Association Between Periodontitis and Cognitive Impairment in Adults: A Systematic Review

Periodontitis is an oral inflammatory disease and may contribute to low-grade systemic inflammation. Based on the contribution of periodontitis to systemic inflammation and the potential role of systemic inflammation in neuroinflammation, many epidemiological studies have investigated a possible association between periodontitis and mild cognitive impairment or dementia. The purpose of this study was to evaluate the clinical/epidemiological evidence regarding the association between periodontitis and cognitive decline in adult patients. A search conducted between September and October 2018 was performed in the electronic databases PubMed, Scopus, Web of Science, The Cochrane Library, LILACS, OpenGrey, and Google Scholar, with no publication date or language restrictions. Analytical observational studies in adults (P—Participants), with (E—Exposure) and without periodontitis (C—Comparison) were included in order to determine the association between periodontitis and cognitive decline (O—Outcome). The search identified 509 references, of which eight observational studies were accorded with the eligibility criteria and evaluated. The results should, however, be interpreted cautiously due to the limited number of studies. This systematic review points to the need for further well-designed studies, such as longitudinal observational studies with control of modifiable variables, as diagnostic criteria and time since diagnosis of periodontitis and cognitive impairment, to confirm the proposed association.

Introduction

As life expectancy has increased and the elderly population has grown, there has been an increase in the prevalence of age-related diseases, as well as mild cognitive impairment (MCI) (1–5). The MCI is a pathological cognitive state with potential progression to dementia, resulting in social and health sequelae (6). According to the World Health Organization (WHO), the number of people living with dementia is expected to triple, from 50 to 152 million by 2050, which is alarming as it is one of the leading causes of mortality and disability in elderly adults (7, 8).

Given the increasing prevalence of age-related diseases, investigating modifiable risk factors for dementia is an essential objective for developing preventative strategies. The known risk factors for dementia include age, presence of apolipoprotein E allele (9), family history and schooling (10–13). Chronic inflammation has also been identified as a risk factor on this disease (14–16).

Periodontitis is a chronic inflammatory and infectious disease of multifactorial etiology, which affects the protective and support tissue of teeth, the periodontium (17). This is the most prevalent disease in the oral cavity, as well as dental caries (18, 19). Studies have proposed that periodontitis induces chronic systemic inflammation, which stimulates the production of inflammatory cytokines, among them interleukin 1β (IL-1β), interleukin 6 (IL-6) and tumor necrosis factor-alpha (TNF-α), and contributes to an increase in the neuroinflammatory response (20–24).

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https://www.frontiersin.org/articles/10.3389/fneur.2019.00323/full