Sleep is not a state of massive system shutdown, but quite the contrary. During sleep, the brain is very active, constantly communicating with the body. Many neurohormones, antibodies, and other molecules also are synthesized during sleep; therefore, when sleep is disrupted, biochemical abnormalities can occur, leading to multisystem disturbances.

Sleep studies have shown that patients with fibromyalgia have disordered sleep physiology. Most of these patients experience unrefreshing sleep with morning fatigue.

To understand abnormal sleep architecture, it is essential to know the basics of normal sleep. Sleep can be divided into 2 main parts, nonrapid eye movement (NREM) and rapid eye movement (REM) sleep, which alternate cyclically through the night, always starting with NREM sleep. In each successive NREM and REM cycle through the night, the amount of NREM sleep decreases and the amount of REM sleep progressively increases. Each cycle, NREM plus REM, lasts about 90 minutes. NREM is divided even further into 4 stages: stage 1 is initial drowsiness; stage 2 is light sleep; and stages 3 and 4 are progressively deeper levels of sleep.

In stages 3 and 4 of NREM sleep, the electroencephalogram (EEG) shows a pattern called delta waves, which are high-amplitude waves (greater than 75 mV) that move slowly (0.5-2 Hz). Much of the body's regulatory work, as well as synthesis of many substances (eg, antibodies, growth hormone, other neurochemicals), occurs during NREM sleep.

REM sleep has a low-voltage mixed-frequency pattern on EEG and is considered dream sleep. In this stage, the body has a complete loss of muscle tone, known as flaccid paralysis, and cannot move. During this part of sleep, consolidation of memories may occur, but there is still disagreement over exactly what occurs with memory during REM sleep. Some investigators found that during waking hours, the brain generates alpha waves with a frequency of 7.5-11 Hz.

Sleep dysfunction is considered an integral feature of fibromyalgia syndrome. Seventy percent of patients with fibromyalgia recognize a connection with poor sleep and an increased pain, along with feeling unrefreshed, fatigued, and emotionally distressed. Several studies have linked abnormal sleep with these symptoms.

Some researchers have studied fibromyalgia and sleep, confirming the disordered sleep physiology in fibromyalgia. This abnormality has been identified as an alpha-wave intrusion sleep anomaly, which occurs during NREM stage-4 sleep. This intrusion into deep sleep causes the patient to awaken or to be aroused into a lighter level of sleep.

Some authors describe the altered sleep physiology and somatic symptoms as a nonrestorative sleep syndrome. This sleep dysfunction is believed to be linked to the numerous metabolic disturbances associated with fibromyalgia, including abnormal levels of neurotransmitters (serotonin, substance P) and neuroendocrine and immune substances (growth hormone, cortisol, and interleukin-1). These authors propose that these metabolic imbalances are responsible for the increase in symptoms associated with this alpha-wave intrusion sleep disorder by impairing tissue repair and disturbing the immunoregulatory role of sleep. Studies show that the greatest amount of alpha-wave intrusions occur during the first few hours of sleep, decreasing throughout the night to normal levels by early morning. Some researchers note that this hypothesis correlates well with patients' frequent reporting that their best sleep is obtained in the early morning hours just prior to arising.

Sleep Disorders – – National Sleep Foundation – http://www.sleepfoundation.org/primary-links/how-sleep-works

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