Inflammation and epigenetic ageing are largely independent markers of biological ageing and mortality.

Limited evidence exists on the link between inflammation and epigenetic ageing. We aimed to 1) assess the cross-sectional and prospective associations of 22 inflammation-related plasma markers and a signature of inflammaging with epigenetic ageing; 2) determine whether epigenetic ageing and inflammaging are independently associated with mortality. Blood samples from 940 participants in the Melbourne Collaborative Cohort Study, collected at baseline (1990-1994) and follow-up (2003-2007) were assayed for DNA methylation and 22 inflammation-related markers, including well-established markers (e.g., interleukins and C-reactive protein) and metabolites of the tryptophan-kynurenine pathway. Four measures of epigenetic ageing (PhenoAge, GrimAge, DunedinPoAm and Zhang) and a signature of inflammaging were considered, adjusted for age, and transformed to Z-scores. Associations were assessed using linear regression, and mortality hazard ratios (HR) and 95% confidence intervals (95%CI) were estimated using Cox regression. Cross-sectionally, most inflammation-related markers were associated with epigenetic ageing measures, although with generally modest effect sizes (regression coefficients per SD≤0.26) and explaining altogether between 1% and 11% of their variation. Prospectively, baseline inflammation-related markers were not, or only weakly, associated with epigenetic ageing after 11 years of follow-up. Epigenetic ageing and inflammaging were strongly and independently associated with mortality, e.g. inflammaging: HR=1.41, 95%CI=1.27-1.56, P=2x10-10; which was only slightly attenuated after adjustment for four epigenetic ageing measures: HR=1.35, 95%CI=1.22-1.51, P=7x10-9). Although cross-sectionally associated with epigenetic ageing, inflammation-related markers accounted for a modest proportion of its variation. Inflammaging and epigenetic ageing are essentially non-overlapping markers of biological ageing and may be used jointly to predict mortality.