What is the difference between Chronic Obstructive Pulmonary Disease (COPD) and asthma?

Difference Between COPD and Asthma

The critical distinguishing feature is reversibility of airflow obstruction: COPD is characterized by largely irreversible airflow limitation (post-bronchodilator FEV1/FVC <0.70 with minimal reversibility), while asthma demonstrates variable and often reversible airflow limitation that responds significantly to bronchodilators or corticosteroids. 1, 2

Key Distinguishing Features

Airflow Limitation Pattern

• COPD: Chronic airflow limitation that progresses slowly over years and is, by definition, largely irreversible 1
• Asthma: Variable airflow limitation that is often reversible either spontaneously or with therapy, with marked improvement on spirometry with bronchodilators or glucocorticosteroids 2

Age of Onset and Risk Factors

• COPD: Typically develops after age 40 in patients with significant smoking history or occupational exposures 2
• Asthma: May begin at any age, often in childhood, and is often associated with atopy and allergic conditions 2

Primary Etiology

• COPD: The single most important cause is cigarette smoking, which dominates all other aetiological factors 1
• Asthma: Often associated with airway hyperresponsiveness to various stimuli, atopy, and allergic conditions 2

Pathophysiological Differences

Anatomic Site and Structural Changes

• COPD: Predominantly affects small airways, with emphysema on imaging and decreased diffusing capacity common 2
• Asthma: Reticular basement membrane thickening is a prominent feature 3

Inflammatory Patterns

• COPD: Characterized by bronchoalveolar lavage (BAL) neutrophilia and CD8+ T-cytotoxic lymphocyte infiltrations in the airway wall 3
• Asthma: Cellular infiltration with eosinophils and CD4+ T-helper lymphocytes are prominent features, with eosinophilic inflammation pattern in adult asthma 3, 1

Clinical Presentation Differences

Symptom Characteristics

• COPD: Progressive dyspnea during physical exertion in early stages and at rest in later stages, with chronic productive cough 4
• Asthma: Paroxysmal dyspnea with shortness of breath, often dry cough mainly at night, frequently associated with allergies 4

Disease Progression

• COPD: Progressive disease with FEV1 decline of approximately 70 ml per year, with 10-year survival of about 30% in community surveys 1
• Asthma: It is possible to live with asthma into old age with appropriate management 4

Important Clinical Caveats

Diagnostic Challenges

• The presence or absence of cough and sputum, wheeze at any time of day or night, a partial response to bronchodilators, or a family history of chest disease are unhelpful in differentiating between chronic asthma and COPD 1
• Differentiation of severe COPD from chronic severe asthma is difficult since some degree of improvement in FEV1 (reversibility) can often be produced by bronchodilator therapy 1

Asthma-COPD Overlap

• Approximately 20% of patients with obstructive airways diseases have features of both conditions 1
• These patients have the highest risk of mortality (HR 1.45), followed by COPD alone (HR 1.28) and asthma alone (HR 1.04) 1
• Overlap is diagnosed when a patient has the defining characteristic of COPD (incompletely reversible airflow limitation) as well as features of asthma 1

Treatment Implications

COPD Treatment Approach

• First-line therapy with long-acting bronchodilators (LAMAs or LABAs) 2
• Add inhaled corticosteroids only for patients with frequent exacerbations despite optimal bronchodilator therapy, blood or sputum eosinophilia, or features of asthma-COPD overlap 2

Asthma Treatment Approach

• First-line therapy with inhaled corticosteroids (ICS) as controller medication, with short-acting beta-agonists as needed for symptom relief 2
• ICS/LABA combination for persistent symptoms 2

Critical Treatment Distinction

• Tiotropium (a LAMA) is not indicated to treat asthma, as the safety and effectiveness in asthma have not been established 5