Plasma levels of immune system activation markers Neopterin and Kynurenine-to-Tryptophan Ratio, and oral health among community-dwelling adults in Norway: a population-based, cohort study.

Objective: Periodontitis is a condition characterised by inflammation. Neopterin and kynurenine-to-tryptophan ratio (KTR) are markers of immune system activation in response to inflammation whose elevated levels are linked to higher incidence and poorer prognosis of various systemic diseases. Their potential association with oral health remains underexplored. The aim of this study was to prospectively investigate the associations between these biomarkers and periodontal health status among community-dwelling adults in Hordaland County, Norway.

Materials and methods: Neopterin and KTR were measured in 1,298 participants of the Hordaland Health Study, 1997-1999. Information on oral health indicators was obtained from the 'Hordaland-Oral Health Survey', 2020-2022. Ordinal logistic regression and negative binomial regression were used to explore the association between biomarkers and periodontitis, tooth loss, and current inflammation (extend of sites with pocket depth ≥4mm and bleeding on probing) and odds ratios (OR) and incidence rate ratios (IRR), along with respective 95% confidence intervals (CI) were reported.

Results: No association was found between biomarker levels and periodontitis [neopterin: OR = 0.96, 95% CI: 0.69-1.33 for fourth (Q4) vs. first quartile (Q1); KTR: OR = 0.85, 95% CI: 0.61-1.18 for Q4 vs. Q1], tooth loss [neopterin: IRR = 1.00, 95% CI: 0.94-1.06 for Q4 vs. Q1; KTR: IRR = 0.97, 95% CI: 0.91-1.03 for Q4 vs. Q1) or extend of inflammation [neopterin: OR = 0.87, 95% CI: 0.70-1.09 for Q4 vs. Q1; KTR: OR = 0.98, 95% CI: 0.78-1.23 for Q4 vs. Q1].

Conclusion: Plasma levels of neopterin and KTR were not prospectively associated with periodontal health and number of missing teeth.