Clinical efficacy study of LED red and infrared light therapy for chronic non-specific low back pain

Abstract

To evaluate the efficacy and safety of an LED red and infrared light therapy for the treatment of chronic nonspecific low back pain. From September to December 2022, 176 patients diagnosed with chronic non-specific low back pain were enrolled and randomly assigned to two groups: the experimental group (n = 89) and the control group (n = 87). The experimental group received treatment with the test device (630 + 850 nm, 15 + 6 mW/cm²) combined with rehabilitation training, whereas the control group received a sham device (630 nm, 1 mW/cm²) alongside rehabilitation training. After 28 days of treatment, clinical efficacy was assessed using the Visual Analogue Scale (VAS) score. The total effective rate was 80.90% in the experimental group and 27.59% in the control group, with a rate difference of 53.31%. The experimental group showed significantly better outcomes compared to the control group.(p < 0.0001). The Japanese Orthopaedic Association (JOA) score in the experimental group was significantly higher than that in the control group (p < 0.0001). No serious adverse events occurred during the trial, and all reported adverse events were unrelated to the device. The LED red and infrared light therapy device may serve as a safe and beneficial intervention for chronic nonspecific low back pain. Trial registration number: ChiCTR2600117704 (Retrospectively registered). Date of registration: 2026-01-28.

Introduction

Low back pain (LBP) is one of the most prevalent musculoskeletal disorders worldwide [1]. Chronic nonspecific low back pain (CNSLBP), which accounts for approximately 90% of all LBP cases, significantly impairs patients’ quality of life [2]. The primary treatment goals for CNSLBP are to improve physical function, restore normal activity, prevent disability, and maintain work capacity [3]. Common management strategies include pharmacotherapy, physical/rehabilitation therapy, and cognitive behavioral therapy, among others [3]. The long-term administration of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) can lead to various complications, including gastrointestinal, cutaneous, and renal adverse effects. Therefore, investigating a safe treatment modality with no significant side effects is necessary [2].

Photobiomodulation (PBM), also known as low-level laser therapy (LLLT) [4], has been widely used in recent decades to alleviate pain associated with various musculoskeletal disorders [5]. A recent randomized controlled trial by Kuzu et al. [6] specifically demonstrated the efficacy of both high-intensity and low-intensity laser therapy in improving pain and functional outcomes in patients with lumbar disc herniation, further supporting the therapeutic potential of light-based modalities for spinal conditions. The analgesic mechanisms of PBM are considered multifactorial. Experimental evidence indicates that light irradiation can induce peripheral nerve blockade, inhibit central synaptic activity, modulate neurotransmitter release, reduce muscle spasms and interstitial edema, and exert anti-inflammatory effects [7]. Despite growing evidence that PBM relieves pain and improves function in CNSLBP, prior research still has notable limitations. First, most trials used low-level laser therapy [5]. Traditional laser devices are expensive, bulky and restricted to hospital use, making them unsuitable for long-term home treatment for recurrent CNSLBP. Second, most studies applied only single-wavelength light [8]. Large-sample randomized controlled trials are still lacking to confirm the synergistic effects of combined 630 nm red and 850 nm infrared LED light on CNSLBP. The clinical application of phototherapy has a long history. A large number of scientific studies have confirmed that light can bring therapeutic effects to human tissues and organs through energy penetration [3, 9, 10]. Red light and near-infrared light exhibit strong tissue penetration capabilities, reaching deep-seated structures and demonstrating significant therapeutic potential for subcutaneous, muscular, and tendinous tissues [11]. This study used an LED red and infrared light therapy device (630 nm + 850 nm) to treat patients with chronic non-specific low back pain. The findings are reported as follows.

Materials and methods

Study design

This was a prospective, randomized, single-blind, parallel sham-controlled superiority multicenter clinical trial. The study protocol was compliant with the ethical principles of the Declaration of Helsinki and was approved by the institutional review board at all study sites. Patients were recruited from September to December 2022 at three hospitals in two provinces. All subjects signed a written declaration of informed consent.

A simple random sequence was generated using a computer-produced random number list. Allocation concealment was implemented via sequentially numbered, sealed opaque envelopes. The randomization procedure was conducted by an independent researcher who was not involved in participant enrollment, treatment administration, or outcome assessment. In this single-blind design, only participants were blinded to group allocation. Blinding was maintained by employing active and sham devices that were identical in appearance, operation, and indicator light. All outcome measurements, including VAS score, JOA score and patient satisfaction assessment, were self-completed by participants under the unified guidance of clinicians.

Sample size calculation

The key parameters were set as follows:

• One-sided significance level α = 0.025;

• Power 1-β = 80% (β = 0.20);

• Assumed overall response rate: 90% in the experimental group () and 73% in the control group ();

• Between-group difference   

• Superiority margin

The calculated minimum sample size was 78 subjects per group. After accounting for a 10% dropout rate, block randomization, and clinical operational factors, the final sample size was set at 176 subjects.

Study patients

A total of 176 patients with chronic non-specific low back pain were randomly divided into two groups: the experimental group (n = 89; 29 males and 60 females; mean age 45 years, range 20–72) and the control group (n = 87; 34 males and 53 females; mean age 47 years, range 20–74), as shown in Fig. 1.

Fig. 1.

The study flow chart

The inclusion criteria were as follows: (1) age ≥ 18 years; (2) a diagnosis of chronic nonspecific low back pain, met the criteria outlined in the Chinese Expert Consensus on the Diagnosis and Management of Acute/Chronic Nonspecific Low Back Pain, with a disease duration of ≥ 12 weeks and a Visual Analogue Scale (VAS) score of ≥ 4; and (3) voluntary participation in the trial with a signed informed consent form.

Participants were excluded from the study based on the following criteria: Presence of infection, rash, skin damage on the irradiated area; Epilepsy; Hemorrhagic or hemolytic diseases; Severe dysfunction of a single or multiple organs; Liver and kidney dysfunction; Individuals who had undergone surgery on the lumbar and thoracic vertebrae in the past; The treatment area is: Spinal canal stenosis, nerve root compression, spinal fractures; Porphyria; During the trial, it was necessary to continue taking: Quinolones, Tetracyclines, Sulfonamides, Griseofulvin, Hydrochlorothiazide, Amiodarone, Sulfonylurea hypoglycemic drugs, Antidepressants and Antipsychotics, etc., which significantly affect photosensitivity; Atrioventricular block, Sinus node disease, Atrial fibrillation, Ventricular fibrillation, etc., severe arrhythmias; Wearing a pacemaker or having metal implants in the body; Patients with malignant invasive tumors; Mentally incompetent or unable to understand the requirements of the trial; Pregnant, lactating or having a pregnancy intention within the last month; Heavy drinking; Individuals who have participated in other clinical trials of medical devices or drugs within the previous 1 month; Other situations that are not suitable for inclusion.

Study treatments

The experimental group used the LED red and infrared light therapy device (Beijing Charmwin Light Medical Technology Co., Ltd., CY-1004C), with the technical specifications of the device shown in Table 1, and the external appearance of the device was depicted in Fig. 2. All participants self-administered the treatment at home by applying the device to the painful lower back region. The device is a flexible wearable patch that can be worn directly on the lumbodorsal area, with the light source placed in direct contact with the skin. Two 20-minute irradiation sessions were conducted daily, with an interval of at least 3 h between sessions. The wearable device did not restrict the patient’s posture; participants could continue their normal daily activities (e.g., sitting, standing, walking) during treatment. The control group received treatment with a sham device (CY-1004C-T) that was identical in appearance to the test device. This sham device emits only very low‑power visible red light and does not emit any infrared light or therapeutic radiation. Participants were advised to avoid taking analgesics as much as possible during the trial. In cases where pain became unbearable and medication was necessary, participants were allowed to take either ibuprofen or celecoxib for pain relief. The dosage and duration of any analgesic use were required to be recorded. In addition, all participants were asked to discontinue any other physical therapies (e.g., massage, acupuncture, heat pack) during the 28-day trial. After 28 consecutive days of home treatment, all participants returned to the hospital for outcome evaluations using the VAS and JOA scores. To avoid the immediate effect of the last treatment session, assessments were scheduled at least 12 h after the final treatment.

Table 1.

Illumination parameters of the LED red and infrared light therapy device

Items	CY-1004C	CY-1004C-T
Wavelength	630 nm ± 10 nm 850 nm ± 10 nm	630 nm ± 10 nm (no infrared light)
Power density	red light 15 mW/cm2 infrared light 6 mW/cm2	red light 1 mW/cm2
Rated voltage	220VAC	220VAC
Rated power	30 W	30 W
Irradiation time	20 min	20 min

Fig. 2.

LED red and infrared light therapy device

Parameters and assessments

Efficacy observation indicators

The intensity of low back pain was assessed using the Visual Analogue Scale (VAS) [12], which ranges from 0 to 10, with a higher score indicating more severe pain. Based on the rate of pain improvement, the therapeutic outcomes were categorized into four grades: Markedly effective, effective, improved, and ineffective. The overall effective rate was calculated as the proportion of cases with outcomes rated as “Markedly effective” plus “effective.” Lumbar function was evaluated using the Japanese Orthopaedic Association (JOA) [13]assessment scores. The JOA score ranges from 0 to 29, where a lower score indicates more severe lumbar dysfunction.

Criterion of therapeutic effect

The primary outcome of this trial was the change in low back pain intensity, which was quantified using the VAS. The rate of pain improvement was calculated using the following formula:

Based on this improvement rate, therapeutic efficacy was categorized into four grades:

• Markedly effective: Improvement rate > 80%;

• Effective: Improvement rate between 50% and 80%;

• Improved: Improvement rate between 20% and 49%;

• Ineffective: Improvement rate < 20%;

• The overall effectiveness rate was defined as the percentage of cases achieving an “Markedly effective” or “Effective” outcome, calculated as: [(Number of “Markedly effective” cases + Number of “Effective” cases) / Total number of cases] × 100%.

Patient satisfaction with the product

Patient product usage satisfaction is evaluated based on the subjective feelings of patients after using the product. The specific evaluation grades are: very dissatisfied, dissatisfied, generally satisfied, satisfied, and very satisfied. Overall satisfaction = satisfied + very satisfied, overall dissatisfaction = generally satisfied + dissatisfied + very dissatisfied.

Statistical analysis

Statistical analysis was conducted using the SAS 9.4 statistical analysis software. Measurement data were analyzed using t-test or nonparametric test; Enumeration data were analyzed using χ² test (or Fisher’s exact test); and ranked data were analyzed using rank-sum test. The primary efficacy indicator was evaluated using superiority testing, with the superiority threshold set at 0. All statistical tests were conducted using two-sided tests, and a p-value less than or equal to 0.05 was considered to indicate a statistically significant difference. The primary efficacy analysis was based on the full analysis set (FAS/ITT). Because there were no missing data, complete case analysis was applied.

Results

Baseline characteristics

As shown in Table 2, the baseline characteristics in terms of physical examinations were well-balanced between groups.

Table 2.

Baseline characteristics of the participants

Characteristic	Index	The experimental group	The control group	Total	Statistical magnitude	P
Age, years	N(Missing)	89 (0)	87 (0)	176 (0)	T test	0.1171
	Mean(SD)	44.6 (12.8)	47.4 (11.6)	46.0 (12.3)	1.5700
	Median	45	47	46.5
gender	Male n(%)	29 (32.58%)	34 (39.08%)	63 (35.80%)	Chi-squared test
	Female n(%)	60 (67.42%)	53 (60.92%)	113 (64.20%)	0.8078	0.3688
	Total(Missing)	89 (0)	87 (0)	176 (0)
Height, cm	N(Missing)	89 (0)	87 (0)	176 (0)	T test
	Mean(SD)	165.6 (7.0)	166.3 (7.8)	165.9 (7.4)	0.6800	0.4975
	Median	165	165	165
Weight, kg	N(Missing)	89 (0)	87 (0)	176 (0)	T test
	Mean(SD)	65.22 (10.33)	65.33 (10.97)	65.27 (10.62)	0.0700	0.9468
	Median	63.50	64.00	63.75

Pain improvement rate (VAS score)

A comparison of low back pain VAS scores before and after treatment for both groups is shown in Fig. 3. The experimental group demonstrated a significantly higher pain improvement rate compared to the control group, and the difference was statistically significant (p < 0.0001), as detailed in Table 3.

Fig. 3.

Low back pain VAS scores before and after treatment

Table 3.

The comparison of pain improvement rates

Items	Index	The experimental group	The control group
pain improvement rates	N(Missing)	89 (0)	87 (0)
	Mean(SD)	62.58% (29.06%)	29.82% (24.28%)
	Median	66.67%	33.33%
	T test	-8.11
	P	< 0.0001

Total effective rate

The experimental group demonstrated a significantly higher overall response rate than the control group (80.90% vs. 27.59%, respectively; rate difference: 53.31%; p < 0.0001), as detailed in Table 4.

Table 4.

Total effective rate

Items	Index	The experimental group	The control group
Evaluation grade of effectiveness	Markedly effective n(%)	15 (16.85%)	0 (0.00%)
	Effective n(%)	57 (64.04%)	24 (27.59%)
	Improved n(%)	13 (14.61%)	34 (39.08%)
	Ineffective n(%)	4 (4.49%)	29 (33.33%)
Evaluation of therapeutic efficiency	Markedly effective +Effectiven(%)	72 (80.90%)	24 (27.59%)
	Improved+Ineffectiven(%)	17 (19.10%)	63 (72.41%)
	Total(Missing)	89 (0)	87 (0)
	Statistical magnitude(CMH)	50.1472
	P	< 0.0001
	95% confidence interval for the rate difference	53.31% (39.47%, 64.05%)

Lumbar function (JOA score)

The comparison of JOA scores before and after treatment in the two groups is shown in Fig. 4. The average score of the experimental group increased by 4.3, while that of the control group increased by 3.5. As shown in Table 5.

Fig. 4.

The JOA scores before and after treatment in the two groups

Table 5.

JOA

Items	Index	Selection period		Treatment period(28 ± 3 days)
		The experimental group	The control group	The experimental group	The control group
JOA	N(Missing)	89 (0)	87 (0)	89 (0)	87 (0)
	Mean(SD)	22.6 (3.3)	22.1 (3.6)	26.9 (2.0)	25.6 (2.6)
	Min, Max	13.0, 28.0	12.0, 28.0	19.0, 29.0	16.0, 28.0
	95% CI			0.61–1.99
	P			< 0.0001

Satisfaction rate evaluation

After 28 days of treatment, the overall satisfaction rate of the experimental group was 97.70%, while that of the control group was 58.62%. There was a statistically significant difference in the satisfaction rate of product usage between the two groups (p < 0.0001).

Safety evaluation

The incidence of adverse events was 5.62% (5/89) in the experimental group and 12.64% (11/87) in the control group. All reported adverse events were mild in severity, with the most common including upper respiratory tract infections, cough, and fever. No serious adverse events occurred during the study, and all adverse events were assessed as unrelated to the investigational devices.

Discussion

Low back pain is a major global public health issue. Roughly 90% of cases are non-specific low back pain (NLBP), which affects about 540 million adults and ranks top among causes of global disability [14]. Current international guidelines primarily recommend non-pharmacological therapies as the first-line approach, advising cautious and limited use of analgesic medications [15, 16]. Common non-pharmacological treatments include exercise, psychological intervention, acupuncture and manual therapy, yet they have drawbacks like unsustained long-term effects and inconsistent outcomes [17]. LED red and infrared light therapy, as a non-pharmaceutical and non-invasive physical treatment method, has advantages such as high safety, strong penetration, and ease of home use compared with traditional treatment methods. It is especially suitable as an auxiliary or alternative option for patients with drug contraindications or those seeking minimally invasive treatment.

This randomized controlled trial evaluated the clinical efficacy of red and near-infrared light therapy in patients with NSLBP. The results demonstrated that the experimental group receiving phototherapy showed significant improvements in both pain intensity (measured by VAS score) and lumbar dysfunction (assessed by JOA score) compared to the control group. The between-group difference in VAS score improvement was 2 points, which exceeded the minimal clinically important difference (MCID) of 1.5 points [18] for chronic nonspecific low back pain, indicating a clinically meaningful treatment effect. For the JOA scale, the widely accepted MCID threshold is 2.5 points [19]. While the experimental group’s within-group JOA improvement of 4.3 points surpassed this cutoff and represented tangible functional recovery for individual patients, the post-treatment intergroup JOA difference of only 1.3 points failed to reach the MCID, meaning this statistically significant gap brought limited clinical superiority over sham intervention. These findings are consistent with previous studies [20] and support the use of phototherapy as an effective non-pharmacological intervention for CNSLBP.

The mechanism of phototherapy may involve multiple biological effects, including promoting cell proliferation [21], accelerating the healing process, facilitating tissue regeneration, preventing cell apoptosis [22], anti-inflammatory [23] and pain relief [24]. One of the primary mechanisms of PBM is the stimulation of mitochondria [25]. By regulating the activity of cytochrome c oxidase (CCO), it promotes electron transfer, which can generate more adenosine triphosphate (ATP), regulate redox reactions and induce transcription factors [26]. Furthermore, PBM can enhance local microcirculation and elevate the pain threshold [27]. Additionally, the thermal effect of infrared radiation can accelerate the chemical reaction process of local tissues, causing the dilation of capillaries, improvement of blood circulation, and promotion of swelling subsidence. By studying the expression of pain-related inflammatory factors and chemokines in peripheral blood mononuclear cells (PBMCs), Yi et al. [28] found that red light and infrared light irradiation could significantly reduce the expression levels of IL-4 and IL-6 in PBMCs, thereby alleviating pain caused by local sterile inflammation.

Red light and near-infrared light, due to their lower photon energy and excellent tissue penetration ability, demonstrate great application potential in the PBM field. It is worth emphasizing that the mechanism of action of PBM is different from that of traditional laser medicine. The latter mainly relies on the selective killing of diseased cells. Therefore, LED light sources not only achieve similar therapeutic effects as laser light sources, but also possess higher safety, more convenient operation, and greater portability [22]. The accessibility of existing phototherapy equipment is relatively low, mainly concentrated in hospitals and other medical institutions. Considering the characteristics of chronic non-specific low back pain, such as high recurrence rate and long treatment period, patients need to frequently visit the hospital for treatment, which to some extent limits the application of phototherapy. LED can achieve the form of flexible wearable irradiation, allowing patients who have been suffering from low back pain for a long time to receive treatment at home, breaking through the limitations of treatment location and time. However, the standardization of treatment parameters remains a challenge, and the individualized adjustment of wavelength selection and irradiation frequency still requires further exploration. In summary, LED red and infrared light therapy is a viable and effective method for managing chronic non-specific low back pain, with simple operation that favors its clinical translation.

While our study demonstrates the efficacy of LED therapy in reducing pain and improving function, optimal management of chronic nonspecific low back pain often requires a multimodal approach. Recent evidence suggests that combining physical modalities with optimized exercise strategies, such as those manipulating the focus of attention during movement re-education, may yield additional benefits [29]. Future studies should investigate the potential synergistic effects of LED therapy and targeted motor learning interventions.

Several limitations of this study should be acknowledged. First, The clinicians who guided participants’ self-assessment knew the group allocation, which may cause potential detection bias for these subjective outcomes. Second, the follow-up duration was only 28 days. Given the chronic nature of nonspecific low back pain, the long-term durability of treatment effects at 6 months or 1 year remains unknown, which represents a major limitation. Third, the absence of objective inflammatory or biological markers means mechanistic evidence relies solely on subjective patient-reported outcomes. Fourth, no treatment diaries or usage logs were collected to monitor adherence to the 28-day twice-daily home therapy, which may bias efficacy results. Future double-blind trials with longer follow-up, biomarker testing and adherence recording are needed.

This study was retrospectively registered nearly three years after data collection ended. Late registration removes the protection against selective outcome reporting, which represents an important methodological limitation, even though all procedures strictly followed the original fixed protocol.

Author contributions

XB Tang: Design experiments and review articles.B Yi: Administrative or material support and obtain research funding.J He: Design experiments, administrative or material support and obtain research funding.DY Kou, N Jing and BD Cao: Conduct research, collect data and analyze/interpret data.N Song: Design experiments, statistical analysis and manuscript drafting.YL Wang: Statistical analysis, manuscript editing and reviewAll the authors gave the final approval of the version to be published.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. This study was approved by the Ethics Committee of the First Affiliated Hospital of Baotou Medical College, Inner Mongolia University of Science and Technology (Ethics Review No. 27, 2022), the Clinical Trial Ethics Committee of Hebei PetroChina Central Hospital (IRB2022-083-01), and the Clinical Trial Ethics Committee of Xingtai Orthopedic Hospital (QXLL-2022-0002). It was also registered for clinical trials, with the registration number: 20220214.

Consent to participate

All individual subjects signed a written declaration of informed consent to participate the current study.

Competing interests

The authors declare no competing interests.

Trial registration number

ChiCTR2600117704 (Retrospectively registered). Date of registration: 2026-01-28.