Accelerated epigenetic ageing worsens survival and mediates environmental stressors in fibrotic interstitial lung disease

Background The role of epigenetic ageing in the environmental pathogenesis and prognosis of fibrotic interstitial lung disease (fILD) is unclear. We evaluated whether ambient particulate matter with diameter ≤2.5 μm (PM 2.5 ) and neighbourhood disadvantage exposures are associated with accelerated epigenetic ageing, and whether epigenetic age is associated with adverse clinical outcomes in patients with fILD. Methods This multicentre, international, cohort study included patients with fILD from the University of Pittsburgh (UPitt, n=306) and University of British Columbia (UBC, n=170). 5-year PM 2.5 exposures were estimated using satellite-derived hybrid models. Neighbourhood disadvantage was calculated using US and Canadian census-based metrics. Epigenetic age difference (EAD=epigenetic age−chronological age) was calculated using GrimAge analysis of blood DNA methylation data. Linear models assessed associations of exposures with EAD. Cox models assessed associations of EAD with transplant-free survival. Causal mediation analysis evaluated EAD mediation of exposure–survival relationships. Results Median epigenetic age was 11.7 years older than chronological age in patients with fILD. In combined cohort analysis, each interquartile range (IQR) increase in PM 2.5 was associated with 2.88 years (95% CI 1.39–4.38; p<0.001) increased EAD. In UPitt, each IQR neighbourhood disadvantage increase was associated with 1.16 years (95% CI 0.22–2.09; p=0.02) increased EAD. Increased EAD was associated with worse transplant-free survival (hazard ratio 1.17 per 1-year increase in EAD, 95% CI 1.10–1.24; p<0.001), with EAD mediating 40% of the PM 2.5 –survival relationship and 59% of the neighbourhood disadvantage–survival relationship. Epigenetic age was also more strongly associated with transplant-free survival than chronological age. Conclusions Epigenetic age acceleration is associated with worse survival and mediates adverse exposure impacts in fILD.