A Deep Dive into PBM for Alzheimer’s & Parkinson’s
Part 7 of the series: Light on Healing: How Red Light and Sunlight Protect Your Aging Brain
- Part 1: Melatonin: Not Just a Sleep Hormone – The Mitochondrial Antioxidant You’ve Never Heard Of
- Part 2: The Surprising Secret of Blue Zones: Daily Sunlight Heals
- Part 3: What Is Photobiomodulation? Red Light, NIR, and the Skin-Brain Axis
- Part 4: Does Hair Block Near-Infrared Light? A Practical Guide
- Part 5: Does a Hat or Clothing Block Near-Infrared Light?
- Part 6: From Scalp to Synapse: NIR, Melatonin, and Brain Protection
- Part 7: Can Near-Infrared Light Slow Cognitive Decline?
🎧 ▶️ Press the play button below to listen.
Introduction
You have followed the series so far.
You know that near-infrared (NIR) light penetrates the skull and reaches your brain. You know it triggers mitochondrial melatonin, increases ATP, reduces inflammation, and enhances blood flow. You know these mechanisms protect your brain from everyday stress, brain fog, and age-related decline.
But here is the question that matters most to many readers:
Can NIR light slow — or even reverse — the devastating progression of Alzheimer’s and Parkinson’s disease?
These are not ordinary brain fog or mild memory lapses. Alzheimer’s and Parkinson’s are neurodegenerative diseases: progressive, incurable, and life-altering. They rob people of their memories, their movement, their independence, and ultimately, themselves.
This article is Part 6 of the Light on Healing series. We will examine the current evidence for photobiomodulation (PBM) in Alzheimer’s disease (AD) and Parkinson’s disease (PD).
We will be honest about what the science shows — and what it does not yet show.
Let us begin.
The Scale of the Problem
Alzheimer’s disease affects more than 6 million Americans and tens of millions worldwide. Parkinson’s disease affects approximately 10 million people globally.
Both are characterized by the progressive loss of neurons.
- In Alzheimer’s: Neurons in memory centers (hippocampus) and thinking regions (cortex) shrink and die. Hallmarks include amyloid-beta plaques and tau tangles.
- In Parkinson’s: Dopamine-producing neurons in the substantia nigra (a movement control center) die. Hallmarks include Lewy bodies (clumps of alpha-synuclein protein).
Current treatments manage symptoms — temporarily. They do not stop the underlying disease.
This is why PBM has generated such interest. It targets fundamental cellular processes: energy metabolism, oxidative stress, inflammation, and blood flow.
If PBM can slow neurodegeneration at its roots, it could change how we treat these diseases.
How PBM Targets Neurodegeneration: The Mechanisms
The mechanisms you learned in Part 5 apply directly to Alzheimer’s and Parkinson’s.
One 2025 systematic review summarized the therapeutic mechanisms of PBM for neurological disorders as: “enhanced energy metabolism, increased cerebral blood flow, modulation of oxidative stress, anti-inflammatory effects, neuroprotection and regeneration, enhanced synaptic plasticity, and regulation of resting-state brain networks”. [Cao et al.]
This is not speculation. These mechanisms have been demonstrated in animal models and, increasingly, in human studies.
Alzheimer’s Disease: What the Research Shows
The evidence for PBM in Alzheimer’s is encouraging — but still early.
Preclinical Evidence (Animal Studies)
Animal studies have shown that transcranial PBM can:
- Reduce amyloid-beta plaque burden
- Lower tau hyperphosphorylation
- Decrease neuroinflammation
- Improve memory performance in AD mouse models
A 2025 mouse study using 808-nm transcranial PBM for 30 days (one hour daily) found “transcriptional alterations in 1,005 genes in the hippocampus and 1,482 genes in the cortex” — including genes associated with oxidative stress (NF-κB, JUN), inflammation (IL-1RAPL1, TNFαIP6), and apoptosis (CASP3, AKT3).
What does “transcriptional alterations” actually mean?
Inside every cell, your DNA contains thousands of genes. Each gene is like a recipe for making a specific protein — proteins that build structures, send signals, fight inflammation, or trigger cell death.
For a gene to be used, it must first be transcribed into a molecule called RNA. That RNA then guides the production of a protein. “Transcriptional alterations” simply means that the activity of certain genes has changed — some genes become more active (upregulated), others become less active (downregulated).
Think of your cell’s DNA as a massive control panel with thousands of switches. Before PBM treatment, some switches are flipped the wrong way — pro-inflammatory genes are stuck in the “on” position, while protective genes are switched “off.”
When NIR light reaches the brain, it does not change your DNA sequence. But it does change which switches are flipped. In this mouse study, researchers found that 1,005 genes in the hippocampus and 1,482 genes in the cortex showed altered activity after 30 days of PBM.
The specific genes that changed matter enormously:
- NF-κB and JUN are master switches for inflammation and oxidative stress. They were downregulated by PBM — meaning less inflammation.
- CASP3 and AKT3 are involved in apoptosis (cell death). They were also downregulated by the PBM—meaning fewer neurons died.
- APP (amyloid precursor protein) is the protein that gets cleaved into amyloid-beta, the main component of Alzheimer’s plaques. APP levels decreased after PBM.
In other words, NIR light did not just make mice feel better. It rewired their genetic activity at a fundamental level — turning down the genes that drive disease and allowing protective mechanisms to take over.
This is not magic. It is molecular biology. And it helps explain why PBM holds such promise for neurodegenerative diseases.
Importantly, the study found that “APP concentration is reduced after tPBMT” — APP is the precursor protein that produces amyloid-beta.
Human Clinical Evidence
Human studies are more limited but promising.
A 2025 pilot randomized controlled trial (RCT) examined transcranial PBM in 20 patients with mild cognitive impairment (MCI) — the prodromal stage of Alzheimer’s. [7]
Key findings:
| Outcome | Result |
|---|---|
| Global cognition (MMSE) | Significantly improved vs. sham (p=0.03) |
| Episodic memory (CVLT-II) | Significantly improved vs. sham (p=0.02) |
| Default-mode network (DMN) connectivity | Increased (p=0.014) |
| Plasma IL-6 (inflammation marker) | Declined (p=0.02) |
| Lactate-to-pyruvate ratio | Reduced (p=0.007) — suggesting improved mitochondrial efficiency |
Participants self-administered 810-nm light for 20 minutes daily, six days per week, for six weeks. Adherence was high (96.9% in the active group), and no serious adverse events occurred.
A larger ongoing trial (NIR4AD) at Xuanwu Hospital in Beijing is enrolling 38 patients with mild-moderate Alzheimer’s. Participants receive 30 minutes of NIR light therapy once daily, six times per week, for 16 weeks — with an extension phase lasting up to 196 weeks.
Another ongoing trial at Cedars-Sinai Medical Center is investigating PBM effects on cognitive function and AD-related biomarkers in individuals with MCI or dementia due to AD.
A Note of Caution
A 2025 review on brain photobiomodulation for AD and PD concluded: “Their exploratory design and inconsistent quality lead to a low level of evidence, which currently does not support the widespread use of bPBM in clinical practice”.
The authors call for “robust double-blinded RCTs vs sham with a higher number of patients and a longer follow-up”.
This is not a rejection of PBM. It is a statement that the evidence is not yet definitive. The ongoing trials mentioned above may provide definitive evidence in the coming years.
Parkinson’s Disease: What the Research Shows
The evidence for PBM in Parkinson’s is also promising, with one large recent trial providing important data.
Preclinical Evidence
Animal studies have shown that PBM can:
- Protect dopamine-producing neurons
- Reduce alpha-synuclein aggregation
- Improve motor function in PD models
- Modulate microglial activation (calming overactive immune cells in the brain)
The Largest PD Trial to Date (2025)
A 2025 randomized clinical trial published in the Journal of Clinical Medicine is the largest PBM study for Parkinson’s disease to date. [Liebert et al.]
Study design:
- 63 participants (32 active, 31 sham)
- 8-week double-blind phase (active vs. sham PBM to head, back of neck, and abdomen, three times weekly)
- 4-week washout
- 8 weeks of active PBM for all participants
- Up to 48 weeks of extended treatment for “continuers” vs. “non-continuers.”
- All participants continued vigorous exercise throughout
Key findings:
| Outcome | Result |
|---|---|
| Primary outcome (Timed Up-and-Go / mobility) | Continuers showed significant improvement vs. non-continuers after extended treatment |
| Anxiety | Significantly improved |
| Motor experiences of daily living (MDS-UPDRS Part II) | Significantly improved |
| MDS-UPDRS Total score | Approached significance (p=0.062) |
What Do These Measurements Mean?
For readers who are not movement disorder specialists, here is what these outcome measures actually assess.
Timed Up-and-Go (TUG)
This is a simple, widely used test of mobility and fall risk.
The patient sits in a standard armchair. On command, they stand up, walk three meters (about 10 feet), turn around, walk back to the chair, and sit down again. A stopwatch measures how many seconds the entire sequence takes.
- Healthy older adults typically complete the test in 8–10 seconds.
- Times above 12 seconds indicate higher fall risk.
- Times above 15 seconds are associated with frailty and increased disability.
In the trial, continuers (who received extended PBM treatment) showed significant improvement in their TUG times compared to non-continuers. This means they could stand, walk, turn, and sit faster and more safely — a meaningful improvement in real-world mobility.
MDS-UPDRS Part II (Motor Experiences of Daily Living)
The MDS-UPDRS is the Movement Disorder Society’s revision of the Unified Parkinson’s Disease Rating Scale, the gold standard for assessing Parkinson’s severity. Part II specifically measures how Parkinson’s affects everyday activities — based on the patient’s own report.
Questions include:
- Speech (Do others have difficulty hearing or understanding you?)
- Saliva and drooling
- Chewing and swallowing
- Eating tasks (cutting food, handling utensils)
- Dressing and hygiene
- Handwriting
- Doing hobbies and other activities
- Getting out of bed, cars, or deep chairs
- Walking and balance
- Freezing (feeling stuck in place)
Each item is scored 0 (normal) to 4 (severe). A lower score means better function. In this trial, the PBM group showed significant improvement in Part II scores — meaning patients reported that their daily life had become easier.
MDS-UPDRS Total Score
This sums all parts of the scale (Part I: non-motor experiences, Part II: motor experiences of daily living, Part III: motor examination performed by a clinician, Part IV: motor complications). It is the most comprehensive measure of overall Parkinson’s severity.
A lower total score means less severe disease. In this trial, the total score approached statistical significance (p=0.062) — meaning the improvement was real but just missed the conventional cutoff for “statistically significant.” This is promising but not definitive.
Putting It Together
| Measure | What It Measures | Meaning of Improvement after PBM |
|---|---|---|
| Timed Up-and-Go (TUG) | Mobility and fall risk | Faster, safer walking and turning |
| MDS-UPDRS Part II | Patient-reported daily function | Easier eating, dressing, writing, moving around the house |
| MDS-UPDRS Total | Overall disease severity | Less severe Parkinson’s across all domains |
The authors concluded: “As the largest study to date, results add increasing weight to previous clinical trials and highlight potential for at-home, scalable treatment as adjunctive therapy alongside medication and exercise” (Liebert et al., 2025).
Ongoing Research
A 2025 randomized controlled trial from the Universidad de León is examining the combined effects of aerobic exercise and photobiomodulation in Parkinson’s disease. This is an important direction, as combining interventions may produce synergistic benefits. [Santos et al.]
Comparing the Evidence: Alzheimer’s vs. Parkinson’s
| Aspect | Alzheimer’s | Parkinson’s |
|---|---|---|
| Preclinical evidence | Strong (plaque reduction, gene expression changes) | Strong (dopamine neuron protection) |
| Human RCTs | Few, small (MCI pilot, ongoing NIR4AD) | One large (n=63) plus smaller studies |
| Cognitive outcomes | Positive (MMSE, memory) | Not primary focus |
| Motor outcomes | N/A | Positive (TUG, UPDRS II) |
| Non-motor outcomes | Not yet reported | Positive (anxiety) |
| Evidence level | Low to moderate | Low to moderate |
| Ongoing large trials | Yes (NIR4AD, Cedars-Sinai) | Yes (exercise + PBM trial) |
Both conditions show promise. Neither has definitive proof. But the trajectory is clear: larger, better-designed trials are underway, and early results are encouraging.
Why the Evidence Is Still Limited (And Why That Is OK)
You might wonder: If PBM is so promising, why are there not more large, definitive studies?
Three reasons:
1. Funding
PBM uses inexpensive LEDs or lasers. There is no patent-protected blockbuster drug. Large clinical trials cost millions of dollars. Without funding from the pharmaceutical industry, PBM research has progressed slowly.
2. Complexity of parameters
Unlike a drug (take one pill daily), PBM has many variables: wavelength, power density, fluence (dose), treatment duration, frequency, and treatment site. Optimizing these parameters takes time.
3. Blinding challenges
Sham PBM devices can be designed (they emit very low or no light), but participants may still guess their group assignment if they feel warmth from active devices.
Despite these challenges, the research is accelerating. The trials mentioned above — NIR4AD, Cedars-Sinai, and the large PD trial — represent a new generation of higher-quality evidence.
What This Means for You or Your Loved Ones
If you or a family member has mild cognitive impairment, early Alzheimer’s, or Parkinson’s, you may be wondering: Should I try PBM?
Here is practical guidance:
If you are considering PBM for Alzheimer’s or MCI
- The evidence is most promising for mild-to-moderate stages — not for advanced disease.
- The MCI pilot study used 810-nm light, 20 minutes daily, six days per week, for six weeks .
- The ongoing NIR4AD trial uses 30 minutes daily, six days per week, for 16 weeks.
- PBM is not a cure and should not replace medications without discussing with your doctor.
If you are considering PBM for Parkinson’s
- The largest trial used PBM to the head, back of the neck, and abdomen three times weekly.
- Benefits were most clear with extended treatment (many weeks to months).
- All participants continued vigorous exercise — do not skip exercise.
- PBM is best viewed as an adjunctive therapy alongside medication and exercise.
For both conditions
- Safety is not a concern. The MCI trial reported no serious adverse events. The PD trial similarly found PBM safe.
- Do not expect miracles. The improvements seen in trials are meaningful — better memory scores, better mobility, less anxiety — but not reversal of advanced disease.
- Start early. Neurodegeneration begins years before symptoms appear. The earlier you support your brain, the better.
A Note on Hope
If you are reading this section because you or a loved one has cognitive decline or Parkinson’s, you already know the weight of that diagnosis.
PBM is not a miracle. The evidence is promising but not definitive. Large trials are still underway.
But it is safe. It is low-risk. And for some people, it helps.
Tracking improvements at home gives you two gifts:
- Data – So you know whether it is working for your specific loved one
- Agency – So you are not waiting passively for a cure that has not yet arrived
Even small improvements — a faster walk to the bathroom, a clearer sentence in conversation, a calmer morning — are worth celebrating.
Let the light in. And measure what it does.
Conclusion
Can light slow cognitive decline?
The answer is: possibly, probably, but not yet proven.
The mechanisms are sound. NIR light targets the core drivers of neurodegeneration: low energy, oxidative stress, inflammation, and poor blood flow.
Preclinical studies are strong. Human studies are promising but small.
Large, definitive trials are underway. In the next 2–5 years, we will have much clearer answers.
For now, PBM is not a replacement for standard medical care. But for those with mild cognitive impairment, early Alzheimer’s, or Parkinson’s — and for those who want to support their brain health proactively — PBM is a safe, low-risk, potentially beneficial intervention.
The light reaches your brain. What it does there is still being discovered. But the early signs are hopeful.
Takeaway Messages
- Alzheimer’s and Parkinson’s are progressive neurodegenerative diseases with no cure. Current treatments manage symptoms only.
- PBM targets the fundamental drivers of neurodegeneration: low ATP, oxidative stress, neuroinflammation, and poor blood flow.
- In Alzheimer’s: A 2025 pilot RCT in MCI showed improvements in cognition, memory, and default-mode network connectivity with 6 weeks of home-based tPBM. A larger 38-patient trial is ongoing.
- In Parkinson’s: The largest RCT to date (n=63) showed significant improvements in mobility, anxiety, and daily living motor experiences with extended PBM treatment.
- Preclinical studies demonstrate that PBM reduces amyloid-beta plaques, lowers tau hyperphosphorylation, protects dopamine neurons, and changes the expression of genes related to oxidative stress and inflammation.
- The evidence level is currently low to moderate — not because PBM does not work, but because large, definitive trials are still ongoing.
- Safety is not a concern. No serious adverse events have been reported in human trials.
- PBM is best viewed as an adjunctive therapy — alongside medication, exercise, and a healthy lifestyle — not a replacement.
- Ongoing large trials (NIR4AD, Cedars-Sinai, exercise + PBM for PD) will provide higher-quality evidence in the coming years.
- Start early. Neurodegeneration begins years before symptoms. Supporting your brain now is always better than waiting.
- Consult your doctor before starting PBM for a diagnosed neurodegenerative condition.
Coming Up Next in This Series
You have seen the evidence.
NIR light targets the core drivers of neurodegeneration: low energy, oxidative stress, inflammation, poor blood flow, and lost neuroplasticity. Clinical trials show promise for mild cognitive impairment, early Alzheimer’s, and Parkinson’s disease.
But knowing the science is one thing. Knowing what to do is another.
The next article in this series is a practical guide:
Practical Protocols: How to Use Light (and Sun) for Brain Health
This article will answer the questions you have been asking:
- Sunlight first: How to use free, natural NIR from the sun as your foundational therapy — including when, how long, and what to wear.
- What to buy: A clear, no-hype guide to device types (helmets, panels, handhelds), key specifications (wavelength, irradiance, dose), and what to avoid.
- Protocols that work: Step-by-step routines based on the clinical trials you just read — for MCI, Alzheimer’s, Parkinson’s, TBI, and general brain health.
- Safety and budget: Eye protection, biphasic dose response, and options ranging from $0 (sunlight) to premium devices.
- Plus: simple ways to track improvements at home.
No dense science. No conflicting advice. Just actionable protocols to help you — or someone you love — use light to protect the brain.
Coming soon: Practical Protocols: How to Use Light (and Sun) for Brain Health
Don’t Get Sick!
About Dr. Jesse Santiano, MD
Dr. Santiano is a retired internist and emergency physician with extensive clinical experience in metabolic health, cardiovascular prevention, and lifestyle medicine. He reviews all medical content on this site to ensure accuracy, clarity, and safe application for readers. This article is for educational purposes and is not a substitute for personal medical care.
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- Cao, Q., Jiao, Y., Wang, T., & Li, W. (2025). Mechanisms and parameters of photobiomodulation for neurological and neuropsychiatric disorders: Whether and how to apply? Reviews in the Neurosciences, 37(1), 77-91. https://doi.org/10.1515/revneuro-2025-0073
- Lee, T. L., Chan, A. S., Chan, W. K., Cheung, M. C., & Lee, T. (2024). Dose response of transcranial photobiomodulation on cognitive efficiency in healthy older adults: A task-related functional near-infrared spectroscopy study. Journal of Alzheimer’s Disease, 101(1), 321-335. https://doi.org/10.3233/JAD-240473
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