Light Bulb Stimuli to Reduce Chronic Pain

This pilot, randomized, double-blind, crossover clinical trial is designed to evaluate the feasibility of administering a chromatic light intervention and to explore its effects on pain severity and pain sensitivity in adults with fibromyalgia or chronic widespread pain and fatigue.

Following informed consent and enrollment, baseline assessments will be performed which will include demographic and health questionnaires, validated patient-reported outcome measures, and quantitative sensory testing (QST), including assessments of conditioned pain modulation, temporal summation, and pressure pain threshold.

Participants will then be randomly assigned to one of two treatment sequences:

S-cone stimulating chromatic light during Treatment Period 1 followed by equal-energy white light during Treatment Period 2.

Equal-energy white light during Treatment Period 1 followed by S-cone stimulating chromatic light during Treatment Period 2.

The study utilizes commercially available "TUO" programmable light bulbs that deliver pre-programmed light spectra. Participants will receive study equipment, including five programmed light bulbs, portable lamps, and an illuminometer to verify that the intervention light intensity is at least twice the ambient room illumination. Participants will use the assigned light condition for 2 hours daily, ideally between 5:00 a.m. and 10:00 a.m., for 7 consecutive days while engaging in normal daily activities.

At the end of the first treatment period, participants will return for repeat patient-reported outcome assessments and quantitative sensory testing. Participants will then complete a 1-week washout period during which no light intervention is administered, although daily symptom surveys will continue. Following washout, participants will cross over to the alternate light condition and complete a second 7-day treatment period identical to the first.

After completion of the second treatment period, participants will undergo final intervention assessments, return study equipment, and enter a 1-week follow-up period with continued daily symptom monitoring. At the final study visit, participants will complete follow-up questionnaires and optional quantitative sensory testing.

The primary objective is to determine the feasibility and acceptability of delivering chromatic light therapy for 2 hours daily across two treatment periods. Secondary objectives include evaluating whether chromatic light exposure reduces chronic pain severity and pain sensitivity to a greater extent than an equal-energy white light control condition. Approximately 40 participants will be enrolled, and total participation time will be approximately 35 days. Risks associated with the intervention are expected to be minimal and primarily include potential light sensitivity or discomfort and standard risks related to data confidentiality.

• S-Cone Stimulating Chromatic Light (Device): Participants receive exposure to S-cone stimulating chromatic light delivered via programmed TUO light bulbs. Light is administered for 2 hours daily for 7 consecutive days, ideally between 5:00 a.m. and 10:00 a.m.. Participants use the light in their home environment while engaging in normal daily activities. Light intensity is maintained at a minimum of twice the ambient room illumination using an illuminometer provided by the study. This intervention is designed to selectively stimulate short-wavelength-sensitive (S-cone) photoreceptors.
• Equal-Energy White Light (Device): Participants receive exposure to a light that appears equal-energy white that flickers along the L/M axis delivered via programmed TUO light bulbs. Light is administered for 2 hours daily for 7 consecutive days, ideally between 5:00 a.m. and 10:00 a.m. Participants use the light in their home environment while engaging in normal daily activities. Light intensity is maintained at a minimum of twice the ambient room illumination using an illuminometer provided by the study. This intervention serves as the control condition for comparison with the S-cone stimulating chromatic light intervention.

Primary outcomes

• Percentage of participants completing follow-up visits after each intervention period [Throughout study participation (35 days)]: Feasibility will be assessed by percentage of participants completing follow-up visits after each intervention period.
• Percentage of daily flash surveys completed during the two 7-day stimulation periods [Throughout the two 7-day stimulation periods (14 eligible survey timepoints during active treatment period)]: Feasibility will be assessed by percentage of daily flash surveys completed during the two 7-day stimulation periods (14 eligible survey time points).
• Percentage of prescribed light stimulation sessions completed based on participant self-report [Throughout the two 7-day stimulation periods (14 eligible survey timepoints during active treatment period)]: Feasibility will be assessed by percentage of prescribed light stimulation sessions completed based on participant self-report.

Secondary outcomes

• Pain Intensity [Baseline, post-treatment period 1 (Day 14), post-treatment period 2 (Day 28), and follow-up (Day 35)]: Pain severity will be measured using an 11-point Numeric Rating Scale (NRS), where 0 represents no pain and 10 represents the worst pain imaginable. Mean pain scores following S-cone stimulating light and equal-energy white light conditions will be compared.
• Pressure Pain Threshold [Baseline, post-treatment period 1 (Day 14), and post-treatment period 2 (Day 28).]: Pressure pain threshold will be assessed using a pressure algometer applied to the trapezius muscle. Outcomes will be recorded in kilograms of force per square centimeter (kgf/cm\^2). Higher values indicate greater pain tolerance and reduced pain sensitivity.
• Temporal Summation [Baseline, post-treatment period 1 (Day 14), and post-treatment period 2 (Day 28).]: Temporal summation will be assessed using a 256 millinewton (mN) pinprick stimulator. Pain intensity ratings following a single stimulus and a train of 10 repetitive stimuli will be used to quantify central pain facilitation. Lower temporal summation values indicate reduced pain sensitivity.
• Conditioned Pain Modulation [Baseline, post-treatment period 1 (Day 14), and post-treatment period 2 (Day 28).]: Conditioned pain modulation will be calculated as the difference in pressure pain threshold measured before and after a conditioning cold-water stimulus. Greater increases in pressure pain threshold following conditioning indicate more effective endogenous pain inhibition.

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Adults ≥ 18 years of age.
* Individuals who have been diagnosed with fibromyalgia or suffer from chronic widespread pain and fatigue.
* An average pain severity ≥4 on the 0-10 NRS over the month prior to enrollment.
* Pain symptoms present for 3 months or longer.
* Pain must be present in 4 out of 5 body regions.
* A score of ≥7 on the Widespread pain index (WPI) and ≥5 on the symptom severity scale (SSS), or 4-6 on the WPI and ≥9 on the SSS in the 2016 Fibromyalgia Questionnaire.
* Willingness to adjust light levels in home environment so that the illumination (measured in lux) provided by the light bulbs is twice the ambient room illumination (also measured in lux).
* Willingness to use study lightbulbs for 2 consecutive hours a day for 7 consecutive days according to study specifications for both conditions (total of 14 days using lightbulbs)
* Alert and oriented, and able to provide informed consent
* Ability to read and speak English to complete validated questionnaires.

Exclusion Criteria:

* Vision disorders or conditions resulting in severe vision impairment or blindness
* Individuals with self-report of color blindness, uveitis or cataracts.
* Prisoner Status
* Pregnancy
* History of photosensitivity or sensitivity to scintillating (mildly flickering) light.
* History of seizure disorder.
* Individuals living in households with people who have a history of seizure disorders.
* Analgesic treatment plan changes anticipated in the next 3 months (surgery, analgesic medication changes, injections, pain procedures, etc.).
* Other history or condition that would, in the investigator's judgment, indicate that the individual would highly likely be non-compliant with the study or unsuitable for the study

• Matt Mauck, MD, PhD, Principal investigator, UNC Chapel Hill School of Medicine