Rheumatoid arthritis (RA) and chronic obstructive pulmonary disease (COPD) have a significant bidirectional association, which is partially mediated by systemic inflammation, according to study findings published in Rheumatology.
Researchers explored whether a longitudinal reciprocal association existed between RA and COPD and the potential role of systemic inflammation in this association. The findings are based on an analysis of middle-aged and elderly adults from the UK Biobank (UKB).
The longitudinal association between RA and COPD was evaluated via a cross-lagged panel model and multivariable Cox proportional hazard regression and logistic regression models. Potential inflammatory mechanisms underlying the association between RA and COPD were analyzed by causal mediation analysis. A total of 160 inflammatory cells and inflammatory factors were identified as possible mediators.
The study cohort included 403,045 participants with complete data, of whom 4755 were diagnosed with RA (1.2%; 53% aged ≥60 years; 67% female), 6989 were diagnosed COPD (1.7%; 64% aged ≥60 years; 45% female), and 391,525 were without RA and COPD at baseline (97%; 40% aged ≥60 years; 52% female).
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Systemic inflammation in RA patients partially mediates their high risk of developing COPD, and the higher level of CRP in COPD patients increases incident RA.
Patients who had RA at baseline were more likely to have COPD at follow-up (β1 =0.018, P <.001), after adjustment for covariates. COPD at baseline also was a risk factor for RA at follow-up (β2 =0.010, P <.001).
Of the participants who did not have COPD at baseline, 1.1% were diagnosed with RA. In this group, the difference in COPD incidence between participants with and without RA was statistically significant in comparable follow-up periods (9.1% vs 3.5%). COPD risk also was increased in patients with RA after adjustment for all confounders (Cox model: hazard ratio [HR], 1.65; 95% CI, 1.50-1.83; logistic model: odds ratio [OR], 1.85; 95% CI, 1.66-2.07).
Among participants without RA at baseline, COPD prevalence was 1.7%. The incidence of RA among patients with COPD was 3.2%, which was significantly increased compared with that in individuals without COPD (1.1%). After adjustment, baseline COPD was associated with an increased risk of RA at follow-up (Cox model: HR, 1.67; 95% CI, 1.44-1.92; logistic model: OR, 1.70; 95% CI, 1.47-1.97).
Baseline RA and later occurrence of COPD were mediated by 5 inflammatory factors after controlling for multiple testing (false discovery rate <0.05). C-reactive protein mediated 7.83% of the association in the COPD to RA path.
In citing study limitations, the researchers noted that RA and COPD were defined according to self-reported physician diagnosis of the diseases, which may have led to recall bias. In addition, the analysis excluded individuals lost to follow-up or who had died before they had RA or COPD, which may have led to survivor bias. Furthermore, most participants were White and were healthier and were less likely to smoke than the general population.
“The findings support the bidirectional link between RA and COPD,” stated the study authors. “Systemic inflammation in RA patients partially mediates their high risk of developing COPD, and the higher level of CRP in COPD patients increases incident RA. These findings emphasize the necessity of early screening and proactive management of RA and COPD to prevent comorbidities in a timely manner.”
