Asthma and COPD Overlap Syndrome (ACOS) - Causes, Diagnosis, and Treatment

Introduction

Asthma and chronic obstructive pulmonary disease (COPD) have long been recognized as distinct respiratory conditions, each with its own set of characteristics and treatment approaches. However, in recent years, a growing body of evidence has emerged highlighting the existence of a significant overlap between these two conditions, giving rise to a new entity known as asthma-COPD overlap syndrome (ACOS). This article aims to provide a comprehensive overview of ACOS, exploring its definition, clinical features, diagnosis, and management strategies.

What Is Asthma and COPD Overlap Syndrome?

Asthma and COPD overlap syndrome describes patients displaying features of both asthma and COPD. Marked by persistent, non-reversible airflow limitation and heightened inflammation, its definition varies among populations. Generally, ACOS is identified by a combination of asthma and COPD symptoms like episodic breathlessness, wheezing, cough, and variable airflow limitation.

What Are the Causes of Asthma and COPD Overlap Syndrome?

The causes of asthma-COPD overlap syndrome (ACOS) are multifactorial and often involve a combination of genetic, environmental, and lifestyle factors. Understanding the various contributors to ACOS is essential for effective management and prevention. Here are key factors associated with the development of ACOS:

Genetic Predisposition:

• Genetic factors play a role in the susceptibility to both asthma and COPD. Individuals with a family history of respiratory diseases may have a higher risk of developing ACOS.

• Specific genetic variations may influence how the immune system responds to environmental triggers, contributing to the inflammatory processes seen in ACOS.

Environmental Exposures:

• Tobacco Smoke: Cigarette smoking is a well-established risk factor for both asthma and COPD. Individuals exposed to tobacco smoke are at an increased risk of developing ACOS.

• Occupational Exposures: Certain occupational exposures to dust, fumes, and chemicals can contribute to the development or exacerbation of ACOS, especially in individuals with a genetic predisposition.

Respiratory Infections:

• Recurrent respiratory infections, particularly during childhood, may contribute to the development of asthma and COPD. ACOS can be triggered and worsened by viral infections like respiratory syncytial virus (RSV) and rhinovirus.

Allergic Sensitivities:

• Allergens, such as pollen, mold, pet dander, and dust mites, can trigger asthma symptoms in susceptible individuals. Allergic sensitivities may coexist with the chronic inflammation seen in COPD, contributing to the development of ACOS.

Chronic Airway Inflammation:

• Persistent inflammation in the airways is a hallmark of both asthma and COPD. Chronic exposure to irritants, pollutants, and allergens can lead to ongoing inflammation, contributing to the overlap of these conditions.

Age and Aging Process:

• Aging is associated with changes in lung structure and function. As individuals age, there may be a natural decline in lung function, making them more susceptible to developing respiratory conditions, including ACOS.

Obesity:

• Obesity is a risk factor for both asthma and COPD. Excess weight can affect respiratory function and contribute to systemic inflammation, further complicating the overlap between these conditions.

Airway Remodeling:

• Long-term exposure to inflammation and repeated exacerbations can lead to structural changes in the airways, a process known as airway remodeling. This remodeling may contribute to the persistent airflow limitation seen in ACOS.

Immunological Factors:

• Dysregulation of the immune response is a common feature in both asthma and COPD. Imbalances in immune cells and cytokines may contribute to the chronic inflammation and bronchoconstriction observed in ACOS.

What Are the Clinical Features of Asthma and COPD Overlap Syndrome (ACOS)?

The following are the symptoms of asthma and COPD overlap syndrome:

• ACOS patients often experience a combination of symptoms from both asthma and COPD. These may include recurrent episodes of wheezing, coughing, chest tightness, and shortness of breath.

• The symptoms are usually chronic and may worsen over time, impacting the patient's quality of life.

Airflow Limitation:

• A crucial characteristic of ACOS is the enduring airflow restriction, setting it apart from pure asthma. Evaluation via spirometry reveals a diminished FEV1/FVC ratio, indicating non-reversible limitation.

Inflammatory Response:

• ACOS involves chronic inflammation in the airways, similar to both asthma and COPD. Eosinophilic and neutrophilic inflammation may coexist, influencing the response to treatment.

What Are the Modalities to Diagnosis Asthma and COPD Overlap Syndrome?

The following are the investigation done to diagnose asthma and COPD overlap syndrome -

Clinical Assessment:

• The diagnosis of ACOS relies on a thorough clinical evaluation, including a detailed medical history and physical examination.

• The presence of both reversible airflow limitation and fixed airflow limitation is crucial for identifying ACOS.

Spirometry and Lung Function Tests:

• Spirometry is a key diagnostic tool for assessing airflow limitations. A reduced FEV1/FVC ratio supports the diagnosis of ACOS.

• Additional lung function tests, such as bronchodilator reversibility testing, may help differentiate ACOS from asthma or COPD alone.

Inflammatory Biomarkers:

• Examining blood eosinophil counts and measuring fractional exhaled nitric oxide (FeNO) levels offers valuable insights into the inflammatory aspects of ACOS.

• Elevated eosinophil counts may indicate a response to corticosteroid therapy.

Imaging Studies:

• To evaluate lung damage and exclude other respiratory conditions, medical professionals may employ chest X-rays and computed tomography (CT) scans.

What Are the Management Strategies of Asthma and COPD Overlap Syndrome?

The following are the ways to manage asthma and COPD overlap syndrome -

Pharmacological Therapy:

• Inhaled corticosteroids (ICS) and long-acting bronchodilators (LABA) are often prescribed to control inflammation and improve airflow.

• The choice of medications may depend on the predominant inflammatory component – eosinophilic or neutrophilic.

Bronchodilator Therapy:

• Short-acting bronchodilators (SABA) or short-acting anticholinergics (SAMA) can provide quick relief from acute symptoms.

• Long-acting bronchodilators, including LABA and long-acting anticholinergics (LAMA), may be used for sustained bronchodilation.

Smoking Cessation:

• As smoking is a major risk factor for both asthma and COPD, smoking cessation is a crucial component of ACOS management.

Pulmonary Rehabilitation:

• Pulmonary rehabilitation programs can enhance exercise capacity, decrease symptoms, and improve the overall quality of life for ACOS patients.

Patient Education:

• Patient education is vital in managing ACOS, helping individuals understand their condition, recognize triggers, and adhere to prescribed medications.

What Are the Prognosis and Complications?

Prognosis:

• The prognosis of ACOS varies among individuals, with factors such as age, smoking history, and severity of symptoms influencing outcomes.

• Early diagnosis and management can significantly improve long-term prognosis.

Complications:

• ACOS may lead to complications such as respiratory infections, exacerbations, and a decline in lung function if not adequately managed.

• Regular monitoring and prompt intervention can help prevent complications.

Conclusion:

Asthma-COPD overlap syndrome represents a complex and challenging respiratory condition that requires a nuanced approach to diagnosis and management. As our understanding of ACOS continues to evolve, ongoing research is essential to refine diagnostic criteria and therapeutic strategies. Healthcare professionals, through recognizing and addressing ACOS's unique traits, can customize interventions, improving patient outcomes, and elevating the quality of life. Moving forward, collaborative efforts between clinicians, researchers, and patients are crucial for advancing our understanding and refining the management of ACOS.