TABLE 2.
Summary of the systematic review and meta‐analyses
Author, year | Research question or objective | Database searched | Search period | Language | Study design of included studies | Meta‐analysis | Heterogeneity | Risk of bias assessment tools | Publication bias | Main results | Main conclusion | Reference |
---|---|---|---|---|---|---|---|---|---|---|---|---|
Alakhali et al, 2018 | Is periodontal disease a potential risk factor for nonalcoholic fatty liver disease? | PubMed/MEDLINE, Scopus, Embase and Web of Science | Up to May 30, 2018 | English | 9 cross‐sectional studies, 1 cohort study, 1 case‐control study, and 1 case report | No | High (value was not reported) | Strengthening of Reporting of Observational studies in Epidemiology–based quality analysis | Not mentioned | All studies except one found significant associations between clinical and/or microbial periodontal parameters and nonalcoholic fatty liver disease | Periodontitis may be a risk factor for development and progression of nonalcoholic fatty liver disease | 26 |
Wijarnpreecha et al, 2020 | To compare the risk of nonalcoholic fatty liver disease among patients with periodontitis versus individuals without periodontitis, by identifying all relevant studies and combining their results together | Ovid MEDLINE and EMBASE | Up to December 2019 | No limitation | 1 cohort study and 4 cross‐sectional studies | Yes |
Based on periodontal probing depth: high for unadjusted odds ratio (I 2 = 94%, P < 0.00001) moderate for adjusted odds ratio (I 2 = 67%, P = 0.02) Based on clinical attachment level: not significant for unadjusted odds ratio (I 2 = 0%, P = 0.88) moderate for adjusted odds ratio (I 2 = 58%, P = 0.09) |
Newcastle‐Ottawa quality assessment scale for cohort studies and case‐control studies Modified version of Newcastle‐Ottawa quality assessment scale for cross‐sectional studies |
No evidence |
When periodontal probing depth >3.5‐4 mm was used as independent variable, pooled unadjusted odds ratio of 1.48 (95% confidence interval: 1.15‐1.89) decreased to 1.13 (95% confidence interval: 0.95‐1.35) and lost its significance. When clinical attachment level >3 mm was used as independent variable, pooled unadjusted odds ratio of 1.13 (95% confidence interval: 1.07‐1.20) deceased to 1.08 (95% confidence interval: 0.94‐1.24) and lost significance |
Metabolic conditions, not periodontitis itself, were the predisposing factor for nonalcoholic fatty liver disease | 28 |
Chen et al, 2020 | To evaluate whether periodontal disease and tooth loss are associated with liver disease, including nonalcoholic fatty liver disease, liver cirrhosis, liver cancer and other chronic liver disease | PubMed and Embase | Up to March 2020 | Not mentioned |
Association between periodontitis and nonalcoholic fatty liver disease: 3 cross‐sectional studies and 2 cohort studies Association between periodontitis and elevated transaminase level: 2 cohort studies |
Yes |
Association between periodontitis and nonalcoholic fatty liver disease: Not significant (I 2 = 48.5%, P = 0.10) Association between periodontitis and elevated transaminase level: not significant (I 2 = 0%, P = 0.37) |
Not mentioned | No evidence | Positive associations between periodontal disease and nonalcoholic fatty liver disease (odds ratio 1.19, 95% confidence interval: 1.06‐1.33), and elevated transaminase level (odds ratio 1.08, 95% confidence interval: 1.02‐1.15) | There are positive associations between periodontal disease and nonalcoholic fatty liver disease risk | 27 |