The Association between Periodontitis and Nonalcoholic Fatty Liver Disease: A Systematic Review and Meta-analysis

Background and Aims: Recent studies have suggested an association between periodontitis and nonalcoholic fatty liver disease (NAFLD) although the results were inconsistent. The current systematic review and meta- analysis was conducted with the aim to comprehensively investigate this possible association by identifying all relevant studies and combining their results together. Methods: A comprehensive literature review was conducted utilizing the MEDLINE and EMBASE databases through December 2019 to identify all studies that compared the risk of NAFLD among patients with periodontitis to individuals without periodontitis. Effect estimates from each study were extracted and combined using the random-effect, generic inverse variance method of DerSimonian and Laird. Results: A total of five studies with 27,703 participants fulfilled the eligibility criteria and were included in the meta-analysis. All five studies reported the magnitude of association between NAFLD and periodontitis that was diagnosed based on the periodontal pocket depth of > 3.5-4 mm. The pooled OR of unadjusted analysis was 1.48 (95%CI: 1.15-1.89; I 2 92%). However, when adjusted results from the primary studies were used, pooled OR decreased to 1.13 and lost its statistical significance (95%CI: 0.95–1.35; I 2 67%). Three studies reported the magnitude of association between NAFLD and periodontitis that was diagnosed based on a clinical attachment level of ≥ 3 mm. The pooled OR of unadjusted analysis was 1.13 (95%CI: 1.07-1.20; I 2 0%). However, when adjusted results from the primary studied were used, pooled OR decreased to 1.08 and lost its statistical significance (95%CI: 0.94–1.24; I 2 58%). Conclusions: The study found a significant association between periodontitis and NAFLD. However, the association lost its significance when various metabolic parameters were adjusted, suggesting that those metabolic conditions, not periodontitis itself, were predisposing factors for NAFLD.