Neurodegenerative diseases have been often associated with sleep disorders, mainly when they are characterized by abnormal accumulation of alpha-synuclein, such as multiple system atrophy (MSA), Parkinson's disease (PD) and Lewy body disease (LBD).[21][22][23][24][25][26][27] For instance, people diagnosed with PD have often presented different kinds of sleep concerns, commonly regard to insomnia (around 70% of the PD population), hypersomnia (more than 50% of the PD population), and REM sleep behavior disorder (RBD) - that may affect around 40% of the PD population and it is associated with increased motor symptoms.[21][22][23][24][25][27] Importantly, RBD has been also highlighted as a strong precursor of developing dementia in PD patients over several years in prior, which seems to be a great opportunity for improving the treatments of the disease.[22][24]
Histamine plays a role in wakefulness in the brain. An allergic reaction over produces histamine causing wakefulness and inhibiting sleep[37] Sleep problems are common in people with allergic rhinitis. A study from the N.I.H. found that sleep is dramatically impaired by allergic symptoms and that the degree of impairment is related to the severity of those symptoms [2]s[38] Treatment of allergies has also been shown to help sleep apnea.[39]
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]
Get back to sleep when you wake up at night. Whether you have a sleep disorder or not, it’s normal to wake briefly during the night. If you’re having trouble getting back to sleep, try focusing on your breathing, meditating, or practicing another relaxation technique. Make a note of anything that’s worrying you and resolve to postpone worrying about it until the next day when it will be easier to resolve.
A review of the evidence in 2012 concluded that current research is not rigorous enough to make recommendations around the use of acupuncture for insomnia.[40] The pooled results of two trials on acupuncture showed a moderate likelihood that there may be some improvement to sleep quality for individuals with a diagnosis insomnia.[40]:15 This form of treatment for sleep disorders is generally studied in adults, rather than children. Further research would be needed to study the effects of acupuncture on sleep disorders in children.
In the UK, knowledge of sleep medicine and possibilities for diagnosis and treatment seem to lag. quotes the director of the Imperial College Healthcare Sleep Centre: "One problem is that there has been relatively little training in sleep medicine in this country – certainly there is no structured training for sleep physicians."[55] The Imperial College Healthcare site[56] shows attention to obstructive sleep apnea syndrome (OSA) and very few other sleep disorders. Some NHS trusts have specialist clinics for respiratory and/or neurological sleep medicine.
Primary sleep disorders are most common in men and women over the age of 65. About half of the people claim to have some sleep problem at one point. It is most common in the elderly because of multiple factors. Factors include increased medication use, age-related changes in circadian rhythms, environmental and lifestyle changes [3] and pre diagnosed physiological problems and stress. The risk of developing sleep disorders in the elderly is especially increased for sleep disordered breathing, periodic limb movements, lestless legs syndrome, REM sleep behavior disorders, insomnia and circadian rhythm disturbances.[3]

As suggested by its name, PLMD is an involuntary movement disorder. (An older name, nocturnal myoclonus , is rarely used anymore.) People with this problem experience sudden, involuntary leg movements during the night, such as kicking or jerking. The difference between this and restless leg syndrome is that, unless the kicking wakes you up, you don't know you're doing it. You don't experience the tingling and discomfort that leads you to consciously move your legs, as with restless leg syndrome. At least 80 percent of people with restless leg syndrome have PLMD, but the reverse isn't true.
Another systematic review noted 7-16% of young adults suffer from delayed sleep phase disorder. This disorder reaches peak prevalence when people are in their 20s.[57] Between 20 and 26% of adolescents report a sleep onset latency of >30 minutes. Also, 7-36% have difficulty initiating sleep.[59] Asian teens tend to have a higher prevalence of all of these adverse sleep outcomes than their North American and European counterparts.[59]
There are many possible causes of restless legs syndrome, including kidney failure, nerve disorders, vitamin and iron deficiencies, pregnancy, and some medications (such as antidepressants). Recent studies have shown a strong genetic link and researchers have been able to isolate a gene that may be responsible for at least 40% of all cases of the disorder.
One factors that could explain this change in sleep architecture is a change in circadian rhythm, which regulates sleep.[29] A disruption of the circadian rhythm would therefore generate sleep disturbances.[29] Some studies show that people with AD have a delayed circadian rhythm, whereas in normal aging we will find an advanced circadian rhythm.[29][31]
The natural internal clock that controls our 24-hour cycle of sleep and waking, circadian rhythms are easily upset by changes in schedule, and they're greatly affected by light and darkness. Jet lag is the best known circadian rhythm disorder, but this sensitive inner clock can also be disrupted by changes in routine resulting in an erratic sleep schedule.