A subgroup analysis for smoking and periodontal status found that smokers with chronic periodontitis exhibited significantly higher levels of sIgA [98] and lower plasma OPG concentrations (P = 0.007) but higher sRANKL/OPG ratio (P = 0.01) than smokers without periodontitis [103]; however, smokers and nonsmokers with periodontitis exhibited similar values for plasma sIgA, sRANKL, and OPG concentrations. This evidence concerns the gene TNFRSF11B and periodontitis.