Chow R.T. et al. - Photobiomodulation and Neck Pain: A Systematic Review and Meta-Analysis

This meta-analysis included 16 randomized trials and 820 patients with neck pain. It reported a reduction in pain immediately after treatment for acute pain, and up to 22 weeks after the end of treatment for chronic pain.

What this publication measured

Neck pain is common and costly, and the authors note that there is limited evidence of the effectiveness of pharmacological treatment for it, and that such treatment is associated with adverse effects. This systematic review with meta-analysis evaluated photobiomodulation, referred to in the article as low-intensity laser therapy: nonthermal laser irradiation applied to painful areas.

The authors searched electronic databases to identify randomized controlled trials comparing photobiomodulation—regardless of wavelength—to a placebo or an active treatment for acute or chronic neck pain. The primary outcome measure was pain intensity, expressed in millimeters on a 100-mm visual analog scale.

One point is worth noting: this meta-analysis appeared in *The Lancet* in 2009. It is the only meta-analysis on photobiomodulation published in this journal, making it a milestone in the field. This fact stems from the journal’s editorial standing, not from additional evidence: it is the figures below that matter.

Key Findings

Sixteen randomized trials involving a total of 820 patients were included. The results are presented separately for acute and chronic pain.

• Acute pain: a relative risk of improvement of 1.69 (95% CI 1.22 to 2.33) in favor of photobiomodulation compared with placebo, based on two trials
• Chronic pain, categorical data: relative risk of improvement of 4.05 (95% CI 2.74 to 5.98), based on five trials
• Pain intensity: a reduction of 19.86 mm on the visual analog scale (95% CI 10.04 to 29.68), based on eleven trials
• Follow-up 1 to 22 weeks after the end of treatment: sustained reduction of 22.07 mm (95% CI 17.42 to 26.72), across seven trials
• Adverse effects: mild and no different from those of the placebo

How photobiomodulation works for this indication

The article does not test any mechanisms and merely describes the application of nonthermal laser irradiation to painful sites. The explanations put forward in the literature therefore remain hypothetical in this context: absorption of red and near-infrared light by mitochondrial chromophores, local modulation of the inflammatory response, and effects on nociceptive fibers. None of these has been demonstrated by the data presented, which are based solely on clinical criteria.

Limits You Should Know

Several subgroups are based on only a few trials: two for acute pain and five for categorical data on chronic pain. The confidence intervals are wide, particularly for the 19.86 mm reduction, whose lower limit is as low as 10.04 mm. Wavelengths varied from one trial to another, which limits the ability to translate the results into precise parameters. The summary provides neither power nor the number of sessions.

Most importantly, this publication dates back to 2009—more than fifteen years ago. More recent studies have been published since then, and the recommended parameters may have changed. These results should be interpreted in light of the current literature.

What This Means in Practice

These data place photobiomodulation among the documented noninvasive treatment options for neck pain, with adverse effects comparable to those of a placebo in the included trials. They do not guarantee individual outcomes and are not a substitute for prescribed treatment. Since the abstract does not specify any parameters, the development of a treatment protocol should be left to a trained professional.

Frequently Asked Questions

Does photobiomodulation relieve neck pain?

In this meta-analysis of 16 trials involving 820 patients, it was associated with a reduction of 19.86 mm on a 100-mm scale. This is the average result observed in these trials; it is not a guarantee for any given individual.

How long do the effects last after the sessions end?

Seven trials provided follow-up data ranging from 1 to 22 weeks after the end of treatment. The reduction remained evident, with a difference of 22.07 mm. Beyond that, this publication provides no further information.

Are there any side effects?

The authors note that the adverse effects observed were mild and did not differ from those reported in the placebo groups. This observation pertains to the included trials and does not replace medical advice.

Reference

Chow RT, Johnson MI, Lopes-Martins RAB, Bjordal JM. Efficacy of low-level laser therapy in the management of neck pain: a systematic review and meta-analysis of randomized placebo- or active-treatment-controlled trials. Lancet, 2009. PMID 19913903. 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.