黑料网

As the global population ages, the prevalence of cognitive impairments, such as dementia and Alzheimer’s disease, has risen sharply. Research into the factors contributing to cognitive decline has expanded beyond traditional risk factors like genetics and lifestyle choices to include the role of the oral microbiome. The human oral cavity is home to a diverse microbiome, which plays a crucial role in maintaining oral and systemic health. Dysbiosis, or an imbalance in the microbial communities, has been linked to various systemic diseases, and emerging evidence suggests a potential connection between oral microbiome dysbiosis and cognitive impairment in older adults. This article examines the role of oral microbiome dysbiosis in cognitive decline, particularly in elderly individuals, and explores the potential mechanisms by which this disruption may contribute to neurodegeneration [1].

Oral Microbiome and Its Role in Health

The oral cavity hosts a complex and dynamic ecosystem of microorganisms, including bacteria, fungi, viruses, and archaea. This microbial community is essential for maintaining oral health by preventing the colonization of pathogenic microbes, aiding in digestion, and modulating immune responses. However, when the balance of these microbes is disturbed referred to as dysbiosis it can contribute to various oral diseases, including periodontitis and tooth decay, and extend its impact to systemic health [2, 3].

Oral dysbiosis is typically characterized by an overgrowth of harmful pathogens, such as Porphyromonas gingivalis and Fusobacterium nucleatum, while beneficial microbes, including Lactobacillus and Bifid bacterium, are reduced. This microbial imbalance can lead to chronic inflammation and the release of bacterial toxins into the bloodstream, potentially affecting distant organs, including the brain.

Link Between Oral Microbiome Dysbiosis and Cognitive Decline

Recent studies have suggested that oral microbiome dysbiosis is a significant risk factor for cognitive decline, particularly in aging populations. The most compelling evidence stems from research that demonstrates a potential pathway linking periodontal disease caused by dysbiosis in the oral microbiota with cognitive impairments such as Alzheimer’s disease and dementia. Inflammation plays a central role in both oral disease and neurodegeneration, and oral pathogens may be a driving force behind this systemic inflammatory response.

Oral pathogens, such as Porphyromonas gingivalis, have been found in the brains of individuals with Alzheimer’s disease, raising questions about how these bacteria might directly contribute to the development of neurodegeneration. Studies suggest that oral bacteria can enter the bloodstream through inflamed gums and subsequently travel to the brain, where they may trigger neuroinflammation. This process can lead to the activation of microglial cells, the brain's immune cells, which release pro-inflammatory cytokines that damage neurons and accelerate cognitive decline [4].

Mechanisms of Oral Dysbiosis Inducing Neurodegeneration

Several mechanisms are proposed to explain how oral microbiome dysbiosis contributes to cognitive decline. One of the primary mechanisms is the systemic inflammation initiated by oral pathogens. Bacteria from the oral cavity can enter the bloodstream through periodontal tissues, carrying bacterial toxins such as lipopolysaccharides (LPS). Once in circulation, these toxins can reach the brain, where they interact with the immune system and induce a state of chronic neuroinflammation.

Neuroinflammation is a hallmark of many neurodegenerative diseases, including Alzheimer's disease. The brain’s immune cells, or microglia, become activated in response to these inflammatory signals, leading to the release of cytokines and other molecules that promote neuronal damage. Over time, this chronic neuroinflammatory environment can accelerate the progression of cognitive decline by impairing synaptic function, promoting amyloid plaque deposition, and increasing neuronal cell death.

Another proposed mechanism is the direct interaction between oral bacteria and the brain. Porphyromonas gingivalis, a key pathogen in periodontal disease, has been shown to not only induce inflammation but also invade neural tissues. This bacterium produces proteases that degrade host proteins, contributing to amyloid plaque formation a characteristic feature of Alzheimer’s disease. The presence of P. gingivalis in the brain further supports the hypothesis that oral pathogens play a direct role in the pathogenesis of cognitive decline [5].

Impact of Oral Hygiene on Cognitive Function

The relationship between oral hygiene practices and cognitive health is another important area of research. Poor oral hygiene, which often leads to the accumulation of plaque and the development of periodontal disease, can exacerbate oral dysbiosis and contribute to systemic inflammation. Regular brushing, flossing, and dental check-ups are essential for maintaining a healthy oral microbiome and preventing conditions like periodontitis, which are known to be associated with cognitive impairment.

Recent studies have shown that individuals with better oral hygiene and fewer instances of periodontal disease exhibit better cognitive function in old age compared to those with poor oral health. Conversely, older adults who experience tooth loss and untreated periodontal disease may face an increased risk of developing cognitive disorders, suggesting that maintaining oral health could be an important strategy for mitigating cognitive decline.

Oral Health Interventions for Cognitive Protection

Given the potential connection between oral microbiome dysbiosis and cognitive decline, oral health interventions may provide a novel approach to preventing or slowing down neurodegeneration in elderly individuals. Targeted periodontal treatments, such as scaling and root planning, have been shown to reduce the levels of harmful oral bacteria and improve oral health, which could, in turn, alleviate systemic inflammation and potentially reduce the risk of cognitive impairment [6- 8].

Additionally, the use of probiotics and other microbiome-modulating therapies may offer a promising avenue for restoring balance to the oral microbiome and reducing the risk of neurodegenerative diseases. Probiotics have been shown to enhance the growth of beneficial microbes while inhibiting the growth of pathogenic bacteria, potentially improving both oral and cognitive health [9, 10].

Conclusion

The growing body of evidence linking oral microbiome dysbiosis to cognitive decline underscores the importance of maintaining good oral health, particularly in aging populations. Dysbiosis in the oral cavity may contribute to neurodegeneration through mechanisms of systemic inflammation, direct bacterial invasion, and the activation of neuroinflammatory pathways. As the field of oral microbiome research continues to evolve, further studies are needed to better understand the precise mechanisms at play and to explore the potential for targeted oral health interventions as part of a comprehensive strategy to mitigate cognitive decline in older adults. Improving oral health may not only prevent dental diseases but also protect cognitive function, enhancing the quality of life in aging populations.

1. K枚kt眉rk Dalcali B, Ta艧 AS (2021) J Relig Health 60:4417-4434.

, ,

2. Mathew-Geevarughese SE, Corzo O, Figuracion E (2019) Primary care 46:399-413.

, ,

3. Palevsky PM (2018) Nephron 140:111-1115.

, ,

4. Zuber K, David J (2018) JAAPA 31: 17-25.

, ,

5. Moresco RN, Bochi GV, Stein CS, De Carvalho JAM, Cembranel BM, et al. (2018) Clin Chim Acta 487:15-21.

, ,

6. Lippe M, Johnson B, Mohr SB, Kraemer KR (2018) Am J Hosp Palliat Care 35:1235-1244.

, ,

7. Martins Pereira S, Hern谩ndez-Marrero P, Pasman HR, Capelas ML, Larkin P, et al. (2021) Palliat Med 35:130-141.

, ,

8. Oluyase AO, Hocaoglu M, Cripps RL, Maddocks M, Walshe C, et al. (2021) J Pain Symptom Manage 62:460-470.

, ,