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Central Neurology and Cognition
Published on
July 23, 2026

Xu W. et al. - Photobiomodulation, tDCS, and rTMS in Alzheimer's Disease: A Network Meta-Analysis

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A Bayesian network meta-analysis of 35 randomized trials published in 2026 compared photobiomodulation, tDCS, and rTMS in people with Alzheimer’s disease. Photobiomodulation was found to have the greatest estimated effects on overall cognition, with an average gain of 3.14 points on the MMSE, and was as well tolerated as the other two techniques.

What this study measured

Drug treatments for Alzheimer’s disease provide only modest and temporary benefits. The authors, affiliated with Tongji Medical College at Huazhong University, sought to determine which of the three main noninvasive brain stimulation techniques has the greatest impact on cognition: photobiomodulation, transcranial direct current stimulation (tDCS), or repetitive transcranial magnetic stimulation (rTMS).

The protocol was registered in advance on PROSPERO (CRD420251006868) and follows the PRISMA-NMA guidelines. Only randomized controlled trials were included: 34 publications corresponding to 35 trials, involving 1,559 participants. The primary outcome was global cognition, measured by the MMSE and the ADAS-Cog scale; the secondary outcomes were feasibility, assessed based on dropout rates, and safety, assessed based on adverse events.

Key Findings

All three techniques improved overall cognition compared with the control group. Photobiomodulation ranked highest on both scales, but its advantage over the other approaches is based on indirect comparisons.

  • MMSE, photobiomodulation vs. control: mean difference of 3.14 points (95% credibility interval: 1.71 to 4.60).
  • ADAS-Cog, photobiomodulation vs. control: -8.01 points (95% credible interval: -12.82 to -3.13); a lower score indicates an improvement in this case.
  • Indirect comparison with rTMS on the ADAS-Cog: -5.24 points (95% credible interval: -10.23 to -0.12).
  • Indirect comparison with rTMS on the MMSE: 1.57 points (95% credible interval: -0.02 to 3.18), which is not statistically significant.

These trends remained consistent across subgroups, based on baseline cognitive level and duration of the interventions. Dropout rates and adverse effects were comparable among the three techniques.

How photobiomodulation works for this indication

The proposed mechanism remains hypothetical. Red and near-infrared light is thought to be absorbed by cytochrome c oxidase, a complex in the mitochondrial respiratory chain, which would promote ATP production and energy metabolism in neurons. Modulation of oxidative stress and inflammation, as well as an effect on cerebral blood flow, have also been suggested. These findings are based on preclinical studies and were not measured in the included trials.

Limits You Should Know

The advantage over rTMS is based on indirect comparisons, which are less robust than a head-to-head trial, and the difference on the MMSE did not reach statistical significance. The credibility intervals are wide, indicating a lack of precision. With 1,559 participants across 35 trials, the average study size remains small, and the authors themselves call for large-scale trials. The abstract does not specify either the light parameters or the duration of follow-up after the end of the sessions: there is no evidence to suggest that the benefits are sustained.

What This Means in Practice

This study does not establish photobiomodulation as a treatment for Alzheimer’s disease. It indicates that, in the published trials, photobiomodulation is at least on par with tDCS and rTMS in terms of its effects on overall cognition, with comparable tolerability, which justifies considering it a serious avenue of research. The specific parameters—wavelength, power, and number of sessions—are not reported in this abstract and varied from one trial to another.

Frequently Asked Questions

Is photobiomodulation more effective than rTMS for Alzheimer's disease?

It achieved a better score on the ADAS-Cog scale, with a difference of 5.24 points. On the MMSE, the difference of 1.57 points was not statistically significant. These comparisons are indirect, as no study has directly compared the two techniques.

How many patients were included in the study?

The analysis includes 1,559 participants from 35 randomized controlled trials. This is a significant sample size for this field of research, but modest compared to drug trials conducted for Alzheimer’s disease.

Are there any side effects?

The authors report comparable dropout rates and adverse effects across the three techniques. The abstract does not specify the nature of these effects. If you have a neurodegenerative disease, talk to your doctor before considering any complementary approaches.

Reference

Xu W, Chen J, Zhou Y, et al. Comparative efficacy and safety of photobiomodulation, transcranial direct current stimulation, and repetitive transcranial magnetic stimulation in Alzheimer’s disease: a network meta-analysis of randomized controlled trials. Lasers in Medical Science, 2026. PMID 42487022. 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.