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. 2021 Aug 31;87(1):204–240. doi: 10.1111/prd.12387

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