What is Asthma and COPD Overlap?
Asthma and chronic obstructive pulmonary disease (COPD) are the most frequent lung diseases doctors see in their practice. They share similar traits and symptoms, including similar results in lung function tests. This is why a term “asthma-COPD overlap” (ACO) was coined to define cases that show features of both asthma and COPD. The term was first introduced by a researcher named Gibson in 2009.
ACO is a lung condition that shows both the signs of asthma and COPD or mainly COPD combined with improved breathing after using certain medications and a high count of a type of white blood cell called eosinophils. Although there has been an increase in cases being identified as ACO, there’s no globally accepted name for this condition yet – as shown by the latest report from the Global Initiative for Chronic Obstructive Lung Disease (GOLD).
Commonly, ACO is identified in people over the age of 40 who have a history of asthma and issues with airflow obstruction. According to the Global Initiative for Asthma (GINA) and GOLD, these patients usually have chronic symptoms like coughing, wheezing, repeated lower respiratory tract infections, and show characteristics of both asthma and COPD. This quick overview will focus on explaining how patients with ACO are diagnosed, their symptoms, and how they are treated.
What Causes Asthma and COPD Overlap?
There’s no single cause for ACO, or a blocked airflow condition that lies somewhere between asthma and COPD. Instead, it’s usually a combination of factors that lead to both asthma and COPD, such as cigarette smoking and environmental triggers. Many studies have found that tobacco use is the biggest risk factor for COPD. For example, a study of 8045 people found that those who smoked for 25 years were more likely to develop COPD than non-smokers, with rates of 36% compared to 8%.
Another risk factor for both asthma and COPD is an increased sensitivity to allergens or other external triggers. A study involving 9651 people found that those with this increased sensitivity had a higher chance of developing COPD over 11 years. The risk factors for COPD also include asthma and, surprisingly, a condition called ‘atopy’, which is a tendency to develop allergic conditions. This was confirmed by a study of 1025 men, average age 61, which found that atopy increased the risk of COPD. This variety of risk factors contributes to the development of ACO.
Risk Factors and Frequency for Asthma and COPD Overlap
ACO, or Asthma-COPD Overlap, is a disease that is difficult to define precisely, which makes it hard to accurately track how common it is. However, some estimates suggest that 2-3% of people may have ACO, based on doctors’ diagnoses and certain test results combined with symptoms.
The estimated prevalence of ACO appears to be higher than either Asthma or COPD individually, with the prevalence ranging between 2-12% for COPD and 5-17% for asthma. In the United States, around 3.7% of people are estimated to have ACO, while in China it’s lower at about 0.61%.
- There isn’t a clear definition of ACO, which makes it hard to estimate its prevalence accurately.
- It’s estimated that 2-3% of people have ACO.
- The disease seems to be more common than either asthma or COPD individually, with prevalence for those diseases ranging from 2-12% and 5-17%, respectively.
- In the US, about 3.7% of people are believed to have ACO.
- In China, the prevalence is lower, at around 0.61%.
Identifying the exact size of the population affected by ACO is difficult without a clear definition of the disease. Among people who have either asthma or COPD alone, it’s estimated that as many as a third may also have ACO. The disease also appears to be more common among women and people who are obese.
- Ambiguity in defining ACO makes it difficult to identify its exact prevalence.
- Up to a third of people with either asthma or COPD alone may also have ACO.
- ACO seems to be more common in women and individuals who are obese.
Research has shown that ACO tends to be more common among people with less education and lower socioeconomic status than COPD alone. Also, patients with ACO often have a harder time controlling their symptoms than those with either asthma or COPD alone.
- Studies suggest ACO is more prevalent in people with lower educational attainment and socioeconomic status than COPD alone.
- People with ACO often struggle more to manage their symptoms than people suffering from either asthma or COPD alone.
Signs and Symptoms of Asthma and COPD Overlap
Asthma and Chronic Obstructive Pulmonary Disease Overlap (ACO) is a condition that combines symptoms of both asthma and COPD. These symptoms are typically:
- Cough
- Production of sputum (a mix of saliva and mucus)
- Shortness of breath
- Wheezing
People with ACO usually experience these symptoms more frequently than those with just asthma or COPD. Specifically, they have flare-ups or ‘exacerbations’ about 4 to 5 times more often. This also leads to more visits to the emergency department and higher rates of hospital admission.
When a doctor examines a person with ACO, they often notice signs of ‘hyperinflation’, which means the lungs are over-expanded with air, similar to what is found in chronic obstructive lung disease. But sometimes, they may not find any abnormal signs during periods when the symptoms are not active.
Testing for Asthma and COPD Overlap
The first evaluation step for suspected ACO, or Asthma-COPD Overlap, involves a pulmonary function test. This test measures the level of FEV1, the “forced expiratory volume” that the lungs can expel in one second, which helps estimate the severity of the disease. People with ACO usually show an increasing level of FEV1 or forced vital capacity (FVC) after bronchodilation by more than 10% of the predicted value. With asthma, the increase would be larger, typically more than 15%.
However, even after bronchodilation, people with ACO often continue to display abnormally low FEV1 and FEV1/FVC levels. Meanwhile, asthma patients typically show normal post-bronchodilation levels.
For an ACO diagnosis, patients must satisfy three main criteria and at least one minor criterion, defined by a global panel of experts in 2016. The major criteria are: being at least 40 years old, having chronic airflow obstruction (post-bronchodilator FEV1/FVC 0.70 or less), a smoking history of at least ten packs per year, and a history of asthma before age 40 or more than a 400 milliliter increase in FEV1 after bronchodilator use.
Minor criteria include having a prior record of atopy or allergic rhinitis, displaying a significant bronchodilator response in FEV1 (at least 200 ml and 12% from baseline values on two or more visits), or having a high count of peripheral blood eosinophil (at least 200 cells/mL).
Further tests might include counting peripheral eosinophils, measuring immunoglobulin E levels, and screening for respiratory allergens. A high IgE level (more than 100 international units/mL) or a high peripheral eosinophil level (over 200 cells/microL) might point to ACO or asthma.
When a patient reports difficulty breathing (dyspnea), doctors often obtain a chest radiograph. Chest x-rays can show lung hyperinflation indicative of ACO, but they might not conclusively distinguish between asthma, COPD, and ACO.
Treatment Options for Asthma and COPD Overlap
Dealing with Asthma-COPD Overlap (ACO) involves both non-drug-related measures and drug treatments. Non-drug-related measures include quitting smoking to slow down disease worsening and avoiding other types of smoke. Vaccinations against flu and pneumonia can help as these infections are common triggers for worsening ACO symptoms. Proper instruction on how to use inhalers and referral to a specialist program designed to improve lung health (pulmonary rehabilitation) are also helpful.
Medicines are also used. Inhalers containing anti-inflammatory drugs called corticosteroids and medicines called bronchodilators are common treatments, but doctors are still uncertain about the best bronchodilator to use. The Global Initiative for Asthma (GINA) and the Global Initiative for Obstructive Lung Disease (GOLD) both advise starting asthma therapy after diagnosing ACO, due to the important role of corticosteroids in treating symptoms similar to those of asthma. However, less is known about this approach because people with ACO are not usually included in medical trials for asthma and COPD.
Patients with ACO should also have quick access to a fast-acting bronchodilator for sudden symptom flare-ups. Also, it’s important to avoid using medications known as Long-Acting Beta-Agonists (LABA) on their own without corticosteroids in patients who have symptoms of asthma. Furthermore, research is suggesting that higher numbers of a particular type of blood cell (eosinophils) are linked to better results with inhaled corticosteroids in people with COPD.
It’s wise to avoid using LABA drugs alone in asthmatics, based on a study called the Salmeterol Multicenter Asthma Research Trial (SMART). This study found that in its 28-week trial period, salmeterol raised the rate of death from respiratory conditions and asthma in some groups of patients, notably African Americans. Therefore, the same principle should apply to people with COPD who might also have ACO.
In terms of combination therapy with LABA and inhaled corticosteroids, studies showed promising results, with one 2015 trial indicating improved breathing measurements (FEV1) in ACO patients. If symptoms persist after these treatments, “triple therapy,” including an added drug called a Long-acting muscarinic antagonist (LAMA), may be necessary.
Biological treatments, a newer class of drugs, have been shown to reduce worsening episodes and the use of oral steroids in asthma patients. Some therapies target specific components of the immune response (such as omalizumab or anti-interleukin-5 therapies) and have shown potential benefits in some patients. However, the best candidates for these type of treatments still need to be identified, and some trials have yielded mixed results.
A medication called Dupilumab, which stops the chemicals IL-13 and IL-4 from working, improves lung function and reduces severe attacks. This drug is potentially better for patients higher levels of a certain type of blood cell (eosinophils).
Macrolide drugs, which have multiple effects including fighting bacteria, reducing inflammation, and modulating the immune response, are often used in chronic breathing problems. They may be useful in patients with ACO who frequently get worse and have non-eosinophilic characteristics, but more research is needed.
What else can Asthma and COPD Overlap be?
There are several long-term lung diseases that can resemble Asthma-COPD Overlap (ACO), including heart failure, bronchiectasis, and bronchiolitis obliterans. These conditions should be considered when trying to diagnose ACO.
Heart failure can sometimes be mistaken for ACO because it also causes wheezing. However, symptoms like difficulty breathing when lying down, waking up in the middle of the night struggling to breathe, fine crackling sounds on lung examination, and specific signs on chest X-rays can help identify heart failure.
Bronchiectasis is another condition that might appear as ACO. In bronchiectasis patients, physical check shows distinct crackling sounds, potential finger clubbing (a condition where fingers and nails thicken), and abnormal findings on CT scans and chest X-rays.
Bronchiolitis obliterans is often seen after viral infections, bone marrow transplants, or in conjunction with connective tissue diseases. CT scan results commonly show tree-bud like nodules and a patchwork pattern in the lung tissue.
What to expect with Asthma and COPD Overlap
ACO, or Asthma-COPD Overlap, has been linked to more severe symptoms, a decreased quality of life, and more frequent attacks of severe illness. This condition is also related to a faster decline in lung functionality. One study indicated that patients with ACO tend to suffer from frequent and severe attacks more often than those with just COPD, and they also are more likely to be hospitalized.
The same study found that individuals who frequently experience these attacks also experience a greater loss in lung function. It appears that lowered FEV1, a measurement of lung function, is linked to an increase in the severity of the disease, particularly in individuals with ACO. Additionally, another study found that patients with ongoing asthma that also have chronic airflow restriction face a higher mortality rate.
Possible Complications When Diagnosed with Asthma and COPD Overlap
People who suffer from ACO, a condition that combines symptoms of COPD and asthma, may face the same complications as those dealing with either COPD or asthma alone. These complications can include recurring respiratory illnesses, lung-related issues, and even troubles with the heart. Specifically, ACO patients are more prone to pneumonia. This increased risk can exacerbate their condition, resulting in more frequent hospital visits. It is also possible for ACO patients to develop heart-related complications like pulmonary hypertension, especially if their condition doesn’t improve despite treatment.
Common Complications:
- Recurrent respiratory infections such as pneumonia
- Pneumothorax – a collapsed lung
- Hypoxia – low oxygen levels
- Cardiovascular events
- Frequent hospitalizations due to increased pneumonia risk
- Pulmonary hypertension
Preventing Asthma and COPD Overlap
ACO, or Asthma-COPD Overlap, is a lung condition that combines elements of asthma and COPD, making it harder for people to breathe. It’s often caused by various risk factors associated with both asthma and COPD. For those with ACO, their airways, which are the branches carrying air throughout the lungs, may become filled with mucus and contract. The air sacs can get damaged too, leading to fatigue and shortness of breath.
One distinguishing feature between ACO and COPD or asthma alone is that ACO leads to more frequent symptom flare-ups. To prevent COPD from developing, it’s crucial to avoid risk factors which can either cause the disease or make it worse.
Smoking is a major cause, and quitting can significantly improve one’s health. If one has other risk factors for asthma, smoking can lead to ACO and intensify symptoms. Healthcare professionals can provide support for those who want to stop smoking.
It’s also essential to reduce the risk of infections, which can make ACO symptoms worse. By getting certain vaccinations such as the annual flu shot, the pneumococcal vaccine, and the COVID-19 vaccine, people can lower their risk.
In addition, avoiding triggers like dust or pollution that make breathing more difficult is another important preventative measure.
