Korada H.Y. et al. - Photobiomodulation and Neuropathic Pain in Diabetic Peripheral Neuropathy

This systematic review included 8 studies on photobiomodulation in peripheral neuropathy associated with type 2 diabetes and reported improvements in neuropathic pain, nerve conduction velocity, and plantar pressure distribution. No aggregated data are provided, and non-randomized studies were included, which significantly weakens the strength of this conclusion.

What this study measured

Peripheral neuropathy is a serious complication of type 2 diabetes. It most often manifests as neuropathic pain and impaired sensation resulting from damage to small nerve fibers. The authors note that changes in pressure distribution under the foot are a major risk factor for ulceration.

They conducted a systematic review of four databases: PubMed, Web of Science, CINAHL, and Cochrane. The objective was to analyze studies on photobiomodulation for neuropathic pain and on the distribution of plantar pressure in people with diabetic neuropathy. Both randomized and non-randomized studies were included, for a total of eight studies.

Key Findings

The results are presented solely in qualitative terms, without any quantitative summary.

• 8 included studies, both randomized and non-randomized
• 4 databases searched: PubMed, Web of Science, CINAHL, Cochrane
• Neuropathic pain: improvement reported in the included studies
• Nerve conduction velocity: reported improvement
• Distribution of plantar pressure: reported reduction, presented as a risk factor for foot ulcers
• No effect size, no confidence interval, no pooled results

The authors conclude that photobiomodulation may be a noninvasive and inexpensive way to improve these parameters. This statement is more definitive than the data support.

How Photobiomodulation Affects the Peripheral Nerves

The mechanisms discussed remain hypothetical. Red or near-infrared light is thought to be absorbed by mitochondrial cytochrome c oxidase, which would increase ATP production. A reduction in oxidative stress and modulation of inflammatory pathways are also described, along with the hypothesis that this creates an environment more conducive to axonal regeneration. This review does not test any of these mechanisms.

Limits You Should Know

The main limitation is the lack of quantitative synthesis. This is a systematic review without a meta-analysis: no means, no differences between groups, no confidence intervals, and no effect sizes are reported. Readers therefore cannot determine whether the improvement described is marginal or clinically meaningful.

The evidence base is limited to eight studies and includes both randomized and non-randomized trials, which increases the risk of selection and measurement bias. The abstract mentions neither a risk of bias assessment, nor a grading of the level of evidence, nor an analysis of heterogeneity. Wavelengths, doses, and the number of sessions are not specified, even though they vary greatly from one study to another and determine all results in photobiomodulation. The authors’ affirmative conclusion contrasts with this lack of specific data.

What This Means in Practice

This review points to a potential avenue of inquiry, not proof of efficacy. It does not allow for the establishment of a treatment protocol or the quantification of any benefit. For people with diabetes, blood glucose control, foot care, and prescribed treatments remain the foundation of care. Any wound or loss of sensation in the foot requires prompt medical attention, and potential use of this approach should be discussed with the care team.

Frequently Asked Questions

Does photobiomodulation reduce neuropathic pain in diabetes?

The eight studies included in this review report an improvement in neuropathic pain. No specific values or confidence intervals are provided. It is therefore impossible to say by how much the pain would decrease or in what proportion of patients.

Does photobiomodulation affect nerve conduction?

The authors report an improvement in nerve conduction velocity in the included studies. This outcome measure is objective, but no values are provided, and the number of studies involved is not specified. This finding requires confirmation through randomized trials.

Is a systematic review without a meta-analysis sufficient to draw conclusions?

A systematic review organizes the search for studies in a reproducible manner, which is preferable to a narrative review. Without a meta-analysis, it does not produce any combined estimate of the effect. When it also includes non-randomized studies, as in this case, the level of evidence remains moderate and is insufficient to establish efficacy.

Reference

Korada HY, Arora E, Maiya GA, Rao S, Hande M, Shetty S, Gundmi S, Anche P, Amravadi S. Effectiveness of Photobiomodulation Therapy on Neuropathic Pain, Nerve Conduction, and Plantar Pressure Distribution in Diabetic Peripheral Neuropathy—A Systematic Review. Current Diabetes Reviews, 2023. PMID 37622461. View the study on PubMed

This summary is provided for informational purposes only and does not constitute medical advice. Photobiomodulation is not a substitute for prescribed treatment. Consult a healthcare professional.