Circadian Light Exposure Adjustment for Restfulness (CLEAR)

January 29, 2026 updated by: University of Arizona
Many young children are exposed to light int he evening hours before bedtime. Children's biological clocks are highly sensitive to evening light exposure, which can delay the timing of the clock and make it harder to fall asleep. The purpose of this study is to test three strategies (adjustment to home lighting, amber-tinted glasses, clear glasses) to reduce evening light exposure in children ages 5-6 years with parent-reported sleep onset difficulties in order to improve their sleep and the timing of their biological clock. This study takes place over approximately 5 weeks. After baseline assessments of children's sleep timing, light exposure, cognition, and circadian rhythms, they will be randomly assigned to one of three interventions to reduce evening light exposure for two weeks. After the two-week intervention period, the baseline measures are repeated and parents are interviewed about their and their child's experiences with the intervention.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

Evening sleep difficulties are common in young children and can contribute to behavioral and health problems. Sleep timing is regulated in part by the circadian clock, which is highly sensitive to light exposure. Light in the hour before bedtime can suppress melatonin, delay circadian timing, and make it harder for children to fall asleep. Despite evidence of high circadian sensitivity to evening light, few studies have tested interventions to improve sleep timing in early childhood using light-based strategies.

This study evaluates the feasibility, acceptability, and preliminary efficacy of two light-mitigation strategies to advance sleep and circadian timing in children aged 5 to 6 years with parent-reported sleep onset difficulties. Children will participate in a five-week study consisting of baseline assessments, a two-week intervention period, and post-intervention assessments. Parents of enrolled children will provide written informed consent for their child's participation. Children are under age 7 years and are not required to provide formal assent.

Baseline assessments will include sleep timing, duration, and quality measured via actigraphy, circadian phase assessed with salivary dim-light melatonin onset (DLMO), parent-reported sleep behaviors, and a cognitive battery. Children will then be randomly assigned to one of three interventions: (1) smart home lighting to reduce evening short-wavelength light, (2) amber-tinted glasses worn in the hour before bedtime, or (3) clear glasses as a sham control. Interventions will last two weeks, with adherence monitored throughout.

After the intervention, all assessments will be repeated, and parents will participate in structured interviews to report on the feasibility and acceptability of the assigned strategy. Exploratory measures will include baseline pupillary light response to examine individual differences in photosensitivity as potential moderators of intervention effects.

Data from this study will inform the feasibility and acceptability of light-based interventions in young children (Aim 1), provide preliminary evidence of effects on sleep and circadian timing (Aim 2), and explore whether photosensitivity moderates response to the interventions (Exploratory Aim 3).

Study Type

Interventional

Enrollment (Estimated)

60

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Child

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Inclusion requires that children are aged 5.0-6.9 years at the time of enrollment with a parent-reported sleep onset of ≥ 60 min after parents' desired bedtime at least three nights per week.

One adult parent of each participating child will also take part in the study. Parents must be able to provide consent for themselves and their child and to complete the interview at the end of the study.

Exclusion Criteria:

  • Children are excluded for the following reasons:

    • All sleep disorders as indicated on the telephone screener or by clinical cut-off scores on the Children's Sleep Habits Questionnaire (CSHQ), except for insomnia or DSWPD as features of these disorders are directly targeted by the intervention. Secondary analyses will explore if outcomes differ among participants with or without parent-reported symptoms consistent with these diagnoses.
    • Physical abilities that interfere with assessments (e.g., visual impairment), developmental disabilities (e.g., autism, attention-deficit/hyperactivity disorder (ADHD), pervasive developmental disorder), epilepsy or other neurological disorders, metabolic disorders, medical conditions that commonly require treatments or assessments during the night (e.g., cancer, diabetes, active asthma), current infection or lead poisoning; a head injury involving loss of consciousness in the past 6 months.
    • Current use of medications affecting daytime sleepiness, the circadian system, or light sensitivity.
    • Eye disorders or color blindness (determined with Ishihara Color Vision Test); corrected vision with eyeglasses is permitted.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Amber Tinted Glasses
Wearing "blue-blocker" glasses (lenses that filter out the blue portion of the visible spectrum) can reduce the melatonin suppression and alertness effects of evening light exposure in both adults and adolescents, as well as advance the timing of the circadian clock and sleep onset, compared with participants wearing placebo lenses. This intervention will examine their efficacy in advancing young children's sleep and circadian timing. Children will be given a pair of glasses (Block Blue Light), with amber-tinted lenses (advertised as blocking 100% of light from 380-550 nm. Children will wear the glasses starting 1 h before parent's selected bedtime each evening across the two-week intervention. Parents will also complete a daily diary detailing when the glasses are worn.
Device: Amber Tinted Glasses
Children will wear amber-tinted glasses in the evening hours before bedtime to reduce exposure to short-wavelength (blue) light. The glasses are intended to reduce circadian disruption associated with evening light exposure.
Sham Comparator: Clear Glasses
The sham comparator consists of the same protocols for the amber-tinted glasses, except that children will wear a pair of glasses with clear lenses (advertised as blocking 50% of light from 400-500 nm), which are significantly less effective at blocking short-wavelength light.
Device: Clear Glasses
Children will wear clear glasses in the evening hours before bedtime. This sham intervention controls for wearing glasses without reducing light exposure.
Experimental: Smart Lightbulbs
The presence of more blue light in the home is associated with later circadian timing in both school-aged children and adults. This intervention will adjust the evening home lighting environment to be less stimulating to children's circadian clocks. Smart light bulbs (dimmable and color tunable LED bulbs) will be installed in participants' homes light fixtures, or in the child's bedroom, bathroom, as well as areas the child is likely to spend time in after dinner (i.e., living room, playroom). The researchers will program the lights to transition to a lower CCT and dimmer intensity to achieve the recommended evening mEDI of 10 lux starting 1 h before the child's parent-selected bedtime.
Device: Smart Lightbulbs
Smart light bulbs will be installed in the child's home and programmed to reduce short-wavelength light exposure during evening hours before bedtime.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Intervention Feasibility
Time Frame: Throughout the two-week intervention period.
Feasibility will be assessed using adherence/compliance rates to assigned intervention protocols.
Throughout the two-week intervention period.
Acceptability
Time Frame: Week 5
Acceptability will be assessed using parent-reported qualitative interviews conducted post-intervention.
Week 5

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Circadian Timing
Time Frame: Assessed once in Week 2 and once in Week 5
Dim light melatonin onset, a measure of circadian timing, will be assessed via saliva samples.
Assessed once in Week 2 and once in Week 5
Sleep Timing
Time Frame: Throughout the 5 week protocol
Throughout the duration of the study, the child will wear a wrist actigraph which records sleep timing and light exposure. The actigraph is a watch-size monitor worn on the non-dominant wrist, providing continuous imputation of sleep-wake states via arm activity. These data will be used to examine changes in habitual sleep timing, sleep onset latency.
Throughout the 5 week protocol
Light Exposure
Time Frame: Throughout the 5 week protocol.
Measured by the wrist-worn actigraph watch in 1-min epochs throughout data collection. These data provide an objective measure of the child's light exposure throughout the protocol (including compliance with the home lighting intervention) and will be used to examine changes in habitual light exposure.
Throughout the 5 week protocol.
Sleep-Related Behaviors
Time Frame: Assessed once in Week 1 and once in Week 5
Change in parent-reported sleep behaviors assessed via validated questionnaires.
Assessed once in Week 1 and once in Week 5

Other Outcome Measures

Outcome Measure
Measure Description
Time Frame
Pupillary Light Response
Time Frame: Baseline
Baseline pupillary light response will be assessed as a measure of individual differences in photosensitivity.
Baseline
Cognitive Functioning
Time Frame: Assessed once in Week 1 and once in Week 5
Change in cognitive performance from pre- to post-intervention assessed using a standardized cognitive battery (NIH Toolbox).
Assessed once in Week 1 and once in Week 5

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Arizona

Collaborators

National Heart, Lung, and Blood Institute (NHLBI)

Investigators

  • Principal Investigator: Lauren E Hartstein, PhD, University of Arizona

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

January 15, 2026

Primary Completion (Estimated)

December 1, 2029

Study Completion (Estimated)

July 31, 2030

Study Registration Dates

First Submitted

January 7, 2026

First Submitted That Met QC Criteria

January 29, 2026

First Posted (Actual)

February 6, 2026

Study Record Updates

Last Update Posted (Actual)

February 6, 2026

Last Update Submitted That Met QC Criteria

January 29, 2026

Last Verified

January 1, 2026

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • STUDY00005764: CLEAR
  • K01HL181331 (U.S. NIH Grant/Contract)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

No identifiable data will be shared. Only de-identified study data will be made available for research purposes.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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