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[Association between periodontitis and Alzheimer disease: a meta analysis].

PURPOSE
To evaluate the association between periodontitis and Alzheimer's disease.


METHODS
Databases of PubMed, Embase, CNKI, VIP and WanFang databases were searched for the relevant observational studies focusing on the association between periodontitis and Alzheimer's disease. The deadline was January 2019. Data quality evaluation and extraction were independently conducted by two authors. Meta analysis was performed using RevMan 5.2 software.


RESULTS
Four case-control, five cross-sectional and two cohort studies were included. One cohort study and four case-control studies treated periodontitis as the exposure factor, all five cross-sectional studies and the other cohort study treated Alzheimer's disease as the exposure factor. The results of meta analysis showed that patients with periodontitis had a higher risk of Alzheimer's disease (RR=1.22, 95%CI: 1.13-1.33, P<0.00001), and the risk was more higher in patients with severe periodontitis(RR=1.54, 95%CI:1.05-2.26, P=0.03<0.05); but there was no significant difference in the risk of Alzheimer's disease in patients with moderate periodontitis (RR=1.19, 95%CI: 0.98-1.44, P=0.07>0.05). The results of meta-analysis also showed that probing depth in patients with Alzheimer's disease was significantly higher than that of the control group (MD=2.58, 95%CI: 0.17-4.99, P=0.04<0.05), as well as clinical attachment loss (MD=1.27, 95%CI: 0.43-2.10, P=0.003<0.05), plaque index (MD=1.14, 95%CI: 0.85-1.44, P<0.00001) and the percentage of bleeding on probing (MD=21.11%, 95%CI: 18.23%-23.99%, P<0.00001). Furthermore, the number of present teeth in patients with Alzheimer's disease was significantly less than that of the control group (MD=-3.77, 95% CI: -6.89- -0.65, P=0.02<0.05).


CONCLUSIONS
The current evidence indicates that periodontitis is associated with Alzheimer's disease and patients with periodontitis (especially severe periodontitis) probably have a higher risk of developing Alzheimer's disease, and patients with Alzheimer's disease tend to have poorer periodontal health. However, the number of existing studies is limited and more clinical evidences are needed to support the correlation between these two diseases.