The clinical features of the overlap between COPD and asthma

Respiratory Research

Table 1 Characteristics of COPD cases (GOLD stage 2 or greater) with and without physician-diagnosed asthma.

	COPD Only	COPD and Asthma	p-value
Total Subjects	796	119	--
Race:
Non-Hispanic white	672 (84.4)	79 (66.4)	< 0.0001
African American	124 (15.6)	40 (33.6)
Gender
Male	423 (53.1)	61 (51.3)	0.77
Female	373 (46.9)	58 (48.7)
Age, years	64.7 (8.2)	61.3 (8.9)	0.0001*
Pack-years of smoking	55.1 (27.3)	43.7 (20.7)	< 0.0001*
Current smoker	270 (34.2)	46 (38.7)	0.35
BMI kg/m²	27.8 (6.0)	28.1 (6.7)	0.87*
GOLD Stage
2	408 (51.3)	61 (51.3)	0.99**
3	251 (31.5)	38 (31.9)
4	137 (17.2)	20 (16.8)
BODE Index	3.0 (2.1)	3.2 (1.9)	0.28*
SGRQ	38.6(20.5)	44.0 (21.9)	0.0075*
6MWT (ft)	1140.2 (431.9)	1158.8 (430.1)	0.78*
Severe exacerbations	140 (17.6)	39 (32.8)	0.0003
Frequent exacerbations	114 (18.0)	41 (42.7)	< 0.0001
Hay fever	204 (27.8)	65 (57.0)	< 0.0001
Inhaled corticosteroid use	387 (49.4)	80 (69.0)	0.25***
FEV₁ % predicted	49.4 (18.4)	49.2 (17.5)	0.85*
FVC % predicted	76.6 (17.9)	78.3 (17.3)	0.23*
FEV₁/FVC	0.48 (0.13)	0.48 (0.12)	0.62*
Presence of bronchodilator response, ATS definition	270 (36.0)	46 (41.1)	0.30
Post bronchodilator % change in FEV₁	8.7 (12.1)	10.2 (12.5)	0.33*
Percent Emphysema, -950HU	15.8 (13.5)	13.7 (12.3)	0.18*
Percent gas-trapping, -856HU	42.1 (20.3)	43.1 (20.5)	0.69*
Airway wall thickness Pi10	3.78 (0.12)	3.80 (0.14)	0.34*

Values are presented as mean (SD) or N (%).
Abbreviations and definitions: COPD = chronic obstructive pulmonary disease; Hay fever = self report of a history of hay fever; BODE index = body mass index, airflow obstruction, dyspnea and exercise capacity index; SGRQ = St George's Respiratory Questionnaire; 6MWT = 6 minute walk test; Severe Exacerbations = presence of COPD exacerbation resulting in presentation to emergency room or hospital admission in year prior to presentation; Frequent exacerbations = two or more COPD exacerbations in the year prior to enrollment; FEV₁ = forced expiratory volume in 1 second; FVC = forced vital capacity; Bronchodilator response = an increase in FEV₁ of > 12% and 200 ml after administrator of bronchodilator; Pi10 = square root wall area of a hypothetical airway of 10 mm internal perimeter. Data compared using Fisher's exact test unless otherwise stated. *Wilcoxon rank sum analysis. **Chi-square analysis. ***p value adjusted for FEV₁.

ISSN: 1465-993X