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Is sleep simply turning off the brain and going into a deep coma?

Sleep is much more complex than you may think. In fact it is a state of being just as important as being awake. Some people believe that sleep is a waste of time, and they try to sleep as little as possible to be more productive within more waking hours. The consequences of this mistaken thinking are detrimental. These people tend to be chronically tired and mentally unfocused. They are also liable to get sick more often and in the long run, their health suffers.

“I’m so tired!” When you hear these words you can almost bet that it’s because of improper sleep. But, what is it that we really do while we sleep?

Sleep is a complex and vital part of our daily routine. Sleep is not simply “turning down” the brain and resting. It is rather a complex set of behavior with a neurochemical basis. With the setting of the sun and changes in our environment that come with it, certain messages are sent to our brain. Within our brain, just behind our eyes, lie a set of nerve cells (suprachiasmic nucleus) that act as our internal clock. These groups of cells have intrinsic rhythm that acts as our “clock” and function as mediator of our circadian rhythm. These cells are under direct influence of light, especially the sun. After the sun sets, there are series of neurochemical changes that take place including a rise in our melatonin level which eventually leads us to sleep.

There are also temperature changes in our body that follow circadian pattern. Our body temperature is lowest during the deepest part of sleep. As our body starts to “warm up”, we awaken in the morning. Body temperature continues to rise during the day with a slight dip in the mid-afternoon (“afternoon dip”). When our body temperature falls we generally tend to feel sleepy. This is why we feel sleepy after lunch, not necessarily because of a heavy meal. Our level of alertness seems to follow our temperature curve. Our body temperature peeks after dinner, and then starts to cool down. This is when we get sleepy. It is interesting to know that our internal clock, the suprachiasmic nucleus, sits just above the hypothalamus, the master controller of our metabolism.

At the onset of sleep, an interesting phenomenon occurs. We all recognize that our muscles relax as we fall asleep. If you see someone become sleepy, their facial muscles begin to relax even before there are fully asleep. The eyes get “heavy” as the person has difficulty keeping them open. The head starts to nod if they happen to be sitting up. If you observe carefully as one falls asleep there is sudden relaxation of the whole body as he/she enters sleep. The upper airway also relaxes along with chest wall muscles. This results in a change in the breathing pattern and a slight under-breath during sleep. Some of us start to snore with relaxation of the airways, and in individuals with sleep apnea their upper airway collapses as they start having apneic episodes.

Sleep is organized into non-REM and REM sleep. These two sleep states appear to be as distinctly different as awake is to sleep. Non-REM is divided into stages one through four. Stage 3 and 4 is known as delta sleep or slow wave sleep. Non-REM is thought to be more of “brain resting” as there is decrease in energy consumption by the brain. We generally start our sleep with light sleep entering into slow wave sleep. Most young kids have an increased amount of slow wave sleep compared to adults. In kids it is during the first stage of slow wave sleep that growth hormone is released by the brain. Increased level of exercise has shown increased slow wave sleep, and it is thought that this stage of sleep has some kind of restorative function. During the night, the brain cycles between non-REM and REM sleep at approximately 90-minute cycles. As night progresses, REM phase becomes longer. About 25% of our sleep is spent in REM sleep.

As you may know, REM stands for rapid eye movement. REM is also referred to as active sleep or paradoxical sleep. Interestingly, in REM our brain is highly active and utilizes more energy than when we are awake. REM is thought to be a primitive type of sleep and it is the first sleep seen in the developing brain. Because the brain is highly “turned on”, other interesting phenomenon occurs. Our brain literally paralyzes our body to prevent it from moving. There are series of changes that occur in the brain stem resulting in near complete paralysis that occur at the level of the spinal cord. In fact, our spinal reflexes such as knee jerk reflex is absent during REM. If you have ever awakened and were paralyzed for a few seconds, literally could not move even though you’re awake, this is when your brain delayed turning off part of the REM mechanism. Most people have experienced this feeling and occasional episodes are thought to be normal. REM is also associated with the dream state and when people are awakened during REM they usually will have a vivid dream recall.

The question was what happens when we sleep. Honestly, we are not sure. But we know what happens when sleep is partially deprived. The most obvious changes we notice are that the person is tired and lacks energy. There is also a noticeable lack of concentration. Even if the sleep-deprived person is not tired studies have shown that with a minimal decrease in sleep-time, day time performance suffers. There is strong evidence that your metabolism will be disturbed. Chronic sleep deprivation has been shown to slow your metabolism leading to weight gain as well as fatigue. Various hormones that are released by the brain to control being awake and being asleep also appear to control hunger and satiety, and vice versa. Your immune function also appears to be directly related to sleep pattern. Lack of proper sleep will compromise the overall immune system leading to illness. Severe sleep deprivation studies done in animals often result in the animal dying, with overwhelming infections. In fact, the most efficient way to improve your immune function is to optimize sleep.

There are strong psychological affects from lack of sleep. Other than being tired, sleepy people tend to be cranky and short tempered. Chronic sleep loss is associated with fatigue and depressed mood. Divorce rate among couples with sleep problems is much higher than average. In fact, the most treatable cause of attention deficit disorder is sleep deprivation, the most common form being sleep apnea.

We know sleep has various important functions, but we still try to get by on less sleep and more caffeine. There is really no substitute for sleep, especially for growing kids and young adults. Setting a regular sleep pattern is the basis of good sleep hygiene.

Inchel C. Yeam, MD, FCCP Diplomate, American Board of Sleep Medicine,
Pulmonary & Critical Care Medicine,
American Board of Internal Medicine