The chronic bronchitic phenotype of COPD: an analysis of the COPDGene Study

Abstract

Background: Chronic bronchitis (CB) in patients with COPD is associated with an accelerated lung function decline and an increased risk of respiratory infections. Despite its clinical significance, the chronic bronchitic phenotype in COPD remains poorly defined.

Methods: We analyzed data from subjects enrolled in the Genetic Epidemiology of COPD (COPDGene) Study. A total of 1,061 subjects with GOLD (Global Initiative for Chronic Obstructive Lung Disease) stage II to IV were divided into two groups: CB (CB+) if subjects noted chronic cough and phlegm production for ≥ 3 mo/y for 2 consecutive years, and no CB (CB-) if they did not.

Results: There were 290 and 771 subjects in the CB+ and CB- groups, respectively. Despite similar lung function, the CB+ group was younger (62.8 ± 8.4 vs 64.6 ± 8.4 years, P = .002), smoked more (57 ± 30 vs 52 ± 25 pack-years, P = .006), and had more current smokers (48% vs 27%, P < .0001). A greater percentage of the CB+ group reported nasal and ocular symptoms, wheezing, and nocturnal awakenings secondary to cough and dyspnea. History of exacerbations was higher in the CB+ group (1.21 ± 1.62 vs 0.63 ± 1.12 per patient, P < .027), and more patients in the CB+ group reported a history of severe exacerbations (26.6% vs 20.0%, P = .024). There was no difference in percent emphysema or percent gas trapping, but the CB+ group had a higher mean percent segmental airway wall area (63.2% ± 2.9% vs 62.6% ± 3.1%, P = .013).

Conclusions: CB in patients with COPD is associated with worse respiratory symptoms and higher risk of exacerbations. This group may need more directed therapy targeting chronic mucus production and smoking cessation not only to improve symptoms but also to reduce risk, improve quality of life, and improve outcomes.

Trial registry: ClinicalTrials.gov; No.: NCT00608764; URL: www.clinicaltrials.gov.

Figure 1.

Dyspnea, quality of life, and BODE index in each group. A, MMRC scores. B, SGRQ scores. C, BODE index scores. MMRC scores, SGRQ scores, and BODE index scores in the CB+ group were significantly higher than in the CB− group. Data are presented as median (interquartile range). *P < .0001. †P = .033. BODE = BMI, airway obstruction, dyspnea, exercise capacity; CB = chronic bronchitis; MMRC = Modified Medical Research Council; SGRQ = St. George Respiratory Questionnaire.

Figure 2.

Exacerbation rate in each group. A, Total exacerbation rate. B, History of severe exacerbations. Both total exacerbation rate (data are presented as mean ± SE) and history of severe exacerbations were significantly greater in the CB+ group than in the CB− group. *P < .0001. †P = .0238. pt = patient. See Figure 1 legend for expansion of other abbreviation.