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OSAKA - If people exhibit abnormal behaviour while sleeping, such as shouting or getting up suddenly and acting violently, they may be suffering from REM sleep behaviour disorder (RBD). Symptoms of the disease are more frequently manifested as people get older, so the number of RBD sufferers is likely to increase in an aging society.
As RBD sufferers may injure themselves or disturb their family members, specialists recommend they undergo treatment.
During a normal night of sleep, rapid eye movement sleep (REM sleep) and non-rapid eye movement sleep (non-REM sleep) alternate continuously.
Dreams occur during REM sleep, when the brain is nearly awake. At that time, the brain usually issues a command that restricts movements of nearly all muscles, except those necessary for breathing.
However, RBD sufferers have trouble inhibiting muscle functions for some reason and act according to what is happening in their dreams.
Two years ago, a 67-year-old man in Toyonaka, Osaka Prefecture, started getting out of bed while sleeping almost every night, shouting "Thieves are here!" and "Fire!"
His family was concerned and sent him for a magnetic resonance imaging (MRI) brain scan and dementia test. None of the tests revealed any problems.
However, his abnormal behaviour continued. One night when he got out of bed, he fell down and broke his collarbone.
Early this year he went for a consultation at the Osaka Kaisei Hospital's Sleep Medical Center in Yodogawa Ward, Osaka, where he was diagnosed with RBD.
According to Mitsutaka Taniguchi, a chief physician at the centre, RBD sufferers often dream about violent or disagreeable incidents, such as "quarreling with someone" or "being attacked by an animal."
They also shout, like the Osaka man, and wildly move about. Unlike the nonsensical sleep talking heard when, for example, people are turning over, RBD victims speak clearly and their speech makes sense. When woken up during an attack, they can remember the dream they were having at the time.
To diagnose RBD, polysomnography testing is performed in addition to a doctor's consultation. The test can distinguish REM sleep from non-REM sleep based on brain waves and muscle movements. If patients begin showing symptoms of RBD when they are in REM sleep, they are officially diagnosed with the disorder.
To treat RBD, Clonazepam, an antiepileptic drug, is prescribed.
The medicine has proven effective for many RBD sufferers. The 67-year-old man became almost completely free of RBD symptoms on the first day he began taking the medication.
RBD sufferers need to take medicine on a regular basis. If they forget or stop taking their pills, their RBD symptoms return. However, even without medicine, symptoms can sometimes be reduced simply by refraining from alcohol.
It is believed many RBD sufferers are men in their 50s and older.
Although there are no domestic statistics available for the disease, overseas reports state it occurs in 0.38 per cent of the general population and in 0.5 per cent of those aged 65 and older.
The disease is often detected by family members living with RBD sufferers or friends who share the same room with an affected person during an overnight trip.
Sufferers have difficulty recognising the disorder on their own. Therefore, people living alone need to be cautious.
It is said RBD is caused by an abnormality in the pons, which is located on the brain stem. Its cause is unknown, but it can be triggered by excessive alcohol intake or stress.
Overseas reports show that in nearly half of all RBD sufferers, the disorder develops into Parkinson's disease or a condition known as dementia with Lewy bodies.
However, Taniguchi said based on his clinical experience RBD sufferers do not have to overly fear such developments.
About 400 RBD sufferers have been treated at his centre. Some of them first experienced symptoms of the disorder more than 10 years ago, and most of them have avoided progressions to worse diseases.
Taniguchi said: "Some RBD sufferers were on the verge of jumping out the window. If their symptoms are left untreated and get worse, sufferers are more likely to hurt themselves and their family members sleeping next to them. If you are concerned about your habit of tossing and turning or talking in your sleep, consult a sleep specialist."