Due to rapidly increasing knowledge about sleep in the 20th century, including the discovery of REM sleep in the 1950s and circadian rhythm disorders in the 70s and 80s, the medical importance of sleep was recognized. The medical community began paying more attention than previously to primary sleep disorders, such as sleep apnea, as well as the role and quality of sleep in other conditions. By the 1970s in the US, clinics and laboratories devoted to the study of sleep and sleep disorders had been founded, and a need for standards arose.
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]
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.
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.

Obstructive sleep apnea (OSA) affects around 4% of men and 2% of women in the United States.[63] In general, this disorder is more prevalent among men. However, this difference tends to diminish with age. Women experience the highest risk for OSA during pregnancy.[64] Also, they tend to report experiencing depression and insomnia in conjunction with obstructive sleep apnea.[65] In a meta-analysis of the various Asian countries, India and China present the highest prevalence of the disorder. Specifically, about 13.7% of the Indian population and 7% of Hong-Kong's population is estimated to have OSA. The two groups experience daytime OSA symptoms such as difficulties concentrating, mood swings, or high blood pressure,[66] at similar rates (prevalence of 3.5% and 3.57%, respectively).[63]


Due to rapidly increasing knowledge about sleep in the 20th century, including the discovery of REM sleep in the 1950s and circadian rhythm disorders in the 70s and 80s, the medical importance of sleep was recognized. The medical community began paying more attention than previously to primary sleep disorders, such as sleep apnea, as well as the role and quality of sleep in other conditions. By the 1970s in the US, clinics and laboratories devoted to the study of sleep and sleep disorders had been founded, and a need for standards arose.

Recent studies, however, have shown that several factors can interrupt this neurogenesis.[29] These include stress and prolonged sleep deprivation (more than one day).[29] The sleep disturbances encountered in AD could therefore suppress neurogenesis and thus impairing hippocampal functions.[29] This would therefore contribute to diminished memory performances and the progression of AD.[29] And progression of AD would aggravate sleep disturbances.[29] It is a second vicious circle.  

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.
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]
Waking up in the middle of the night to use the bathroom is such a common problem it has a name: nocturia . As we get older, our bodies' ability to hold fluids for long periods decreases, thanks to a decline in antidiuretic hormones. According to the National Sleep Foundation, 65 percent of older adults have sleep deprivation resulting from waking up frequently to use the bathroom.
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