Key Takeaway
29 of 35 human studies (83%) found that transcranial photobiomodulation improved cognitive function, with strongest evidence in dementia and mild cognitive impairment
Summary
This systematic review analyzed 35 human studies from 1987 to 2022, evaluating whether transcranial photobiomodulation (tPBM) can improve cognitive function across various populations. The majority of studies (82.9%) reported positive cognitive outcomes following tPBM treatment.
All nine studies examining patients with subjective memory complaints, mild cognitive impairment, and dementia reported positive results. Traumatic brain injury studies also showed a high success rate (87.5%). However, stroke trials showed initial positive trends but failed to reach statistical significance in phase III.
Methods
- Systematic review of three databases (PubMed, Scopus, Web of Science)
- Search period from 1987 to May 2022
- 35 human studies included
- Assessed cognitive outcomes across populations including dementia, MCI, TBI, and stroke
Key Results
- 29 of 35 studies (82.9%) reported positive cognitive improvements
- All 9 dementia/MCI studies showed positive results
- 7 of 8 TBI studies (87.5%) showed positive effects
- Common protocol: 810nm NIR, 20-25 mW/cm², 1-10 J/cm²
- Stroke trials did not reach statistical significance at phase III
Limitations
- Only about half the reviewed clinical trials were randomized controlled trials
- Heterogeneity in PBM protocols (wavelength, dose, duration) across studies
- Publication bias toward positive results
- Many studies had small sample sizes
- Lack of standardized outcome measures across studies