Although we do not know the causual relationship, we know that the more the AD progresses, the more we find sleep disorders. In the same way, the more sleep disorders there are, the more the disease progresses, forming a vicious circle. Taken this into account, sleep disturbances are no longer a symptom of AD and relationship between sleep disturbances and AD is bidirectional.
Throughout the decades as more research and studies were conducted, the amount of sleep disorders being discovered began to rapidly increase. In 1990 The AASM, along with other professional societies including the European Sleep Research Society, The Japanese Society of Sleep Research, and the Latin American Sleep Society published the International Classification of Sleep Disorders (ICSD), which is a "primary diagnostic, epidemiological, and coding resource for clinicians and researchers in the field of sleep and sleep medicine."
Delayed sleep phase disorder (DSPD), inability to awaken and fall asleep at socially acceptable times but no problem with sleep maintenance, a disorder of circadian rhythms. Other such disorders are advanced sleep phase disorder (ASPD), non-24-hour sleep–wake disorder (non-24) in the sighted or in the blind, and irregular sleep wake rhythm, all much less common than DSPD, as well as the situational shift work sleep disorder.
Insomnias This type of sleep disorder involves the inability to fall asleep or stay asleep. MORE>>Hypersomnias Hypersomnias are a group of sleep disorders that causes a person to be excessively sleepy. People with a hypersomnia may fall asleep at times that are inconvenient or even dangerous, such as at work or while driving. MORE>>Sleep Related Breathing Disorders Sleep disorders that involve difficulty breathing during sleep are classified as sleep related breathing disorders. Obstructive sleep apnea is the most common disorder of this type, however there are a number of variations of sleep apnea. MORE>>Circadian Rhythm Sleep-Wake Disorders Conditions in which the sleep times are out of alignment. A patient with one of these disorders does not follow the normal sleep times at night. MORE>>Parasomnias Parasomnias are a group of sleep disorders that involve unwanted events or experiences that occur while you are falling asleep, sleeping or waking up. MORE>>Sleep Movement Disorders This classification of sleep disorders includes conditions that cause movement during or prior to sleep. These disorders can make it difficult to fall asleep or stay asleep, or to get restful sleep. MORE>>
Both night terrors and sleepwalking arise during NREM sleep and occur most often in children between the ages of 3 and 5 years old. A night terror can be dramatic: Your child may wake up screaming, but unable to explain the fear. Sometimes children who have night terrors remember a frightening image, but often they remember nothing. Night terrors are often more frightening for parents than for their child. Sleepwalkers can perform a range of activities -- some potentially dangerous, like leaving the house -- while they continue to sleep.
The most common sleep disorder is insomnia. Others are sleep apnea, narcolepsy and hypersomnia (excessive sleepiness at inappropriate times), sleeping sickness (disruption of sleep cycle due to infection), sleepwalking, and night terrors. Management of sleep disturbances that are secondary to mental, medical, or substance abuse disorders should focus on the underlying conditions.
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. 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). More than 65% of people with Alzheimer's disease suffer from this type of sleep disturbance.
One factors that could explain this change in sleep architecture is a change in circadian rhythm, which regulates sleep. A disruption of the circadian rhythm would therefore generate sleep disturbances. Some studies show that people with AD have a delayed circadian rhythm, whereas in normal aging we will find an advanced circadian rhythm.
What to do: If you suspect you have a circadian rhythm disorder, take steps to get your body onto a regular sleep schedule. Choose a bedtime and wake-up time that work for you, and follow the same routine each day, even on weekends. This can be tough for those who have to get up early during the week but like to stay up later on weekends, but do your best to craft a compromise between your work week and weekend habits. The important thing is to avoid the trap of sleeping from 10 p.m. to 6 a.m. during the week, then suddenly shifting to late nights and late mornings on the weekends. This will inevitably leave you with insomnia on Sunday night, which in turn sets you up to start the week exhausted on Monday morning.