Photobiomodulation for Diabetic Peripheral Neuropathy

Effectiveness of Photobiomodulation Therapy in Enhancing Nerve Function and Quality of Life Among Patients With Diabetic Peripheral Neuropathy: A Randomized Controlled Trial

Diabetic peripheral neuropathy (DPN) is a common complication of long-term diabetes, affecting approximately 50 percent of patients. It causes tingling, numbness, and burning pain primarily in the feet, which reduces quality of life. Photobiomodulation therapy (PBMT), also known as low-level laser therapy, is a non-invasive treatment that may improve nerve function by reducing inflammation and promoting cellular repair. This randomized controlled trial aims to evaluate the effectiveness of PBMT in improving nerve function and quality of life in patients with DPN. A total of 36 participants with type 2 diabetes and DPN will be randomly assigned to either a treatment group receiving PBMT (900 nm wavelength, 25W, 1000 Hz frequency) or a control group receiving sham laser therapy. The intervention will be applied to the dorsum and plantar surface of the foot every other day for 6 weeks. Outcomes include pain intensity measured by the Numeric Pain Rating Scale, Neuropathic pain measured by Leeds Assessment of Neuropathic symptoms and signs scale, Nerve function measured by Michigan Neuropathy Screening Instrument and quality of life measured by the NORFOLK QOL DN questionnaire, assessed at baseline and after the intervention period.

This study is a randomized, double-blind, sham-controlled clinical trial. Participants will be enrolled from Move Better Clinic and Madinah Teaching Hospital in Faisalabad, Pakistan.

Randomization and allocation concealment: Eligible participants will be randomly assigned in a 1:1 ratio to either the photobiomodulation therapy group or the sham laser group. Randomization will be performed using a computer-generated random number table. Allocation will be concealed in sequentially numbered, opaque, sealed envelopes that will be opened only after baseline assessment.

Blinding: Participants will be blinded to their group assignment because both groups will undergo the same procedure with the same device; only the experimental group will receive active laser. Outcome assessments will be performed by a physiotherapist who remains blinded to group assignment. The therapist delivering the intervention cannot be blinded, but all data entry and statistical analysis will be performed using coded group identifiers.

Sample size calculation: Sample size of 36 participants (18 per group) was calculated using Rao Software based on a previous study by Suganthirababu et al. (2018), assuming a power of 80% and alpha of 0.05.

Statistical analysis: Data will be analyzed using IBM SPSS software. Normality of data distribution will be tested using the Shapiro-Wilk test. For normally distributed data, within-group differences will be analyzed using paired t-tests, and between-group differences will be analyzed using independent t-tests. For non-normally distributed data, appropriate non-parametric tests (Wilcoxon signed-rank and Mann-Whitney U) will be used. A p-value less than 0.05 will be considered statistically significant.

Inclusion Criteria:

• Diagnosis of type 2 diabetes mellitus
• Diagnosis of diabetic peripheral neuropathy
• Age 18 years or older
• Male and female participants
• Pain duration of 6 months or more
• Numeric Pain Rating Scale (NPRS) score of 3 or greater out of 10 at baseline
• No acute infections at the time of enrollment

Exclusion Criteria:

• Skin lesions, infections, or ulcers in the treatment area
• Severe heart disease or kidney dysfunction
• Mental illness or malignant tumors
• Presence of pacemaker or implanted electrical device
• Chronic alcohol or drug abuse
• Patients unwilling to provide informed consent
• Pregnancy
• Post-surgical cases (heart or brain surgery) within 30 days
• History of stroke