The study aims to investigate the status of circadian rhythm and sleep quality in ICU patients and their influence factors. And explore the pathway of circadian rhythm on ICU delirium.

The hypothesis of study is that icu patients experience circadian and sleep rhythm disorder, especially in patient who have delirium.

Delirium is an acute and fluctuating alteration of mental state characterized by a disturbance in attention, level of consciousness and cognition. At present, there is no unified conclusion on the pathogenesis of delirium. There are many different hypotheses, such as the neuroinflammation hypothesis, the neuronal aging hypothesis, the oxidative stress hypothesis, the neurotransmitter hypothesis, the neuroendocrine hypothesis and the circadian rhythm disturbance hypothesis. Among them, the circadian rhythm disturbance hypothesis believes that the circadian rhythm disorder caused by various reasons, which leads to sleep disturbance and melatonin secretion disorder promotes the occurrence of acute cognitive impairment, which in turn leads to the occurrence of delirium. Circadian rhythm refers to the rhythm of any biological process in the human body that repeats and maintains within 24 hours without external stimulation. By far, the most common way to measure circadian rhythm is through vital signs rhythms, hormone secretion (cortisol and melatonin levels), and sleep-wake cycle.

Due to the special environment and treatment needs in ICU make patients' circadian rhythm easily broken, and produced a large latent harm to patients. Most studies are in the process of delirium and sleep research, selecting a small subgroup to evaluate the circadian rhythm indicators of patients, and the overall relationship between delirium and circadian rhythm is not clear.

Thus, the study aims to investigate the status of circadian rhythm and sleep quality in ICU patients and their influence factors, and explore the pathway of circadian rhythm action on ICU delirium.

Inclusion Criteria:

• Aged above 18
• RASS>-4

Exclusion Criteria:

• History of mental or psychological illness
• The patient remained in coma or deep sedation
• Delirium was occurring at the time of admission
• Unable to fully participate in delirium testing, including blind, deaf, illiterate or inability to understand Chinese
• Neurosurgery and maternal patients

Patients aged above 18 who are admitted to ICU will be screened for eligibility.