Summary:
In adults diagnosed with diabetic polyneuropathy experiencing neuropathic pain (n=55), low-power laser therapy (LPLT) using 808 nm and 905 nm wavelengths at 6 J/cm² administered three times weekly for four weeks significantly reduced pain scores and improved quality of life compared to low-frequency ultrasound (LFU) therapy and control group receiving no active treatment, though it was associated with no significant adverse effects, demonstrating safety and tolerability of both physical therapy modalities.
| PICO | Description |
|---|---|
| Population | Fifty-five adults diagnosed with diabetic polyneuropathy (DPN) experiencing neuropathic pain requiring symptomatic management. |
| Intervention | Low-power laser therapy (LPLT) using dual wavelengths (808 nm and 905 nm) at 6 J/cm² energy density, applied three times weekly for four weeks. |
| Comparison | Low-frequency ultrasound (LFU) therapy and a control group receiving no active physical therapy treatment. |
| Outcome | LPLT significantly reduced pain scores and improved quality of life compared to both LFU and control. Both LPLT and LFU were well tolerated with no major adverse events reported. |
Clinical Context
Diabetic polyneuropathy affects approximately 50% of patients with diabetes over their lifetime, with painful diabetic neuropathy occurring in 25-30% of those affected. The condition manifests as burning, shooting, or stabbing pain typically in a “stocking-glove” distribution, often worst at night and significantly impairing sleep and quality of life. Despite its prevalence, painful DPN remains one of the most challenging diabetes complications to treat effectively.
Pharmacological treatments—including duloxetine, pregabalin, gabapentin, and tricyclic antidepressants—provide only partial relief for most patients and carry significant side effect burdens including sedation, cognitive impairment, and dependence potential. Many patients cannot tolerate effective doses or experience inadequate pain control even at maximum therapy. This therapeutic gap has driven interest in non-pharmacological approaches that might provide pain relief without systemic drug effects.
Low-power laser therapy (also called photobiomodulation or cold laser) delivers specific wavelengths of light to tissues, theoretically promoting cellular energy production, reducing inflammation, and modulating pain signaling. While the mechanism remains incompletely understood, LPLT has shown promise in various painful conditions. This study compared LPLT to another physical therapy modality (ultrasound) and no treatment to establish relative efficacy for DPN pain.
Clinical Pearls
1. LPLT Outperformed Both Ultrasound and No Treatment: Low-power laser therapy demonstrated superior pain reduction compared to low-frequency ultrasound, suggesting not all physical therapy modalities are equivalent for DPN pain. The specific mechanism of LPLT may be particularly relevant to neuropathic pain pathways.
2. Quality of Life Improved Alongside Pain Reduction: The improvement in quality of life measures indicates that pain reduction translated to meaningful functional benefit for patients. Painful DPN significantly impacts sleep, mood, and daily activities, making quality of life a clinically relevant endpoint.
3. Four-Week Treatment Duration Was Sufficient: Significant benefits were achieved within a 4-week treatment course (12 sessions), representing a reasonable treatment commitment for patients. Duration of benefit after treatment cessation was not reported and represents an important clinical question.
4. Excellent Safety Profile: No significant adverse effects were reported with either LPLT or LFU, an important advantage over pharmacological treatments that often cause dose-limiting side effects. The non-invasive, non-systemic nature of these modalities may allow use in patients who cannot tolerate oral medications.
Practical Application
Consider referring patients with painful diabetic neuropathy who have inadequate response to or cannot tolerate pharmacological therapy for low-power laser therapy evaluation. LPLT may be particularly valuable as adjunctive treatment to reduce medication requirements and associated side effects. Identify physical therapy or pain management clinics with appropriate laser equipment and experience treating neuropathic pain.
Set realistic expectations: the study shows statistically significant improvement, but complete pain relief is unlikely. Frame LPLT as a component of multimodal pain management rather than a standalone cure. The three-times-weekly treatment schedule for four weeks requires patient commitment and access, which may limit feasibility for some patients.
Ensure optimal glycemic control alongside any pain treatment, as hyperglycemia contributes to ongoing nerve damage and pain. Address modifiable risk factors including blood pressure, lipids, and smoking. Physical therapy modalities address symptoms but don’t treat the underlying neuropathy progression.
Broader Evidence Context
This study adds to a growing body of evidence supporting photobiomodulation for neuropathic pain conditions. Previous smaller studies and systematic reviews have suggested LPLT benefit for DPN, but methodological quality has been variable. The inclusion of an active comparator (ultrasound) strengthens interpretation compared to studies comparing only to sham or no treatment.
Current clinical practice guidelines for painful DPN focus primarily on pharmacological management, with limited guidance on physical therapy modalities. As evidence accumulates, future guideline updates may incorporate recommendations for LPLT as an adjunctive option.
Study Limitations
Small sample size (n=55) limits statistical power and subgroup analysis. Duration of benefit after treatment cessation was not assessed. Blinding was not described and may have been incomplete for a physical therapy intervention. Specific treatment parameters (exact wavelengths, power output, treatment area) affect reproducibility. Comparison to pharmacological treatment or placebo laser was not performed.
Bottom Line
Low-power laser therapy significantly reduces pain and improves quality of life in patients with painful diabetic polyneuropathy compared to ultrasound therapy or no treatment, with no reported adverse effects, supporting LPLT as a safe adjunctive option for DPN pain management.
Source: Heidari Almasi, Minoo, et al. “Effectiveness of low-power laser therapy and low-frequency ultrasound in reducing pain in patients with diabetic polyneuropathy: A randomized controlled trial.” Read article
