Parasomnias occur due to abnormal transitions between the three primary states of being wake, rapid eye movement (REM) sleep, and non rapid eye movement (NREM) sleep. These different states may overlap or intrude into one another, and it is the overlap of wakefulness and NREM sleep that gives rise to confusional arousals, and the intrusion of REM sleep into waking that produces REM sleep behaviour disorder (Matwiyoff et al, 2010). Parasomnias may have genetic basis, but occurrence is usually triggered by heavy physical activity, febrile illness, sleep deprivation, excessive caffeine drinks, hypnotics, and emotional stress. Intake of alcohol increased occurrence of confusional arousal, night terror, and sleepwalking, while heavy intake of caffeinated drink increased occurrence of sleep walking in a population study (Oluwole, 2010).
Confusional arousals Sleepwalking Sleep terrors
Sleep-wake transition disorders
Rhythmic movement disorder Sleep starts Sleep-talking Nocturnal leg cramps
Parasomnias usually associated with REM sleep
Nightmares Sleep paralysis
Impaired sleep-related penile erections Sleep-related painful erections REM sleep sinus arrest REM sleep behavior disorder
Congenital central hypoventilation syndrome Sudden infant death syndrome Benign neonatal sleep myoclonus
Table 1. The International Classification of Sleep Disorders classification of parasomnias
Heredity was described for many forms of parasomnias but detailed genetic studies are lacking. The composition of non-REM and REM sleep was shown to have genetic roots. Especially the amount of slow-wave sleep was recently shown to be genetically predisposed by a specific gene, the retinoid acid receptor beta encoding gene (Young, 2008; Maret et al., 2005).
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