Influence of Nocturnal Light Exposure on the Impairment of Glucose Tolerance Induced by Chronic Sleep Restriction

This project is designed to test for the first time whether glucose metabolism is differentially impaired by sleep restriction with and without additional exposure to artificial light at night (ALAN).

Study Overview

• Status: Completed
• Conditions: Sleep; Glucose Intolerance; Sleep Deprivation
• Intervention / Treatment: Other: Sleep Restriction with ALAN first, then Sleep Restriction without ALAN; Other: Sleep Restriction without ALAN first, then sleep restriction with ALAN

Detailed Description

Laboratory studies have shown that sleep restriction to 4-6h per night for durations varying from one to 14 days reduces glucose tolerance in otherwise healthy adults, but the mechanisms by which insufficient sleep impairs glucose metabolism are still unknown. Current theories are based on the premise that the adverse metabolic consequences are caused by reduction in the duration of sleep per se. However, sleep curtailment is typically accompanied by longer exposure to artificial light at night (ALAN), which is an environmental endocrine disrupter that profoundly disrupts circadian rhythms.

The investigators have previously reported that acute circadian misalignment induced hyperglycemia comparable to pre-diabetic states in a third of otherwise healthy participants. Since then, the investigators have shown that even when the circadian phase of participants was realigned, prior exposure to 2 ½ weeks of chronic sleep restriction combined with a history of recurrent circadian disruption induced even more deleterious effects on glucose metabolism, in which pancreatic beta cells failed to respond adequately to increased glucose levels. Moreover, both night and rotating shift work (which induce circadian disruption) are associated with increased risk for metabolic problems. Night shifts can lead to acute increases in glucose and insulin levels, although some studies report reduced insulin release in response to meals consumed during the night. Given that circadian disruption has been shown to independently adversely affect metabolism, and exposure to ALAN adversely impacts metabolism in animals, it is important to understand the extent to which circadian disruption contributes to the observed impact of sleep curtailment on metabolism. No previous studies of the metabolic impact of sleep restriction in humans have controlled for this additional exposure to ALAN, thus confounding the effects of sleep restriction with the effects of circadian disruption caused by extended exposure to ALAN.

• Study Type: Interventional
• Enrollment (Actual): 14
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Massachusetts
    • Boston, Massachusetts, United States, 02115
      • Brigham and Women's Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 20 years to 40 years (Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Healthy adults with conventional and regular sleep-wake timing
• Non-smokers
• Completion of medical, psychological, and sleep screening tests
• Able to spend 33 consecutive days/nights in the laboratory
• Normal color vision

Exclusion Criteria:

• History of neurological or psychiatric disorder
• History of sleep disorder or regular use of sleep-promoting medication
• Current prescription, herbal, or over-the-counter medication use
• Traveling across 2 or more time zones within past 3 months
• Donating blood within past 8 weeks
• Worked night or rotating shift work within past 3 years
• Hearing impairment, visual impairment
• History of eye trauma or surgery
• Drug or alcohol dependency

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Sleep Restriction with ALAN, then Sleep Restriction without ALAN; Participants first received Sleep Restriction with extended duration Artificial Light At Night (ALAN), during which sleep episodes were shortened to 5 hours and participants remained in room lighting for the full wake episode (19h room light, 5h darkness). After a washout of 10 days, participants received Sleep Restriction without ALAN, during which sleep episodes were shortened to 5 hours but participants were kept in dim light for the extra time awake (14h room light, 5h dim light, 5h darkness).	Other: Sleep Restriction with ALAN first, then Sleep Restriction without ALAN; Sleep restriction with 90 lux lighting for 19hr/day first, followed by Sleep restriction with 90 lux lighting for 14hr/day; Other Names: ALAN first
Experimental: Sleep Restriction without ALAN, then Sleep Restriction with ALAN; Participants first received Sleep Restriction without extended duration Artificial Light At Night (ALAN), during which sleep episodes were shortened to 5 hours but participants were kept in dim light for the extra time awake (14h room light, 5h dim light, 5h darkness). After a washout of 10 days, participants received Sleep Restriction with extended duration ALAN, during which sleep episodes were shortened to 5 hours and participants remained in room lighting for the full wake episode (19h room light, 5h darkness).	Other: Sleep Restriction without ALAN first, then sleep restriction with ALAN; Sleep restriction with 90 lux lighting for 14hr/day first, followed by Sleep restriction with 90 lux lighting for 19hr/day; Other Names: ALAN second

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Impairment of Insulin Sensitivity	Insulin sensitivity (Si) is assessed via minimal model analysis, a mathematical model developed by Bergman and colleagues. Higher values represent better insulin sensitivity and lower values represent impaired insulin sensitivity. The mean change in Si between exposure and baseline is reported for each arm.	Change between Study Day 7 vs. Study Day 15 and Study Day 24 vs. Study Day 32
Impairment of Glucose Tolerance	Test the hypothesis that exposure to one week of sleep restriction with concurrent exposure to extended duration ALAN (LD 19:5) will induce greater impairment of glucose tolerance than exposure to one week of sleep restriction without extended duration ALAN (LD 14:10). Glucose tolerance will be calculated as the area under the curve from minutes 0-120 following a mixed meal tolerance test	Change between Study Day 6 vs. Study Day 14 and Study Day 23 vs. Study Day 31
Duration of Nocturnal Melatonin Secretion	Test the hypothesis that exposure to one week of sleep restriction with concurrent exposure to extended duration ALAN (LD 19:5) will acutely reduce the duration of nocturnal melatonin secretion as compared to baseline more than exposure to one week of sleep restriction without extended duration ALAN (LD 14:10). Duration of nocturnal melatonin secretion will be determined by the duration of time at which melatonin levels are above a threshold calculated as 25% of peak-to-trough amplitude at baseline in dim light.	Change between Study Day 14-15 (overnight) vs. Study Day 31-32 (overnight)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Acute Insulin Response to Glucose	Acute Insulin Response as calculated with minimal model analysis, a mathematical model developed by Bergman and colleagues, and represents early insulin release in the body to manage blood glucose levels. Higher values represent a better response and lower values represent a worse response. The mean change in AIRg between exposure and baseline is reported for each arm.	Change from study day 7 to 15 compared to change from study day 24 to 32
Glucose Effectiveness	Glucose Effectiveness as calculated using minimal model analysis, a mathematical model developed by Bergman and colleagues. It represents how well the body can normalize blood glucose independent of insulin. Higher glucose effectiveness (Sg) is generally associated with better metabolic health outcomes.	Change from study day 7 to 15 vs change from study day 24 to 32
Insulin Area-under-the-curve	Insulin area under the curve (AUC) as calculated with trapezoidal method between 0-120min following mixed meal tolerance test.	Change between Study Day 6 vs. Study Day 14 and Study Day 23 vs. Study Day 31
Duration of Endogenous Melatonin Secretory Profile	Test the hypothesis that exposure to one week of sleep restriction with concurrent exposure to extended duration ALAN (LD 19:5) will reduce the duration of the endogenous melatonin secretory profile more than exposure to one week of sleep restriction without extended duration ALAN (LD 14:10). Duration of nocturnal melatonin secretion will be determined by the duration of time at which melatonin levels are above a threshold calculated as 25% of peak-to-trough amplitude at baseline in dim light.	Study Day 15-16 vs Study Day 32-33

Collaborators and Investigators

• Sponsor: Brigham and Women's Hospital
• Investigators: Principal Investigator: Charles A Czeisler, PhD, MD, Brigham and Women's Hospital

Study record dates

Study Major Dates

• Study Start (Actual): March 15, 2022
• Primary Completion (Actual): February 20, 2024
• Study Completion (Actual): May 30, 2024

Study Registration Dates

• First Submitted: April 20, 2021
• First Submitted That Met QC Criteria: April 27, 2021
• First Posted (Actual): May 3, 2021

Study Record Updates

• Last Update Posted (Estimated): October 14, 2025
• Last Update Submitted That Met QC Criteria: September 23, 2025
• Last Verified: September 1, 2025

More Information

Terms related to this study

• Keywords: Melatonin; Sleep; Glucose Intolerance; Artificial Light At Night; Chronic Sleep Restriction
• Additional Relevant MeSH Terms: Neurologic Manifestations; Nervous System Diseases; Mental Disorders; Metabolic Diseases; Glucose Metabolism Disorders; Sleep Wake Disorders; Dyssomnias; Hyperglycemia; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Signs and Symptoms; Sleep Deprivation; Glucose Intolerance
• Other Study ID Numbers: 2021P000961

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
• product manufactured in and exported from the U.S.: No