Periodontal disease and the risk of Alzheimer's disease and mild cognitive impairment: a systematic review and meta-analysis

Background Results of studies on the association between periodontal disease (PD) and Alzheimer's disease (AD) or mild cognitive impairment (MCI) are inconsistent, and a previous meta-analysis published in 2017 included inadequate studies and is thus outmoded. This study aims to systematically evaluate the correlation between PD and the risk of AD or MCI. Methods The following electronic databases were screened by two investigators independently, without restriction of language: CENTRAL (Cochrane library), PubMed (MEDLINE), EMBASE, China National Knowledge Interne, China Science and Technology Journal Database, Wanfang Data, www.ClinicalTrials.gov, and WHO International Clinical Trials Registry Platform. Meta-analysis was conducted using random-effects model or fixed-effects model according to the heterogeneity of included studies. Results Thirteen eligible studies, of which eight reported AD (291 114 participants) and eight reported MCI (4805 participants), were included in this meta-analysis. The pooled results showed that compared with the non-PD population, the risk of AD and MCI in PD patients was significantly higher (for AD: odds ratio (OR) = 1.78, 95% CI 1.15-2.76; for MCI: OR = 1.60, 95% CI 1.24-2.06), and especially in those with severe PD (for AD: OR = 4.89, 95% CI 1.60-14.97; for MCI, OR = 2.32, 95% CI 1.24-4.36). Conclusions This meta-analysis indicated that PD was related to an elevated risk of AD and cognitive impairment, and that it should receive early intervention.