What is the difference between bronchitis and asthma?

Distinguishing Bronchitis from Asthma

Bronchitis is a self-limited acute respiratory infection lasting less than 3 weeks, while asthma is a chronic inflammatory disorder characterized by reversible airflow obstruction, bronchial hyperresponsiveness, and underlying airway inflammation that persists over time. 1

Key Diagnostic Distinctions

Temporal Pattern

• Acute bronchitis presents as an isolated episode of cough with or without sputum production lasting no more than 3 weeks, and the diagnosis should only be made after ruling out pneumonia, common cold, acute asthma, or COPD exacerbation 1
• Asthma manifests as recurrent episodes of coughing (particularly at night or early morning), wheezing, breathlessness, and chest tightness that occur repeatedly over time 1
• Patients with two or more similar episodes of "acute bronchitis" within 5 years have a 65% likelihood of actually having mild asthma that was misdiagnosed 1, 2

Pathophysiology

• Bronchitis involves acute inflammation of the bronchial airways, typically viral in origin (>90% of cases), without the chronic inflammatory cascade or bronchial remodeling seen in asthma 3
• Asthma is characterized by chronic airway inflammation involving mast cells, eosinophils, T lymphocytes, and epithelial cells, leading to bronchial hyperresponsiveness, airway edema, mucus hypersecretion, and eventual airway remodeling with sub-basement fibrosis and smooth muscle hypertrophy 1

Clinical Presentation

• Bronchitis typically presents with constitutional symptoms (fever, muscle aches, fatigue) alongside cough, often accompanied by upper airway symptoms like nasal discharge and sore throat 1
• Asthma demonstrates variable and reversible airflow obstruction with exaggerated bronchoconstrictor responses to various stimuli (allergens, irritants, exercise, cold air) 1
• Approximately one-third of patients presenting with acute cough are misdiagnosed with acute bronchitis when they actually have acute asthma 1, 2

Critical Diagnostic Pitfalls

The Recurrence Pattern

• Do not assume repeated episodes of "bronchitis" represent multiple infections—this pattern strongly suggests underlying asthma that requires chronic management rather than episodic treatment 1, 2
• The only reliable diagnostic tool is prospective evaluation to determine whether the episode is isolated (bronchitis) or part of a recurring pattern (likely asthma) 1

Duration Matters

• If cough persists beyond 3 weeks, acute bronchitis is no longer the diagnosis, and other conditions must be considered including asthma, upper airway cough syndrome, gastroesophageal reflux disease, or postinfectious cough 1
• At 8 weeks duration, the cough transitions from subacute to chronic, requiring systematic evaluation for asthma as a primary consideration 2

Reversibility Testing

• Asthma demonstrates reversible airflow obstruction that responds to bronchodilators, whereas bronchitis does not show this characteristic pattern of reversibility 1
• Spirometry showing bronchodilator responsiveness or bronchial hyperresponsiveness on methacholine challenge testing supports asthma diagnosis 2

Overlapping Features That Complicate Diagnosis

Bronchial Hyperresponsiveness

• Approximately 40% of previously healthy individuals develop transient bronchial hyperresponsiveness after acute respiratory infections, though this typically resolves within 6 weeks 2
• Chronic bronchitis patients can demonstrate bronchial hyperreactivity and respond to bronchodilators, creating diagnostic confusion with asthma 4, 5

Inflammatory Patterns

• While asthma classically involves eosinophilic inflammation, exacerbations of both asthma and bronchitis can show increased neutrophilia, making inflammatory patterns similar during acute episodes 6
• The presence of airway inflammation may be the common link between airflow obstruction and hyperreactivity in both conditions 4

Practical Clinical Approach

Initial Assessment

• Obtain chest radiograph to exclude pneumonia, which fundamentally changes management from bronchitis 1, 3
• Assess for characteristic asthma features: nocturnal or early morning symptoms, exercise-induced symptoms, seasonal variation, family history of atopy 1
• Document whether this is a first episode or recurrent pattern 1, 2

When to Suspect Asthma Instead of Bronchitis

• History of two or more similar episodes in the past 5 years 1, 2
• Symptoms predominantly at night or early morning 1
• Presence of wheezing, particularly if recurrent 1
• Symptoms triggered by specific exposures (allergens, exercise, cold air) 1
• Family history of asthma or allergic diseases 1

Management Implications

• Bronchitis requires only symptomatic treatment; routine antibiotics are NOT recommended for immunocompetent adults 3
• Asthma requires chronic anti-inflammatory treatment with inhaled corticosteroids as the cornerstone of therapy, not just bronchodilators 1
• Continuous bronchodilator treatment without anti-inflammatory therapy in patients with underlying asthma accelerates decline in lung function 7