Association between Dietary Inflammatory Index and Periodontitis: A Cross-Sectional and Mediation Analysis

Inflammation-modulating elements are recognized periodontitis (PD) risk factors, nevertheless, the association between dietary inflammatory index (DII) and PD has never been appraised. We aimed to assess the association between DII and PD and the mediation effect of DII in the association of PD with systemic inflammation. Using the National Health and Nutrition Examination Survey 2009–2010, 2011–2012 and 2013–2014, participants who received periodontal exam and provided dietary recall data were included. The inflammatory potential of diet was calculated via DII. PD was defined according to the 2012 case definition. White blood cells (WBC), segmented neutrophils and C-reactive protein (CRP) were used as proxies for systemic inflammation. The periodontal measures were regressed across DII values using adjusted multivariate linear regression and adjusted mediation analysis. Overall, 10,178 participants were included. DII was significantly correlated with mean periodontal probing depth (PPD), mean clinical attachment loss (CAL), thresholds of PPD and CAL, WBC, segmented neutrophils and DII (p < 0.01). A linear regression logistic adjusted for multiple confounding variables confirmed the association between DII and mean PPD (B = 0.02, Standard Error [SE]: 0.02, p < 0.001) and CAL (B = −0.02, SE: 0.01, p < 0.001). The association of mean PPD and mean CAL with both WBC and segmented neutrophils were mediated by DII (from 2.1 to 3.5%, p < 0.001). In the 2009–2010 subset, the association of mean CAL with serum CRP was mediated by DII (52.0%, p < 0.01). Inflammatory diet and PD may be associated. Also, the inflammatory diet significantly mediated the association of leukocyte counts and systemic inflammation with PD.

Participants 6 a) Cohort study-Give the eligibility criteria, and the sources and methods of selection of participants. Describe methods of follow-up.
Case-control study-Give the eligibility criteria, and the sources and methods of case ascertainment and control selection. Give the rationale for the choice of cases and controls.
Cross-sectional study-Give the eligibility criteria, and the sources and methods of selection of participants.
(b) Cohort study-For matched studies, give matching criteria and number of exposed and unexposed.
Case-control study-For matched studies, give matching criteria and the number of controls per case.
nut-6 Report particular dietary, physiological or nutritional characteristics that were considered when selecting the target population.

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Variables 7 Clearly define all outcomes, exposures, predictors, potential confounders, and effect modifiers. Give diagnostic criteria, if applicable. nut-11 Explain categorization of dietary/nutritional data (e.g., use of N-tiles and handling of nonconsumers) and the choice of reference category, if applicable.

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Statistical Methods 12 (a) Describe all statistical methods, including those used to control for confounding (b) Describe any methods used to examine subgroups and interactions.
(c) Explain how missing data were nut-12.1 Describe any statistical method used to combine dietary or nutritional data, if applicable.

nut-12.2
Describe and justify the method for energy adjustments, intake modeling, and use of weighting factors, if applicable.

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addressed.
(d) Cohort study-If applicable, explain how loss to follow-up was addressed.
Case-control study-If applicable, explain how matching of cases and controls was addressed.
Cross-sectional study-If applicable, describe analytical methods taking account of sampling strategy.
(e) Describe any sensitivity analyses. measurement error, i.e,. from a validity or calibration study.

Results
Participants 13 (a) Report the numbers of individuals at each stage of the study-e.g., numbers potentially eligible, examined for eligibility, confirmed eligible, included in the study, completing follow-up, and analyzed.
(b) Give reasons for non-participation at each stage.
(c) Consider use of a flow diagram.
nut-13 Report the number of individuals excluded based on missing, incomplete or implausible dietary/nutritional data.

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Descriptive data 14 (a) Give characteristics of study participants (e.g., demographic, clinical, social) and information on exposures and potential population or consumers only were used to obtain results.

Outcome data 15
Cohort study-Report numbers of outcome events or summary measures over time.
Case-control study-Report numbers in each exposure category, or summary measures of exposure.
Cross-sectional study-Report numbers of outcome events or summary measures.
Make clear which confounders were adjusted for and why they were included. Other analyses 17 Report other analyses done-e.g., analyses of subgroups and interactions and sensitivity analyses.
nut-17 Report any sensitivity analysis (e.g., exclusion of misreporters or outliers) and data imputation, if applicable.

Discussion
Key results 18 Summarize key results with reference to study objectives.

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Limitation 19 Discuss limitations of the study, taking into account sources of potential bias or imprecision. Discuss both direction and magnitude of any potential bias.

nut-19
Describe the main limitations of the data sources and assessment methods used and implications for the interpretation of the findings.

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Interpretation 20 Give a cautious overall interpretation of results considering objectives, limitations, multiplicity of analyses, results from similar studies, and other relevant evidence.
nut-20 Report the nutritional relevance of the findings, given the complexity of diet or nutrition as an exposure.

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Generalizability 21 Discuss the generalizability (external validity) of the study results.

Other information
Funding 22 Give the source of funding and the role of the funders for the present study and, if applicable, for the original study on which the present article is based.

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Ethics nut-22.1 Describe the procedure for consent and study approval from ethics committee(s).