Association of Obesity with Symptoms and Quality of Life in COPD: Results from COSYCONET

Abstract

Background: Body weight plays an intricate role in COPD, as obesity can impair lung function and thus might affect COPD categorization. We asked to which extent overweight/obesity affects conventional COPD scores taking into account lung function and potential restrictive patterns (PRISm, preserved ratio and impaired spirometry). Methods: Patients of the COSYCONET cohort were included. Outcomes were the modified Medical Research Council (mMRC) questionnaire, the COPD Assessment Test (CAT), CAT question #4 (dyspnea upon exertion), the St George's Respiratory Questionnaire (SGRQ) and its domains, and the EQ-5D-VAS (EuroQoL-5-dimension) questionnaire for generic quality of life. Body mass index (BMI) was categorized into <25, >= 25 to <30, and >= 30 kg/m2. The relationship between outcomes and predictors including airway obstruction, lung hyperinflation, air trapping and CO diffusing capacity was assessed by generalized linear models in a repeated measures design. Results: Data from visits 1, 3, 4 and 5 were available in n=2478, 1855, 1291 and 944 patients, respectively, of whom 169, 132, 95 and 63 fulfilled the PRISm criterion. For mMRC, CAT total, CAT dyspnoea (#4), EQ-5D-VAS, SGRQ total, Activity and Impact, scores were higher in the upper two BMI categories compared to the lower one (p<0.05 each), without further significant dependence on PRISm or an interaction between BMI and PRISm. For SGRQ Symptoms, only the upper BMI category showed a significantly higher score. All scores depended (p<0.05 each) on lung function and exacerbation history in terms of GOLD group E. Conclusion: For common indicators of the burden from COPD, BMI played a significant role by increasing these scores even if confounders were taken into account. Compared to the lowest BMI category, there was a continuous increase with overweight and obesity. Categorization into PRISm did not influence the relationship between BMI and symptom scores. The underlying mechanisms probably involve mechanical but also systemic factors. Based on this, COPD categorizations based on the scores studied probably should consider the effects of BMI.