Abstract: Patients with cognitive impairment have a high prevalence of sleep disorders with various manifestations, including insomnia, daytime hypersomnia, sleep breathing disorders, abnormal sleep, restless legs syndrome, sleep rhythm disorders, etc. Alzheimer disease (AD) is the most common type of cognitive impairment. About 73% of Chinese AD patients of Han ethnicityare associated with sleep disorders, among which 53% are related to varying degrees of sleep rhythm disorders. Sleep disorders in AD patients are more prominent in the middle and later stages, so the disturbance of sleep rhythm has always been considered as the result of AD-related neurodegenerative changes, such as "sunset phenomenon". However, recent studies have shown that disturbed sleep rhythms may be involved in the initiation of AD. Prospective follow-up studies abroad found that the cognitively normal elderly with disordered sleep rhythm was more prone to AD after 5-10 years. At present, there is still no in-depth research on how sleep rhythm disorder promotes neurodegenerative changes. This paper reviews the researches on AD-related pathology and biomarkers caused by sleep rhythm disorder.