**Background:** Periodontitis is a chronic inflammatory disease affecting over half the world's population and is associated with cardiovascular disease, cancer, and respiratory disease. Serum lipids have been shown to influence periodontitis severity, with lipid-mediated inflammatory responses playing a key role. The atherogenic index of plasma (AIP), calculated as log10(triglycerides/HDL-C), is considered a more effective cardiovascular disease marker than traditional lipid measures. This study aimed to investigate the association between periodontitis and AIP in a large nationally representative sample of U.S. adults.
**Methods:** This cross-sectional analysis used data from the 2009–2014 NHANES cycles. From 30,468 total participants, 26,097 were excluded due to missing AIP data (n=20,975), missing periodontitis classification (n=4,524), or missing covariate data (income, marriage, education, smoking, drinking, BMI), leaving 4,371 participants. Periodontitis was classified using CDC-AAP definitions into no, mild, moderate, and severe categories. AIP was calculated as log10(triglycerides/HDL-C) and categorized into quartiles (Q1: -1.093 to -0.266; Q2: -0.266 to -0.049; Q3: -0.049 to 0.178; Q4: 0.178 to 1.698). Covariates included age, sex, BMI, ethnicity, annual family income, education, smoking, and alcohol consumption. Multivariable logistic regression and stratified analyses were performed. Statistical significance was set at P=0.05.
**Key Results:** The final sample included 4,371 participants (50.1% male, 49.9% female), aged 30–80 years, representing approximately 60 million U.S. adults. Periodontitis prevalence was 50% (4% mild, 35% moderate, 11% severe). AIP ranged from -1.09 to 1.70 (median -0.05). Baseline characteristics showed significant differences across AIP quartiles for age (P=0.05), sex (P<0.0001), BMI (P<0.0001), ethnicity (P<0.0001), annual family income (P=0.002), education (P<0.0001), smoking (P<0.0001), drinking (P<0.0001), and periodontitis (P=0.002). Univariate logistic regression showed AIP was significantly associated with periodontitis presence: Q2 OR 1.36 (95% CI 1.07–1.74, P=0.01), Q3 OR 1.60 (95% CI 1.24–2.06, P<0.001), Q4 OR 1.64 (95% CI 1.26–2.14, P<0.001) compared to Q1. AIP was not associated with periodontitis severity (all P>0.05). In multifactorial logistic regression adjusting for all covariates (Model 3), the association between periodontitis and AIP was no longer significant (trend P=0.341). Stratified analyses revealed significant associations in never-smokers (trend P<0.001), females (trend P=0.003), age 30–40 (trend P=0.003) and 40–50 (trend P<0.001) groups, and BMI ≤25 (trend P=0.01) and 25–30 (trend P=0.01) groups. After full adjustment in non-smoking participants, the association remained significant (Model 3: trend P=0.031), with Q4 showing OR 1.672 (95% CI 1.066–2.624, P=0.027) compared to Q1.
**Clinical Implications:** This study found that the association between AIP and periodontitis is confounded by smoking status. In non-smoking adults, higher AIP is significantly associated with increased odds of periodontitis, suggesting that dyslipidemia may be an independent risk factor for periodontal disease in this subgroup. The findings support screening for periodontitis in non-smoking patients with elevated AIP and suggest that lipid management could potentially benefit periodontal health. However, due to the cross-sectional design, causal relationships cannot be established. Limitations include inability to exclude confounding from diabetes, hypertension, and other lipid-affecting conditions, and the need for further investigation into mechanisms underlying the smoking interaction.