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Ahhh, sweet sleep.  I love to sleep, yet many times, I get so little of it.  Humans have biological rhythms, known as circadian rhythms that are controlled by a biological clock and work on a daily time scale.  Circadian rhythms are directly related to the amount of natural and artificial light we receive, and how our wake/sleep cycles correspond to that light.  A person’s desire and ability to fall asleep is influenced by both the length of time since the person woke from an adequate sleep, and by these internal rhythms.  It is referred to as a rhythm because it is intended to be consistent.  Everyone’s rhythms are different, so we are ready for sleep and wakefulness at different times of the day.

We spend about one-third of our lives asleep.  Sleep is a required activity, not an option, it is important for normal motor and cognitive function.  Circadian rhythms  affect body temperature, alertness, appetite, hormone secretion etc. as well as sleep timing.   Sleep actually appears to be required for survival.  In fact, in one study, rats deprived of sleep died within two to three weeks, a time frame similar to death due to starvation.  After sleeping, we recognize changes that have occurred, as we feel rested and more alert.  A good nights sleep can change my entire perspective on things.  If I went to bed angry or sad, I usually feel much better in the morning.  If I am wrestling with an important decision, many times I wake up with a clarity on the decision that I could not reach the day before.  Doctors recommend an average of 7 – 8 hours of sleep per night for adults, and 8 – 9 hours of sleep for school age children and teenagers.

As important as sleep is, we often equate it to something we want rather than something that we need.  We regularly deprive ourselves of sleep in the name of hard work.  I think we don’t always relate good sleep habits to our everyday health in the same way we consider diet and exercise to be essential to our health.  The truth is, our circadian rhythms are crucial to our mental and physical health.  For instance, the functions of many organ systems are linked to our sleep cycle, such as:

• Endocrine system. Most hormone secretion is controlled by the circadian clock or in response to physical events. Sleep is one of the events that modify the timing of secretion for certain hormones. Many hormones are secreted into the blood during sleep. For example, scientists believe that the release of growth hormone is related in part to repair processes that occur during sleep. Follicle stimulating hormone and luteinizing hormone, which are involved in maturational and reproductive processes, are among the hormones released during sleep. In fact, the sleep-dependent release of luteinizing hormone is thought to be the event that initiates puberty. Other hormones, such as thyroid-stimulating hormone, are released prior to sleep.
• Renal system. Kidney filtration, plasma flow, and the excretion of sodium, chloride, potassium, and calcium all are reduced during both NREM and REM sleep. These changes cause urine to be more concentrated during sleep.
• Alimentary activity. In a person with normal digestive function, gastric acid secretion is reduced during sleep. In those with an active ulcer, gastric acid secretion is actually increased and swallowing occurs less frequently.

When sleep deprived, humans may experience many symptoms in a long list of problems such as, difficulty concentrating, memory lapses, slowed word recall, headaches, loss of energy, fatigue, lethargy, aching muscles, dizziness and nausea, increased blood pressure, increased risk of diabetes, fibromyalgia, obesity, and emotional instability such as temper tantrums in children and depression in adults.  The prevalence of problem sleepiness is high and has serious consequences, such as drowsy driving or workplace accidents and errors.  Loss of sleep creates an overwhelming and uncontrollable need to sleep and affects virtually all physiological functions.

For all that we may have accomplished, how much more could we achieve when we regulate our circadian rhythm?  What are your thoughts on sleep or the lack of it?