How Important is Sleep?

As more and more is discovered about sleep, scientists are realizing the importance of sleep on our overall mental and physical health. Unbelievably, we spend one-third of our life sleeping or approximately 122 days a year. However, it is estimated that 63% of Americans get less than 8 hours of sleep and 31% get less than 7 hours of sleep. Furthermore, two-thirds of Americans say the do not sleep well at least three nights a week. If you feel drowsy during the day, experts say you have not had enough sleep.

 As we age, the amount of sleep we need decreases. Not only does the amount of sleep decrease with age, but the amount of rapid eye movement (REM) sleep decreases. Newborns sleep approximately 16 hours per day and spend half that time in REM sleep. Adults need approximately 8 hours of sleep per night and spend 20% of that time in REM sleep. Older people (50 - 85 years of age) sleep approximately 5.75 to 6 hours per night and 15% of the time in REM sleep. With older people, it is a common misconception they need less sleep. They need approximately the same amount of sleep as then they were younger. However, older people do have a tendency to sleep lighter and for shorter periods of time.

 Sleep can be divided into types: non-rapid eye movement (NREM) and rapid eye movement (REM) NREM sleep occurs in four stages. These stages progressively lead to a deeper level of sleep. During stage one, the body relaxes and begins to fall asleep. You are able to awaken easily. This stage may last from 5 to 10 minutes. In stage 2, light sleep occurs. Muscles alternate between relaxing and contracting. The heart rate slows. Body temperature decreases. Your body prepares for a deeper level of sleep. In stage 3, the body progresses into a deeper sleep. This stage is called slow-wave or delta-wave sleep. Stage four is the deepest level of sleep. Although most people associate REM sleep with dreams, in actuality, more dreams occur in NREM sleep.

After these four stages, REM sleep occurs. During this stage, the eyes move rapidly back and forth. Brainwave patterns are similar to wakefulness, but the muscles are paralyzed. It is thought the paralyzation occurs so dreams are not acted out. The face, leg, and fingers may twitch. The heart rate and respiration increase and become erratic. Intense dreaming occurs. With each cycle of sleep, REM sleep progressively lengthens. The first stage of REM may be 10 minutes, whereas, the last stage may last an hour. It takes up approximately two hours of a person’s sleep a night.

 Although researchers do not fully understand the purpose of sleep, these may be some of the reasons:

• It restores the body’s energy.
• It gives the body a chance to repair itself and regenerate.
• It helps the brain organize and store memories.
• It may recharge the brain. Adenosine signals the brain when it needs sleep. Adenosine triphospate (ATP) releases energy to fuel reactions. With each burst of energy, ATP loses it triphospate molecule, and the adenosine binds to receptors. Rising levels of adenosine signal the brain it needs rest. Although scientists once thought that caffeine induced alertness by blocking sedating mechanisms in the body, they now know that caffeine blocks the the receptors adenosine binds to.
• In newborns, REM sleep may help develop the central nervous system.

Since sleep is responsible for the body’s restorative functions, the lack of sleep can be deleterious upon an individual’s health. The consequences of sleep deprivation can affect the following areas:

• Reduced performance and lack of concentration cause impaired learning.
• Depression. People who are depressed have shorter lengths of REM sleep. It is also a viscous circle. Depression may cause sleep loss and vice-versa.
• Increased mental illness
• Decreased immune system function
• Increased pain perception
• Decreased ability to metabolize glucose and an increased risk of diabetes.
• Less than five hours of sleep per night increases the risk of high blood pressure or worsening blood pressure. In a study at the University of Chicago, researchers found that for every hour sleep was reduced, the risk of high blood pressure increased by 37%.
• May trigger the release of stress hormones and an increased risk of heart attacks and strokes.
• An increased risk of breast and colon cancer. Melatonin fights abnormal cell growth, especially in breast cancer and colon cancer. Since melatonin is released at night, less sleep means less melatonin. Thus, a reduced cancer-fighting ability.
• Increased car accidents and occupational accidents
• Increased inflammation. Chronic or systemic inflammation can cause a variety of diseases and conditons.
• During a 5-year study, researchers found extremes in sleep duration are related to to more abdominal fat in individuals younger than 40 years of age. While six to seven hours were considered normal, the extremes were defined as five hours or less and eight hours or more. Individuals with less sleep had a higher body mass index (BMI). Excess abdominal fat is a known risk for many diseases.

If a person is a sleep deprived, once normal sleep returns, the body tries to compensate for it by REM rebound. With REM rebound, there is a significant increase in the length of stage 1 sleep and REM. However, when the loss of sleep continues, researches have found that animals no longer try to make up for the loss of sleep despite the sleep deficit. Therefore, since the loss of sleep is so damaging to the health, it is imperative one try to get the proper amount of sleep.