESS SLEEP”. Older people need just as much sleep but their ability to obtain continuous sleep is broken and therefore limited so that they may need to get their sleep over more phases e.g. siesta.
- “YOU CAN GET BY WITH JUST 4 HOURS SLEEP”. Known as the Margaret Thatcher myth (“Sleeping is for wimps”) this is seriously in error. Most adults are in need of 7 to 8 hours of restful sleep per day
- “YOU CAN CATCH UP ON YOUR SLEEP AT THE WEEKENDS”. Sleep lag or jet lag or sleep deficit is significant and cannot be made up easily in one weekend.
- “Teenagers are lazy so they stay in bed more”. Teenagers need at least 9 hours of sleep per 24 hours and may require more. Fifty years ago the average 16 year old would have had 9 hours sleep per night but now there is data to show that an average teenager is getting less than 6 per night. The consequences for brain growth and development are considerable.
- “SNORING IS HARMLESS”. Snoring may be more than a nuisance, it can be a significant marker of a condition called sleep apnoea. Investigation for sleep apnoea is worthwhile and by addressing it many patients recover healthy sleep and better overall health
- “SLEEPING PILLS ARE HARMLESS”. Sleeping pills should only be prescribed for brief periods and then only under medical supervision. Long term use of sleeping pills is endemic in Ireland and is a significant health risk. Some surveys suggest that up to 60% of patients attending clinics are on long term hypnotic medication. These agents work on a brain inhibitory system called GABA 2 and they are only briefly effective in inducing sleep. Long term use has been associated with increased rates of mental and physical problems.
- “EVERYONE NEEDS 8 HOURS SLEEP A NIGHT”. Our need for sleep is individual and relates to our stage in life. The average new-born sleeps for 18 hours per day. The average teenager needs at least 9 hours per day and the average adult benefits from 7 to 8 hours. Despite this we now know that availability for sleep is under threat in modern times.
- “WATCHING TV HELPS YOU FALL ASLEEP and DRINKING ALCOHOL WILL GIVE YOU A BETTER NIGHT’S SLEEP”. Neither of these is true. In fact alcohol is a detriment to the passage of sleep from stage one to four. So that apart from the diuretic effect of alcohol the sleep destructive effect means that the night cap actually wakes the sleeper in the first 3 hours or so.
By Prof. Jim Lucey, Medical Director of St Patrick’s Mental Health Services