Efficacy and Safety of Photobiomodulation Therapy for Motor Symptoms in Parkinson's Disease: A Systematic Review and Meta-Analysis.
Efficacy and Safety of Photobiomodulation Therapy for Motor Symptoms in Parkinson's Disease: A Systematic Review and Meta-Analysis.
Where did the research take place?
The study site has not been established. Author addresses may differ from where the research occurred.
Boston, US · Author affiliation
Neuromodulation Center and Center for Clinical Research Learning, Harvard Medical School, Spaulding Rehabilitation Hospital, Boston, MA 02129, USA.Location evidence
CR · Author affiliation · country only
Research Unit, The Regenerative Medicine Institute, Avenida Escazú, Torre Lexus 206, San José 10203, Costa Rica.Location evidence
São Carlos, BR · Author affiliation
Neuroscience and Neurological Rehabilitation Laboratory, Physical Therapy Department, Federal University of São Carlos, São Carlos 13565-905, Brazil.Location evidence
Lima, PE · Author affiliation
Vicerrectorado de Investigación, Unidad de Investigación para la Generación y Síntesis de Evidencias en Salud, Universidad San Ignacio de Loyola, Lima 15023, Peru.Location evidence
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Original abstract
Background: Parkinson's disease (PD) is a progressive neurodegenerative disorder causing disabling motor dysfunction and substantial socioeconomic burden. Photobiomodulation (PBM), a noninvasive red/near-infrared light therapy, has shown preclinical promise, but its clinical efficacy and safety in PD remain uncertain. Objectives: To systematically evaluate the efficacy and safety of PBM on motor outcomes in PD. Methods: This PRISMA-compliant systematic review was prospectively registered in PROSPERO (CRD420261411269). Databases were searched through May 2026. Randomized and non-randomized trials in adults with PD were included. Two reviewers independently screened studies, extracted data, and assessed risk of bias (RoB 2.0; ROBINS-I). Where data permitted, random-effects meta-analyses used mean difference (MD) with REML estimation and Hartung-Knapp-Sidik-Jonkman confidence intervals. Results: Eight trials (n = 279) were included, exhibiting substantial heterogeneity in wavelength, device type, stimulation sites, and dosimetry. PBM was safe and well tolerated, with only minor adverse effects. Meta-analysis of four RCTs found no significant effect on MDS-UPDRS-III (MD = -1.37 points, 95% CI: -5.55 to 2.80; I2 = 20.6%) or TUG (MD = -0.52 s, 95% CI: -5.03 to 3.99; I2 = 55.1%). An exploratory TMWT meta-analysis (k = 2) yielded MD = -0.65 s (95% CI: -1.78 to 0.49; I2 = 0.0%), with direction consistently favoring PBM. Individual effect sizes ranged from negligible (d = 0.03-0.06) to small-to-moderate (d = 0.41). Conclusions: PBM appears safe, feasible, and acceptable in PD, but current evidence does not support clinically meaningful motor benefits. Heterogeneous protocols, small samples, and absent target-engagement biomarkers limit definitive interpretation. Well-powered standardized trials with mechanistic endpoints are needed.