This Trial Examines How Last Meal Composition and Timing Affect Sleep Quality and Circadian Gene Expression Among Medical Residents. Recruitment Not Yet Started; Study Begins Dec 2025 and Ends Dec 2026. (CHRONO-MED)

CHRONO-NUTRITION INTERVENTIONS FOR IMPROVING SLEEP QUALITY: The Impact of Last Meal Composition and Timing on Sleep Quality Among Medical Residents at Hospitals

This randomized controlled trial aims to evaluate the effects of last meal composition and timing on sleep quality and circadian gene expression among medical residents in Jordanian hospitals. Sleep disturbances are common in this population due to long working hours, high stress, and irregular eating schedules. Chrono-nutrition, the science of aligning food intake with circadian rhythms, may provide a practical approach to improving sleep and overall well-being.

Participants will be randomly assigned to one of three groups:

1. High-carbohydrate last meal (≈80% of dinner calories from carbohydrates),
2. High-protein last meal (≈40-50% of dinner calories from protein),
3. Control group consuming a balanced standard meal. Each participant will consume the assigned meal 3-4 hours before bedtime for two weeks. Sleep quality will be measured using the Pittsburgh Sleep Quality Index (PSQI) and smartwatch-derived parameters, while salivary samples collected pre- and post-intervention will be analyzed for CLOCK and BMAL1 gene expression. The study will also include dietary, anthropometric, and physical activity assessments.

This study has been approved by the Institutional Review Board of the University of Jordan (IRB No. 491/2025). Recruitment has not yet started. Enrollment is expected to begin in December 2025, with primary data collection completed by June 2026 and final study completion by December 2026.

Study Overview

• Status: Enrolling by invitation
• Conditions: Sleep Quality; Circadian Rhythm; Meal Timing; Medical Residents; Nutrition Intake
• Intervention / Treatment: Dietary supplement: High-Carbohydrate Last Meal; Dietary supplement: High-Protein Last Meal; Dietary supplement: Balanced Standard Dinner

• Study Type: Interventional
• Enrollment (Estimated): 90
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Jordan
  • Amman, Jordan
    • University of Jordan hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Currently enrolled and working in Jordanian hospitals.
• Not currently following a specific diet or weight-loss program.
• Willing to comply with study protocol and intervention meals for two weeks. Provide written informed consent before participation.

Exclusion Criteria:

• Presence of any chronic medical condition (e.g., diabetes, thyroid disorders, gastrointestinal, cardiovascular, or respiratory diseases).
• Diagnosed sleep disorders, such as insomnia, sleep apnea, or restless legs syndrome.
• Mental health disorders (stress, anxiety, or depression diagnosed or medicated).
• Pregnancy or lactation.
• Use of medications or herbal supplements known to affect sleep (e.g., melatonin, chamomile, ashwagandha, lavender).
• Caffeine dependence exceeding moderate levels ( >400 mg caffeine/day).

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: High-Carbohydrate Last Meal; Dinner ≈30% of daily kcal; ~80% of dinner kcal from carbs; consumed 3-4 h before sleep for 2 weeks.	Dietary supplement: High-Carbohydrate Last Meal; Dinner ≈30% daily kcal; ~80% carb; taken 3-4 h before sleep for 2 weeks
Experimental: High-Protein Last Meal; ≈30% of daily kcal; ~38-54% of dinner kcal from protein; consumed 3-4 h before sleep for 2 weeks.	Dietary supplement: High-Protein Last Meal; Dinner ≈30% daily kcal; ~38-54% protein; 3-4 h before sleep for 2 weeks.
Active Comparator: Balanced Standard last meal; Standard balanced dinner (per usual guidelines), same timing (3-4 h pre-sleep) and 2 weeks duration.	Dietary supplement: Balanced Standard Dinner; Standard macronutrient distribution; same timing (3-4h pre-sleep) and 2-week duration.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in Sleep Quality (PSQI Global Score)	Sleep quality will be assessed using the Pittsburgh Sleep Quality Index (PSQI) before and after the 2-week intervention. The PSQI total score (0-21) will quantify subjective sleep quality; higher scores indicate poorer sleep	Baseline and 2 weeks post-intervention

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in CLOCK Gene Expression	CLOCK mRNA expression will be measured in salivary samples collected pre- and post-intervention using RT-PCR. Relative quantification (ΔCt method) will determine expression changes.	Baseline and 2 weeks post-intervention
Change in BMAL-1 Gene Expression	BMAL-1 mRNA levels will be analyzed in the same saliva samples via real-time PCR. Changes will be compared across meal groups.	Baseline and 2 weeks post-intervention
Change in Total Sleep Duration	Total sleep duration will be objectively measured using smartwatch data and expressed as average nightly sleep duration. Unit of Measure: Minutes per night	1 week baseline and 2 weeks during intervention
Change in Sleep Efficiency	Sleep efficiency will be calculated as the percentage of total sleep time divided by time in bed using smartwatch data. Unit of Measure: Percentage (%)	1 week baseline and 2 weeks during intervention
Change in Sleep Stage Distribution	Sleep stage distribution (light, deep, and REM sleep) will be assessed using smartwatch data and expressed as percentage of total sleep time. Unit of Measure: Percentage (%)	1 week baseline and 2 weeks during intervention
Change in Average Heart Rate During Sleep	Average heart rate during sleep will be measured using smartwatch data. Unit of Measure: Beats per minute (bpm)	1 week baseline and 2 weeks during intervention

Collaborators and Investigators

• Sponsor: University of Jordan
• Investigators: Principal Investigator: Hadeel A Ghazzawi, professor, The University of Jordan School of Agriculture

Study record dates

Study Major Dates

• Study Start (Actual): December 1, 2025
• Primary Completion (Estimated): January 1, 2026
• Study Completion (Estimated): May 1, 2026

Study Registration Dates

• First Submitted: December 16, 2025
• First Submitted That Met QC Criteria: January 4, 2026
• First Posted (Actual): January 14, 2026

Study Record Updates

• Last Update Posted (Actual): January 14, 2026
• Last Update Submitted That Met QC Criteria: January 4, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Nervous System Diseases; Mental Disorders; Sleep Wake Disorders; Sleep Disorders, Intrinsic; Dyssomnias; Sleep Initiation and Maintenance Disorders
• Other Study ID Numbers: University of Jordan 491/2025

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No