What is Severe Asthma?
Researchers have learned that 5-10 percent of asthmatics do not respond well to traditional asthma medications, making their asthma difficult to control. In order to better help these asthmatics, researchers now categorize them under a special asthma subtype called Severe Asthma. So, what is severe asthma, and what does it mean if you have it?
What is it? Sally Wenzel, professor of medicine at the University of Pittsburgh, defines severe asthma as “patients who require high dose inhaled glucocorticoid (GC), or continuous or near continuous oral GC treatment to maintain asthma control or who never achieve control despite that treatment.” It was defined as an asthma subtype less than 15 years ago.
What is it not****? Severe asthma must not be confused with other causes of difficult to treat asthma, including:
Asthma exacerbated by uncontrolled asthma triggers (You have allergic asthma and have attacks when exposed to molds)
Asthma that is poorly controlled due to nonadherence (You do not take your medicines)
Disorders that mimic asthma (you have sinus infections)
Asthma exacerbated by comorbid conditions (you have asthma and allergies, or asthma and GERD; controlling one means controlling the other)
What does a diagnosis of severe asthma mean**?** It means that you have:
Chronic Airway Inflammation. This makes airways hypersensitive to asthma triggers, exposure to which causes the smooth muscles that wrap around them to spasm. This narrows or obstructs the airways. A second response is increased sputum production, further obstructing airways. This causes intermittent asthma symptoms like wheezing and shortness of breath. This response is completely reversible, and can be prevented and treated with typical asthma medications. This is seen in all asthmatics.
Airway Remodelling. This is also referred to as airway scarring. It’s associated with a permanent thickening of the walls lining airways, particularly smaller airways. This makes them chronically narrowed or chronically obstructed. The cause of this remains a mystery, although some speculate it has to do with asthma left untreated long-term, or too many severe asthma attacks. Another common cause is chronic inhalation of chemicals, such as those in tobacco and wood smoke. It causes persistent symptoms; it makes you feel short of breath even on a good asthma day. This response is irreversible, and there is at present no treatment. This is similar to what happens in COPD, and is only present in severe asthmatics.
These two components together act as a “double whammy,” making asthma difficult to control. This probably means you also have:
Air trapping. Air can get past chronically narrowed airways but has a hard time getting back out. This causes air to become trapped inside your lungs.
Airflow limitation. This is best observed by a prolonged expiration. Sometimes it may seem you can exhale forever and never get all the air out. You can’t generate enough flow to blow out a candle.
Fewer treatment options. No medicine treats airway remodelling. You respond poorly to traditional asthma medications, like inhaled corticosteroids. However, a new treatment called bronchial thermoplasty does show promise.
More frequent and severe asthma attacks. Their airways are increasingly brittle and narrow making them increasingly prone to more severe attacks compared to those with typical asthma.
Lots of doctor appointments. They’ll need to see doctors who specialize in this type of asthma. They are also prone to more frequent and unscheduled doctor visits compared to those with typical asthma.
Lots of fees. While they consist of only 5-10 percent of asthmatics, they consume up to half the cost of asthma in both the U.S. and Europe.
Unanswered questions. So, why is it that only 5-10 percent of asthmatics develop severe asthma? Researchers are working overtime to answer this question and to create special guidelines and medicinal options to help them achieve optimal control of their disease.
Here is some of what is presently understood. Researchers believe the immune response that occurs in severe asthmatics is different than what occurs in traditional asthmatics. For instance, immune cells (called CD4-T cells) secrete different inflammatory proteins (particularly interferon gamma) than the same cells in traditional asthmatics. This makes their airways hypersensitive in such a way that does not respond to corticosteroids.
So what does this mean**?** It signifies hope for better treatment options. Researchers also discovered that mice that lacked the interferon gamma protein may develop traditional asthma but not Severe Asthma. Using computer models, they compared gamma protein with asthma genes, and learned that as interferon gamma levels rose, a protein called leukocyte protease inhibitor (SLPI) dropped. They later learned that boosting SLPI levels reduced airway hyperreactivity in animal models.
The Burden. It is well established that severe asthma accounts for a majority of healthcare costs for asthma. The true impact of severe asthma on people’s lives was revealed in a survey released in September, 2015.Of 850 severe asthmatics surveyed, 25% reported daily symptoms, and 71% reported weekly symptoms. Likewise, 32% said it affected their social life, 23% said it affected their working life, 18% said it affected their family life, and 17% said it affected their sex life.
Conclusion. A proper diagnosisan may lead your doctor to the best treatment options to helping you obtain ideal control of your disease. Ongoing research should equal better breathing in the near future for all asthmatics.
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John Bottrell is a registered Respiratory Therapist. He wrote for HealthCentral as a health professional for Asthma and Chronic Obstructive Pulmonary Disease (COPD).