Asthma is a chronic but reversible disease of the respiratory tract where the airways become narrow, swollen, and may produce extra mucus which results in difficulty in the passage of air as we breathe. The burden of asthma, as assessed by disability-adjusted life-years, ranked 22nd among all diseases worldwide. According to World Health Organization estimates, 300 million people worldwide suffer from asthma.
It has been seen that asthma is more prevalent in westernized societies than in rural or developing regions. The highest rates of asthma symptoms were noticed in western countries such as the United Kingdom, Australia, and New Zealand. While the lowest prevalence was seen in Africa and the Indian subcontinent.
For both adolescents and children, the prevalence of asthma in the Asia-Pacific region was in the middle rank among the world. But the studies have also documented that the prevalence of asthma and atopic conditions is rapidly increasing during the past two decades in Asia due to increased urbanization and air pollution.
37% of children with asthma in the Asia-Pacific region reported that this condition had resulted in an absence from school or work in a study, and 40% reported being hospitalized, visiting the emergency department, or making unscheduled emergency visits to other healthcare facilities.
Causes and Risk Factors of AsthmaSome of the known risk factors of asthma are:
- Environmental allergens e.g., house dust mites, animal allergens, cockroach allergens, fungi, etc.
- Viral respiratory tract infections
- Exercise, hyperventilation
- Gastroesophageal reflux disease
- Chronic sinusitis or rhinitis
- Aspirin or no steroidal anti-inflammatory drug hypersensitivity
- Use of beta-adrenergic receptor blockers (including ophthalmic preparations)
- Environmental pollutants
- Occupational exposure(e.g., plants, latex, gums, diisocyanates, anhydrides, wood dust, and fluxes)
- Irritants (e.g., household sprays, paint fumes)
- Emotional factors or stress
- Perinatal factors such as prematurity increased maternal age and maternal smoking.
Signs and symptoms of AsthmaThe main signs and symptoms of asthma are:
- Wheezing, which means breathing out with a whistling sound in the chest.
- Shortness of breath
- Chest pain
- Difficulty in sleeping due to breathing problems.
For some people, asthma signs and symptoms flare up in certain situations:
- Exercise-induced asthma: It is worse when the air is cold and dry.
- Occupational asthma: It occurs in the workplace due to irritants such as chemical fumes, gases, or dust.
- Allergy-induced asthma: It is triggered by airborne substances. For example, pollen, mold spores, cockroach waste, or particles of skin and dried saliva shed by pets.
Classification of AsthmaAsthma is classified into four categories, as follows:
- Mild intermittent asthma: Here the symptoms are mild and last up to two days a week and up to two nights a month.
- Mild persistent asthma: The symptoms occur more than twice a week, but no more than once in a single day.
- Moderate persistent asthma: The symptoms occur once a day and more than one night a week.
- Severe persistent asthma: Symptoms are seen throughout the day on most days and frequently at night.
Diagnosing AsthmaThe diagnosis of asthma is done based on history, clinical examination, and lung function tests. Some major tests your doctor may request are:
- Spirometry with a post-bronchodilator response: It is the primary test to establish the asthma diagnosis. In this procedure, it is analyzed how much air is exhaled after a deep breath and how fast one can breathe out. If the lung function improves with the use of a bronchodilator, the diagnosis is likely asthma.
- Exercise spirometry: It is the standard method for assessing patients with exercise-induced asthma. The oxygen levels and heart rate of the patient are monitored while s/he runs on a treadmill. This will show if exercise triggers your symptoms.
- Irritant challenge: The patient is exposed to an asthma trigger, like smoke, perfume, or chemicals to see if these exacerbate their symptoms.
- Methacholine challenge test: This test is more commonly used for adults than children. When methacholine is inhaled, the airways contract as a reflex and narrow. During this test, if the lung function drops by at least 20%, it is asthma.
- Peak flow meter: It is a simple device that helps to measure how hard the patient can breathe out.
- Pulse oximetry measurement: It is important in all patients with acute asthma to measure oxygen levels in the blood.
- Chest radiograph: It remains the initial imaging evaluation in most individuals with symptoms of asthma. However, in most patients with asthma, chest X-ray findings are normal or may indicate hyperinflated lungs.
- Others: allergy tests, FeNO tests, sputum eosinophils level, etc
Treatment of AsthmaThe main goal of the treatment is:
- To prevent symptoms
- To minimize disability from acute episodes
- To prevent functional and psychological morbidity to provide a healthy lifestyle
Pharmacologic management includes the use of relief and control agents. The control agents are used to stop acute asthma attacks. They include inhaled corticosteroids, long-acting bronchodilators, theophylline, leukotriene modifiers, anti-IgE antibodies, anti-interleukin (IL)–5 antibodies, and anti–IL-4/IL-13 antibodies.
Relief medications provide a long-term cure and also help prevent exacerbations. They include short-acting bronchodilators, systemic corticosteroids, and ipratropium.
The treatment of asthma is based on 'stepwise therapy' which means that the medications should be added or deleted as per the frequency and severity of the symptoms.
Patient education is very important to help them recognize the triggers and take steps to avoid triggers. It is important to track the breathing to make sure that the medications are keeping symptoms under control. Children and the elderly must be guided repeatedly about the proper use of inhaler therapy. Environmental exposures and irritants play a strong role in symptom exacerbations. Once the offending allergens are identified, it is wise to avoid them.
Asthma and Ongoing Clinical TrialsOther promising new approaches for the management of asthma are:
- Newer monoclonal antibodies like itolizumab, dupilumab: The monoclonal antibodies bind to the specific receptor in cells and block the activation of immune cells called the T lymphocytes that helps to suppress the pro-inflammatory mediators and decrease the inflammatory response.
- Phosphodiesterase 4 inhibitors (PDE4): It allows for examination of a mechanism that potentially links obesity and asthma and also helps treat hyperinsulinemic, overweight asthmatics.
- Clinical trials are being conducted towards targeting the origin of the inflammatory cascade in allergic asthma to treat the disease at its roots.
- Bronchial thermoplasty: It is a novel intervention for asthma that utilizes controlled thermal energy to treat the airway wall during a series of bronchoscopy procedures.
- CSJ117 is another drug under clinical trial. It is an antigen-binding antibody fragment (Fab) that is supposed to suppress the immune cells known as type 2 helper T-cell, responsible to mediate symptoms of asthma.
- Recent studies have suggested that aspirin use can reduce the risk of adult-onset asthma. A few others have shown that some individuals with asthma improve after challenges with aspirin or non-steroidal anti-inflammatory drugs (NSAIDs).
- Clinical studies are also being conducted for identifying the predictive biomarkers for the diagnosis and treatment of Asthma and COPD.
- Sell K2 is another drug under clinical trial. It is supposed to block the movement of key inflammatory cells into the lungs and consequently improve lung function.
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