Asthma and COPD are both lung diseases that have obstructive respiratory patterns. In both cases, the problem is not getting (enough) air into the lungs but rather “getting it out” once inhaled. This is due to a problem in the airways, which in these disease processes become narrowed, offering more resistance to air movement.
There are, however, differences between asthma and COPD, the most significant being that airway resistance in asthma is reversible. With prompt treatment, the airway obstruction is eliminated allowing the anatomy of the lungs to remain normal. In COPD, there are persistent changes resulting from chronic airway obstruction. As a result of the air not being completely exhaled after each breath, there is overexpansion off the lungs. A phenomenon called, “air trapping” occurs, leading to hyperinflation of the lungs, frequently seen on chest x-rays.
The resulting consequences are progressive loss of the natural elasticity that normal lungs have, so affected individuals have to work harder with each breath. This requires using more muscles (to breathe) which results in shortness of breath that’s not treatable with standard bronchodilators.
The traditional thinking is that asthma and COPD are two distinct diseases because the causes are different. Asthma is a disease of inflammation where the inner lining of the bronchi swells, narrowing the passages where air flows. When the inflammation is treated, the swelling subsides and air passes freely. COPD is a disease which can start with inflammation, but as the process continues, there is tissue destruction with permanent (irreversible) damage.
This distinction between the two conditions, however, may not be quite this simple. There are some cases where you have features of both conditions in an individual – overlap syndrome. When this situation occurs with asthma and COPD, it’s identified as ACOS (asthma/COPD overlap syndrome). Essentially, one respiratory condition overlaps with the other.
Certain individuals who have asthma will go on to develop COPD as well. A July 2018 Canadian study published in the Annals of the American Thoracic Society suggests that there is a gender predisposition for this overlap process. Over four thousand women were included in this study that spanned over 14 years and 1,701 or 42 percent of the women who had asthma went on to also develop COPD.
The researchers tried to identify certain characteristics in this group of women that would help lead to preventive measures, so that COPD risk could be limited. There was reason to believe that individual risk factors play a larger role than common factors such as exposure to fine particulate matter (PM) in air pollution. None the less, exposure to PM 2.5 (2.5 microns particles measured in parts per million) was also evaluated as a possible risk factor, and it was found to raise COPD risk in these subjects, although to a lesser extent.
Being diagnosed with obesity is one condition that has some relevance in the discussion of overlap risk. If you are breathless, it may be entirely attributed to the excess weight and a missed diagnosis of respiratory inflammation and asthma can raise the risk of it progressing to COPD and ACOS.
Not surprisingly, smoking more than the equivalent of one pack off cigarettes per day for over 5 years, was a strong predictor for progression of asthma to COPD, but there was also a significant number of women (38 percent) who developed ACOS who never smoked.
This is not the first study that highlighted gender as a risk factor for COPD.
I’ve also previously discussed gender differences in COPD population highlighting risk factors including:
- Women have smaller airways, so smoking cigarettes results in “more concentrated exposure.”
- Women have more airway hyper-responsiveness and are therefore more susceptible to smoke than men.
- Women have more recently entered work force sectors initially dominated by men, that expose them to agents that cause chronic airway damage.
- The ECLIPSE study, which identified surrogate end points in those with COPD, and showed that women have higher rates of co-morbidities (osteoporosis, depression, anxiety disorder) which lead to a worse perception of quality of life, resulting in progression of COPD.
- There was also the suggestion that there may be over-diagnosis of COPD in women since they are more likely to seek health for their (respiratory) complaints.
This Canadian study found additional gender data. For one thing, women make up a larger proportion of the non-smoker population who develop COPD. Other common factors in this (female) population at risk for ACOS include obesity, rural living, and lower education and socio-economic levels. This would imply lower access to care for asthma and lower compliance with treatment, even though in Canada, access to care should not be a problem because of their healthcare system. Limitations of the study included lack of data on exposure to secondhand smoke and air pollution over the full course of the study.
There are findings in this study that can help to reduce the risk of ACOS because they are modifiable:
- Healthcare providers should look for warning signs that asthma is progressing. The reason for the progression from asthma to COPD is that chronic inflammation of the airways if not adequately treated, will lead to permanent changes in the lungs called “remodeling.” That sets the stage for COPD to develop because this permanent obstruction in the airways will lead to incomplete expiration and “air trapping,” which causes hyperinflation and emphysema. If you have asthma, talk to your doctor about your risk for ACOS.
- It’s important to institute treatment (and compliance) while the process is still reversible. There are tools that can help to distinguish airway inflammation as the cause of breathlessness, such as exhaled nitrous oxide (ENO) test. This would be especially helpful as a test in people with obesity, to identify asthma. Ask your doctor if you should have symptoms of breathlessness evaluated to rule out asthma.
- It’s also important to highlight the importance of physical activity - not only in preventing obesity, but also in helping to maintain respiratory integrity and to help reduce the risk of other co-morbidities associated with COPD. Discuss an exercise program with your doctor.
- Once asthma is diagnosed, there are clear guidelines for stepwise treatment. Unfortunately, there is a high rate of poor compliance with treatment. Patients when symptom free, often abandon maintenance medications. That reality can raise the risk of progression to COPD among individuals who have a higher risk for ACOS. Take your prescribed medications and see your doctor regularly so he can monitor your asthma.
- Smoking cessation is always an important health goal, but it is especially important among individuals with asthma who are at higher risk of ACOS. Talk to your doctor about smoking cessation options.
- Air pollution with high particulate matter levels and work environment may not be completely under control of the individual, but if you feel that your work environment is contributing to or exacerbating symptoms of asthma, talk to your manager about possible accommodations.