Alzheimer's link: Oral health infections lead to a systemic link associated with memory loss

Oct. 1, 2017
Lori Schmitz-Parr, RDH, reviews literature regarding a systemic link between periodontal disease and Alzheimer's.

By Lori Schmitz-Parr, RDH

During the last decade, researchers have discovered increasing evidence that demonstrates the link between oral health and systemic health. Inflammatory diseases, including periodontal disease, compromise the body’s ability to fight infections and can exacerbate systemic diseases. Scientific studies have shown correlations between periodontal disease and diabetes, cardiovascular disease, and more recently, a plausible link between periodontal disease and Alzheimer’s.

This article will discuss Alzheimer’s disease and periodontal disease and their symptoms. It will also discuss the links between the two, as well as the dental professional’s role in treatment and prevention.

Alzheimer’s disease

The most common form of dementia, Alzheimer’s disease (AD), is a neurodegenerative disorder primarily affecting cognitive ability and psychiatric health. Alzheimer’s is defined by the Alzheimer’s Foundation of America as “a progressive, degenerative disorder that attacks the brain’s nerve cells, or neurons, resulting in loss of memory, loss of thinking and language skills, and behavioral changes.”1 There are two main types of Alzheimer’s - familial onset (early onset), and late onset, also referred to as LOAD. LOAD accounts for 98% of all cases and occurs in adults ages 65 and older, with the prevalence increasing by nearly 50% at age 85.1 According to the latest Alzheimer’s facts and figures, 5.5 million American adults are afflicted with the disease, and the number is projected to increase to 16 million by 2050.2

AD is a complex, chronic brain disorder diagnosed by obtaining a thorough, detailed medical history, conducting lab tests and brain scans, and performing a physical exam and neuropsychological tests to determine cognitive skills. Symptoms of AD can be attributed to other forms of dementia and dozens of other ailments, so a proper diagnosis is crucial. Although a diagnosis of up to 90% accuracy can be made, absolute confirmation of the disease is only possible by examining the brain through an autopsy.1

AD has many symptoms and characteristics, some presenting earlier than others. The Alzheimer’s Foundation of America reports that early symptoms include memory loss that disrupts daily life, difficulty problem solving, confusion with time and place, inability to communicate or understand what’s being said, difficulty performing everyday tasks such as bathing, brushing teeth, and getting dressed, and difficulty perceiving visceral information such as the need to urinate or pain from a toothache.1

The foundation also states that depression, changes in personality, agitation, and hallucinations are the most significant psychiatric characteristics. Alzheimer’s is the sixth leading cause of death in the United States and the only top 10 disease that cannot be prevented, cured, or even slowed, perhaps until now.1

The definitive pathogenesis of Alzheimer’s is unknown. A recent study by Olsen and Singhrao discovered that in addition to the trademark indicators of beta-amyloid plaques and neurofibrillary tangles, other indicators of the disease’s neuropathology are inflammatory pathogens.3 The authors state that the inflammatory pathology may be linked to the presence of a peripheral inflammatory infection such as periodontal disease, due to the presence of periodontal-associated bacteria found in AD brains.3

Periodontal disease

Periodontal disease is considered a low-grade, chronic, inflammatory disease. It is characterized by the presence of pathogenic bacteria that cause gingival inflammation, bone loss, attachment loss, tooth mobility, and if left untreated, tooth loss. Most people are not aware that they have periodontal disease because they do not visit a dentist on a regular basis, and the disease usually does not cause discomfort. However, according to the article “CDC: Half of Americans Have Periodontal Disease,” 47.2% of American adults have some degree of periodontal disease, with the prevalence increasing to 70.1% in adults 65 and older.4

Mode of transportation of microbes to the brain

One of the most common ways microbes reach the brain is through the bloodstream. During chewing, flossing, and dental treatment, periodontal bacteria are released into the bloodstream and can remain there for up to three hours. In a healthy person, bacteremia is contained by the immune system. However, in older adults with a compromised immune system, bacteria can remain in periodontal pockets and continue to be released.

Another way microbes reach the brain is by crossing the blood-brain barrier. With age, the presence of an overabundance of bacteria and microorganisms compromises the integrity of the blood-brain barrier, making it easy for microbes to invade and destroy nerve tissue. The increased permeability of the blood-brain barrier with age results in promoting AD.3

The links: Oral bacteria

In the oral cavity, a plethora of bacteria are found in the sticky plaque biofilm that covers the many surfaces in the mouth. Additionally, deep periodontal pockets can form and collect plaque and debris and harbor a high number of pathogenic bacteria. Oral bacteria associated with periodontal disease and implicated in AD include P. gingivalis, T. forsythia, F. nucleatum, and P. intermedia.3 Six oral Treponema spirochetes, T. denticola, T. pectinovorum, T. vincenti, T. amylovorum, T. maltophilum, and T. socranskii, have also been found in AD brains.3 The notable characteristics about spirochetes in relation to their link to AD include being neurotropic in nature, meaning they specifically target and destroy nerve tissue, induce and contribute to inflammation, and form amyloid plaques and neurofibrillary tangles, the hallmark indicators of AD.5

In a study of 2,355 subjects over the age of 60, higher levels of antibodies to periodontal pathogens where found in the subjects who were cognitively intact at baseline but then developed AD, than those who did not develop AD.3 Another study conducted in 60 subjects with mild to moderate AD showed a sixfold increase in rate of cognitive decline after six months.6 Furthermore, this study showed an increase in periodontal-associated pro-inflammatory cytokines after six months.6 In addition to demonstrating a strong correlation between periodontal disease and AD, it is indicative that periodontal disease was present prior to the onset of AD.3

HSV-1 and oral candidiasis

In addition to periodontal disease, other oral health infections common in adults age 65 and older are the oral herpes simplex virus (HSV-1) and oral candidiasis. Approximately 70% of adults over the age of 50 have the HSV-1 virus.3 It is generally latent in the peripheral nervous system and can be activated by high levels of stress, illness, or fatigue. Research shows that once activated, the virus decreases the body’s ability to fight infection, thereby increasing the likelihood of developing periodontal infections.3 Additionally, it produces pro-inflammatory factors, adding additional challenges to an already compromised system. These effects of the virus result in producing high levels of HSV-1 proteins found in the amyloid plaques associated with AD, creating a strong correlation between HSV-1 and AD.3

It’s been reported that oral yeasts can be present in ulcerated periodontal pockets in teeth treated by root canal therapy, and on the mucosa under partials and dentures.3 The report goes on to state that because dentures often harbor high amounts of oral candida, denture stomatitis, an inflammatory condition of the mucosa, can occur. Research shows that because of denture stomatitis, a systemic fungal infection (systemic mycosis) occurs, which has been recently reported in AD patients, creating an additional link between oral disease and AD.3

The elderly and oral health

Today’s elderly population places greater importance on oral and overall health than previous generations, and as a result they have maintained their natural dentition longer. However, with age come health issues such as depression, high blood pressure, arthritis, and heart disease. While xerostomia resulting from medications taken for these health issues can contribute to poor oral health, other factors also contribute to poor oral health in elderly patients.7 Many have arthritis, poor dexterity, poor vision, and limited mobility, which make brushing, flossing, rinsing, and using oral hygiene aids difficult. Also, many elderly people do not drive and rely on others for transportation, making access to regular, preventive dental care almost impossible. These issues collectively contribute to chronic oral infections, increased periodontal pocket depth, alveolar bone loss, and subsequent tooth loss. With a compromised dentition, the ability to chew and consume a proper diet may lead to nutritional deficiencies, which adds another risk factor.

Dental professional’s role

When a diagnosis of AD or any other form of dementia is made, the focus becomes understanding and managing the disease, helping the person remain independent for as long as possible, and maintaining quality of life. Some of the most important factors for dental professionals to consider when treating Alzheimer’s patients are exercising increased patience and understanding, using simple terms, and using a slow, gentle approach.

When speaking with their caregivers, patients should be included as much as possible to avoid having them feel left out. Treatment and instructions should be written down and given to patients and caregivers for future reference. It’s important to keep in mind that patients may repeat themselves, be easily startled, be combative, and become apprehensive. Also, it is imperative to recognize that dementia patients have good and bad days.

It is important to educate and provide Alzheimer’s patients and caregivers with the tools to help with good oral hygiene habits. More frequent recare appointments, exams, radiographs, and fluoride treatments are all recommended. Oral hygiene instructions given to caregivers should include how to brush properly with an electric toothbrush, how to rinse with an alcohol-free, antibacterial mouth rinse, and how to remove, clean, and insert removable prostheses. Simply having patients rinse their mouths after eating is beneficial to prevent the development of rampant caries.

Products to help alleviate xerostomia should also be considered and include over-the-counter gels, toothpastes, rinses, and lozenges. Many of the lozenges, and a few oral rinses, contain xylitol, which have been shown to prevent tooth decay. In addition to lozenges, sugar-free citrus candy containing xylitol is helpful because the citrus component helps stimulate saliva flow. Keeping the oral cavity moist and stimulating saliva flow is important because saliva acts as a natural cleanser and reduces the likelihood of caries. As the dementia progresses, patients may need to be shown how to do simple tasks such as removing the cap on the toothpaste and applying the toothpaste to the brush.

Preventing a problem is much easier and less costly than treating the problem, especially in patients afflicted with Alzheimer’s. Finally, it is important to encourage caregivers to use their own judgment when assisting with patients’ oral hygiene to help reduce upsetting their patients and to maintain patients’ comfort and sense of security.

Because recent studies have revealed several plausible links between periodontal disease and AD, it is vital that dental professionals educate caregivers and stress the importance of good oral hygiene in their patients. Even after the diagnosis of Alzheimer’s, it is imperative to continue treatment of these patients to avoid further complications from poor oral health and periodontal disease.

Dental professionals need to take the initiative to educate Alzheimer’s patients and their caregivers to try to prevent periodontal disease as much as possible so that the disease does not cause further damage to the brain. Perhaps the key to slowing down the progression of Alzheimer’s is as simple as exemplary oral hygiene and preventive dentistry. RDH

Lori Schmitz-Parr, RDH, has over 28 years of experience in the dental field. She started her career as a dental assistant and has been practicing clinical dental hygiene for the last 13 years. Most recently she has worked in a clinical research setting examining subjects for oral mucositis using the OMI-20 index. She is currently working full time in dental hygiene, pursuing a bachelor’s degree in health sciences at Rutgers University, and presenting seminars about oral disease and Alzheimer’s disease. Lori is passionate about promoting preventive oral care, educating health-care professionals about oral-systemic links, and educating caregivers on proper oral hygiene techniques. She can be contacted at [email protected].


1. Alzheimer’s Foundation of America. Alzheimer’s website. Updated April 10, 2016. Accessed April 28, 2017.
2. Latest Alzheimer’s Facts and Figures. Alzheimer’s website. Accessed April 28, 2017.
3. Olsen I, Singhrao SK. (2015). Can oral infection be a risk factor for Alzheimer’s disease? Journ of Oral Microbio, 7(1), 29143-29169. doi:10.3402/jom.v7.29143.
4. CDC: Half of American Adults Have Periodontal Disease. American Academy of Periodontology website. Published March 29, 2016. Accessed April 28, 2017.
5. Miklossy J. (2011). Alzheimer’s disease-a neurospirochetosis. Analysis of the evidence following Koch’s and Hill’s criteria. Journ of Neuroinflammation, 8:90, doi: 10.1186/1742-2094-8-90.
6. Ide M, Harris M, Stevens A, et al. Periodontitis and cognitive decline in Alzheimer’s disease. website. Accessed July 29, 2017.
7. Foltyn P. Aging, dementia, and oral health. Australian Dent Journ, 60, 86-94. doi:10.1111/adj.12287.

Additional references

Giesey N, Mazur J. Treating Alzheimer’s patients: Tips for dental hygienists. DentistryIQ website. Published June 2, 2016. Accessed July 31, 2017.

Gurav AN. Alzheimer’s disease and periodontitis-an elusive link. Revista da Associação Médica Brasileira, 60(2), 173-180. doi:10.1590/1806-9282.60.02.015