Asthma
Table 1: Clinical Features of Asthma and Chronic Obstructive Pulmonary Disease Overlap Syndrome Compared with Either Disease Alone
Asthma Onset
Risk factors Symptoms
Family history FEV1/FVC ratio
FEV1 % predicted Early or late COPD Mid-life
Atopy, irritants, airway hyper-responsiveness Smoking Intermittent cough, dyspnoea and wheeze, worse at night or early morning Frequently present <70 % >80 %
Bronchodilator response Present Overlap Syndrome
May have asthma early in life Smoking
May be present <70 % <80 % Absent
Slowly progressive cough and dyspnoea Slowly progressive cough and dyspnoea, intermittent worsening with wheeze May be present <70 % <80 % Partial
COPD = chronic obstructive pulmonary disease; FEV1 = forced expiratory volume in one second; FVC = forced vital capacity. Adapted with permission from Journal of Allergy and Clinical Immunology.10
emphysema and airflow obstruction and identify 11 distinct syndromes, six of which are a result of overlap between the primary syndromes (see Figure 1). Table 1 describes the clinical features of asthma, COPD and the overlap syndrome between them.10
Why is the Overlap Syndrome Important? Overlap between asthma and COPD is common. A study analysed 9,131 patients of age 40–64 years from administrative Medicaid databases and discovered that up to 16 % of patient between the ages of 50 and 64 years had concurrent diagnosis of asthma and COPD.11 In older adults, the overlap becomes even more common, as demonstrated by a study of data in the UK General Practice Research Database, which reported that combinations of two of the three conditions of asthma, chronic bronchitis and COPD were present in over 40 % of adults above 60 years of age.12
Clinicians are often confused as to how and if they should differentiate asthma from COPD.5
Both COPD and asthma remain underdiagnosed
and under treated, especially in older adults. Also, patients with overlap of asthma and COPD differ considerably from those with isolated conditions and tend to have a lower health-related quality of life.13 Ironically, however, research trials of either condition frequently exclude the patients with overlap syndrome, which makes the results of these studies less applicable to these patients. There is a growing need to address this issue and develop an integrated approach to better evaluate and treat patients with overlapping asthma and COPD.
Adult subjects with active asthma are as much as 12 times more likely to acquire COPD over time than subjects with no active asthma.14 Signs that identify patients with asthma predisposed to developing COPD may already be present at the early stages of the disease, a finding with potential implications for the prevention of COPD. Available evidence suggests that, primarily, the overlap syndrome is an inflammatory airway disease. People with asthma and incomplete reversibility show an increase in airway neutrophils, with the intensity of neutrophilia correlated with a decline in the rate of decline in lung function (as measured by forced expiratory volume in one second
[FEV1]). The numbers of eosinophils also increase significantly in people with obstructive airway diseases (including the asthma and COPD overlap syndrome) compared to those in healthy controls.5
It is
unclear how oxidative stress and protease–antiprotease balance influence the pathophysiology of people who have COPD with concomitant asthma symptoms. Regardless, the assessment of type and degree of airway remodelling and the evaluation of inflammatory markers might prove useful in the future to characterise phenotypically those patients with coexisting asthma and COPD,7
102 Asthma
Areas 6, 7 and 8 represent the asthma and chronic obstructive pulmonary disease (COPD) overlap syndromes. Reprinted with permission of the American Thoracic Society. Copyright © American Thoracic Society.9
COPD = chronic obstructive pulmonary disease.
and also help plan preventative strategies and prioritise the options in the treatment armamentarium.
Treatment Goals and Challenges
The goals of treatment of the asthma and COPD overlap syndrome are the same as those of either condition: reduce exposure to risk factors, reduce symptoms, maintain lung function and normal activity, prevent exacerbations, reduce mortality and minimise adverse effects of treatment. However, clinicians are faced with unique challenges when treating the overlap syndrome, which include:
•
The association between coexisting asthma and COPD and the proportion of each condition in each patient may be unclear.
• Although there are clear algorithms and guidelines for both asthma and COPD, there are no specific guidelines for managing the overlap syndrome.
• Owing to the lack of studies on the group of patients with coexisting asthma and COPD, the treatment is based largely on extrapolation of data derived from studies on patients with either condition alone.
•
It has not been possible to identify markers of individual susceptibility to specific risk factors, to specific disease
EUROPEAN RESPIRATORY DISEASE
Figure 1: Non-proportional Venn Diagram Showing the Number of Overlapping Syndromes in Patients with Asthma, Emphysema and Chronic Bronchitis
Chronic bronchitis
111 5
3 8 67 10 9 Airflow obstruction 2 Emphysema
4
COPD
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