Low-grade systemic inflammation is linked with chronic diseases. Periodontitis, diet quality, and obesity are associated with systemic inflammation, yet their simultaneous association with salivary or serum markers of inflammation remains unexplored. This thesis aimed to evaluate their association with inflammation in the oral cavity and with serum C-reactive protein (CRP) concentration.

This study was based on the subsamples from three population-based surveys conducted by the National Institute for Health and Welfare: the DILGOM study (n = 584), the Health 2000 survey (n = 165), and participants attending Health 2000 and Health 2011 surveys (n = 3434). The periodontal status was assessed by a salivary-based Cumulative Risk Score (DILGOM study) and by clinical examination (Health 2000 study). Dietary habits were collected with a food frequency questionnaire. The Dietary Inflammatory Index (DII) was used to analyze the diet’s inflammatory potential and the Baltic Sea Diet Score to assess the adherence to the Baltic Sea diet. Key outcome variables included salivary cytokines (e.g. interleukin [IL]-1, IL-6, IL-10) and serum CRP concentration.

Periodontal status was associated with the concentrations of most salivary cytokines, whereas obesity was associated with higher IL-6 levels in participants with worse periodontal status and lower TNF- and IL-10 levels in participants with non-periodontitis. Association between DII and salivary cytokines was not found. Serum CRP was higher in participants with advanced periodontitis, also when combined with the index of diet quality. In addition, advanced periodontitis combined with non-adherence to the Baltic Sea diet increased the odds of having serum CRP  2mg/l after 11 years, but this disappeared after adjusting for confounding factors.

In conclusion, salivary cytokines were mainly associated with periodontal status but less with obesity and not at all with diet. An association also existed between periodontitis and serum CRP, and this association was stronger than with diet and serum CRP. A slight synergistic association of diet and periodontitis existed with serum CRP, which remained significant even after 11 years.