Is COPD worse in people who also have asthma?
Smokers with COPD who had asthma earlier in life had similar lung function to those with COPD alone but worse quality of life and far more frequent flare-ups.
Source
The clinical features of the overlap between COPD and asthma
Study at a glance
- Design
- Cross-sectional — Cross-sectional comparison within the multicentre COPDGene study of COPD patients (GOLD 2-4) with versus without physician-diagnosed asthma before age 40, adjusted for age, sex, race and pack-years.
- N
- N=915 · 915 COPD subjects with asthma history available (119 with asthma, rest COPD only), from the first 2500 COPDGene participants; a secondary analysis without the age limit included 1026.
- Population
- Non-Hispanic white and African American current or former smokers aged 45-80 with at least 10 pack-years and GOLD stage 2-4 COPD, from 21 US centres
- Outcome
- Respiratory exacerbations in the prior year, St George's Respiratory Questionnaire quality of life, BODE index, spirometry, six-minute walk and chest CT emphysema, gas trapping and airway wall measures
Structured fields used in claim comparison tables when every cited study has a complete layer.
What they did
Using data from the first 2500 participants of COPDGene, a large US study of smokers, the researchers selected 915 people with moderate to very severe COPD. They compared the 119 who reported a doctor's diagnosis of asthma before age 40 with those who had COPD alone. Groups were compared on flare-ups (exacerbations) in the previous year, a respiratory quality-of-life questionnaire, lung function tests, a six-minute walk, and CT-scan measures of emphysema, air trapping and airway walls, with regression models adjusting for age, sex, race and smoking.
What they found
About 13% of the COPD group had early-onset asthma; they were younger, had smoked less and were more often African American. Despite similar lung function, walking distance and BODE scores, they had worse quality of life (about 5.2 points higher on the St George's questionnaire, a clinically meaningful difference), were nearly twice as likely to have had a severe exacerbation and more than three times as likely to be frequent exacerbators. On CT they showed more air trapping but no more emphysema, and African American race doubled the odds of having asthma alongside COPD.
The limits
What it doesn't show
Because the data are cross-sectional, the study cannot show how asthma and COPD interact over time or whether asthma causes the more severe course. Asthma was defined by self-report of a past doctor's diagnosis, which can be mistaken, and exacerbations were recalled for the prior year rather than tracked prospectively. Participants had not stopped their inhalers before spirometry, which may have hidden differences in bronchodilator response, and the sample was restricted to heavy smokers who were white or African American, so it may not generalise to other groups.
Key terms
- COPD
- Chronic obstructive pulmonary disease: a long-term lung disease, usually caused by smoking, in which airflow out of the lungs is persistently limited.
- Asthma-COPD overlap
- Patients who have features or diagnoses of both asthma and COPD, a group often excluded from trials of either disease.
- Exacerbation
- A flare-up of respiratory symptoms that needs extra treatment such as steroids, antibiotics or a hospital visit; frequent exacerbators have two or more a year.
- St George's Respiratory Questionnaire (SGRQ)
- A questionnaire measuring health-related quality of life in lung disease, where higher scores mean worse quality of life.
- Gas trapping
- Air that stays in the lungs after breathing out, seen on expiratory CT scans and thought to reflect small-airway disease.
- GOLD stage
- A grading of COPD severity based on how much the forced expiratory volume in the first second of a hard breath out (FEV1) is reduced.
Flashcards
0 of 10 answers reviewed
Research intelligence for this paper
See its role on concept claims, tensions it is part of, placement history, and related discoveries.
Quiz yourself
What fraction of the COPD subjects reported asthma diagnosed before age 40?
Common questions
If lung function was the same, why did the overlap group do worse?
Spirometry measures airflow limitation but not how often the airways become inflamed. The overlap group had more exacerbations and more air trapping, suggesting that airway inflammation and small-airway disease, rather than emphysema, drive their worse symptoms.
Why did the researchers only count asthma diagnosed before age 40?
Restricting to early-onset asthma makes it more likely that the asthma came before the COPD and was not a mislabelled COPD symptom; a secondary analysis without this limit gave consistent results.
What should clinicians do differently based on this study?
The authors suggest that COPD patients with a history of asthma should be recognised as a higher-risk group and managed with a focus on preventing exacerbations.
More on Respiratory medicine