Feature
Asthma
COPD
ACOS
Age of onset
Usually childhood onset but can commence at any age.
Usually > 40 years of age
Usually age ≥40 years, but may have had symptoms in childhood or early adulthood
Pattern of respiratory symptoms
Symptoms may vary over time (day to day, or over longer periods), often limiting activity. Often triggered by exercise, emotions including laughter, dust or exposure to allergens
Chronic usually continuous symptoms, particularly during exercise, with ‘better’ and ‘worse’ days
Respiratory symptoms including exertional dyspnea are persistent but variability may be prominent
Lung function
Current and/or historical variable airflow limitation, e.g. BD reversibility, AHR
FEV1 may be improved by therapy, but post-BD FEV1/FVC < 0.7 persists
Airflow limitation not fully reversible, but often with current or historical variability
Lung function between symptoms
May be normal between symptoms
Persistent airflow limitation
Persistent airflow limitation
Past history or family history
Many patients have allergies and a personal history of asthma in childhood, and/or family history of asthma
History of exposure to noxious particles and gases (mainly tobacco smoking and biomass fuels)
Frequently a history of doctor- diagnosed asthma (current or previous), allergies and a family history of asthma, and/or a history of noxious exposures
Time course
Often improves spontaneously or with treatment, but may result in fixed airflow limitation
Generally, slowly progressive over years despite treatment
Symptoms are partly but significantly reduced by treatment. Progression is usual and treatment needs are high
Chest X-ray
Usually normal
Severe hyperinflation & other changes of COPD
Similar to COPD
Exacerbations
Exacerbations occur, but the risk of exacerbations can be considerably reduced by treatment
Exacerbations can be reduced by treatment. If present, comorbidities contribute to impairment
Exacerbations may be more common than in COPD but are reduced by treatment. Comorbidities can contribute to impairment
Airway inflammation
Eosinophils and/or neutrophils
Neutrophils ± eosinophils in sputum, lymphocytes in airways, may have systemic inflammation
Eosinophils and/or neutrophils in sputum.
Table 16.2
Features that if present favor asthma or COPD
More likely to be asthma if several of …a | More likely to be COPD if several of…a |
|---|---|
□ Onset before age 20 years | □ Onset after age 40 years |
□ Variation in symptoms over minutes, hours or days | □ Persistence of symptoms despite treatment |
□ Symptoms worse during the night or early morning | □ Good and bad days but always daily symptoms and exertional dyspnea |
□ Symptoms triggered by exercise, emotions including laughter, dust or exposure to allergens | □ Chronic cough and sputum preceded onset of dyspnea, unrelated to triggers |
□ Record of variable airflow limitation (spirometry, peak flow) | □ Record of persistent airflow limitation (post-bronchodilator FEV 1 /FVC < 0.7) |
□ Lung function normal between symptoms | □ Lung function abnormal between symptoms |
□ Previous doctor diagnosis of asthma | □ Previous doctor diagnosis of COPD, chronic bronchitis or emphysema |
□ Family history of asthma, and other allergic conditions (allergic rhinitis or eczema) | □ Heavy exposure to a risk factor: tobacco smoke, biomass fuels |
□ No worsening of symptoms over time. Symptoms vary either seasonally, or from year to year | □ Symptoms slowly worsening over time (progressive course over years) |
□ May improve spontaneously or have an immediate response to BD or to ICS over weeks | □ Rapid-acting bronchodilator treatment provides only limited relief. |
□ Normal | □ Severe hyperinflation |
16.3 Epidemiology of ACOS
In elderly patients, it is not easy to accurately diagnose ACOS, because of the confounding influence of airway remodeling due to aging, long-term illness, etc. In an epidemiological study based on a population survey, the incidences of asthma, COPD, and ACOS were reported to be 2 %, 8.4 %, and 0.9 %, respectively [18], and according to reports based on the International Statistical Classification of Diseases and Related Health Problems (ICD10), the incidence was in the range of approximately 0.9–16.1 % [19–21]. Thus, the results of epidemiological studies are varied. The incidence tends to be higher in patients referred to specialists on account of possible difficulty in management. According to a cohort study by Cosio BG et al. [22], 15 % of 831 patients with COPD had ACOS, and in a study by Hardin M et al. [23], 13 % of 915 patients with COPD had ACOS. A review of the literature revealed that 12.1–55.2 % of patients with COPD had ACOS [24]. Furthermore, according to a publication by the GINA [11], 15 % of patients with COPD have ACOS. In general, approximately 10–20 % of patients with COPD are thought to have an asthmatic component [25]. The incidence is higher in elderly patients: it has been reported that approximately a half of all COPD patients aged 65 years or older have ACOS [26].
On the other hand, patients diagnosed as having asthma appear to develop irreversible airflow obstruction, namely, COPD, with age, because approximately 5 % have severe asthma and some are smokers. Milanese M et al. [27] reported that 29 % of 350 asthmatic patients aged 65 years or older had COPD. According to another report, 13.3–61.0 % of all asthmatic patients had ACOS [24, 28]. In humans, lung growth continues until early adulthood and is completed by the age of 30 years. Lung volume increases and pulmonary function measured in terms of the forced expiratory volume in 1.0 s (FEV1) is maintained. Even normal individuals show progressive airway obstruction with time, i.e., the FEV1 deceases by 25–50 mL each year even during early adulthood. The FEV1 has been shown to decrease by 80 and 150 mL per year in patients with asthma and COPD, respectively. There is limited evidence to suggest whether the annual rate of reduction of the FEV1 can be used to differentiate between asthma and COPD. With the increasing longevity of the population, an increase in the number of patients with long-term asthma, such as those developing asthma in childhood, and those with severe asthma may affect the epidemiology of ACOS. Development of COPD in patients with asthma can be diagnosed based on a history of smoking, findings on imaging (e.g., computed tomography [CT]), pulmonary function testing to determine the pulmonary diffusing capacity, etc. On the other hand, it is not easy to diagnose the development of asthma in patients with COPD. In specialized medical institutions, fractional exhaled nitric oxide (FeNO) and serum IgE levels can be measured; however, in nonspecialized institutions, these cannot be measured, and the diagnosis has to be made on the basis of the clinical findings. In particular, in elderly patients, differentiation based on clinical findings has to be carefully made.
16.4 Importance of ACOS (Table 16.3)
Table 16.3
The importance factors of ACOS (compared with asthma and COPD)
Factors | Reference |
|---|---|
(1) High exacerbation frequency | |
Low health-related quality of life | |
(2) High medical cost | |
High medical service requirement | |
(High hospitalization frequency) | |
(3) Association with asthmatic death |
16.4.1 High Incidence of Exacerbations and Low Health-Related Quality of Life (HRQoL)
The reported percentage of patients with ACOS experiencing frequently repeated exacerbations is 42.7 %, 2–3 times higher than that in patients with COPD (15 %) [21, 23]. The number of hospitalizations increases with repeated exacerbations and is reported to be the highest for patients with ACOS, followed by those with COPD and asthma (ACOS >> COPD > asthma). The HRQol is significantly lower in patients with ACOS than in those with asthma [21, 29, 30].
16.4.2 High Medical Costs and Medical Care
Because ACOS patients have a higher frequency of exacerbations than those with asthma or COPD alone, and ACOS is progressive, treatment and hospitalization costs are higher in ACOS patients. Gerhardsson de Verdier M et al. [31] conducted a comparison of the 12-month medical costs between 26,060 patients with asthma (without COPD) and 6505 patients with ACOS, which revealed twofold higher medical costs in ACOS patients than in asthmatic patients. In addition, Shaya FT et al. [32] performed a 2-year comparison between 3702 patients with asthma, 3455 patients with COPD, and 2064 patients with ACOS, which revealed that ACOS patients required nearly 5 times more medical services than patients with asthma or COPD. The overall patient profile has to be taken into account for the management of ACOS [30].
16.4.3 High Mortality (Relationship with Death from Asthma)
The mortality from ACOS is higher than that from asthma or COPD alone [25]. On the other hand, the number of deaths from asthma has shown a tendency to decrease over time, with elderly patients aged 65 years or older accounting for approximately 90 % of all deaths from asthma [28]. Considering that elderly patients with asthma show a high frequency of complication by COPD, deaths from ACOS may account for nearly 40 % of all deaths from asthma.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
