Asthma and COPD are both common lung diseases with very similar symptoms. Doctors have long had difficulty in diagnosing a patient when they presented with respiratory symptoms as to which category the patient falls into. Usually asthma is more likely in younger patients and COPD in older patients. However the mechanisms behind the symptoms for asthma and COPD are different and it is likely that 15%-25% of patients with obstructive lung disease actually suffer from both conditions simultaneously. When both of these occur in the same patient it is now known as Asthma COPD Overlap Syndrome or ACOS. Awareness is increasing but it is agreed that patients with ACOS suffer more frequent exacerbations, have a poorer quality of life, experience a more rapid decline in lung function, have a higher mortality rate and consume a disproprtionate amount of healthcare resources compared with patients who suffer from Asthma or COPD alone. However distinguishing ACOS from asthma or COPD is still problematic.

Asthma is defined as a disease characterized by chronic inflammation of the airways. With patients having a history of respiratory symptoms such as wheezing, shortness of breath, chest tightness and a cough. These symptoms can vary over time and in intensity.

COPD is defined as a common and preventable disease, caused by chronic exposure to damaging gases or particles such as smoking. This causes chronic inflammation in the airways and lungs which is also progressive.

ACOS is defined as the patient suffering limited lung airflow with several symptoms that are usually associated with either asthma or COPD. Therefore if you have symptoms from both categories then you can be diagnosed with ACOS.
Unfortunately research on ACOS is limited as most research trials investigating COPD have excluded patients with asthma and vice-versa and also excluded those that presented with both. Also many patients have been misdiagnosed with asthma when in fact they may have COPD or ACOS.

So what is the difference?
All three conditions are chronic diseases and all patients will complain of a cough, dyspnea and wheezing.
Asthma and ACOS share the feeling of a tight chest.
Asthma patients tend to never have had smoked.
COPD and ACOS patients tend to have been exposed to burning fossil fuels, gases or have smoked.
ACOS may be diagnosed in patients that have had long-standing asthma or have had airway remodelling.
COPD and ACOS is usually diagnosed in patients older than forty although ACOS patients usually have had symptoms earlier in life in one form or another, whereas asthma is usually found in patients younger than 40 years of age. Asthma can manifest in childhood, fade away and then may reappear in adulthood at a later date.
Asthma symptoms tend to vary day to day and occur more often at night and linked to triggers such as pollen and dust and exercise. The symptoms also respond well to the right medication and treatment.
ACOS and COPD symptoms tend to be more persistent, improve less dramatically with treatment and progressively get worse.
All three diseases suffer exacerbations but patients with ACOS suffer them three times as frequently and much more severely compared to asthma or COPD alone.
Patients with long-standing asthma may begin to suffer with airway-remodelling which results in incomplete reversibility of airflow and the patient can begin to look more like someone with COPD.
With all these conflicting symptoms which may fall into multiple categories it is still a long and complicated process for a doctor to be able to diagnose their patient properly but once your GP has pieced together all your symptoms, history since a child and performed respiratory tests they should be able to place you in the correct category and treat your accurately.
ACOS is still a fairly newly recognised disease but it has allowed a new understanding of the interplay of asthma and COPD and new research topics are being investigated to aid in understanding all three diseases more accurately.
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