Sleep

Sleep is a natural bodily state characterized by a lack of consciousness and inactivity of voluntary muscles.  It involves an impaired ability to react to stimuli however is a period of heightened anabolism which accentuates the body’s ability to grow and repair the immune system, nervous system, muscular and skeletal systems.  Sleep is an important part of anybodies life (we sleep for roughly 1/3 of our life) and allows us to maintain regular daily activity.  There are massive consequences to the body and mind if a person doesn’t get enough sleep and this will be discussed further in the post.

Sleep stages

Sleep is divided into 2 broad stages; REM (rapid eye movement) sleep and non-REM sleep.  Each type is distinct from each other physiologically, neutrally and psychologically.  Non-REM sleep is further divided into 4 other stages and we cycle through these four stages and into REM sleep then back into non-REM sleep.  REM sleep accounts for around 20-25% of total sleep and is the stage of sleep associated with memorable dreaming and atonia (paralysis during dreaming).

Our circadian rhythm, or biological clock controls our sleep-wake patterns which are controlled by hormone release.  The circadian rhythm works with adenosine which is a neurotransmitter that is associated with wakefulness.  Adenosine is created throughout the day with high levels of adenosine leading to sleep.  In diurnal animals (day walkers), the circadian rhythm causes sleepiness by a release of melatonin that lowers the body’s core temperature.  There is a gradual fluctuation of cortisol during the day which is governed by the circadian rhythm as well.  Cortisol has a role in controlling sleep-wake patterns as high levels of cortisol cause a heightened sense of awareness and consciousness while low cortisol levels are associated with lower levels of consciousness.

Optimal sleep

An optimal amount of sleep is a meaningless statement unless it is looked at in relation to that person’s circadian rhythm.  Even if you sleep for the “optimal” amount but it occurs at the wrong time of day for your rhythm, that sleep is ineffective.  It seems that the amount of sleep needed by an individual is governed by their circadian rhythm as there are two markers that need to occur in the middle of your sleep pattern and before waking for sleep to be effective.  1)  You need a maximum concentration of melatonin and 2) minimum core temperature.  Human sleep can vary among individuals and a person’s sleep is considered effective if there is no day-time sleepiness or dysfunction.  A lack of sleep is associated with an increased of mortality through weight gain, hypertension and Type 2 Diabetes.  A person can be in a state known as sleep debt from not getting enough sleep.  The larger the debt, the more severe the symptoms.  Sleep debt causes mental, physical and emotional fatigue.  It causes a decreased ability of the individual to perform higher level cognitive functions with the frontal lobes of the brain being particularly susceptible.

Functions of sleep

This is a hotly debated topic within the circles of sleep academia and the research is largely incomplete.  After 50 years of research into sleep, William Dement said on the functions of sleep “the only reason we need to sleep that is really, really solid is because we get sleepy”.  There are a few things however that have been shown to be affected by sleep such as restoration of the immune system, somatic growth of an organism and muscular repair.  The immune system is weakened by a lack of sleep with white blood cell counts decreased by as much as 20% in sleep deprived mice.  A lack of sleep affects the release of growth hormone in adult men, so for all you crossfitters and weightlifters out there, get some sleep or forever face mediocrity.  It has also been found that sleep is inversely proportional to the size of an organism and directly related to basal metabolic rate.  An animal or person with a higher metabolic rate needs more sleep than a person or animal with a lower metabolic rate.

Sleep has also been shown to affect working memory and higher level cognitive functions such as decision making and reasoning, with a lack of sleep dramatically affecting these functions.  REM sleep is also associated with the processing of procedural knowledge.

Effect of food and drink 

What we eat and drink have an affect our body. We all know this, which is why we stay away from certain foods and why we eat others. Sleep is just another function of our body that can be disturbed by what we put in our mouth. Alcohol is used by a lot of people to help them get to sleep but it has been associated with an increase in disrupted sleep and reduced REM sleep. Caffeine and other stimulants (including sugar, natural sweeteners and pretty much anything that contains anything ending in –ose) affect sleep by increasing the amount of insulin and cortisol in the body. When we ingest these our blood sugar rises and causes an increase in insulin. When your blood sugar drops again, cortisol is released and high levels of cortisol keep us awake, that’s what coffee’s for right? Having these things late in the day will disrupt your sleep and leave you feeling flat and in need of more stimulants.