|Dementia is often accompanied by various types of sleep disorders associated with neurotransmission disturbances caused by cortical and subcortical atrophy in different aspects and areas, depending on the underlying disease. In Alzheimerâs disease (AD), that is one of the most common causes of dementia, sleep disorder is observed in about 28% of the patients; when stratified by severity, it is observed in about 25% of those with mild to moderate AD and in 50% of those with severe AD. When compared with normal elderly subjects, the main sleep of AD patients is characterized by intermittent sleep (increased frequency and wake duration after sleep onset (WASO)) and a decrease in deep sleep and REM sleep. Also observed are an increased ratio of daytime sleep relative to the total daily sleep duration and increased percentage of deep sleep and REM sleep in the daytime nap. the sleep disorders which cannot sleep at the time when oneself or society wanted are said the Circadian Rhythm Sleep Disorder (CRSD).CRSD in AD patients progresses with increasing disease stage and it is also associated with poor quality sleep, daytime hypersomnia, night delirium, and sundowning syndrome, a condition characterized by excitement occurring in the evening hours.
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