['Periodontitis is considered to promote atherosclerosis and cardiovascular diseases through increased low-grade systemic inflammation. However, there is no information on the long-term impact of periodontitis on systemic inflammation from cohort studies. Thus, this study aims to assess the impact of periodontitis on systemic inflammation (fibrinogen and white blood cells (WBC)) in a population-based longitudinal survey in north-eastern Germany.', 'The study sample comprised 2622 subjects from the Study of Health in Pomerania with complete 5- and 11-year follow-ups. Periodontitis was assessed by probing depth and clinical attachment level. Multilevel regression analyses were applied to evaluate associations between periodontitis measures and i) fibrinogen/WBC count using 11-year follow-up data and ii) respective z-scores of fibrinogen/WBC count using 5- and 11-year follow-up data. We adjusted for common cardiovascular risk factors and stratified analyses by abdominal obesity (P for interaction <0.10).', 'In lean subjects, beta-coefficients of mean probing depth were B\xa0=\xa00.13 (0.08-0.019; P\xa0<\xa00.001) for fibrinogen and B\xa0=\xa00.50 (0.37-0.64; P\xa0<\xa00.001) for WBC count using 11-year follow-up data only. For lean subjects, models using z-scores confirmed that increased mean probing depths were associated with increased fibrinogen z-scores (B\xa0=\xa00.14 (0.09-0.18; P\xa0<\xa00.001)) and increased WBC z-scores (B\xa0=\xa00.16 (0.11-0.20; P\xa0<\xa00.001)). Consistent results were found for mean clinical attachment levels. For abdominally obese subjects, relations between periodontitis measures and levels of inflammation markers were less pronounced or non-significant.'] Does abdominal obesity modify long-term associations between periodontitis and markers of systemic inflammation?