Lung Function Decline in COPD - Relations to Changes in Symptom Burden, Inflammation, and Comorbidities.

Purpose: The study aims to improve the knowledge on the associations between comorbidities, symptom burden, inflammatory biomarkers and lung function deterioration in chronic obstructive pulmonary disease (COPD).

Materials and methods: Of the 572 COPD subjects initially included in the 2014-2016 Tools for Identifying Exacerbations in COPD study in Sweden, 228 had lung function data at the 7-year follow-up. Symptom burden was assessed by the modified British Medical Research Council scale of dyspnoea (mMRC), the COPD Assessment Test (CAT) and the Clinical COPD Questionnaire (CCQ). Relative lung function decline was assessed as decline in forced expiratory volume in one second (FEV₁) from baseline/year.

Results: Lower baseline symptom burden (mMRC, CAT and CCQ), higher FEV₁ and FEV₁% predicted, higher forced vital capacity (FVC) and having atrial fibrillation were associated with larger absolute FEV₁ decline. Associations were found for having atrial fibrillation at baseline and larger relative FEV₁ decline (Beta = -1.60, p = 0.005). Increased symptom burden (value at follow-up minus value at baseline), assessed by mMRC, CAT and CCQ, was positively associated with both larger absolute FEV₁ decline (mMRC: Beta = 6.4, p = 0.009; CAT: Beta = 1.63, p = 0.002; CCQ: Beta = 10.6, p < 0.001) and larger relative FEV₁ decline (mMRC: Beta = 0.44, p = 0.003; CAT: Beta = 0.13, p < 0.002; CCQ: Beta = 0.82, p < 0.001). Moreover, an increase in C-reactive protein (CRP) levels at follow-up was related to larger, both absolute and relative, FEV₁ decline (Beta = 1.14, p = 0.031 and Beta = 0.07, p = 0.019, respectively).

Conclusions: Changes in systemic inflammation and symptom burden between two visits were positively associated with a 7-year lung function decline.