by What are Asthma and COPD?
Asthma and chronic obstructive pulmonary disease (COPD) are both chronic lung diseases. However, they differ in their causes, mechanisms, and typical characteristics. Asthma involves narrowed airways that react to triggers like allergens, smoke or exercise. This leads to recurring periods of wheezing, chest tightness, shortness of breath and coughing. In contrast, COPD mainly involves damage to the lungs over many years due to inhaling irritating gases or particulate matter, most often from cigarette smoking. The damage in COPD is not fully reversible and worsens over time. Common symptoms of Asthma and COPD include breathlessness, chronic cough, and sputum production.
Overlap Between the Conditions
While asthma and COPD appear different on the surface, there is growing evidence that they overlap in some people. It’s estimated that up to 30% of individuals diagnosed with one condition may also have characteristics of the other. Genetic and environmental factors play a role in how and why this happens. Those with a mix of asthma and COPD are older on average and have a longer smoking history than ‘pure’ asthma patients. They also tend to have more severe disease and a poorer quality of life compared to those with only one diagnosis.
Shared Pathways of Inflammation
A major reason for the overlap is that both involve chronic inflammation in the lungs. Asthma is driven by eosinophilic inflammation, whereas COPD primarily involves neutrophilic inflammation. However, many patients exhibit a mixed inflammatory pattern with elevated levels of both eosinophils and neutrophils in their airways and lungs. Persistent lung inflammation from environmental exposures like smoking can transform initially allergen-driven eosinophilic asthma into a smoking-related illness with neutrophil dominance over time. This transition period is where asthma and COPD features can co-exist.
Genetic Susceptibility
Genetics play an important role in susceptibility. Individuals with specific gene variants affecting immune responses and lung development are more likely to develop either asthma or COPD based on their environmental exposures. However, having certain genes, like those related to production of inflammatory cytokines, may predispose some to developing overlapping features of both conditions. This could explain mixed phenotypes seen in family studies where relatives of asthma or COPD patients are themselves at elevated risk for either disease.
Diagnosis and Management Challenges
The blend of asthma and COPD characteristics creates diagnostic and management challenges for physicians. Spirometry, which measures airflow limitation, may not clearly differentiate the two. Symptoms alone are unreliable for differentiating them as well. Therefore, integrating clinical features, risk factor history, inflammatory cell profiles in sputum or airways, response to treatments, and advanced tests like CT scans become important for making an accurate diagnosis. Treatment requires a comprehensive approach addressing both eosinophilic and neutrophilic airway inflammation along with smoking cessation counselling for current smokers.
Unmet Needs in Understanding Overlap Phenotypes
While overlap between asthma and COPD is increasingly recognized, many unanswered questions remain. We do not fully understand the changes that drive initially eosinophilic asthma towards a mixed or neutrophil-dominant pattern over time. Larger population studies are needed to better characterize clinical phenotypes in these overlap groups. Identifying specific biomarkers may help differentiate distinct endotypes within mixed disease. More research is also required to develop optimized treatment regimens tailored for these complex patients. Filling these knowledge gaps will help improve diagnosis and management of individuals where features of them co-exist.
While they were traditionally viewed as distinct conditions, an increasing number of patients exhibit overlapping features. Shared pathways of inflammation, genetic susceptibility and environmental exposures like smoking underlie this clinical blending of the two illnesses. Recognizing and characterizing asthma-COPD overlap phenotypes presents diagnostic and therapeutic challenges but also opportunities to gain mechanistic insights and develop personalized approaches to improve outcomes in these high-risk patients. Continued research efforts aiming to better understand the link between asthma and COPD are important to help address many unmet needs.
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1. Source: Coherent Market Insights, Public sources, Desk research.
2. We have leveraged AI tools to mine information and compile it.
