Asthma-COPD overlap syndrome (ACOS)
Asthma-COPD Overlap Syndrome, often abbreviated as ACOS, is a condition that combines features of both asthma and chronic obstructive pulmonary disease (COPD). For many people, living with respiratory issues can be challenging, but when two major lung conditions overlap, it can feel even more overwhelming.
What is ACOS-syndrome?
ACOS occurs when an individual has symptoms and characteristics of both asthma and COPD simultaneously.
Asthma is typically an inflammatory condition where airways narrow and swell in response to triggers, leading to reversible breathing difficulties.
COPD, on the other hand, involves progressive damage to the lungs, often from long-term exposure to irritants like cigarette smoke, resulting in persistent airflow limitation that’s not fully reversible. In ACOS, these two conditions coexist, creating a unique syndrome that’s more than just the sum of its parts.
The term ACOS was introduced to describe this overlap, but recent guidelines from organizations like the Global Initiative for Chronic Obstructive Lung Disease (GOLD) have moved away from labeling it as a distinct entity. Instead, they emphasize that asthma and COPD are separate disorders that can share traits, such as airway inflammation and partial reversibility of airflow obstruction. Despite this shift, the concept remains useful for clinical practice because patients with overlapping features often experience worse outcomes than those with asthma or COPD alone.
Prevalence estimates vary, but studies suggest that ACOS affects about 15-25% of people with obstructive lung diseases. It’s more common in adults over 40, and the likelihood increases with age—rising from less than 10% in those under 50 to over 50% in people 80 and older. Women may be at higher risk, and smoking history plays a significant role in many cases.
To clarify the differences and overlaps, here’s a comparison table:
| Feature | Asthma | COPD | ACOS |
|---|---|---|---|
| Onset | Often in childhood or young adulthood | Typically after age 40 | Usually in adulthood, often with a history of asthma |
| Airflow Limitation | Reversible with treatment | Mostly irreversible | Partially reversible |
| Main Cause | Allergic or environmental triggers | Smoking or long-term irritant exposure | Combination of both |
| Inflammation Type | Eosinophilic (allergy-related) | Neutrophilic (infection-related) | Mixed, often with eosinophilia |
| Symptoms | Intermittent wheezing, triggered episodes | Persistent cough, shortness of breath | Frequent exacerbations, worse than either alone |
| Progression | Can be controlled, not always progressive | Progressive lung damage | Rapid decline in lung function |
This table highlights why ACOS requires a tailored approach—it’s not just asthma or just COPD.
Symptoms of ACOS
Symptoms of ACOS can be more severe and frequent than in isolated asthma or COPD, leading to a higher burden on daily life. Common signs include:
- Shortness of breath: Often worse during physical activity or at night, and more persistent than in pure asthma.
- Wheezing: A high-pitched whistling sound when breathing, which may occur intermittently or chronically.
- Chronic cough: Frequently productive (with mucus), similar to COPD, but can be triggered like in asthma.
- Chest discomfort: Patient feels pressure in the chest.
- Frequent exacerbations: Sudden worsenings of symptoms, often requiring medical attention. People with ACOS may have more hospital visits due to these flares.
- Reduced lung function: Measured by tests like spirometry, showing lower-than-normal airflow.
Other symptoms might include fatigue, difficulty sleeping due to breathing issues, and increased susceptibility to respiratory infections.
Causes and risk factors
The exact causes of ACOS aren’t fully understood, but it stems from the interplay between genetic, environmental, and lifestyle factors that contribute to both asthma and COPD.
- Smoking:
A major risk factor, as it’s the primary cause of COPD and can worsen asthma. About 62% of people with ACOS are current or former smokers.
- Environmental exposures:
Long-term contact with air pollution, dust, chemicals, or secondhand smoke can damage airways.
- History of asthma:
Many with ACOS had childhood asthma that persists or worsens with age.
- Genetics:
Family history of asthma or COPD increases risk.
- Age and gender:
More common in older adults and possibly women.
- Other factors:
Obesity, low socioeconomic status, and frequent respiratory infections can contribute.
Diagnosis
Diagnosing ACOS involves ruling out pure asthma or COPD and identifying overlapping features. There’s no single test, but a stepwise approach is recommended.
- Medical history: Your doctor will ask about symptoms, triggers, smoking history, and family background.
- Physical exam: Listening to your lungs for wheezing or reduced breath sounds.
- Spirometry: A key lung function test measuring how much air you can exhale forcefully. In ACOS, it shows airflow obstruction that’s partially reversible (unlike fully in asthma or minimally in COPD).
Other tests:
- Bronchodilator response test to check reversibility.
- Fractional exhaled nitric oxide (FeNO) to assess inflammation.
- Chest X-ray or CT scan to rule out other issues.
- Blood tests for eosinophil levels (higher in asthma-like features).
- Allergy testing if asthma triggers are suspected.
Guidelines suggest assembling features favoring asthma (e.g., variable symptoms) or COPD (e.g., persistent limitation) and noting overlaps. If uncertain, a pulmonologist or allergist can help.
Treatment
Treatment for ACOS focuses on controlling symptoms, reducing exacerbations, and improving quality of life. Since it overlaps, therapy often combines asthma and COPD strategies, prioritizing asthma guidelines if coexistence is suspected.
Medications
- Inhaled corticosteroids (ICS): Reduce inflammation; often first-line for asthma features.
- Long-acting beta-agonists (LABA): Relax airways; combined with ICS for better control.
- Long-acting muscarinic antagonists (LAMA): Help with COPD-like symptoms by opening airways.
- Triple therapy: ICS + LABA + LAMA for severe cases.
- Short-acting relievers: For quick symptom relief during flares.
- Oral medications: Like theophylline or biologics (e.g., for high eosinophils) in select cases.
Non-drug treatments
- Pulmonary rehabilitation: Exercise programs to build lung strength and endurance.
- Oxygen therapy: If blood oxygen levels are low.
- Vaccinations: Flu and pneumonia shots to prevent infections.
Treatment is personalized—your doctor may adjust based on response. Avoid self-medicating, as improper use can worsen symptoms.
What can you do yourself
Living with ACOS requires ongoing self-care to minimize flares and maintain health.
- Quit smoking: The most important step; seek support from quit lines or programs.
- Avoid triggers: Stay away from allergens, pollution, and cold air.
- Exercise regularly: Low-impact activities like walking or swimming, guided by rehab.
- Healthy diet: Anti-inflammatory foods (fruits, veggies, omega-3s) to support lung health.
- Monitor symptoms: Use a peak flow meter and follow an action plan for exacerbations.
- Regular check-ups: Track lung function and adjust treatments as needed.
Improving inhaler technique is key—many patients don’t use them correctly, reducing effectiveness.
Prognosis and complications
ACOS often leads to a faster decline in lung function, more frequent hospitalizations, and higher mortality than asthma or COPD alone. However, with proper management, many people lead active lives.
Complications include heart disease, osteoporosis from steroids, and mental health issues like anxiety. Early intervention improves prognosis—studies show better outcomes with tailored therapy.
Frequently asked questions about ACOS
- Is ACOS curable?
No, but symptoms can be well-controlled with treatment.
- How does ACOS differ from severe asthma?
ACOS has more fixed airflow limitation and COPD-like features.
- Can children get ACOS?
It’s rare; mostly affects adults with long-term exposure risks.
- What if treatments aren’t working?
Discuss biologics or clinical trials with your doctor.
- How can I prevent exacerbations?
Follow your action plan, get vaccinated, and avoid triggers.
If you suspect ACOS, see a specialist soon. Resources like the American Lung Association offer free helplines for guidance.