With the intensification of the aging of population, the number of patients with neurodegenerative diseases such as cognitive impairment is increasing. Patients with cognitive impairment often have poor oral health, which previous studies have suggested that may be related to poor oral hygiene habits. However, studies in recent years have shown that oral diseases may accelerate the development of cognitive impairment through infections and other routes. In this article, the correlation and possible mechanisms of oral health including periodontitis, masticatory function, and oral mucosal disease and cognitive impairment will be elaborated.

Siyao Zhang, Jin Liu, Hongying Sun. Research progress on the relationship between cognitive impairment and oral health. Frontiers in Medical Science Research (2022) Vol. 4, Issue 11: 5-11. https://doi.org/10.25236/FMSR.2022.041102.

[1] AAIC 2021: The promise of Alzheimer's research. Alzheimers Dement, 2021. 17(11): p. 1868-1871.

[2] Gu Xinghua, A preliminary study on the correlation between moderate and severe periodontitis and cognitive dysfunction 2019, China Medical University.

[3] Fan Xiao and Liu Weicai, Research progress on the influence of oral ill health on cognitive impairment Journal of Fudan University (Medical Edition), 2016 43(04): p. 485-489.

[4] Xin, H., et al., Periodontal disease and the risk of Alzheimer's disease and mild cognitive impairment: a systematic review and meta-analysis. Psychogeriatrics: the official journal of the Japanese Psychogeriatric Society, 2021.

[5] Nangle, M.R. and N. Manchery, Can chronic oral inflammation and masticatory dysfunction contribute to cognitive impairment? Curr Opin Psychiatry, 2020. 33(2): p. 156-162.

[6] Epp, L.M. and B. Mravec, Chronic polysystemic candidiasis as a possible contributor to onset of idiopathic Parkinson's disease. Bratisl Lek Listy, 2006. 107(6-7): p. 227-30.

[7] Schmidt, R., et al., Early inflammation and dementia: a 25-year follow-up of the Honolulu-Asia Aging Study. Ann Neurol, 2002. 52(2): p. 168-74.

[8] Gao yunyun, et al., Correlation analysis between periodontal plaque microbial infection and periodontitis Chinese Journal of hospital infection, 2015 25(11): p. 2570-2572.

[9] Li Yunxia, Research progress in etiology and clinical treatment of periodontal disease Hebei medicine, 2013 19(03): p. 466-469.

[10] Hajishengallis, G. and T. Chavakis, Local and systemic mechanisms linking periodontal disease and inflammatory comorbidities. Nature reviews. Immunology, 2021. 21(7): p. 426-440.

[11] Beck, J.D., K.H. Philips, and S.S. Rao, Periodontal Disease and Systemic Interactions (Periodontal Medicine): Current Epidemiological Evidence. Current Oral Health Reports, 2020. 7(2).

[12] Glurich, I. and A. Acharya, Updates from the Evidence Base Examining Association between Periodontal Disease and Type 2 Diabetes Mellitus: Current Status and Clinical Relevance. Current Diabetes Reports, 2019. 19(11).

[13] M., L.E., et al., Interrelationship between the Microbial Communities of the Root Canals and Periodontal Pockets in Combined Endodontic-Periodontal Diseases. Microorganisms, 2021. 9(9).

[14] DongHee, K. and H. GyeongSoon, The relationship between periodontal disease and cognitive impairment in older adults of Korea. Special care in dentistry : official publication of the American Association of Hospital Dentists, the Academy of Dentistry for the Handicapped, and the American Society for Geriatric Dentistry, 2021.

[15] Noble, J.M., et al., Periodontitis is associated with cognitive impairment among older adults: analysis of NHANES-III. Journal of neurology, neurosurgery, and psychiatry, 2009. 80(11): p. 1206-1211.

[16] Haiying, G., et al., The Effect of Periodontitis on Dementia and Cognitive Impairment: A Meta-Analysis. International journal of environmental research and public health, 2021. 18(13).

[17] Chen, C.-K., Y.-T. Wu, and Y.-C. Chang, Association between chronic periodontitis and the risk of Alzheimer's disease: a retrospective, population-based, matched-cohort study. Alzheimer's research & therapy, 2017. 9(1): p. 56-56.

[18] Iwasaki, M., et al., Periodontitis, periodontal inflammation, and mild cognitive impairment: A 5-year cohort study. J Periodontal Res, 2019. 54(3): p. 233-240.

[19] Ding, Y., et al., Porphyromonas gingivalis, a periodontitis causing bacterium, induces memory impairment and age-dependent neuroinflammation in mice. Immunity & Ageing, 2018. 15(1).

[20] Nie ran and Zhou Yanmin, Research progress on the correlation between chronic periodontitis and Alzheimer's disease Dental research, 2019 35(05): p. 419-422.

[21] Akiyama, H., et al., Inflammation and Alzheimer's disease. Neurobiol Aging, 2000. 21(3): p. 383-421.

[22] Kamer, A.R., et al., Periodontal disease associates with higher brain amyloid load in normal elderly. Neurobiology of aging, 2015. 36(2): p. 627-633.

[23] Watts, A., E.M. Crimmins, and M. Gatz, Inflammation as a potential mediator for the association between periodontal disease and Alzheimer's disease. Neuropsychiatric disease and treatment, 2008. 4(5): p. 865-876.

[24] Sparks Stein, P., et al., Serum antibodies to periodontal pathogens are a risk factor for Alzheimer's disease. Alzheimer's & dementia : the journal of the Alzheimer's Association, 2012. 8(3): p. 196-203.

[25] Kamer, A.R., et al., Inflammation and Alzheimer's disease: possible role of periodontal diseases. Alzheimers Dement, 2008. 4(4): p. 242-50.

[26] Liu, T.C., et al., Increased risk of parkinsonism following chronic periodontitis: a retrospective cohort study. Mov Disord, 2013. 28(9): p. 1307-8.

[27] Dominy, S.S., et al., Porphyromonas gingivalis in Alzheimer's disease brains: Evidence for disease causation and treatment with small-molecule inhibitors. Sci Adv, 2019. 5(1): p. eaau3333.

[28] Corder, E.H., et al., Gene dose of apolipoprotein E type 4 allele and the risk of Alzheimer's disease in late onset families. Science, 1993. 261(5123): p. 921-3.

[29] James, S.L., et al., Global, regional, and national incidence, prevalence, and years lived with disability for 354 diseases and injuries for 195 countries and territories, 1990-2017: a systematic analysis for the Global Burden of Disease Study 2017. Lancet, 2018. 392(10159): p. 1789-1858.

[30] Lu Qing, Hou Riying, and Wang Yanjun, research progress on the etiology of tooth loss in the elderly at home and abroad Chinese Journal of Gerontology, 2015 35(23): p. 6950-6952.

[31] Jiang Jiapei and Wu Hongkun, effect and mechanism of tooth loss on health status of elderly people Chinese Journal of geriatric Stomatology, 2021 19(03): p. 173-176.

[32] Dan, Z., et al., Periodontal disease increases the risk for onset of systemic comorbidities in dental hospital attendees: An 18-year retrospective cohort study. Journal of periodontology, 2019. 90(3).

[33] Wang Feng, et al., Correlation between oral health status and cognitive function in the elderly Chinese Journal of Geriatrics, 2021 40(04): p. 433-437.

[34] Rajeev, R., et al., Tooth loss and dementia: An oro-neural connection. A cross-sectional study. Journal of Indian Society of Periodontology, 2019. 23(2).

[35] Mummolo, S., et al., Relationship between mastication and cognitive function in elderly in L'Aquila. Int J Clin Exp Med, 2014. 7(4): p. 1040-6.

[36] Li, J., et al., Association between tooth loss and cognitive decline: A 13-year longitudinal study of Chinese older adults. PLoS One, 2017. 12(2): p. e0171404.

[37] Da Silva, J.D., et al., Association between cognitive health and masticatory conditions: a descriptive study of the national database of the universal healthcare system in Japan. Aging (Albany NY), 2021. 13(6): p. 7943-7952.

[38] Takeuchi, K., et al., Tooth Loss and Risk of Dementia in the Community: the Hisayama Study. J Am Geriatr Soc, 2017. 65(5): p. e95-e100.

[39] Gao Wei, et al., The relationship between the number of missing teeth and cognitive impairment in the elderly in Beijing community Chinese Journal of Gerontology, 2015 13(03): p. 164-167+159.

[40] Cardoso, M.G., et al., Relationship between functional masticatory units and cognitive impairment in elderly persons. Journal of Oral Rehabilitation, 2019. 46(5): p. 417-423.

[41] Dintica, C.S., et al., The relation of poor mastication with cognition and dementia risk: a population-based longitudinal study. Aging (Albany NY), 2020. 12(9): p. 8536-8548.

[42] Yamamoto, T. and A. Hirayama, Effects of soft-diet feeding on synaptic density in the hippocampus and parietal cortex of senescence-accelerated mice. Brain Res, 2001. 902(2): p. 255-63.

[43] Weijenberg, R.A., E.J. Scherder, and F. Lobbezoo, Mastication for the mind--the relationship between mastication and cognition in ageing and dementia. Neurosci Biobehav Rev, 2011. 35(3): p. 483-97.

[44] Wilkinson, L., A. Scholey, and K. Wesnes, Chewing gum selectively improves aspects of memory in healthy volunteers. Appetite, 2002. 38(3): p. 235-6.

[45] SCHERDER, E., et al., Functional status of masticatory system, executive function and episodic memory in older persons. Journal of Oral Rehabilitation, 2008. 35(5): p. 324-336.

[46] Chuhuaicura, P., et al., Mastication as a protective factor of the cognitive decline in adults: A qualitative systematic review. International Dental Journal, 2019. 69(5).

[47] Scherder, E., et al., Functional status of masticatory system, executive function and episodic memory in older persons. J Oral Rehabil, 2008. 35(5): p. 324-36.

[48] Oki, K., et al., The impacts of prosthetic interventions on mastication predominance in Kennedy Class Ⅱ patients. J Prosthodont Res, 2021. 65(3): p. 327-331.

[49] Miyaura, K., et al., Rehabilitation of biting abilities in patients with different types of dental prostheses. J Oral Rehabil, 2000. 27(12): p. 1073-6.

[50] Shinogaya, T. and S. Toda, Rehabilitation of occlusal support by removable partial dentures with free-end saddles. Eur J Prosthodont Restor Dent, 2003. 11(3): p. 107-13.

[51] Delwel, S., et al., Chewing Efficiency, Global Cognitive Functioning, and Dentition: A Cross-sectional Observational Study in Older People With Mild Cognitive Impairment or Mild to Moderate Dementia. Front Aging Neurosci, 2020. 12: p. 225.

[52] Eichner, K., [Renewed examination of the group classification of partially edentulous arches by Eichner and application advices for studies on morbidity statistics]. Stomatol DDR, 1990. 40(8): p. 321-5.

[53] He Kun, pan Yahui, and Meng Xiangfeng, effectiveness of Eichner classification in evaluating masticatory function in patients with dentition defect Stomatology, 2017 37(11): p. 1002-1006.

[54] Huang, Y.F., et al., The impact of occluding pairs on the chewing patterns among the elderly. J Dent, 2021. 104: p. 103511.

[55] Ito, K., et al., Risk assessment of lacunar infarct associated with oral conditions: A case control study focused on radiographic bone loss and Eichner classification. J Prosthodont Res, 2022. 66(2): p. 312-317.

[56] Fushida, S., et al., Decrease in posterior occlusal support area can accelerate tooth loss: The Suita study. J Prosthodont Res, 2021. 65(3): p. 321-326.

[57] Wong, F.M.F., Y.T.Y. Ng, and W.K. Leung, Oral Health and Its Associated Factors Among Older Institutionalized Residents-A Systematic Review. International journal of environmental research and public health, 2019. 16(21): p. 4132.

[58] Rabiei, M., et al., Prevalence of oral and dental disorders in institutionalised elderly people in Rasht, Iran. Gerodontology, 2010. 27(3): p. 174-7.

[59] Marynka-Kalmani, K., et al., The lamina propria of adult human oral mucosa harbors a novel stem cell population. Stem Cells, 2010. 28(5): p. 984-95.

[60] Aragón, F., et al., Oral health in Alzheimer's disease: a multicenter case-control study. Clin Oral Investig, 2018. 22(9): p. 3061-3070.

[61] Lauritano, D., et al., Aging and Oral Care: An Observational Study of Characteristics and Prevalence of Oral Diseases in an Italian Cohort. Int J Environ Res Public Health, 2019. 16(19).

[62] Miceli, M.H., J.A. Díaz, and S.A. Lee, Emerging opportunistic yeast infections. Lancet Infect Dis, 2011. 11(2): p. 142-51.

[63] Kottmann, H.E., et al., The underestimated problem of oral Candida colonization-An observational pilot study in one nursing home. Clin Exp Dent Res, 2019. 5(6): p. 683-691.

[64] Olsen, I. and S.K. Singhrao, Can oral infection be a risk factor for Alzheimer's disease? J Oral Microbiol, 2015. 7: p. 29143.

[65] Shi, M., et al., Can Control Infections Slow Down the Progression of Alzheimer's Disease? Talking About the Role of Infections in Alzheimer's Disease. Front Aging Neurosci, 2021. 13: p. 685863.

[66] Carter, C.J., Genetic, Transcriptome, Proteomic, and Epidemiological Evidence for Blood-Brain Barrier Disruption and Polymicrobial Brain Invasion as Determinant Factors in Alzheimer's Disease. J Alzheimers Dis Rep, 2017. 1(1): p. 125-157.

[67] Pisa, D., et al., Direct visualization of fungal infection in brains from patients with Alzheimer's disease. J Alzheimers Dis, 2015. 43(2): p. 613-24.

[68] Wu, Y., et al., Microglia and amyloid precursor protein coordinate control of transient Candida cerebritis with memory deficits. Nat Commun, 2019. 10(1): p. 58.

[69] Antonio, G.-M.J., et al., Prevalence of Drug-Induced Xerostomia in Older Adults with Cognitive Impairment or Dementia: An Observational Study. Drugs & aging, 2016. 33(8).

[70] François, M., et al., Altered cytological parameters in buccal cells from individuals with mild cognitive impairment and Alzheimer's disease. Cytometry A, 2014. 85(8): p. 698-708.

[71] Garcia, A., et al., Super-resolution structure of DNA significantly differs in buccal cells of controls and Alzheimer's patients. J Cell Physiol, 2017. 232(9): p. 2387-2395.

[72] Zarrouk, A. and G. Lizard, DNA and neutral lipid contents of peripheral cells as predictive biomarkers of mild cognitive impairment and Alzheimer's disease: Highlights on the interest of a cytomic approach for the characterization of dementia. Cytometry A, 2015. 87(1): p. 3-4.

[73] Hattori, H., et al., The tau protein of oral epithelium increases in Alzheimer's disease. J Gerontol A Biol Sci Med Sci, 2002. 57(1): p. M64-70.

[74] Arredondo, L.F., et al., Tau Protein in Oral Mucosa and Cognitive State: A Cross-sectional Study. Front Neurol, 2017. 8: p. 554.

[75] Leifert, W.R., et al., Buccal Cell Cytokeratin 14 Correlates with Multiple Blood Biomarkers of Alzheimer's Disease Risk. J Alzheimers Dis, 2015. 48(2): p. 443-52.