Periodontitis risk is influenced by multiple systemic and environmental factors. The investigators aimed to assess the combined impact of urinary nitrate levels and diabetes on the risk of severe periodontitis (stage III/IV) in a population-based sample. The stated objective was to evaluate whether urinary nitrate concentrations modify periodontitis risk overall and in subgroups defined by diabetes.
This was a cross-sectional study using data from the 2009–2014 cycles of the National Health and Nutrition Examination Survey (NHANES). The analysis included individuals aged 30 years and older. The total analytic sample comprised 3,292 participants, of whom 841 (19.28%) had stage III/IV periodontitis and 2,451 (80.72%) did not.
Urinary nitrate levels were measured and categorized into tertiles to create three exposure groups: low, median, and high concentrations. The median tertile served as the reference category for primary comparisons reported in the analysis.
The outcome evaluated was stage III/IV periodontitis. Participants were classified as having stage III/IV periodontitis or not, and these groups formed the dependent variable in logistic regression models examining associations with urinary nitrate tertiles and diabetes.
Multivariable logistic regression models were used to examine the association between urinary nitrate tertiles and the odds of stage III/IV periodontitis. Stratified analyses were performed according to diabetes status to assess subgroup-specific associations.
The multiplicative interaction between urinary nitrate levels and diabetes on periodontitis risk was tested using the likelihood ratio test. To evaluate potential nonlinearity in the relationship between urinary nitrate concentration and severe periodontitis risk in the overall population, the authors used restricted cubic splines.
In the full sample, compared with the median tertile of urinary nitrate, the high nitrate tertile was associated with increased odds of stage III/IV periodontitis (odds ratio [OR] = 1.58, 95% confidence interval [CI]: 1.12 to 2.22). The low nitrate tertile did not show a statistically significant association with periodontitis versus the median tertile (P > 0.05).
Analysis stratified by diabetes status identified differential associations:
Among participants without diabetes, high urinary nitrate levels were associated with higher odds of stage III/IV periodontitis (OR = 1.68, 95% CI: 1.16 to 2.43).
Among participants with diabetes, low urinary nitrate levels were associated with higher odds of stage III/IV periodontitis (OR = 1.66, 95% CI: 1.07 to 2.58).
The interaction between urinary nitrate levels and diabetes on the risk of stage III/IV periodontitis was statistically significant by likelihood ratio test (P = 0.020), indicating a multiplicative interaction in this dataset.
Using restricted cubic splines, the authors reported a statistically significant nonlinear relationship between urinary nitrate levels and the risk of stage III/IV periodontitis in the general population sample. The spline analysis was used to characterize that the association was not strictly linear across the measured nitrate range.
In this NHANES-based cross-sectional analysis of adults aged 30 and older, urinary nitrate concentration and diabetes exhibited a multiplicative interaction in their association with stage III/IV periodontitis risk. High urinary nitrate levels were associated with increased risk among non-diabetic participants, whereas low urinary nitrate levels were associated with increased risk among participants with diabetes. The authors suggest clinicians may need to monitor both blood glucose and urinary nitrate levels to help screen individuals at higher risk of severe periodontitis.
Note: The source abstract provides study design, sample size, effect estimates, interaction P value, and mention of nonlinear modeling. Additional methodological details (for example, specific covariates included in multivariable models, methods of diabetes classification, or urine collection/assay procedures) were not reported in the abstract portion of the source and therefore are not summarized here.