Could Lyme Disease Play a Role in Alzheimer’s Disease?
Lyme disease is not an established cause of Alzheimer’s disease
Researchers are studying possible links involving neuroinflammation, amyloid, and tau
Current evidence shows association, not causation
Could Lyme disease play a role in Alzheimer’s disease? Researchers are investigating that possibility, but the evidence does not establish that Lyme disease causes Alzheimer’s disease.
A 2026 review by Ahuja and colleagues examined whether infection with Borrelia burgdorferi sensu lato—the bacteria responsible for Lyme borreliosis—could contribute to biological processes associated with Alzheimer’s disease.1
The researchers focused particularly on neuroinflammation, amyloid-beta accumulation, and tau pathology. These processes are important because amyloid plaques and abnormal tau are characteristic features of Alzheimer’s disease.
The review brings together laboratory, animal, postmortem, and epidemiological evidence suggesting possible biological overlap between Lyme neuroborreliosis and Alzheimer’s disease. However, the authors emphasize an important limitation: epidemiological findings are mixed, and a causal relationship between Borrelia infection and Alzheimer’s disease has not been established.1
This is a different question from whether Lyme disease can produce cognitive symptoms that resemble dementia. Lyme disease can affect memory, concentration, processing speed, and other neurological functions. The newer research asks a more speculative biological question: could infection-related inflammation contribute to some of the pathological processes involved in neurodegeneration?
Why are researchers studying infection and Alzheimer’s disease?
Alzheimer’s disease is a complex neurodegenerative disorder. Age, genetics, vascular disease, metabolic factors, and other biological processes can influence risk, and researchers continue to investigate additional contributors.
One area of research examines whether infections or the immune responses they trigger could contribute to chronic inflammation in the brain.
That does not mean Alzheimer’s disease is simply an infectious disease. Rather, researchers are asking whether infection could represent one of several environmental or biological factors capable of influencing neurodegenerative pathways in susceptible individuals.
This question is particularly relevant to Borrelia burgdorferi because the organism can involve the nervous system and produce neurologic Lyme disease.
What did the 2026 review find?
Ahuja and colleagues reviewed evidence examining possible connections between Lyme neuroborreliosis and Alzheimer’s disease pathology.1
The authors identified several areas of potential overlap:
- Persistent or prolonged neuroinflammatory responses
- Activation of immune pathways within the nervous system
- Possible effects on amyloid-beta accumulation
- Possible effects on tau-related pathology
- Laboratory and postmortem observations linking Borrelia with Alzheimer’s-associated markers in selected studies
These findings provide biological reasons to continue investigating the hypothesis. They do not demonstrate that people with Lyme disease will develop Alzheimer’s disease or that Borrelia is responsible for Alzheimer’s disease in the general population.
How could neuroinflammation connect Lyme disease and Alzheimer’s disease?
Neuroinflammation refers to inflammatory activity within the brain and nervous system. It involves immune cells, inflammatory signaling molecules, and responses to infection, injury, or abnormal proteins.
Borrelia burgdorferi can stimulate inflammatory responses when it interacts with cells of the nervous system. In Lyme neuroborreliosis, inflammation may accompany meningitis, cranial neuropathy, radiculoneuritis, and other neurological manifestations.
Neuroinflammation is also increasingly recognized as an important component of Alzheimer’s disease biology. The 2026 review therefore examines whether infection-related inflammatory responses could provide one potential bridge between Borrelia infection and neurodegenerative processes.1
But a shared inflammatory pathway does not prove that one disease causes the other. Many infections, injuries, autoimmune conditions, and metabolic disorders can activate inflammatory pathways without causing Alzheimer’s disease.
What is the possible connection with amyloid-beta?
Amyloid-beta is a protein fragment that can accumulate in the brain and form plaques associated with Alzheimer’s disease.
Several laboratory and pathological studies have raised questions about whether infection could influence amyloid production or accumulation.
In a 2006 laboratory study, Miklossy and colleagues exposed mammalian neuronal and glial cells to Borrelia burgdorferi. The researchers reported changes resembling amyloid deposits along with increased beta-amyloid precursor protein and hyperphosphorylated tau.2
Those findings are intriguing, but laboratory experiments cannot establish what happens in people over decades. Demonstrating that a bacterium can induce Alzheimer’s-like cellular responses under experimental conditions is very different from demonstrating that Lyme disease causes Alzheimer’s disease.
Has Borrelia been found in Alzheimer’s brain tissue?
Some investigators have reported evidence of Borrelia burgdorferi in postmortem brain tissue from selected patients with Alzheimer’s disease.
In a 2022 study, Senejani and colleagues examined brain tissue from patients with Alzheimer’s disease or Parkinson’s disease and age-matched controls. The investigators reported Borrelia burgdorferi antigen and DNA in some Alzheimer’s brain specimens and described co-localization of Borrelia-positive structures with amyloid and phosphorylated tau markers.3
The investigators also exposed mammalian cells to Borrelia burgdorferi and reported increased expression of amyloid-beta and phosphorylated tau proteins.3
Again, these findings suggest an association worth investigating. Finding bacterial material near pathological markers does not establish that the organism produced the disease, and results from selected postmortem samples cannot determine how commonly such findings occur in people with Alzheimer’s disease.
What does the epidemiological evidence show?
This is where the hypothesis becomes much less certain.
If Lyme disease were an important cause of Alzheimer’s disease, researchers would expect epidemiological studies to demonstrate a consistent relationship between Borrelia exposure or Lyme disease and later Alzheimer’s disease.
The 2026 review found that the epidemiological literature does not provide a consistent answer. Some studies suggest possible associations, while others have found no clear correlation.1
Other researchers have reached more skeptical conclusions. A critical review by Wormser and colleagues concluded that convincing evidence that Borrelia burgdorferi infection causes Alzheimer’s disease is lacking.4
That disagreement is important. The biological hypothesis is interesting enough to study, but the clinical and epidemiological evidence is not strong enough to conclude that Lyme disease causes Alzheimer’s disease.
Lyme disease can also mimic dementia without causing Alzheimer’s disease
There is another issue that should not be confused with the Alzheimer’s hypothesis.
Neurologic Lyme disease can cause cognitive symptoms including memory problems, slowed processing, difficulty concentrating, word-finding problems, confusion, and what patients often describe as brain fog.
These symptoms can sometimes resemble dementia, particularly in older adults. In selected cases, patients initially thought to have a neurodegenerative disorder have later been diagnosed with Lyme neuroborreliosis or another potentially treatable condition.
This clinical overlap is discussed in more detail in How Lyme Disease Is Misdiagnosed as Alzheimer’s.
But mimicry and causation are two different questions.
A patient can have Lyme-related cognitive impairment that resembles Alzheimer’s disease without having Alzheimer’s pathology. Conversely, a patient with genuine Alzheimer’s disease could also have a history of Lyme disease without the infection having caused the neurodegenerative disorder.
Could treating Lyme disease prevent Alzheimer’s disease?
There is currently no evidence that antibiotic treatment for Lyme disease prevents Alzheimer’s disease.
The 2026 review raises mechanistic questions that may eventually lead researchers toward new biomarkers or preventive strategies, but those possibilities remain investigational.1
It would therefore be premature to use the Alzheimer’s hypothesis as a reason for prolonged or preventive antibiotic treatment in someone without an appropriate clinical indication for Lyme disease treatment.
At the same time, recognized Lyme disease should be diagnosed and treated appropriately. Neurological symptoms deserve careful evaluation because infection, neurodegenerative disease, medication effects, metabolic disorders, sleep problems, vascular disease, and other conditions can produce overlapping cognitive complaints.
Frequently Asked Questions
Does Lyme disease cause Alzheimer’s disease?
There is currently no convincing evidence that Lyme disease causes Alzheimer’s disease. Researchers have identified possible biological connections involving neuroinflammation, amyloid-beta, and tau, but causation has not been established.
Why are researchers studying Borrelia and Alzheimer’s disease?
Borrelia burgdorferi can involve the nervous system and trigger inflammatory responses. Because neuroinflammation is also involved in Alzheimer’s disease, researchers are investigating whether infection-related inflammation could contribute to neurodegenerative pathways in some circumstances.
Has Borrelia been found in Alzheimer’s brain tissue?
Some postmortem studies have reported Borrelia burgdorferi antigen or DNA in selected Alzheimer’s brain samples and co-localization with amyloid or tau markers. These findings are controversial and do not establish that the organism caused Alzheimer’s disease.
Can Lyme disease look like Alzheimer’s disease?
Yes. Neurologic Lyme disease can produce memory problems, confusion, slowed thinking, word-finding difficulty, and other cognitive symptoms that may resemble dementia. This clinical mimicry is different from demonstrating that Lyme disease causes Alzheimer’s disease.
Can antibiotics prevent Alzheimer’s disease in someone who has had Lyme disease?
No evidence currently shows that antibiotic treatment for Lyme disease prevents Alzheimer’s disease. Lyme disease should be treated when clinically indicated, but the possible Lyme-Alzheimer’s connection remains an area of research rather than an established basis for Alzheimer’s prevention.
Clinical Takeaway
The possibility that infection contributes to neurodegeneration is an important area of research, and the 2026 review provides a useful framework for investigating how Borrelia burgdorferi-induced neuroinflammation might intersect with amyloid and tau pathology.
For patients, however, the distinction between hypothesis and established clinical evidence matters. Lyme disease can affect cognition and can sometimes resemble dementia, but that does not mean Lyme disease causes Alzheimer’s disease.
Future longitudinal and mechanistic studies will be needed to determine whether Borrelia exposure meaningfully alters Alzheimer’s risk or pathology in any subgroup of patients.
For now, the evidence supports continued investigation of a possible biological connection—not the conclusion that Lyme disease causes Alzheimer’s disease.
Related Articles
These articles explore related questions involving cognitive symptoms, dementia, neurologic Lyme disease, and diagnostic uncertainty:
When Does Forgetfulness Need a Medical Evaluation?
Is It Dementia, Parkinson’s… or Lyme Disease?
Lyme Disease Misdiagnosis: Why It Happens and What to Know
References
- Ahuja R, Shaban A, Chawla J, Parmar MS. Borrelia burgdorferi-Induced Neuroinflammation in Lyme Disease: A Potential Driver of Alzheimer’s Disease Pathology? Molecular Neurobiology. 2026;63(1):381.
- Miklossy J, Kis A, Radenovic A, et al. Beta-amyloid deposition and Alzheimer’s type changes induced by Borrelia spirochetes. Neurobiology of Aging. 2006;27(2):228-236.
- Senejani AG, Maghsoudlou J, El-Zohiry D, et al. Borrelia burgdorferi Co-Localizing with Amyloid Markers in Alzheimer’s Disease Brain Tissues. Journal of Alzheimer’s Disease. 2022;85(2):889-903.
- Wormser GP, Marques A, Pavia CS, Schwartz I, Feder HM, Pachner AR. Lack of Convincing Evidence That Borrelia burgdorferi Infection Causes Either Alzheimer Disease or Lewy Body Dementia. Clinical Infectious Diseases. 2022;75(2):342-346.
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Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.
Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention
