Asthma Subgroups: Asthma/COPD Overlap Syndrome (ACOS)

Researchers now understand that about 11% of asthmatics also have COPD, and 10-50% of COPDers over the age of 50 also have asthma. When this happens it is generally diagnosed as Asthma/ COPD Overlap Syndrome (ACOS).^1-2 Here is all you need to know about this asthma subgroup.

What is ACOS?

It almost always has an adult onset, being diagnosed after the age of 40. A joint effort by the Global Initiative for Asthma (GINA) and Global Initiative for Chronic Obstructive Lung Disease (GOLD) defines it this way³:

“Asthma-COPD overlap syndrome (ACOS) is characterized by persistent airflow limitation with several features usually associated with asthma and several features usually associated with COPD. ACOS is therefore identified by the features that it shares with both asthma and COPD.”³

What is asthma?

 
It’s associated with chronic, underlying airway inflammation that makes airways hypersensitive (twitchy) to asthma triggers. Exposure to asthma triggers causes this underlying inflammation to worsen, causing asthma attacks, the main feature of which is airflow limitation and shortness of breath. Asthma is reversible.

What does reversible mean?

A key feature of asthma is that it is completely reversible with either time or treatment. Between asthma episodes lung function is usually normal or close to normal. By working with your doctor to obtain good asthma control, asthma attacks can be prevented or made less severe when they do occur. Asthmatics tend to live normal functioning lives between episodes. It can be diagnosed at any time in a person’s life.

What is COPD?

This is an acronym for chronic obstructive pulmonary disease. You can learn more by checking out our COPD site. It’s associated with inflammation of airways and lung tissue due to years of exposure to airborne irritants and chemicals. It’s usually adult-onset, diagnosed after the age of 40. There are typically two diseases associated with COPD.

1. Emphysema Lung units (alveoli) may lose their elasticity and ability to regain their shape after a full inhalation. When lung tissue is affected, alveoli may expand all the way to the chest wall, creating air spaces called bullae. This may pull or stretch airways, thereby causing them to become chronically narrow.
2. Chronic Bronchitis. Epithelial cells lining airways are damaged. This results in inflammation that causes airway changes (remodeling or lung scarring). This makes airway walls thicker than normal, making airways chronically narrow.

What does Not Reversible mean?

 
A key feature of COPD is persistent airflow limitation that is only partially reversible with time or treatment. It may be associated with some degree of persistent (it’s always there) shortness of breath. COPD is also a progressive disease.

What does Progressive mean?

Another key feature of COPD is that it gradually progresses with time. However, by working with your doctor to get a proper diagnosis and treatment, and developing an effective COPD treatment program specifically tailored for you, the progression of this disease can be slowed so you can live longer and better with it. ACOS is often diagnosed in tandem with Severe Asthma

What types of inflammation are involved?

Asthma is generally associated with eosinophilic inflammation, and this makes it very responsive to inhaled corticosteroids. While not all people with COPD smoke, one study showed that asthmatics who smoked were increasingly likely to develop COPD, which is generally associated with neutrophilic inflammation, meaning it is not very responsive to inhaled corticosteroids.^4-5

The combination of eosinophilic and neutrophilic asthma means they usually also have a diagnosis of severe asthma. Because of the type of inflammation present, it’s also sometimes referred to as “Smoking Induced Neutrophilic asthma."

Interestingly, to make matters worse, one study showed that asthmatics who smoked were more sensitive to allergens (dust mites, pollen, etc) than non-smokers. So, this too can impact underlying airway inflammation, making asthma more severe.⁵

What is Severe Asthma?

This is difficult to treat asthma.  It’s an asthma subgroup defined as asthma that only responds to the highest doses of corticosteroids. It is sometimes refractory to corticosteroids, meaning it does not respond to them at all, thereby requiring trials of medicines not traditionally used to treat asthma, such as COPD medicines.  It’s often defined as asthma that requires two or more medicines to obtain any degree of asthma control.^6-7 Because ACOS is associated with permanent airway scarring like COPD, it usually results in a diagnosis of severe asthma.

How is ACOS diagnosed?

If you are diagnosed with severe asthma, ACOS should be ruled out as a potential cause. This begins by a physical examination and a history. For instance, do you have a chronic cough? Have you ever been exposed to chemicals at work or home? Do you, or have you ever smoked? You may likely be expected to undergo  pulmonary function testing, blood tests, sputum tests, x-rays, cat scan, etc.³

What is the treatment? 

If not already on them, treatment includes inhaled corticosteroids, and sometimes the highest doses. The highest doses are usually indicated because, as studies show,  smoking seems to blunt the effects of corticosteroids in those who have a greater than 10 year smoking history. Studies seem to indicate that montelukast (Singulair) and zileuton (Zyflo) may help improve lung function in smokers or former smokers with a blunted response to corticosteroids.^{4-5, 8}

Corticosteroids are often prescribed in tandem with long acting beta adrenergic medicines in combination inhalers like Advair, Symbicort, Dulera, and Breo. Short acting bronchodilators like Albuterol are usually prescribed. A doctor may prescribe COPD medicine like tiotropium (Spiriva) or old asthma medicines like theophylline. Your doctor may also prescribe newer and less proven asthma and COPD medicine. You should also be encouraged to quit smoking, as this has been shown to slow the progression of the disease.⁵

What does the future have in store for those with ACOS?

In the past, those who displayed features of both asthma and COPD were not included in studies, meaning very little was known about ACOS nor how best to treat it. However, thanks to organizations like GINA and GOLD guidelines have been created to guide physicians towards the best strategies for diagnosing and managing ACOS. ^{3, 2}