Date Published:
2017Abstract:
BACKGROUND: Obesity is increasingly associated with COPD, but little is known about the prevalence of ectopic fat accumulation in COPD and whether this can possibly be associated with poor clinical outcomes and comorbidities. The Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints (ECLIPSE) substudy tested the hypothesis that COPD is associated with increased ectopic fat accumulation and that this would be associated with COPD-related outcomes and comorbidities.
METHODS: Computed tomography (CT) images of the thorax obtained in ECLIPSE were used to quantify ectopic fat accumulation at L2-L3 (eg, cross-sectional area [CSA] of visceral adipose tissue [VAT] and muscle tissue [MT] attenuation, a reflection of muscle fat infiltration) and CSA of MT. A dose-response relationship between CSA of VAT, MT attenuation and CSA of MT and COPD-related outcomes (6-minute walking distance [6MWD], exacerbation rate, quality of life, and forced expiratory volume in 1 second [FEV] decline) was addressed with the Cochran-Armitage trend test. Regression models were used to investigate possible relationships between CT body composition indices and comorbidities.
RESULTS: From the entire ECLIPSE cohort, we identified 585 subjects with valid CT images at L2-L3 to assess body composition. CSA of VAT was increased (<0.0001) and MT attenuation was reduced (indicating more muscle fat accumulation) in patients with COPD (<0.002). Progressively increasing CSA of VAT was not associated with adverse clinical outcomes. The probability of exhibiting low 6MWD and accelerated FEV decline increased with progressively decreasing MT attenuation and CSA of MT. In COPD, the probability of having diabetes (=0.024) and gastroesophageal reflux (=0.0048) at baseline increased in parallel with VAT accumulation, while the predicted MT attenuation increased the probability of cardiovascular comorbidities (=0.042). Body composition parameters did not correlate with coronary artery scores or with survival.
CONCLUSION: Ectopic fat accumulation is increased in COPD, and this was associated with relevant clinical outcomes and comorbidities.