Chronic Obstructive Pulmonary Disease (COPD) and Asthma: Similarities and Differences
Updated: July 2015
Originally Posted: July 2009
Updated by: Bradley Chipps, MD
Captial Allergy and Respiratory Disease Center
Folsom, CA, USA
Raquel Watkins, MD
Assistant Professor, Allergy and Immunology
Wake Forest University School of Medicine
Winston Salem, North Carolina USA
Diane Laber, MD
Fellow, Allergy and Immunology
Wake Forest University School of Medicine
Winston Salem, North Carolina USA
Stephen P. Peters, MD, PhD
Professor of Medicine and Pediatrics
Associate Director, Center for Human Genomics
Wake Forest University School of Medicine
Winston Salem, North Carolina USA
Definition of COPD and Asthma
According to the American Thoracic Society (ATS)/ European Respiratory Society (ERS) along with the Global Initiative for Obstructive Lung Disease (GOLD),(1) chronic obstructive pulmonary disease (COPD) is a “preventable and treatable disease with some significant extrapulmonary effects that may contribute to the severity in individual patients. Its pulmonary component is characterized by airflow limitation that is not fully reversible. The airflow limitation is usually progressive and associated with abnormal inflammatory response of the lung to noxious particles or gasses.”
Asthma is similarly characterized by airflow obstruction; however, according to the National Asthma Education and Prevention Program (NAEPP) and the Global Initiative for Asthma,(2) asthma is additionally typified by variable and recurring symptoms, bronchial hyperresponsiveness and underlying inflammation of the airways.
The severity of airways obstruction in COPD is best classified with spirometry.(1,3) COPD is diagnosed on the basis of a post-bronchodilator forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) value of <70. In addition post-bronchodilator FEV1 cutoffs of <80%, 50% and 30% of predicted values are used to further stage disease severity (Table 1).(1)
Asthma severity is determined before treatment with controller medications. Asthma control is determined on the basis of both impairment and risk.(2) Impairment is a function of the frequency of daytime and nocturnal symptoms, short-acting β2-agonist (SABA) use, the degree to which normal activity is affected and lung function. Risk is defined by the frequency of exacerbations requiring oral corticosteroid (OCS) use.
Patients are classified as having intermittent or persistent (mild, moderate or severe) asthma depending on the degree of impairment and risk. The severity of asthma is determined on the basis of which of the following factors is the worst: daytime or nocturnal symptoms, rescue SABA use, lung function or exacerbation frequency.
Patients with intermittent asthma have minimal impairment and risk. They experience daytime symptoms ≤2 days/week and nocturnal awakenings ≤2 times/month, and these symptoms do not interfere with normal activity. The frequency of SABA use is ≤2 days/week. Lung function is preserved, FEV1 is >80% of predicted and normal between exacerbations, and FEV1/FVC is normal. These patients typically have no exacerbations or only one exacerbation per year that requires OCS use.
Mild persistent asthma is characterized by >2 daytime symptoms/week, but not daily, and night time symptoms 3-4 times/month. SABA use occurs >2 times/week, but not daily, and not more than once on any day. Patients with mild persistent asthma report minor limitations in activity, have an FEV1 >80% of predicted and have a normal FEV1/FVC.
Patients with moderate persistent asthma experience daytime symptoms daily and nocturnal symptoms more than once a week, but not nightly. They use a SABA daily and express some limitation in exercise tolerance. FEV1 is >60%, but <80% of predicted, and FEV1/FVC is reduced by > 5% below normal.
Patients with severe persistent asthma experience daytime and nighttime symptoms daily. They use a SABA several times per day, and their activity is extremely limited. FEV1 is <60% of predicted, and FEV1/FVC is reduced by >5% below normal. All patients with persistent asthma are at high risk of need for hospitalization, emergency department (ED) visits or to experience fatal or near fatal episodes of asthma, and generally report ≥2 exacerbations per year that require OCS use.
Asthma control is evaluated by assessment of impairment and risk domain with equal weight (2). Step up and step down therapy is guided by the most involved domain (2). It is important to use a validated control instrument for accurate assessment (20). Very poorly controlled asthma and recent exacerbations are major predictors of future exacerbations (21).
Symptoms and Signs of COPD and Asthma
COPD symptoms differ on the basis of disease severity (Table 1). Most patients with COPD usually first develop a chronic productive cough. However, dyspnea is the hallmark symptom of COPD and usually prompts patients to seek medical care. As disease severity progresses, cough and dyspnea result in decreased exercise tolerance and increased disability. COPD mainly affects the lungs; however, notable systemic effects are also associated with COPD. Patients with COPD often experience changes in their metabolism and in caloric intake. Indeed, 50% of patients with severe disease experience weight loss, which is associated with a poorer prognosis.3 Patients with COPD also develop decreased strength, decreased exercise capacity and a reduced quality of life.3 COPD is associated with an increased risk of cardiovascular disease, respiratory infections, osteoporosis and glaucoma.(3)
Physiologic changes associated with asthma include bronchoconstriction, airway hyperresponsiveness and airway inflammation. Therefore, patients with asthma typically develop wheezing, shortness of breath and cough. Because asthma is also characterized by reversible airway obstruction, its symptoms are intermittent and cover a spectrum from mild-to-severe disease.(4)
Several symptoms overlap in patients with COPD and asthma. Nevertheless, a history of wheezing strongly suggests a diagnosis of asthma, whereas chronic cough productive of sputum is more indicative of COPD.
Causes of COPD and Asthma
Risk factors for both COPD and asthma can be categorized as host and environmental factors. The genetic risk factor that has been most closely linked to COPD is a rare deficiency of α1-antitrypsin.(1) Because only 15% of smokers go on to develop COPD, genetics and other susceptibility factors are thought to play an important role. Polymorphisms in genes related to proteases, antioxidants and inflammation have been found to relate to some of the features characteristic of COPD. Polymorphisms in any of three classes of proteases, the serine proteases, cysteine proteases, and matrix metalloproteinases may lead to development of COPD.15 Antioxidant enzymes known to be present in the airways include glutathione-S-transferase, superoxide dismutase and catalase. Cigarettes smoke causes a large number of free radicals, and alterations in these enzymes may also raise susceptibility to COPD.(15) Many pro- and anti-inflammatory mediators, including TNF-a, IL-1, IL6 and TGF-ß are also felt to be important in the development of COPD.(15) A candidate gene—the promoter polymorphism-1111 in the interleukin-13 gene(5)—was identified in populations with either COPD or asthma. This finding provides additional evidence in support of a genetic susceptibility to COPD and asthma.
Host factors for asthma are not as well delineated, and the genetics of asthma continue to be investigated. However, one theory is that overexpression of T-helper 2 lymphocyte (Th2) allergic cells or underexpression of Th1 non-allergic cells contribute to atopy and asthma. The “hygiene hypothesis” has also been postulated, i.e., that particular infections early in life, exposure to siblings or other children through childcare, decreased use of antibiotics, and “country living” (exposure to farming and anthroposophic lifestyles) are associated with a Th1 response and a decreased incidence of asthma.(2) Obesity, family history, atopy (including food sensitization), exposure to heavy traveled roads, environmental tobacco exposure and male sex are also risk factors for asthma in children. Infection with RSV in childhood has also been shown to have a clear relationship to asthma, but it is unclear if RSV infection leads to asthma, or if children with asthma are more susceptible to RSV infection.(16)
Infection with rhinovirus especially in children who have a persistent allergic diathesis is the more common infection to lead to airway hyperactivity (22).
Once the components of control (impairment and risk) are assessed, asthma can be classified as well controlled, not well controlled or very poorly controlled. Patients with well controlled asthma experience daytime symptoms ≤2days/week, experience nocturnal awakenings ≤2 times/month, use SABAs <2 days/week, have peak flow measurements >80% of the predicted personal best and have scores >20 on ACT. Well controlled asthmatics generally have at least one exacerbation per year. Patients with well controlled asthma should be maintained on their current regimen and undergo a reduction in treatment if they can maintain their level of control for ≥3 months. Patients with not well controlled asthma experience daytime symptoms >2days/week, experience nocturnal awakenings 1-3 times/week, use SABAs >2 days/week, have peak flow measurements 60-80% of the predicted personal best and have ACT score of 16-19. Normal activity is limited in these patients. Treatment involves a one-step increase in pharmacotherapy (see Tables 2 and 3) and revaluation in 2-6 weeks. Patients with very poorly controlled asthma experience daytime symptoms daily, experience nocturnal awakening ?4 times/week, use SABAs several times per day, have peak flow measurements <60% of predicted personal best, and have ACT scores ≤15. Activity is extremely limited in these patients. Therapy involves a one- to two-step increase, consideration of a short course of OCS and reevaluation in 2 weeks. Both not well controlled and very poorly controlled asthmatics usually have ≥2 exacerbations that require OCS use per year. Loss of lung function should be monitored long-term at all levels of control, and side effects associated with medication use can vary from none to significant and should be assessed at every visit.
Environmental factors that serve as risk factors for COPD include inhalation exposures to cigarette smoke, occupational dusts and chemicals and indoor and outdoor pollution. A history of severe respiratory infection during childhood is associated with reduced lung function in adulthood. Additionally, a lower socioeconomic status (SES) is associated with the development of COPD; however, it is not clear whether this association is due to SES or to confounders and exposures commonly linked to lower SES, such as a crowded living environment or poor nutrition.(1)
Two environmental factors have been consistently associated with the development of asthma: sensitization to indoor and outdoor aeroallergens and a history of viral respiratory infections, in particular, rhinovirus infections.(6) Other potential environmental irritants include tobacco smoke and air pollution. Maternal smoking during pregnancy is also a risk factor for the development of asthma. Many children of mothers who smoked during pregnancy wheeze during the first 2-3 years of life but have only a few episodes of wheezing or do not wheeze after age 3 years (transient wheezers). Risk factors for transient wheezing are maternal smoking during pregnancy, younger mothers and smaller airways.6 Other risk factors for the development of asthma are included in the Asthma Predictive Index, which is described in the Tucson Children’s Respiratory Study.6 Having either a parent with asthma or a personal history of atopic dermatitis or two of the following conditions—peripheral blood eosinophilia, physician-diagnosed allergic rhinitis, or wheezing for reasons other than a cold—is associated with more persistent asthma symptoms through the age of 13 years. Further analysis of this patient population indicates that onset of symptoms at 6 years of age, persistent wheezing in early life, sensitization to A. alternata, low airway function at 6 years, and bronchial hyperresponsiveness at 6 years are risk factors for persistence of asthma at age 22. Asthma remittance at age 22 was more common in men than in women, and age at diagnosis was linearly related to FEV1 to FVC ratio at age 22.(17)
Prevention of COPD and Asthma
COPD is a preventable disease. Although primary prevention hinges on tobacco cessation strategies, secondary prevention of COPD centers on early diagnosis, risk factor modification and treatment. However, early diagnosis of COPD is often delayed. In 2002, the third National Health and Nutrition Examination Survey (NHANES III)7 reported that approximately 24 million adults in the USA have evidence of impaired lung function on spirometry; however, only about 50% of these patients have physician-diagnosed COPD, most of which is moderately advanced disease. At this late stage of disease, only tertiary prevention, aimed at preventing the complications of COPD, is effective. Therefore, primary and secondary prevention strategies need to be improved.
Better prevention of COPD can be achieved through compliance with guidelines. Numerous guidelines exist to assist physicians in early diagnosis, prevention of disease progression and management of COPD, including those of GOLD,(1) the American Thoracic Society,(8) the National Collaborating Center for Chronic Conditions and the Canadian Thoracic Society.(10)
Tobacco cessation is of paramount importance for preventing COPD and limiting its progression. GOLD reports that tobacco cessation is the single most clinically effective and cost-effective intervention in COPD.(1) Use of the 5 A’s Strategy—“ask, assess, advise, assist and arrange”—in conjunction with the use of nicotine patches, bupropion, varenicline and telephone follow-up have been shown to be effective in tobacco cessation. Both the influenza and pneumococcal vaccines are recommended for patients with COPD.
Identifying and reducing exposure to risk factors is critical in asthma prevention. Measures should include the prevention of allergic sensitization during the perinatal period.(11) For example, exclusive breast-feeding during the prenatal period has been associated with lower asthma rates in childhood,(11) and exposure to tobacco smoke prenatally and postnatally is associated with deleterious effects on lung development and wheezing in early childhood.
After allergic sensitization has occurred in the setting of asthma, prevention of exposure to known triggers can prevent exacerbations. Common indoor triggers include tobacco smoke, dust mites, furry animals, cockroaches and fungi. Outdoor triggers include aeroallergens and air pollutants. Occupational exposures should also be minimized. Allergen-specific immunotherapy may play a role in preventing the development of asthma in atopic children.(12)
Asthmatics with a history of nasal polyps and aspirin or nonsteroidal anti-inflammatory drug sensitivity should be counseled regarding the risk of severe, fatal exacerbations from the use of these drugs and in certain cases, desensitization may be beneficial. Co-morbidities, such as allergic bronchopulmonary aspergillosis, rhinosinusitis and gastroesophageal reflux, should be considered and treated in patients with poorly controlled asthma. The Centers for Disease Control and Prevention recommend inactivated influenza vaccine for patients (aged 6 months to adult) who have asthma.
Numerous guidelines are also available to aid physicians and other healthcare professionals to better prevent and manage asthma. Two frequently referenced guidelines are those of the NAEPP(2) and the Global Initiative for Asthma (GINA).(11)
Treatment of COPD and Asthma
Treatment of COPD encompasses the use of various medications (in the form of glucocorticoids, β2-agonists, anticholinergics and methylxanthines, used either singly or in combination). Non-pharmacological interventions include health education on managing chronic illnesses, pulmonary rehabilitation with focus on physical and dietary measures, patient education, and smoking cessation intervention programs.
Treatment varies depending on symptoms and disease severity. All patients, regardless of disease severity, should be offered the yearly influenza vaccine. Pneumococcal vaccines should be offered to patients with COPD who are 65 years and older and to patients with COPD younger than 65 who have an FEV1 of <40%. As needed, short-acting bronchodilators can also be used during any stage of illness (from mild to very severe) to improve symptoms. However, regular treatment with one or more long-acting bronchodilator (when needed) should be considered in patients with moderate-to-very-severe disease. In patients with severe COPD and frequent exacerbations, inhaled corticosteroids can reduce exacerbations. The Towards a Revolution in COPD Health (TORCH) trial(13) was a randomized, double-blinded trial involving >6000 patients with COPD in which the effectiveness of combination therapy with salmeterol (50 μg) plus fluticasone propionate (500 μg) given twice per day was compared with that of placebo, salmeterol alone or fluticasone propionate alone. TORCH showed a significant reduction in exacerbations and improvements in health status and spirometric measurements in the patients who received combination therapy compared with those who received placebo. TORCH also showed a 17.5% lower risk of death in the COPD patients who received combination therapy than in those who received placebo (P=0.052).
Treatment guidelines are shown in Table 3 Gina Box 7. Equal severity of risk are determined by post bronchodilator FEV1 or exacerbation history, supplemented by a validated symptom such as mMRC tool (Table 4). The role of ICS must be carefully evaluated in patients with COPD. In patients who do not have evidence of Th2 mediated airway inflammation, withdrawal of ICS with persistence of LABA + LAMA may not lead to significant changes in health status, dyspnea or exacerbation (22).
Long term oxygen therapy improves mortality in COPD patients with respiratory failure but has limited effectiveness in less severe patients. It has also shown positive effects on quality of life, but not on COPD exacerbations.(18,19)
GINA(11) proposes five interrelated components of therapy for the management of asthma: 1) a patient-physician partnership (e.g., asthma action plan); 2) identification and reduction of exposure to risk factors; 3) assessment, treatment and follow-up for asthma; 4) management of exacerbations; and 5) individualized care during pregnancy and for rhinosinusitis and nasal polyps, gastroesophageal reflux, aspirin-exacerbated respiratory disease, and anaphylaxis. Pharmacotherapy for asthma is well delineated in the six-step approach recommended by the NAEPP(2) (Table 2) as well as the five step approach recommended by GINA(11). (Table 3 Box 7).
Epidemiology of COPD and Asthma
COPD is the fourth leading cause of death in the USA.(3) In 2001, the World Health Organization reported that COPD was the fifth leading cause of death in high-income countries and the sixth leading cause of death in low- and middle-income countries.
COPD usually presents in middle age, is slowly progressive and is associated with history of cigarette smoking in 80-90% of patients.(3,10) Patients usually present with a chronic productive cough, and atopy is not a frequent finding. Clinical symptoms are slowly progressive, and airflow limitation is only partially reversible after tobacco cessation and with bronchodilator use. T lymphocytes, with macrophages and neutrophils, are the predominant inflammatory cell types.(1,3)
In 2005, an estimated 22.2 million Americans had asthma: 6.5 million children and 15.7 million adults.(14) The public health impact of asthma is significant. In 2003, asthma accounted for 1.4 deaths/100,000 persons in the USA.(14) According to the National Center for Health Statistics,(14) in 2003, children between the ages of 5 and 17 years with a history of at least one asthma attack in the previous year accounted for 12.8 million missed school days, and adults with a history of at least one asthma attack in the previous year accounted for 10.1 million missed workdays.
GINA estimates that the prevalence of asthma is 300 million persons worldwide. The World Health Organization estimates that 1% of the global disease burden, 15 million disability-adjusted life years, is attributable to asthma. Asthma accounts for 250,000 deaths annually worldwide.(11) Mortality does not correlate with prevalence since countries such as Wales and New Zealand have the lowest asthma-related mortality rate, despite a high prevalence of disease.
The epidemiology of asthma differs from that of COPD in that asthma usually presents early in childhood, and atopy is much more prevalent in asthma than in COPD. Asthma is usually not progressive, although exacerbations can be intermittent and variable. Eosinophils and lymphocytes are the major inflammatory cells in asthma. With appropriate therapy, asthma is completely reversible in most patients.(3)
Asthma COPD Overlap Syndrome
The diagnosis of ACOS syndrome has been defined by GINA document published in May 2014. This can be a very problematic diagnosis, particularly in smokers and older adults. ACOS syndrome is identified by features shared by both asthma and COPD. The evaluation requires a thorough history of the patient’s chronic airways disease, pulmonary function testing and also testing to determine if Th2 mediated airway inflammatory pattern is present, which would suggest a response to inhaled steroid. Table 1 defines severity, and in table 2A the usual features of asthma, COPD and the ACOS syndrome are elaborated. Table 3 gives better definition of expected spirometric measures in the three disease states. Table 4 is a stepwise approach to the definition of patients with chronic airflow limitation. Table 5 allows for specialized investigations to be employed to distinguish asthma and COPD.
Table 1: GOLD1 classification of COPD
Abbreviations: COPD, chronic obstructive pulmonary disease; FEV1, forced expiratory volume in one second; FVC, forced vital capacity; GOLD, Global Initiative for Obstructive Lung Disease.
Table 2: NAEPP2-recommended pharmacotherapy for asthma
Abbreviations: ICS, inhaled corticosteroids; LABA, long-acting ?2-agonists; LTRA, leukotriene receptor antagonists; NAEPP, National Asthma Education and Prevention Program; OCS, oral corticosteroids.
Table 3: Box 7. Stepwise Approach to Asthma Treatment 2
Table 4. Global Strategy for the Management of COPD 23
Table 5. Asthma, COPD and Asthma-COPD Overlap Syndrome 24
Current definitions of asthma and COPD, and clinical description of ACOS
Usual features of asthma, COPD and ACOS
Spirometric measures in asthma, COPD and ACOS
Summary of syndromic approach to diseases of chronic airflow limitation
Specialized investigations sometimes used in distinguishing asthma and COPD
- Rabe KF, Hurd S, Anzueto A, et. al. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: GOLD Executive Summary. Am J Respir Crit Care Med 2007;176:532-555.
- GINA Report, Global Strategy for Asthma Management and Prevention 2014. (Accessed April 2015)
- Wise RA, Tashkin DP. Preventing chronic obstructive pulmonary disease: what is known and what needs to be done to make a difference to the patient? Am J Med 2007;120:S14–S22.
- Decramer M, Selroos O. Asthma and COPD: differences and similarities. Int J Clin Pract 2005;59:385-398.
- Meyers DA, Larj MJ, Lange L. Genetics of asthma and COPD: similar results for different phenotypes. Chest 2004;126:105-110.
- Taussig LM, Wright AL, Holberg CJ, Halonen M, Morgan WJ, Martinez FD. Tucson Children’s Respiratory Study: 1980 to present. J Allergy Clin Immmunol 2003;111:661-675.
- NHANES. (accessed October 2007).
- Celli B, MacNee W, Agusti A, et al. Standards for the diagnosis and treatment of patients with COPD: a summary of the ATS/ERS position paper. Eur Respir J 2004;23:932-946.
- National Collaborating Center for Chronic Conditions. Chronic obstructive pulmonary disease: national clinical guideline on management of chronic obstructive pulmonary disease in adults in primary and secondary care. Thorax 2004;59(suppl 1):i199-i232.
- Canadian Thoracic Society. (accessed October 2007).
- Global Initiative for Asthma. http://www.ginasthma.com (accessed April 2015).
- Moller C, Dreborg S, Ferdousi HA, et al. Pollen immunotherapy reduces the development of asthma in children with seasonal rhinoconjunctivitis (the PAT study). J Allergy Clin Immunol 2002;109(2):251-256.
- Calverly P, Anderson J, Celli B, et al. Salmeterol and fluticasone propionate and survival in chronic obstructive pulmonary disease. N Engl J Med 2007;356:775-789.
- National Center for Health Statistics. Asthma prevalence, health care use and mortality: United States, 2003-05. (accessed October 2007).
- Wood, AM, Stanley RA. The genetics of chronic obstructive pulmonary disease. Respir Res 2006; 7:130.
- Kuehni GE, Spycher BD, Silverman M. Causal links between RSV infections and asthma: no clear answers to an old question. Am J Respir Crit Care Med 2009; 179 (12): 1079-1080.
- Stern DA, Morgan WJ, Halonen M, et al. Wheezing and bronchial hyperresponsiveness in early childhood as predictors of newly diagnosed asthma in early adulthood: a long birth-cohort study. Lancet 2008; 372(9643); 1058-64.
- Medical Research Council Working Party (MRC). Long term domiciliary oxygen therapy in chronic hypoxic cor pulmonale complicating chronic bronchitis and emphysema: report of the Medical Research Council Working Party. Lancet 1981; 1:178. 681-686.
- Kim V, Benditt JO, Wise RA, et al. Oxygen therapy in chronic obstructive pulmonary disease. Proce Am Thorac Soc. 2008; 5:513-518.
- Szefler SJ, Chmiel JF, Fitzpatrick AM, et al. Asthma across the ages: Knowledge gaps in childhood asthma. J Allergy Clini Immunol. 2014;133(1):3-13.
- Chipps, B., Zeiger, R., Borish, L., Wenzel, S., Yegin, A., Hayden, M., Miller, D., Bleecker, E., Simons, E., Szefler, S., Weiss, S., and Haselkorn, T. Key Findings and Clinical Implications from the Epidemiology and Natural History of Asthma: Outcomes and Treatment Regiments (TENOR) Study. J Allergy Clin Immunol. 2012;130:332-42.
- Celli BR, Decramer M, Wedzicha JA et al. An Official Thoracic Society/European Respiratory Society Statement: Research Questions in Chronic Obstructive Pulmonary Disease. Am J Respir Crit Care Med 2015;191(7):e4-e27.
- Global Initiative for Chronic Obstructive Lung Disease. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease. Accessed April 2015).
- http://www.ginasthma.org/. Diagnosis of Diseases of Chronic Airflow Limitation: Asthma COPD and Asthma-COPD Overlap Syndrome (ACOS). (Accessed April 2015).