Sleep apnea, obstructive sleep apnea, obstruction of the airway during sleep, causing lack of sufficient deep sleep, often accompanied by snoring. Other forms of sleep apnea are less common.[10] Obstructive sleep apnea (OSA) is a medical disorder that is caused by repetitive collapse of the upper airway (back of the throat) during sleep. For the purposes of sleep studies, episodes of full upper airway collapse for at least ten seconds are called apneas[11]
Combining results from 17 studies on insomnia in China, a pooled prevalence of 15.0% is reported for the country.[60] This is considerably lower than a series of Western countries (50.5% in Poland, 37.2% in France and Italy, 27.1% in USA).[60] However, the result is consistent among other East Asian countries. Men and women residing in China experience insomnia at similar rates.[60] A separate meta-analysis focusing on this sleeping disorder in the elderly mentions that those with more than one physical or psychiatric malady experience it at a 60% higher rate than those with one condition or less. It also notes a higher prevalence of insomnia in women over the age of 50 than their male counterparts.[61]

Interestingly, the glymphatic cleanrance occurs during the NREM sleep, and more specifically the NREM SWS sleep.[29][30][32] As seen previously, it is a sleep stage that decreases in normal aging.[30] So there is less glymphatic clearance and an increase in AB burden that will form the AB plaques.[32][29][30] Therefor, in AD sleep disturbances will amplify this phenomenon.
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.
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.
In Alzheimer's disease, in addition to cognitive decline and memory impairment, there is also significant sleep disturbances with a modified sleep architecture.[30][29] The latter may consist in sleep fragmentation, a reduction in sleep duration, insomnia, an increase daytime naping, a decreased quantity og some sleep stages and a resemblance between some sleep stages (N1 and N2).[29] More than 65% of people with Alzheimer's disease suffer from this type of sleep disturbance.[29]
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.