Periodontal Disease,tooth Loss,and Gastric Cancer Risk: A Meta-analysis

Background: Nowadays,Gastric cancer is one of the major malignant tumors in the world.There are nearly 1 million cases of newly diagnosed gastric cancer around the world every year,occupying the forefront of newly diagnosis and mortality of malignant tumor.Whether in developed countries or in developing countries,gastric cancers have caused serious public health and economic burden.Although the global mortality of gastric cancer is decreasing slowly,but in China,the morbidity and mortality of gastric cancer is still high.Among them,the incidence of male was higher than that of female,and the incidence rate in rural area was higher than that in city.Gastric cancer is a multifactor disease,which is harmful to human physical and mental health.Oral cavity as the first channel between the external environment and the gastrointestinal tract,food through the mouth into the gastrointestinal tract,oral flora is bound to the food follow into the gastrointestinal tract,while the gastrointestinal tract is the place where food digestion.Therefore,the gum bag may be having some parasitic bacteria such as Helicobacter pylori,these microorganisms through the mouth into the stomach,and in the stomach,it can cause stomach tissue proliferation,the cells produce inflammation,even become carcinoma.There may be some correlation between oral flora and gastrointestinal flora;oral bacteria may affect the survival of gastrointestinal flora,which may affect the development of cancer or other chronic diseases.The tooth is an important part of mastication system.Teeth lost will affect chewing food,nutrient absorption,and change the way of diet.These factors may be related to the occurrence and development of gastric cancer.Objectives: Using the method of Cochrane systematic review and meta-analysis,we aimed to assess the association between periodontal disease,tooth loss and gastric cancer.Methods: We searched Cochrane Library(~2016.12),PubMed(~2016.12),and EMBASE(~ 2016.12).All of observational studies about the relationship between periodontal disease,tooth loss and gastric cancer were searched.We also checked reference lists of all eligible papers.Two reviewers independently extracted data from the selected studies by using a standardized extraction form,and assessed the risk of bias with confirmation of cross-check.Different opinions were resolved through discussion or the third investigator.Statistical analysis was performed using the R software which provided by the R program site(http://www.r-project.org).The evaluation system of periodontal disease,tooth loss and gastric cancer associated with the following indicators: relative risk(RR),Odds Ratio(OR),Hazard Ratio(HR),and its 95% confidence interval(CI).Results: The Meta analysis included 10 articles,involving 14 studies in the literature.There are 5 studies about the relationship between periodontal disease and gastric cancer,and 9 studies about relationship between the loss of teeth and gastric cancer.Because of the differences between the studies,this Meta-analysis has many limitations.The results of Meta-analysis are as follow:(1)for the correlation between periodontal disease and gastric cancer,we used the fixed effect model combined the OR,the combined OR was [OR=1.01,95%CI(0.84-1.22);P = 0.9006].(2)The lowest and highest categories of missing teeth were collected,we used random effect model to consolidate the RR to estimation the risk,and the pooled RR value(RR = 1.34,95% CI = 1.18-1.53;P = 0.001).(3)About the correlation between tooth loss and gastric cancer,it is more obvious in Asian population(RR = 1.37;CI = 95%,1.20-1.57)than in the United States population(RR = 0.96;CI = 95% 0.56-1.64)and Europe(RR = 1.30;CI = 95% 0.75-2.27)(4)for gastric cancer in different anatomical sites.We used the fixed effects model,and the result show that cardiac cancer was 0.95(95% CI = 0.65-1.38)and non cardiac gastric cancer 1.71(95% CI = 1.17-2.50)(5)the sensitivity analysis showed that the Meta-analysis results of stability.Conclusions: According to the results of the Meta analysis,the current evidence is not obviously about the relationship between periodontal disease and the occurrence and development of gastric cancer;but the statistical data analysis results show that a large number of teeth loss may increase the possibility of gastric cancer,especially may increase the occurrence of gastric non-cardia cancer.The conclusion is(1)suffering from periodontal disease does not increase the risk of gastric cancer.There's no significant correlation between the periodontal disease and gastric cancer;(2)the risk of gastric cancer increased with missing teeth in the patients from Asian;(3)the incidence of gastric cancer risk is not significantly increased in the patients with tooth loss in Europe and America;(4)patients with teeth missing may have high risk of gastric non-cardia cancer,although gastric cardiac cancer is not obvious.Due to the current number of clinical research on the correlation between periodontal disease,tooth loss and gastric cancer,a few patients was eligible in this Meta-analysis,the different standards between layered of the studies and adjusted for confounding factors,may had cause some bias,the Meta-analysis has many limitations.Therefore,it's badly in need of a large sample,high quality prospective cohort study in the future,to explore the correlation between periodontal disease,tooth loss and the occurrence and development of gastric cancer.