Distinguishing adult-onset asthma from COPD: a review and a new approach

Abstract

Adult-onset asthma and chronic obstructive pulmonary disease (COPD) are major public health burdens. This review presents a comprehensive synopsis of their epidemiology, pathophysiology, and clinical presentations; describes how they can be distinguished; and considers both established and proposed new approaches to their management. Both adult-onset asthma and COPD are complex diseases arising from gene-environment interactions. Early life exposures such as childhood infections, smoke, obesity, and allergy influence adult-onset asthma. While the established environmental risk factors for COPD are adult tobacco and biomass smoke, there is emerging evidence that some childhood exposures such as maternal smoking and infections may cause COPD. Asthma has been characterized predominantly by Type 2 helper T cell (Th2) cytokine-mediated eosinophilic airway inflammation associated with airway hyperresponsiveness. In established COPD, the inflammatory cell infiltrate in small airways comprises predominantly neutrophils and cytotoxic T cells (CD8 positive lymphocytes). Parenchymal destruction (emphysema) in COPD is associated with loss of lung tissue elasticity, and small airways collapse during exhalation. The precise definition of chronic airflow limitation is affected by age; a fixed cut-off of forced expiratory volume in 1 second/forced vital capacity leads to overdiagnosis of COPD in the elderly. Traditional approaches to distinguishing between asthma and COPD have highlighted age of onset, variability of symptoms, reversibility of airflow limitation, and atopy. Each of these is associated with error due to overlap and convergence of clinical characteristics. The management of chronic stable asthma and COPD is similarly convergent. New approaches to the management of obstructive airway diseases in adults have been proposed based on inflammometry and also multidimensional assessment, which focuses on the four domains of the airways, comorbidity, self-management, and risk factors. Short-acting beta-agonists provide effective symptom relief in airway diseases. Inhalers combining a long-acting beta-agonist and corticosteroid are now widely used for both asthma and COPD. Written action plans are a cornerstone of asthma management although evidence for self-management in COPD is less compelling. The current management of chronic asthma in adults is based on achieving and maintaining control through step-up and step-down approaches, but further trials of back-titration in COPD are required before a similar approach can be endorsed. Long-acting inhaled anticholinergic medications are particularly useful in COPD. Other distinctive features of management include pulmonary rehabilitation, home oxygen, and end of life care.

Keywords: adults; chronic obstructive pulmonary disease; diagnosis; inflammometry; management.

Figure 1

Airway inflammation phenotypes present in sputum from asthma and COPD patients. Notes: (A) Neutrophilic airway inflammation. (B) Eosinophilic airway inflammation. (C) Paucigranulocytic airway inflammation. (D) Mixed neutrophilic/eosinophilic inflammation.

Figure 2

Model of disease components and individualized treatment approach. Note: Reprinted from The Lancet, 376, Gibson PG, McDonald VM, Marks GB, Asthma in older adults, 803–813, Copyright 2010, with permission from Elsevier.

Figure 3

Stepped approach to adjusting asthma medication in adults. Notes: Copyright © 2014 National Asthma Council Australia. Adapted from: Figure: Stepped approach to adjusting asthma medication in adults (Asset ID 31); National Asthma Council Australia. Australian Asthma Handbook, Version 1.0. National Asthma Council Australia, Melbourne, 2014. Available from: http://www.asthmahandbook.org.au. ^†, Montelukast can be added to inhaled corticosteroid as an alternative to switching to ICS/LABA, but is less effective. *, Reliever: Short-acting beta2 agonist (or low-dose budesonide/eformoterol combination for patients using this combination as both maintenance and reliever). §, in addition, manage flare-ups with extra treatment when they occur, and manage exercise-related asthma symptoms as indicated. Abbreviations: ICS, inhaled corticosteroids; LABA, long-acting beta-agonist; SABA, short-acting beta-agonist.

Figure 4

Stepwise management of Stable COPD. Note: Copyright © 2012. Stepwise Management of Stable COPD. Reproduced with permission from the publisher, Lung Foundation Australia. Please visit www.copdx.org.au for the current version. Abbreviations: COPD, chronic obstructive pulmonary disease; COPD-X, Confirm diagnosis, Optimise function, Prevent deterioration, Develop support, manage eXacerbations; FEV₁, forced expiratory volume in 1 second; GP, general practitioner; ICS, inhaled corticosteroids; LABA, long-acting beta-agonist.