Associations between dietary inflammatory potential and COPD: the mediating role of inflammation

Background Chronic obstructive pulmonary disease (COPD) continues to pose a significant global burden, which may be exacerbated by pro-inflammatory diets. This study aimed to investigate the association between the Dietary Inflammatory Index (DII) and the Energy-adjusted Dietary Inflammatory Index (E-DII) and the risk of COPD. Methods A total of 167,440 participants were recruited for a prospective analysis from the UK Biobank. Cox proportional hazards models were employed to analyze the associations of DII and E-DII with COPD. Restricted cubic spline (RCS) and subgroup analyses were also performed. Additionally, mediation analyses were conducted to explore the potential mediating role of inflammatory biomarkers between DII, E-DII and COPD risk. Results During a median follow-up of 13.4 years, 4,041 COPD cases occurred. After adjusting for covariates, each unit increase in DII and E-DII was associated with a 5% [HR: 1.05 (95% CI: 1.04–1.07)] and 20% [HR: 1.20 (95% CI: 1.16–1.25)] higher risk of COPD. Participants in the highest quartile of DII and E-DII scores had a higher risk of COPD compared to those in the lowest quartile, with HR = 1.27 (95% CI: 1.17–1.39) and HR = 1.42 (95% CI: 1.30–1.55). In mediation analyses, C-reactive protein (CRP) showed the highest proportion mediated for both DII and E-DII, followed by systemic immune-inflammation index (SII). Subgroup analyses indicated population heterogeneity, and sensitivity analyses confirmed the robustness of the findings. Conclusion Both DII and E-DII are associated with an increased risk of COPD, and this association may be partially explained by systemic inflammation, particularly CRP and SII.