Connections Between Oral Health and Alzheimer’s Disease
- 17 hours ago
- 7 min read
Sooyun Christina Kim, Amreet Minhas, Beatrice Sixt
Project Smile Global
Alzheimer’s disease (AD) is the most prevalent form of dementia (Silva et al.). Affected individuals exhibit loss of past memories and cognitive functions, often followed by difficulties with speaking and visual perception (Silva et al.). Alzheimer’s disease can be classified into two forms: inherited and sporadic (Harding et al.). The inherited form can be attributed to genetic factors, while the cause of the sporadic form, which is the most common form, remains unclear (Harding et al.). It is known that all AD patients demonstrate accumulation of the amyloid beta protein in the brain (Bali et al. 15307), and that a combination of environmental and genetic factors contribute to the development of sporadic AD (Dorszewska et al. 952). The onset of AD undoubtedly presents challenges in maintaining quality of life, which is detrimental to oral health. Those affected by AD tend to have poor oral health due to gradual cognitive impairment and diminished dexterity (Gao et al.). Therefore, these individuals are more likely to suffer from caries, periodontitis, and xerostomia (dry mouth), among other issues (Gao et al.).
While cognitive decline due to AD is associated with challenges in performing daily tasks (Ming et al. 169), a growing body of research supports the link between the decline of oral health and the progression of AD (Mancini et al. 368). Alzheimer’s patients have fewer teeth, worse oral hygiene, higher infection rates, and worse salivary quantity and quality (Aragón et al.). Those with Alzheimer’s disease also have significantly higher rates of coronal (crown) and cervical (root) caries due to certain medications causing xerostomia, leading to plaque accumulation and periodontal disease (Mancini et al. 369). However, other medications can lead to increased salivation, peristalsis, and vascular smooth muscle relaxation, which can lead to nausea and vomiting, making dental visits difficult for patients (Mancini et al. 369).
Interestingly, the relationship between oral health and Alzheimer’s disease appears to be bidirectional, as poor oral hygiene has also been associated with the development of Alzheimer’s disease (Pruntel et al. 249). Periodontitis, inflammation of the gums, could exacerbate neuroinflammation due to the infiltration of pathogens, leading to neurodegeneration (Pruntel et al. 249). Furthermore, a poor diet can lead to dysbiosis (microbial imbalance), promoting periodontal pathogens such as Porphyromonas gingivalis, which may increase Alzheimer’s disease risk by inducing systemic inflammation (Harding et al.). Poor oral health may therefore contribute to the progression of Alzheimer’s disease, while the disease itself can further impair an individual’s ability to maintain proper oral hygiene.
AD affects oral health through both biological and lifestyle changes. Oral hygiene is often compromised, as patients may forget to brush their teeth. Additionally, cognitive impairments in learning and attention can make it difficult for patients to retain and consistently perform proper oral hygiene practices, which dentists should be mindful of (Cicciu et al. 766). AD patients also have difficulties with motor skills, which can affect toothbrushing, making it difficult to remove plaque (Ribeiro et al. 338). They can also find it difficult to recognize the early signs of carious lesions or the first signs of periodontal disease, like bleeding or deep probing depth (Cicciu et al. 767). It is therefore suggested that poor oral hygiene can lead to AD, which can in turn induce lifestyle and biological changes that lead to worse oral health, leading to a vicious cycle of declining cognitive and oral health. It is essential for individuals with early signs of Alzheimer’s disease to maintain daily oral hygiene routines and attend regular dental examinations, with dentists collaborating with both patients and caregivers to ensure adequate oral health support (Gao et al.).
The development of Alzheimer’s disease is also influenced by socioeconomic status, alongside both genetic and environmental risk factors. While most cases are sporadic, genetic factors play a significant role in disease risk (Silva et al.). Early-onset AD is typically associated with mutations in the genes APP, PSEN1, and PSEN2, whereas late AD cases are associated with polymorphism in the APOE gene (Silva et al.). Environmental risk factors, such as pollution and pesticide exposure, have been suggested to influence the expression and regulation of genes associated with Alzheimer’s disease. During early development, environmental stressors may activate previously silent genes, altering gene regulation through epigenetic modifications such as DNA methylation at promoter regions. Later in life, additional stressors may further influence gene expression (Surish et al.). Individuals in low socioeconomic status (SES) communities are more susceptible to these environmental risk factors, as exposure to pollutants and harmful chemical concentrations is significantly higher in these populations. In North American communities where about 15% of the population has less than a high school education, air pollutant levels are up to 0.47 μg/m³ higher than in communities with higher levels of education (Hajat et al.). In a study on Integrated Pollution Control (IPC) sites, 20% of people in lower socioeconomic neighborhoods lived within 500 m of a site, compared to 3.8% in higher-income areas (Mattias et al.). IPC sites in these areas also produced higher emissions and posed greater pollution risks. This increased exposure to environmental pollutants may contribute to a higher risk of Alzheimer’s disease.
Acquired risk factors also contribute to the development of Alzheimer’s disease. The most common include cardio-cerebrovascular diseases (CCVDs), as well as conditions such as diabetes, hypertension, obesity, and dyslipidemia (Roh et al.). CCVDs, which are conditions that impact blood flow to the brain, such as strokes, lead to dysfunction in the blood-brain barrier (BBB) and reduced cerebral blood flow, decreasing blood cerebral perfusion (Liu et al.; Che Mohd Nassir et al.). Reduced blood flow deprives neurons of oxygen, triggering acidosis, mitochondrial dysfunction, and oxidative stress, which promotes amyloid accumulation (Leszek et al. 154). Simultaneously, BBB dysfunction impairs the clearance of amyloid from the brain. Together, these processes drive amyloid buildup, resulting in neuronal loss and cognitive decline (Silva et al.). Rates of cardio-cerebrovascular diseases are higher in low socioeconomic communities, with low income and education being key determinants (Roh et al.). Type 2 diabetes, hypertension, and obesity also occur more frequently in these populations and can affect cognitive performance. Compared to middle-income groups, the risk of Type 2 diabetes is up to 60% higher (Hsu et al.), and in the United States, hypertension incidence is 11% higher among those living in rural areas (Chaturvedi et al.).
Alzheimer’s disease affects both mental and oral health through factors such as cognitive decline, reduced dexterity, and a diminished quality of life. These effects are further influenced by socioeconomic and environmental factors, which can contribute to a cycle of declining health. It is therefore important for individuals with AD to maintain consistent oral hygiene routines and adequate support systems, with dentists working alongside patients and their caregivers to support optimal outcomes.
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