Narcolepsy is characterized by “sleep attacks” that occur during the day. This means that you will suddenly feel extremely tired and fall asleep without warning. The disorder can also cause sleep paralysis, which may make you physically unable to move right after waking up. Although narcolepsy may occur on its own, it is also associated with certain neurological disorders, such as multiple sclerosis.

Sleep disturbances have been also observed in Alzheimer's disease (AD), affecting about 45% of its population.[22][24][26] Moreover, when it is based on caregiver reports this percentage is even higher, about 70%.[28] As well as in PD population, insomnia and hypersomnia are frequently recognized in AD patients, which have been associated with accumulation of Beta-amyloid, circadian rhythm sleep disorders (CRSD) and melatonin alteration.[22][24][28] Additionally, changes in sleep architecture are observed in AD too.[22][24][26] Even though with ageing the sleep architecture seems to change naturally, in AD patients it is aggravated. SWS is potentially decreased (sometimes totally absent), spindles and the time spent in REM sleep are also reduced, while its latency is increased.[28] The poorly sleep onset in AD has been also associated with dream-related hallucination, increased restlessness, wandering and agitation, that seem to be related with sundowning - a typical chronological phenomenon presented in the disease.[24][28]
"has demonstrated expertise in the diagnosis and management of clinical conditions that occur during sleep, that disturb sleep, or that are affected by disturbances in the wake-sleep cycle. This specialist is skilled in the analysis and interpretation of comprehensive polysomnography, and well-versed in emerging research and management of a sleep laboratory."[51]
In people who have restless legs syndrome, discomfort in the legs and feet peaks during the evening and night. They feel an urge to move their legs and feet to get temporary relief, often with excessive, rhythmic, or cyclic leg movements during sleep. This can delay sleep onset and cause brief awakening during sleep. Restless legs syndrome is a common problem among middle-aged and older adults.
Narcolepsy is a brain disorder that causes excessive daytime sleepiness. There is sometimes a genetic component, but most patients have no family history of the problem. Though dramatic and uncontrolled "sleep attacks" have been the best-known feature of narcolepsy, in reality many patients do not have sleep attacks. Instead, they experience constant sleepiness during the day.
A nocturnal movement disorder, restless leg syndrome can feel like itchiness, tingling, or prickling that makes you feel like you have to move your legs. Your legs may also move without your control while you sleep. You may or may not be aware of waking during the night, but restless leg syndrome causes sleep problems by preventing deep, restful sleep.

At the same time, it has been shown that memory consolidation in long-term memory (which depends on the hippocampus) occurs during NREM sleep.[29][33] This indicates that a decrease in the NREM sleep will result in less consolidation and therefore poorer memory performances in hippocampal-dependent long-term memory.[29][33] This drop in performance is one of the central symptoms of AD.[29]  
A systematic review states 7.6% of the general population experiences sleep paralysis at least once in their lifetime. Its prevalence among men is 15.9% while 18.9% of women experience it. When considering specific populations, 28.3% of students and 31.9% of psychiatric patients have experienced this phenomenon at least once in their lifetime. Of those psychiatric patients, 34.6% have panic disorder. Sleep paralysis in students is slightly more prevalent for those of Asian descent (39.9%) than other ethnicities (Hispanic: 34.5%, African descent: 31.4%, Caucasian 30.8%).[67]

Although the exact mechanisms and the causal relationship between sleep disturbances and AD are not yet clear, these findings already provide a better understanding. In addition, they open up ideas for the implementation of treatments to curb the cognitive decline of patients suffering from this disease. In the same way, it also makes it possible to better target at risk population.

Specialists in Sleep Medicine were originally certified by the American Board of Sleep Medicine, which still recognizes specialists. Those passing the Sleep Medicine Specialty Exam received the designation "diplomate of the ABSM." Sleep Medicine is now a recognized subspecialty within internal medicine, family medicine, pediatrics, otolaryngology, psychiatry and neurology in the United States. Certification in Sleep Medicine shows that the specialist:
If your snoring is loud and uneven, erupts in snorts, or you sound like you're catching your breath or there are gaps in your breathing, these are signs of obstructive sleep apnea, the most severe type of sleep-disordered breathing. People with sleep apnea stop breathing repeatedly during their sleep because of a blockage in the mouth or throat, most commonly the soft tissues in the back of the throat, which collapse and close off.