COPD and asthma

In the past, asthma and COPD were thought to represent clearly distinguishable diseases: asthma was seen as a treatment-responsive and reversible inflammatory process, while COPD has been characterised by fixed and progressive airway narrowing and alveolar destruction not responsive to treatment. Current definitions emphasise these features as the classical form of each disease, but acknowledge that there can be significant overlap between asthma and COPD.^{1,3, 6-8}

• In COPD, some factors contributing to airflow limitation might be amenable to drug treatment - while in asthma, a degree of irreversible airflow limitation can occur in response to poorly controlled inflammation.⁹
• In some patients, airway disease meets diagnostic criteria for both asthma and COPD.
• Some experts consider that asthma and COPD represent different outcomes of a similar pathological process.
• An individual patient's clinical features might be determined by multiple factors including genetic predisposition, the specific type of damage, environmental factors and age.

In practice, it is useful to distinguish between the diagnoses of asthma and COPD in each individual patient's case, because there are important differences between the optimal management for each of these conditions.

Prevalence

Chronic obstructive pulmonary disease occurs almost exclusively in adults, and prevalence increases with age.¹⁰

• Approximately 50% of all smokers develop some airflow limitation, and 15%-20% will develop clinically significant disability.¹
• Approximately 9%-12% of people over 45 years old have symptomatic COPD^11,12
• The number of people with unacknowledged symptoms of chronic, poorly reversible airflow limitation has been estimated to be at least two to three times higher than the number of those with diagnosed COPD.^13,14

Risk factors

Tobacco smoking is the most important risk factor for COPD.

Other risk factors include:

• exposure to environmental tobacco smoke
• exposure to dusts and chemicals in the workplace
• exposure to indoor biomass fuel smoke in people from some traditional cultures
• a strong family history of COPD
• recurrent respiratory infections in childhood
• atopy
• alpha-1-antitrypsin deficiency (uncommon).

The possibility of COPD should be considered in:

• all patients with any other smoking-related disease
• all smokers and ex-smokers over 35 years old.

Content Created (Thursday, 16 November 2006)