Numerous studies support a link between oral and systemic disease. Recent data also suggest that periodontal disease is a significant risk factor for Alzheimer’s disease. This paper provides an overview of Alzheimer’s disease, discusses the etiology and epidemiology of periodontal disease, and outlines several plausible mechanisms accounting for a potential association between oral disease and neurodegeneration. These mechanisms include: 1) metastatic spread of gram-negative bacteria from the oral cavity to the brain via a transient bacteremia; 2) injury to brain tissue from systemic inflammatory mediators produced in response to periodontal pathogens; 3) cerebrovascular injury to brain; 4) genetic predisposition, particularly polymorphisms within the interleukin- 1 gene family; and 5) malnutrition, weight loss, and wasting associated with periodontal disease. Understanding the role of oral disease in dementia is important: Given that there is currently no effective treatment for Alzheimer’s disease, oral disease is a potential risk factor that could be prevented.
Citation: Stein P, Scheff S, Dawson D. Alzheimer’s disease and periodontal disease: mechanisms underlying a potential bi-directional relationship. Grand Rounds Oral-Sys Med. 2006;3:14-24. (Digital version Grand Rounds Oral-Sys Med. 2006;3:14-24d.) (A complimentary copy of this article may be downloaded at www.thesystemiclink.com.)
Key Words: Periodontal disease, Alzheimer’s disease, neurodegeneration, inflammation, dementia
Introduction
All countries are experiencing an increase in the number of people over the age of 65. In the US, changing demographics suggest a much higher number of elderly in the population. 1 Periodontal disease and Alzheimer’s Disease (AD) are chronic conditions that commonly affect the elderly. Numerous cross sectional studies address the oral health status of individuals with AD and dementia. 2-13 Overall, evidence indicates that Alzheimer’s patients exhibit poor oral health, including increased plaque, bleeding, and calculus than age- and gender-matched controls. 10 While it is true that Alzheimer’s patients may be unable to adequately perform oral hygiene measures, thereby facilitating the development of periodontal disease,14 a potential exists for a bi-directional relationship. 15-17 Researchers are now investigating the role of poor oral health and periodontal disease in development of AD. In this paper we provide an overview of AD, review the epidemiology of periodontal disease, and outline biologically plausible mechanisms underlying the relationship between periodontal disease and AD.
Alzheimer’s Disease: An Overview
Alzheimer’s disease is the leading cause of dementia in the US elderly population. Other dementias include vascular dementia, dementia accompanied by Lewy bodies, frontotemporal dementia, Creutzfeldt-Jakob disease, and Parkinson’s disease. AD is a progressive dementia characterized by early short-term memory impairment. The incidence of AD within † the aging population is significant and disturbing: currently, an estimated 4. 5 million Americans have AD, and it is esti- ‡ mated that 14 million will be afflicted by 2050. Approximately 1% of the population between 65 and 69 years of age has been diagnosed with AD, and the incidence increases loga-
Assistant Professor, Anatomy and Neurobiology, University of Kentucky College of Medicine
Associate Director, Sanders-Brown Center on Aging, University of Kentucky
§ Associate Director, Delta Dental of Kentucky Clinical Research Center, Center for Oral Health Research, University of Kentucky
References:
Archives