Most ICU patients experience sleep and circadian disruption (SCD), which causes a profound negative impact on patients, such as prolonged mechanical ventilation, glucose intolerance, and the occurrence of delirium. In order to better promote the alignment of circadian rhythm in ICU patients, this project will explore the prevalence of SCD and a series of influencing factors contributing to SCD in ICU patients, to help construct targeted intervention programs in the future.

The circadian rhythm refers to the oscillation phenomenon of physiological, biochemical, and behavioral life phenomena of organisms with a 24-hour cycle. The circadian rhythm affects multiple physiological indicators, such as the sleep-wake cycle, hormone levels, heart rate, blood pressure, and metabolic functions. Maintaining a normal circadian rhythm is crucial for human health. However, a series of stressful stressors in the ICU, such as lack of normal light-dark cycle changes, high levels of noise, make sleep and circadian rhythm disruption(SCD) common and severe, and such disruption will have serious negative impacts on patients' clinical outcomes. Therefore, there is an urgent need for effective interventions to assist ICU patients in promoting their sleep and circadian rhythms. The first step in intervention is to understand the current incidence and characteristics of ICU SCD, as well as the factors contributing to such disruption.

To date, there has been limited progress on the current status of SCD prevalence in ICUs. On one hand, there may be significant variability in ICU SCD between individual patients and subgroups, On the other hand, this variability may change over time as patients recover from acute illnesses. This heterogeneity from population and time impedes the development of interventions for SCD. Therefore, there is an urgent need to understand the characteristics, trends of SCD in different patients and the factors influencing these changes.

The overall objective of this project is to explore the status and influencing factors of ICU patients' sleep and circadian rhythms in the first 3 days by conducting a longitudinal study using multiple objective subjective indicators, aiming to more accurately and objectively evaluate the changes in patients' circadian rhythms.

Inclusion Criteria:

1. Adult patients older than 18 years old.
2. Patients transferred to ICU during the time period of 8:00-22:00.
3. Stay in the ICU for more than 12 hours and at least one overnight period.
4. Patients or their family members are informed and consent to participate in the research.

Exclusion Criteria:

1. Acute brain injuries within 30 days, such as acute intracranial bleeding, traumatic brain injury, central nervous system infection, or chronic brain injuries lasting over 30 days with an inability to live independently.
2. Previously diagnosed with mild cognitive impairment or Alzheimer's disease.
3. Patients affected by blindness or optic nerve disorder.
4. Patients who are pregnant or breastfeeding.
5. Patient in prone position, hemodialysis, or ECMO therapy during PSG monitoring
6. Imminently dying or with a hospice status.

In the Surgical Intensive Care Unit (SICU) at Zhongshan Hospital, Fudan University, critically ill adult patients from both surgical and medical specialties are admitted in SICU.