Most people with fibromyalgia — more than 75 percent, according to the National Fibromyalgia Research Association — complain of sleep disturbances and daytime fatigue. Experts believe that these feelings of grogginess and sleep deprivation are the result of problems falling asleep and staying asleep.

While some people with fibromyalgia don't remember waking up frequently, others do recall these disruptions to a good night's rest. Either way, these abnormal sleep patterns prevent fibromyalgia sufferers from getting a healthy amount of restful, restorative sleep.

Fibromyalgia's Connection to Impaired Deep Sleep

There are five stages of sleep, and in the course of a normal night's rest, a person will normally cycle through various stages, from light to deep to dreaming, every 90 minutes or so. Dreaming occurs during what's called REM (rapid eye movement) sleep. Interestingly, EEG (brain wave) studies have found that fibromyalgia patients lack the restorative levels of deep, non-REM sleep. It is during these deepest levels of sleep — also known as stages 3 and 4 — that the body restores and refreshes itself. Stage 3 is characterized by moderately deep sleep and stage 4, the deepest sleep phase, is when certain substances like growth hormones are released for body-tissue repair and replenishment.

Research suggests that people with fibromyalgia are constantly aroused by bursts of "awake" brain activity, which limits the amount of time they spend in these critical deep stages of sleep. "On EEG studies, fibromyalgia patients in deep-sleep stages have been found to have alpha waves, which are signs of arousal or wakening," says Patrick Wood, MD, chief medical advisor for the National Fibromyalgia Association. One study found that fibromyalgia patients experience at least twice as many arousals per hour as people without the disorder.

Fibromyalgia's Constant "Fog" and Fatigue

The lack of uninterrupted deep sleep may be the reason why people with fibromyalgia are also plagued by extreme daytime fatigue. In today's world, many people complain of feeling tired, but the exhaustion associated with fibromyalgia is much more severe. Fibromyalgia patients report feeling as if their bodies have been completely drained of energy, which can lead to limited physical and mental functioning.

It's also common for people with fibromyalgia to have problems with concentration, thinking, and even memory, a condition known as "fibro fog." One possible reason: Memories are processed during sleep stages 3 and 4. "During these two stages of sleep, the brain sorts through information accumulated during the day, taking it out of short-term memory and putting it into long-term memory," says Dr. Wood. When the amount of deep sleep is reduced, experts speculate that the body may have a limited ability to repair and replenish the brain's functioning, affecting memory as well as energy.

Brain Chemicals: The Root of the Problem?

While the causes of sleep problems in those with fibromyalgia are not yet completely understood, research is uncovering possible links. One theory is that brain chemicals may be out of whack. "There's very good evidence that fibromyalgia is associated with abnormal amounts of dopamine, which is an energy-related neurotransmitter, or brain chemical," says Dr. Wood. Norepinephrine, another energizing neurotransmitter, and cortisol, a hormone associated with stress, have also been found to be abnormal in fibromyalgia patients. In addition to interfering with restful sleep, neurochemical and hormonal imbalances may exacerbate the pain associated with fibromyalgia, in the opinion of some experts. Other researchers believe that it's the constant pain that triggers deep-sleep abnormalities.

More studies are currently underway that may help uncover more definitive causes of sleep difficulties associated with this painful, life-altering condition. It is hoped that in the next five years or so scientists will have more answers about the connection between fibromyalgia and disordered sleep.