Phenotyping asthma with airflow obstruction in middle-aged and older adults: a CADSET clinical research collaboration.

Background: The prevalence and clinical profile of asthma with airflow obstruction (AO) remain uncertain. We aimed to phenotype AO in population- and clinic-based cohorts.
Methods: This cross-sectional multicohort study included adults ≥50 years from nine CADSET cohorts with spirometry data (N=69 789). AO was defined as ever diagnosed asthma with pre-BD or post-BD FEV ₁ /FVC <0.7 in population-based and clinic-based cohorts, respectively. Clinical characteristics and comorbidities of AO were compared with asthma without airflow obstruction (asthma-only) and chronic obstructive pulmonary disease (COPD) without asthma history (COPD-only). ORs for comorbidities adjusted for age, sex, smoking status and body mass index (BMI) were meta-analysed using a random effects model.
Results: The prevalence of AO was 2.1% (95% CI 2.0% to 2.2%) in population-based, 21.1% (95% CI 18.6% to 23.8%) in asthma-based and 16.9% (95% CI 15.8% to 17.9%) in COPD-based cohorts. AO patients had more often clinically relevant dyspnoea (modified Medical Research Council score ≥2) than asthma-only (+14.4 and +14.7 percentage points) and COPD-only (+24.0 and +5.0 percentage points) in population-based and clinic-based cohorts, respectively. AO patients had more often elevated blood eosinophil counts (>300 cells/µL), although only significant in population-based cohorts. Compared with asthma-only, AO patients were more often men, current smokers, with a lower BMI, had less often obesity and had more often chronic bronchitis. Compared with COPD-only, AO patients were younger, less often current smokers and had less pack-years. In the general population, AO patients had a higher risk of coronary artery disease than asthma-only and COPD-only (OR=2.09 (95% CI 1.26 to 3.47) and OR=1.89 (95% CI 1.10 to 3.24), respectively) and of depression (OR=1.41 (95% CI 1.19 to 1.67)), osteoporosis (OR=2.30 (95% CI 1.43 to 3.72)) and gastro-oesophageal reflux disease (OR=1.68 (95% CI 1.06 to 2.68)) than COPD-only, independent of age, sex, smoking status and BMI.
Conclusions: AO is a relatively prevalent respiratory phenotype associated with more dyspnoea and a higher risk of coronary artery disease and elevated blood eosinophil counts in the general population compared with both asthma-only and COPD-only.
Competing Interests: Competing interests: LL reports consulting fees from AstraZeneca and speaking/lecture fees from Chiesi and IPSA (non-profit) outside the submitted work. CHV reports presentations at symposia and/or served on scientific advisory boards sponsored by Aerogen, AstraZeneca, Boehringer Ingelheim, CSL Behring, Chiesi, GlaxoSmithKline, Grifols, Insmed, Menarini, Novartis, Nuvaira, MedUpdate, Sanofi and Roche outside the submitted work. AA reports grants from GSK, AstraZeneca and Menarini and speaking/lecture fees from GSK, AstraZeneca, Chiesi, Menarini, CIPLA, Zambon, and Sanofi Regeneron outside the submitted work, and is chair of the GOLD board of directors. JAW reports grants from AstraZeneca, Boehringer-Ingelheim, Chiesi, GSK, Novartis, Genentech, and 37Clinical, advisory board fees from AstraZeneca, Epiendo, GSK, Gilead, Novartis, Pieris and Pulmatrix, speaker fees from AstraZeneca, GSK, Boehringer, Recipharm and Novartis, and DSMB chair for Virtus outside the submitted work, and is Editor in Chief of AJRCCM. GGB reports fees for advisory boards and/or lectures from AstraZeneca, Boehringer-Ingelheim, Chiesi, GSK, Merck Sharp & Dohme, Novartis, and Sanofi Regeneron outside the submitted work. HB reports personal fees from AstraZeneca, Boehringer Ingelheim, and GlaxoSmithKline for presentations at scientific meetings outside the submitted work. AL reports speaking/lecture fees from Boehringer-Ingelheim and Novartis, and participation on a advisory board for AstraZeneca, GSK, Novartis, and Boehringer-Ingelheim outside the submitted work. KFC reports advisory board fees from GSK, AstraZeneca, Roche, Novartis, Merck, Nocion, Shionogi and Rickett-Beckinson and has been renumerated for speaking engagements for GSK, AstraZeneca and Merck outside the submitted work. IMA reports investigator-led awards from GSK and Sanofi in addition to travel awards, speakers' fees and advisory board fees from AZ, Chiesi, GSK, Eurodrug, Kineset, Sanofi and Sunovion outside the submitted work. None declared (XB, AE, JG-A, RF, HM, TS, PA, NO, NZK, GCD, ER, JMV and MvdB).
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