The Impact of Glycemic Index on Sleep and Memory Consolidation

Study Overview
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Brief Summary
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The study will test whether the consumption of a low versus a high glycemic index pre-bed drink influences sleep architecture, memory consolidation, nocturnal glucose metabolism, and mood.

Detailed Description
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Few studies have examined the impact of meal composition on sleep. Most research has focused on carbohydrate intake, although reports are sporadic and confounded by the manipulation of other macronutrients. Nonetheless, the pattern of results appears to depend on the nature of the sleep variable under investigation e.g., latency, duration, or efficiency. The study will determine whether manipulating the glycemic index of a pre-bed drink influences sleep architecture, procedural and declarative memory consolidation, nocturnal glucose metabolism, and mood. Participants will stay in the sleep laboratory for three nights, each night separated by one week (visit 1, 2, and 3). The first night is an acclimatisation night. The same procedure will be followed on all three nights, as described below. On the morning of each visit, a continuous glucose monitor will be set up and worn until 8pm the following evening. Participants will be asked to return to the sleep laboratory at 7pm, having fasted for five hours, and asked to consume a standardised evening meal. Several mood questionnaires will be completed throughout the evening and a polysomnography will be set up. Two memory tasks will be administered at approximately 10pm. Immediately after this, participants will consume either water (night 1), or a low glycemic index or high glycemic index drink (night 2 or 3). Participants will retire to bed at approximately 11pm and woken up between 6.30am - 8am, depending on personal preference. In the morning, the memory tasks will be administered again, as well as two mood questionnaires. Participants will be asked to wear a Pro-Diary watch throughout the day, which measures mood and hunger. At 8pm, both the continuous glucose monitor and Pro-diary watch will be collected from the participant.

Official Title
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The Impact of Glycemic Index on Sleep and Memory Consolidation

Conditions
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Sleep Architecture, Cognitive Function, Mood, Glucose Metabolism

Intervention / Treatment
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* Dietary Supplement: Low glycemic index drink
* Dietary Supplement: High glycemic index drink


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Male (given that the menstrual cycle may influence sleep polysomnography) Good health Not taking any medication known to effect sleep or metabolism Normal sleep duration (i.e. between 6.5 - 9 hours of sleep per night) A sleep efficiency score above 80% (Pittsburg Sleep Quality Index) Normal sleep schedule (i.e. fall asleep between 10pm and 12pm) No difficulty sleeping in new places Exclusion Criteria: Diagnosis of any physical or mental disorder e.g. diabetes, cardiovascular disorders, gastrointestinal disorders, sleep problems, epilepsy, or mood disorders Unhealthy weight (BMI over 30) Drink more than 300mg of caffeine per day (3 - 4 standard sized 8-oz cups) Work nights or shifts Smoke/vape Regularly drink alcohol (>3 glasses per day) Used recreational drugs within the last 6 months Take part in >3 hours of vigorous exercise per week Any known food allergies or intolerances Nocturnal eating or regular consumption of alcohol before bed (assessed by the Meal Pattern Questionnaire)

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 35 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: In a randomized, double-blind, and counterbalanced order (AB/BA), participants will receive either a high glycemic index or low glycemic index pre-bed drink. After a 1-week washout period, participants will consume the alternate drink.
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Low glycemic index drink<br>Fruit drink containing low glycemic index sugar. | Dietary Supplement: Low glycemic index drink<br>* Fruit flavoured drink with low glycemic index sugar (300 ml)<br>|
| Experimental: High glycemic index drink<br>Fruit drink containing high glycemic index sugar. | Dietary Supplement: High glycemic index drink<br>* Fruit flavoured drink with high glycemic index sugar (300 ml)<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Sleep onset latency (polysomnography) | Onset of sleep from the time the lights are turned off. | Bedtime (approx. 11.00pm) to wake time (approx 7.30am) | 
| Total sleep time (polysomnography) | The total number of hours of sleep. | Bedtime (approx. 11.00pm) to wake time (approx 7.30am) | 
| Wake after sleep onset (polysomnography) | Hours of wake time after three epochs of sleep have occurred. | Bedtime (approx. 11.00pm) to wake time (approx 7.30am) | 
| Sleep efficiency (polysomnography) | Total sleep time divided by the time from lights out until awakening in the morning. | Bedtime (approx. 11.00pm) to wake time (approx 7.30am) | 
| Sleep stages (polysomnography) | Time spent in each sleep stage. | Bedtime (approx. 11.00pm) to wake time (approx 7.30am) | 
| Arousal index (polysomnography) | Number of arousals throughout the night. | Bedtime (approx. 11.00pm) to wake time (approx 7.30am) | 
| Leeds Sleep Evaluation Questionnaire | Subjective assessment of sleep quality. Scores range from 0 to 30. Higher scores indicate poorer sleep quality. | Administered 10 - 20 minutes after waking up in the morning, | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Glucose response (continuous glucose monitor) | The 2h and 3h incremental area under the curve (iAUC) will be used to assess glycemic response to the pre-bed drink. The mean amplitude of glycemic excursion (MAGE) will be assessed as an indicator for glycemic variability during the night and for 25 hours. | 25 hours during night 2 and night 3 (weeks 2 and 3) | 
| Finger tapping task (procedural memory) | The change in performance from the learning phase to the recall phase. | Completed at 10pm, and between 6.30 - 8am the following morning, on night 2 and night 3 (week 2 and 3). | 
| Story recall task (declarative memory) | The number of content words (nouns, adjectives, and verbs) correctly recalled. | Completed at 10pm, and between 6.30 - 8am the following morning, on night 2 and night 3 (week 2 and 3). | 
| Epworth Sleepiness Scale | Subjective assessment of daytime sleepiness. Scores range from 0 - 24. Higher scores indicate more daytime sleepiness. | Administered at 8pm on the evening after night 2 and night 3 (week 2 and 3). | 
| Mood and hunger | Scores range from 0 - 100. Higher scores indicate stronger feelings. | Completed five times throughout the evening and twice in the morning (immediately after waking up and 20-30 minutes later) on night 2 and night 3 (week 2 and 3). . | 
| Mood | Pro-diary watch | Prompted from 9.30am - 5.30pm after night 2 and night 3 (week 2 and 3). | 
| Actigraphy | Time spent in each sleep stage. | Night 2 and night 3 (week 2 and 3). |