Obesity Is Associated With Increased Morbidity in Moderate to Severe COPD

Abstract

Background: Obesity is prevalent in the United States; however, the impact of obesity on COPD morbidity is unclear. We hypothesized that obesity is associated with worse outcomes in COPD.

Methods: We examined 3,631 participants from the multicenter prospective cohort study Genetic Epidemiology of COPD (COPDGene) who had spirometry-confirmed COPD, a postbronchodilator FEV₁ < 80% predicted, and a BMI ≥ 18.5 kg/m². We conducted logistic and linear regression analyses to determine the association between COPD outcomes and obesity class, adjusting for relevant confounders. The referent for obesity classes included normal/overweight individuals (BMI range, 18.5-29.9 kg/m²).

Results: Overall, 35% of participants were obese, with 21% class I (BMI range, 30-34.9 kg/m²), 9% class II (BMI range, 35-39.9 kg/m²), and 5% class III (BMI ≥ 40 kg/m²). The number of comorbidities increased with increasing obesity class (P < .001). Increasing obesity class was independently associated with worse respiratory-specific and general quality of life (QOL) (St. George's Respiratory Questionnaire score and Short Form-36 score version 2, respectively), reduced 6-min walk distance (6MWD), increased dyspnea (Modified Medical Research Council score ≥ 2), and greater odds of severe acute exacerbation of COPD (AECOPD). The associations between obesity and worse outcomes were independent of the presence of comorbidities, except in the case of SF-36 and severe exacerbations.

Conclusions: Obesity is prevalent among individuals with COPD and associated with worse COPD-related outcomes, ranging from QOL and dyspnea to 6MWD and severe AECOPD. These associations were strengthened when obesity was analyzed as a dose-dependent response. Obesity in patients with COPD may contribute to a worse COPD-related course.

Keywords: COPD; dose response; exacerbation; morbidity; obesity.

Figure 1

A, B, Dose-dependent response to higher obesity class. Adjusted for age, sex, race, education, FEV₁ to height squared ratio, smoking status, and smoking pack-y. Referent in all models includes normal/overweight individuals (BMI range, 18.5-29.9 kg/m²). Markers represent the adjusted β coefficients (A) or adjusted ORs (B) for the association between each obesity class and the specified outcome. Bars represent the 95% CIs for each β coefficient (A) or OR (Panel B). The P values for trend represent the statistical significance of the increase or decrease in the outcome across obesity classes. 6MWD = 6-min walk distance; AECOPD = acute exacerbation of COPD; mMRC = Modified Medical Research Council; SF-36, Short Form-36; SGRQ, St. George’s Respiratory Questionnaire.