Study Design This study is a prospective cohort design conducted at Zhongshan Hospital affiliated with Fudan University. It will involve systematic assessments of sleep quality, nutritional status, and associated clinical outcomes in adult ICU patients over a defined observation period.

Sample Size: An estimated 150 adult patients (≥18 years) will be recruited from the ICU.

Assessments 1. Sleep Quality Assessment:

1. Polysomnography (PSG): Sleep quality and duration will be quantified using PSG, which records brain waves, blood oxygen levels, heart rate, and breathing, as well as eye and leg movements. This will provide a comprehensive picture of sleep architecture and disturbances.
2. Sleep Quality Index: In addition to PSG data, the Pittsburgh Sleep Quality Index (PSQI) will be administered to assess subjective sleep quality, sleep latency, duration, habitual sleep efficiency, sleep disturbances, and daytime dysfunction.

2. Nutritional Status Evaluation:

1. Nutritional Risk Screening Tools: The Nutritional Risk Screening (NRS-2002) and the Malnutrition Universal Screening Tool (MUST) will be applied to assess nutritional risk and identify malnutrition.
2. Biochemical Assessment: Blood samples will be collected to measure biochemical indicators such as serum albumin, transferrin, prealbumin, and other relevant markers of nutritional status.
3. Anthropometric Measurements: Body mass index (BMI) and muscle mass assessments will be conducted using bioelectrical impedance analysis (BIA) or dual-energy X-ray absorptiometry (DEXA) to quantify body composition.

3. Physiological Monitoring:

1. Continuous monitoring of vital signs, including heart rate, blood pressure, and respiratory rate, will be performed.
2. Assessment of immune function through laboratory tests, including white blood cell count and levels of inflammatory markers (C-reactive protein).

4. Complications Tracking:

1. Data on complications such as infections, delayed wound healing, and respiratory failure will be systematically recorded throughout the ICU stay.

This study aims to elucidate the complex interplay between sleep deprivation and malnutrition in ICU patients. By identifying key associations and influencing factors, we hope to inform targeted clinical interventions that can improve patient care, recovery, and quality of life. The findings will serve as a foundation for future research exploring the intricate relationships between sleep and nutritional status in critical care settings.

Inclusion Criteria:

• Adult ICU patients (≥18 years)
• Expected length of stay ≥5 days
• No severe liver or kidney failure (to avoid confounding in nutritional metabolism)

Exclusion Criteria:

• Pre-existing malnutrition upon admission (e.g., BMI <18.5 or weight loss >10% within 6 months)
• Neuromuscular diseases affecting metabolic assessment

Patients who met the inclusion criteria in the ICU of Zhongshan Hospital, Fudan University from August 2025 were enrolled.