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 Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
DOUBLE
Enrollment
90
Dinner ≈30% daily kcal; \~80% carb; taken 3-4 h before sleep for 2 weeks
Dinner ≈30% daily kcal; \~38-54% protein; 3-4 h before sleep for 2 weeks.
Standard macronutrient distribution; same timing (3-4h pre-sleep) and 2-week duration.
University of Jordan Hospital
Amman, Jordan
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
Time frame: Baseline and 2 weeks post-intervention
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.
Time frame: 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.
Time frame: 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
Time frame: 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 (%)
Time frame: 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 (%)
Time frame: 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)
Time frame: 1 week baseline and 2 weeks during intervention
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