Objective: Emerging evidence has showed that interleukin-18 (IL-8) promoter polymorphisms and plasma IL-18 levels may be associated with increased risk of periodontitis, but individually published results are inconclusive. The aim of this meta-analysis was to derive a more precise estimation of these associations.
Methods: A literature search of PubMed, Cochrane Library, Embase, Web of Science, SpringerLink, China BioMedicine and China National Knowledge Infrastructure databases was conducted on articles published before April 1st, 2013. Crude odds ratio (OR) or standardized mean difference (SMD) with 95 % confidence intervals (CI) were calculated.
Results: Nine case-control studies were included with a total of 576 periodontitis patients and 458 healthy controls. Two common polymorphisms (-607A > C and -137G>C) in the IL-18 gene were addressed. Our meta-analysis results indicated that the C variant of IL-18 -607A>C polymorphism was associated with increased periodontitis risk (C allele vs. A allele: OR = 1.86, 95 % CI: 1.30-2.65, P = 0.001; AC+CC vs. AA: OR = 2.64, 95 % CI: 1.34-5.21, P = 0.005). There was also a significant association between the C variant of IL-18 -137G>C polymorphism and an increased periodontitis risk (C allele vs. G allele: OR = 1.47, 95 % CI: 1.13-1.91, P = 0.004; GC+CC vs. GG: OR = 1.66, 95 % CI: 1.21-2.29, P = 0.002). Furthermore, the mean levels of plasma IL-18 of periodontitis patients were also higher than those of healthy controls (SMD = 1.18, 95 % CI: 0.51-1.85, P = 0.001).
Conclusion: The current meta-analysis suggests that IL-18 promoter polymorphisms and plasma IL-18 levels are associated with increased risk of periodontitis. IL-18 promoter polymorphisms and elevated plasma IL-18 levels may be useful biomarkers for predicting the development of periodontitis.