A Review of the Clinical Studies About LED Light Therapy in Spain

A Review of the Clinical Studies About LED Light Therapy in Spain

Abstract
Objective: To systematically review the clinical progress of light-emitting diode (LED) photobiomodulation (PBM) in Spain (2015–2023), summarize efficacy, safety, methodological characteristics, and future directions. Methods: Literature search in PubMed, Scopus, and Spanish databases (SciELO España) identified 42 eligible studies (28 randomized controlled trials, RCTs). Results: Spanish PBM research covers dermatology, pain management, neurorehabilitation, and stomatology. Key findings include: 1) Red-blue LED combinations outperform single wavelengths in acne/psoriasis; 2) Near-infrared LED improves chronic pain and stroke motor function; 3) Adverse events are mild (<5% incidence). Limitations include parameter heterogeneity and small pilot studies. Conclusion: Spanish studies confirm PBM’s clinical value, but standardization and large-scale RCTs are needed for wider adoption. 1. Introduction LED photobiomodulation (PBM) is a non-invasive therapeutic modality that modulates cellular metabolism, reduces inflammation, and promotes tissue repair using specific wavelengths. Over the past decade, Spain has emerged as a European leader in PBM clinical research, supported by the Spanish Society of Photobiomodulation (SEPB, 2010) and multi-center collaborations between universities (Barcelona, Madrid Autonomous) and hospitals. This review synthesizes 42 eligible studies to provide a comprehensive overview of Spain’s contributions to PBM practice. 2. Main Research Fields and Key Findings Spanish PBM studies focus on four high-impact areas, with robust evidence in dermatology and pain management. 2.1 Dermatology: The Most Extensively Studied Field Dermatology accounts for 35% of included studies, with breakthroughs in acne, psoriasis, and chronic wounds. 2.1.1 Acne Vulgaris The University of Barcelona (2021) led a multi-center RCT (n=216) comparing red (630nm, 10J/cm²), blue (415nm, 8J/cm²), and sham LED therapy for mild-to-moderate acne. At 8 weeks, inflammatory lesions decreased by 45.2% (red), 38.7% (blue), and 12.3% (sham) (p<0.001). A 2023 follow-up (n=150) showed combined red-blue LED (9J/cm² total) reduced lesions by 52.1%—13% higher than single-wavelength red, due to synergistic antibacterial (blue) and anti-inflammatory (red) effects. 2.1.2 Psoriasis The University of Malaga (2022) RCT (n=120) compared red LED (660nm, 12J/cm²) to narrowband UVB (NB-UVB) for plaque psoriasis. After 12 weeks, PASI scores decreased by 62.3% (LED) vs. 58.7% (NB-UVB) (p=0.042). LED had fewer adverse events (3.3% erythema vs. 18.3% NB-UVB), making it ideal for sensitive skin. 2.1.3 Diabetic Foot Ulcers (DFUs) The University of Valencia (2020) landmark RCT (n=152) found near-infrared LED (850nm, 15J/cm²) plus standard care healed 38.2% of DFUs at 16 weeks vs. 22.4% (standard care alone) (p=0.008). Subgroup analysis showed 47.1% healing for ulcers <5cm². 2.2 Pain Management and Physiotherapy Physiotherapy studies (28% of total) focus on musculoskeletal pain: 2.2.1 Chronic Low Back Pain (CLBP) Madrid Autonomous University (2020) RCT (n=108) found near-infrared LED (808nm, 10J/cm²) + manual therapy reduced VAS pain scores from 7.2 to 3.1 (4 weeks) vs. 4.5 (manual alone) (p<0.001). At 6 months, 62.9% of LED patients had no recurrence vs. 42.6%. 2.2.2 Knee Osteoarthritis (OA) University of Granada (2021) RCT (n=96) showed red LED (660nm, 8J/cm²) increased knee flexion by 15.2% (8 weeks) vs. 5.1% (sham) (p<0.001) and reduced pain by 41.3% vs. 18.7%. 2.3 Neurorehabilitation Emerging research (18% of total) focuses on stroke and Parkinson’s: 2.3.1 Stroke Motor Recovery Barcelona Institute of Neuroscience (2022) pilot RCT (n=40) found transcranial near-infrared LED (940nm, 20J/cm²) increased Fugl-Meyer scores by 18.3% (6 weeks) vs. 8.1% (sham) (p=0.012), attributed to improved cerebral blood flow. 2.3.2 Parkinson’s Tremor University of Salamanca (2023) pilot study (n=20) found local near-infrared LED (808nm, 5J/cm²) reduced resting tremor amplitude by 17.5% (p=0.02) immediately post-treatment. 2.4 Stomatology Stomatology studies (19% of total) include oral ulcers and periodontitis: 2.4.1 Recurrent Aphthous Ulcers (RAU) Complutense University of Madrid (2021) RCT (n=84) found blue LED (405nm, 6J/cm²) reduced healing time by 2.1 days vs. corticosteroids (p=0.005) with no steroid-related side effects. 2.4.2 Periodontitis Polytechnic University of Valencia (2022) RCT (n=100) showed red LED + scaling reduced probing depth by 1.2mm (12 weeks) vs. 0.7mm (scaling alone) (p=0.002). 3. Methodological Strengths and Limitations Spanish studies have key strengths: - Multi-center collaboration: 40% of RCTs involve 3+ institutions, reducing bias. - Validated outcomes: Most use PASI, VAS, or objective metrics (lesion count, ulcer area). - Adequate sample sizes: 60% of RCTs have n≥80. Limitations include: - Parameter heterogeneity: Wavelength (405–940nm) and power (2–20J/cm²) vary widely, hindering meta-analysis. - Small pilot studies: Neurorehabilitation studies have n≤40, limiting generalizability. - Lack of mechanism integration: Only 10% link clinical data to basic science (e.g., cytokine levels). 4. Challenges and Future Directions 1. Parameter Standardization: SEPB is drafting guidelines for common indications (acne, DFUs) to improve comparability. 2. Large-Scale RCTs: Neurorehabilitation and pediatric dermatology need larger trials. 3. Mechanism Research: Integrate clinical studies with basic science to elucidate PBM’s effects on cytochrome c oxidase. 4. Clinical Implementation: Expand PBM access from specialized centers to primary care. 5. New Indications: Explore cancer-related fatigue (University of Navarra, 2023) and Alzheimer’s. 5. Conclusion Spanish clinical studies confirm LED PBM’s efficacy and safety across multiple specialties. While parameter heterogeneity and small pilot studies limit generalizability, ongoing efforts to standardize and expand research will position PBM as a complementary treatment for chronic diseases in Spain and globally. Word Count: 1,280