Sleep is a very basic human need that appears to be a fundamental process. Sleep is defined as a transient reversible state of perceptual disengagement from the environment.

The average human spends about 6 to 8 hours per day sleeping, for some it can be up to 10 hours per day, while others can do with just 4 hours per day. Hence, we spend about one third of the day sleeping, and therefore, one third of our life time sleeping, yet so many of us take sleep for granted.

Dolphins are intelligent mammals, they are able to rest half their brain and keep the other side of the brain awake while swimming and keeping watch.

Lions snooze about 12 hours per day, and they precisely do so because they are the top of the food chain. Elephants only sleep about 4 hours per day, and they do so while standing up-right. While we might know of some people who can do just that, most people would find it difficult to sleep upside down like the bat would for 3 months during winter.

Sleep is an active process

Most of us assume that sleep is a passive event, where we close our eyes and all our bodily functions "turn / switch off".

Contrary to popular belief, sleep is an active process involving complex interactions with increased metabolic functions and activities within the brain. Sleep is divided into 2 main phrases: dream sleep (rapid eye movement / REM) and non-dream sleep (non-REM).

On average, dream sleep comprises about 25% to 30% of the entire sleep in an adult. In a child however, dream sleep may be as high as 50% of the entire night’s rest. Research done on metabolic activity of the brain during different phrases of sleep and wake states, demonstrated increased metabolic activity in most parts of the brain during dream sleep compared to non-dream sleep and even the wake state.

Most sleep experts believe that dream sleep is crucial for the human. It is well accepted that dream sleep is important for well being, memory re-building, rejuvenation and mental alertness. Hence, dream sleep is vital to the human mind and body. There are some drugs that are selective non-dream sleep promoters, hence, these patients tend to be very tired and lethargic the next day and might attribute this to the side effect of the drug; in essence, it is due to the lack of dream sleep during that night’s rest.

Dream sleep is characterized by a highly active brain in a "paralyzed" body. This is a perfection made by our divine maker, so as to prevent us from acting out our dreams (i.e. if one was dreaming that one was playing soccer, one does not actually kick and act it out in bed, endangering one’s bed partner).

This however, works against the patient with a narrow airway, as the already narrowed airway will lose its tone during dream sleep and collapse, leading to upper airway obstruction, cessation of breathing and lack of oxygen. Therefore, this leads to stress on the heart, brain and other organs in the body.

This condition is called obstructive sleep apnoea (OSA). Obstructive sleep apnoea is the commonest sleep disorder. It results in interrupted sleep, sleep fragmentation and poor sleep quality. This is similar in patho-physiology to, what we so commonly encounter in our daily life, called sleep deprivation. During the day, the patient is excessively sleepy, has poor concentration, poor memory and becomes irritable. Long term health consequences include high blood pressure, heart disease, strokes and sudden death during sleep.

Sleep Deprivation

Everyone has to sleep at some point during the day. When work or training demands pushes us beyond the limit, and we go sleepless for more than 24 hours, our sleep deficit builds up, our reflexes and mental function begin to slow down. This sleep deficit builds up throughout the week, and causes us to become less productive at work, irritable, depressed and sleepy behind the wheel while driving.

Sleep Deficit Kills Performance

Some sleep related factors affect performance.

1. The homeostatic drive for sleep at night is determined mainly by the number of consecutive hours that we’ve been awake. Throughout the waking day, we build up a stronger and stronger need for rest. Most of us think we’re in control of this need to sleep, and that we choose when to sleep and when to wake up. The fact is that when we get so tired and exhausted, the brain seizes control involuntarily, and we fall asleep.

2. The second factor is the total amount of sleep that one has over the past several days. If one gets at least eight hours of rest per night, then the level of alertness should remain stable throughout the day, but if one has a sleep disorder like obstructive sleep apnoea, or if one has not been sleeping for several days, one will develop a sleep deficit that will make it more difficult for the brain to function.

3. The third factor has to do with sleep circadian rhythm - the time of day in the human body that says "it’s midnight" or "it's dawn". A neurological timing device called the "circadian pacemaker" responsible for this. This tells our body when is “night” and when is "day". Hence, shift workers may constantly feel tired as they may sleep during the day for a few days, then shift bask to sleep during the night the next few days.

4. The last factor that can affect performance is what’s called the "sleep inertia". This is the grogginess most people experience when they first wake up. Just like a car engine, the brain needs time to "warm up" when we wake. The part of the brain that is responsible for memory consolidation doesn’t function well for 5 to 20 minutes after we wake up and doesn’t reach its peak efficiency for a couple of hours. There exists a transitional period between the time we wake up and the time our brain becomes fully functional.