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The average individual spends about 2 hours dreaming, mostly during the second half of the night when REM (dream) cycles are longer.
Dreaming arises from signals in the pons which ascend through the thalamus into the cortex. There are also pontine signals that descend through the spinal cord causing motor paralysis. This muscle inhibition prevents motor activity during dreaming and can sometimes be lost, particularly in patients with Parkinson's disease. This entity is called REM sleep behavior disorder.
Respiratory muscles can be affected by this REM sleep paralysis. This may lead to breathing disturbances during dreaming. Changes in dreaming tendencies (e.g. "I feel like I dream all night long" or "I never dream anymore".) may be a sign of a sleep apnea or similar breathing disturbance.
Alcohol is a frequently used hypnotic in the United States. When ingested, alcohol is a potent inhibitor of REM sleep. Abstinence often causes a temporary increased in REM sleep called REM rebound. Other inhibitors of REM sleep include MAO inhibitors and tricyclic antidepressants.
Restless Legs Syndrome
Restless legs syndrome is a condition that causes uncomfortable sensations, primarily in the legs, that generally worsen with inactivity and improve with movement. The condition usually occurs at night or in the evening. The condition was first described by Thomas Willis (the same physician that described the Circle of Willis) in 1672. Despite being known for centuries, specialists describe RLS as ’Äúthe most common condition you've never heard of’Äù as it may affect 10-15% of the adult population. 80% of these patient also kick their legs during sleep, a condition called Periodic Limb Movement Disorder (PLMD). PLMD may greatly reduce sleep quality, lead to excessive daytime sleepiness (EDS), and cause both sleep-onset insomnia and sleep-maintenance insomnia. Thus, this is an important condition to rule out when seeing patients with either insomnia or excessive daytime sleepiness.
There are numerous treatments for the condition but until recently, none were FDA approved. Recently, Requip (ropinerole), a dopamine agonist commonly used to treat Parkinson's disease, received FDA approval in May of 2005 to treat moderate-severe RLS. The drug was studied for RLS in 3 large placebo-controlled studies (TREAT-RLS 1, TREAT-RLS 2, and TREAT-RLS US). In all studies, the drug separated itself from placebo in doses up to 4 mg/day. The medication, which has been used off-label for years, may have competition from another dopamine agonist Mirapex (primapexole) if it gains FDA approval.
Dopamine agonists are regarded by most sleep experts to be first-line therapy for RLS owing to their reduced incidence of augmentation (worsened symptoms over time) and rebound symptoms and well as reduced incidence of side effects. Neurontin (gabapentin), Sinemet (carbidopa/ levodopa), and Klonopin (clonazepam) are also used for RLS as off-label therapy. Conditions such as iron deficiency, pregnancy, renal failure and neuropathy can lead to RLS as well. Patients with RLS can often experience improvement if the underlying condition is treated (iron therapy for iron deficiency) or resolves (a pregnant mother delivers).