A Mendelian randomization study on the association of bone mineral density with periodontitis

Objective: Observational studies indicated that individuals with osteoporosis could be at an increased risk of periodontitis. This study aimed to investigate whether there is a causal association of bone mineral density (BMD) with periodontitis using Mendelian randomization (MR). Materials and Methods: Summary statistics were sourced from genome--wide association study on BMD measured at different skeletal sites, including estimated heel BMD (eBMD, N = 426,824), forearm BMD (FA-BMD, N = 8143), femoral neck BMD (FN-BMD, N = 32,735), and lumbar spine BMD (LS-BMD, N = 28,498). Genetic variants of periodontitis (N = 45,563) and loose teeth (N = 461,031) were used as outcome surrogates. Inverse variance weighted meta-analysis (IVW) was adopted as main analyses. Other sensitivity MR approaches were used to boost power and account for pleiotropy. Results: IVW results suggested no evidence for a causal association of any phenotypes of BMD with periodontitis (eBMD, odds ratio [OR] = 0.984, 95% confidence interval [CI] = 0.885--1.083; FA--BMD, OR = 1.028, 95% CI = 0.864--1.193; FN--BMD, OR = 1.033, 95%CI = 0.896--1.169; LS--BMD, OR = 0.991, 95%CI =0.878--1.103; all P > 0.65). Such null associations were consistent through other sensitivity MR approaches. Similarly, no significant causal effects of BMD on loose teeth were found. Conclusions: Within the limitation of the study, our MR estimates suggested that a decreased BMD is unlikely to substantially increase the risk of periodontitis.