Green Light Exposure Improves Pain and Quality of Life in Fibromyalgia Patients: A Preliminary One-Way Crossover Clinical Trial

Abstract

Objective: Fibromyalgia is a functional pain disorder in which patients suffer from widespread pain and poor quality of life. Fibromyalgia pain and its impact on quality of life are not effectively managed with current therapeutics. Previously, in a preclinical rat study, we demonstrated that exposure to green light-emitting diodes (GLED) for 8 hours/day for 5 days resulted in antinociception and reversal of thermal and mechanical hypersensitivity associated with models of injury-related pain. Given the safety of GLED and the ease of its use, our objective is to administer GLED as a potential therapy to patients with fibromyalgia.

Design: One-way crossover clinical trial.

Setting: United States.

Method: We enrolled 21 adult patients with fibromyalgia recruited from the University of Arizona chronic pain clinic who were initially exposed to white light-emitting diodes and then were crossed over to GLED for 1 to 2 hours daily for 10 weeks. Data were collected by using paper surveys.

Results: When patients were exposed to GLED, but not white light-emitting diodes, they reported a significant reduction in average pain intensity on the 10-point numeric pain scale. Secondary outcomes were assessed by using the EQ-5D-5L survey, Short-Form McGill Pain Questionnaire, and Fibromyalgia Impact Questionnaire and were also significantly improved in patients exposed to GLED. GLED therapy was not associated with any measured side effects in these patients.

Conclusion: Although the mechanism by which GLED elicits pain reduction is currently being studied, these results supporting its efficacy and safety merit a larger clinical trial.

Trial registration: ClinicalTrials.gov NCT03677206.

Keywords: Complementary Therapy; EQ-5D-5L; Fibromyalgia; Green Light.

© The Author(s) 2020. Published by Oxford University Press on behalf of the American Academy of Pain Medicine. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Figures

Figure 1.

Study design: one-way crossover clinical trial. Twenty-five patients with fibromyalgia were screened for the study, and two patients refused to enroll. Twenty-three patients were assigned to the control WLED group first. Two patients withdrew immediately from the study because of lack of effect or inability to secure the time needed to conduct the study. Analysis did not include these two patients. After 10 weeks of daily WLED, all of the 21 patients who finished the WLED treatment underwent a 2-week washout period and were then crossed over to the GLED treatment.

Figure 2.

Pain score evaluation before and after WLED and GLED exposure. (A) WLED exposure did not significantly change the pain intensity baseline represented by bar on the left hand side of panel A for patients with fibromyalgia evaluated with the NPS (n = 21), and (B) GLED exposure statistically decreased the baseline represented by bar on the left hand side of panel B pain intensity for patients with fibromyalgia evaluated with the NPS (n = 21, Wilcoxon matched-pairs signed rank test, ***P < 0.001). NPSI = initial NPS; NPSF = final NPS. (C) Results represent NPS score improvement in both WLED and GLED groups. Values correspond to the initial score subtracted from the final score. Patients exposed to GLED reported significantly higher NPS pain reduction than patients exposed to WLED (n = 21, Mann-Whitney test, ***P < 0.001). (D) Patients exposed to GLED for greater than 1.5 hours/day (>1.5 h/day) reported slightly higher, but not statistically significant, NPS pain reduction than that of patients exposed to GLED for less than 1.5 hours/day (<1.5 h/day) (n = 10–11, Mann-Whitney test, P = 0.4750).

Figure 3.

FIQ scores before and after WLED or GLED exposure. (A) WLED exposure produced a small but statistically significant reduction in FIQ. (B) GLED exposure produced a statistically significant larger reduction in the FIQ (scale 0–100, where 0 = no impact from fibromyalgia, and 100 = worst possible impact from fibromyalgia). Data are presented as average ± SEM (n [WLED] = 19, n [GLED] = 16, Wilcoxon matched-pairs signed rank test, *P < 0.05, ***P < 0.001). (C) Results represent FIQ score improvement in both WLED and GLED groups. Values correspond to the initial score subtracted from the final score. Patients exposed to GLED reported significantly higher FIQ score improvement than did patients exposed to WLED (n [WLED] = 19, n [GLED] = 16, Mann-Whitney test, ***P < 0.001).

Figure 4.

Patients’ subjective improvement of several criteria after WLED or GLED exposure. WLED exposure produced minimal improvement in several parameters for patients with fibromyalgia, whereas GLED exposure produced significant improvement in all parameters. Data are presented as average ± SEM (n [WLED] = 18–19, n [GLED] = 12–21, Mann-Whitney test, ***P < 0.001).

Figure 5.

Quality of life and patients’ perception of their own health after WLED or GLED exposure. (A) WLED exposure produced a small but statistically significant improvement in the quality of life and patients’ perception of their own health as measured by the EQ-5D-5L survey (n = 20, Wilcoxon matched-pairs signed rank test, *P < 0.05). (B) GLED exposure produced greater and statistically significant improvement in the quality of life and the patients’ perception of their own health as measured by the EQ-5D-5L survey (n = 17, Wilcoxon matched-pairs signed rank test, **P < 0.01). (C) Results represent EQ-5D-5L score improvement in both WLED and GLED groups. Values correspond to the initial score subtracted from the final score. Patients exposed to GLED reported significantly higher EQ-5D-5L scores than did patients exposed to WLED (n [WLED] = 21, n [GLED] = 17, Mann-Whitney test, *P < 0.05). (D) WLED exposure produced a small but statistically significant improvement of the quality of life and patients’ perception of their own health as measured by the EQ 5 D-5L survey (n = 21, Wilcoxon matched-pairs signed rank test, *P < 0.05). (E) GLED exposure also produced a significant improvement of the quality of life and the patients’ perception of their own health as measured by the EQ 5 D-5L survey (n = 17, Wilcoxon matched-pairs signed rank test, ***P < 0.001). (F) Results represent patients’ own perception of improvement in both the WLED and GLED groups, as reported in the EQ-5D-5L. Values correspond to the initial score subtracted from the final score. Patients exposed to GLED did not report a significantly higher improvement in their perception of their own health (n [WLED] = 21, n [GLED] = 17, Mann-Whitney test, P = 0.2275). Data are presented as average ± SEM.

Figure 6.

SF MPQ scores before and after WLED exposure in patients with fibromyalgia. WLED exposure significantly decreased 6 of the 15 baseline values for patients with fibromyalgia in the SF MPQ. Data are presented as average ± SEM (n = 20, Wilcoxon matched-pairs signed rank test, *P < 0.05, **P < 0.01).

Figure 7.

SF MPQ scores before and after GLED exposure in patients with fibromyalgia. GLED exposure significantly decreased 12 of the 15 baseline values for patients with fibromyalgia in the SF MPQ. For each parameter, the top bar represents the Before GLED value while the bottom bar represent the After GLED value. Data are presented as average ± SEM (n = 18, Wilcoxon matched-pairs signed rank test, *P < 0.05, **P < 0.01, ***P < 0.001).