Background: The pathogenesis of periodontitis may be related to host-mediated inflammatory and immune responses caused by accumulation of oral microbial plaque. Nutrients have anti-inflammatory and pro-inflammatory capabilities. Dietary intake of antioxidants and micronutrients is associated with the inflammatory burden of the diet. The Composite Dietary Antioxidant Index (CDAI) is a composite index for assessing the antioxidant properties of a diet, and the relationship with periodontitis is unclear. The aim of this study was to investigate the relationship between periodontitis and CDAI.

Method and materials: The study was a cross-sectional design and included 7,471 participants from the National Health and Nutrition Examination Survey (NHANES) 2009 to 2014 database. Participants were divided into experimental and control groups according to the relevant criteria, where the control group consisted of participants with no/mild periodontitis (including 3,646 participants) and the experimental group consisted of participants with moderate/severe periodontitis (including 3,825 participants). First, baseline characteristics of the two groups of participants were compared. Weighted logistic regression analyses was used to explore the relationship between periodontitis and CDAI. The linear relationship between the two was assessed using restricted cubic spline. Finally, subgroup analyses were used to assess model stability.

Results: Differences between the two groups of participants were statistically significant in age, sex, race, education, ratio of household income to poverty, body mass index, smoking status, drinking status, and prevalence of diabetes. CDAI, as a continuous variable, was not found to be significantly associated with periodontitis. The CDAI was converted to categorical variables according to quartile. In model 1, participants in the second and third quartile groups had a lower risk of developing periodontitis compared with participants in the lowest quartile group (OR [95% CI] 0.810 [0.681, 0.963], P = .021; OR [95% CI] 0.811 [0.691, 0.951], P = .014; respectively). In model 2, participants in the second, third, and fourth quartile groups had a lower risk of developing periodontitis compared to the lowest quartile group (OR [95% CI] 0.803 [0.660, 0.978], P = .0349; OR [95% CI] 0.753 [0.632, 0.897], P = .003; OR [95% CI] 0.753 [0.617, 0.920], P = .008; respectively). There was a non-linear relationship between CDAI and periodontitis (P non-linearity = .0055), with the inflection point occurring at a CDAI equal to 0.6342.

Conclusion: There is a nonlinear relationship between CDAI and periodontitis in US adults. However, further prospective studies are still needed to validate the results.