Signs and symptoms
Asthma is characterized by recurrent episodes ofAssociated conditions
A number of other health conditions occur more frequently in people with asthma, includingCauses
Asthma is caused by a combination of complex and incompletely understood environmental and genetic interactions. These influence both its severity and its responsiveness to treatment. It is believed that the recent increased rates of asthma are due to changingEnvironmental
Many environmental factors have been associated with asthma's development and exacerbation, including, allergens, air pollution, and other environmental chemicals. Smoking during pregnancy and after delivery is associated with a greater risk of asthma-like symptoms. LowHygiene hypothesis
TheGenetic
Family history is a risk factor for asthma, with many different genes being implicated. If one identical twin is affected, the probability of the other having the disease is approximately 25%. By the end of 2005, 25 genes had been associated with asthma in six or more separate populations, including GSTM1, IL10,Medical conditions
A triad ofExacerbation
Some individuals will have stable asthma for weeks or months and then suddenly develop an episode of acute asthma. Different individuals react to various factors in different ways. Most individuals can develop severe exacerbation from a number of triggering agents. Home factors that can lead to exacerbation of asthma includePathophysiology
Asthma is the result of chronic inflammation of the conducting zone of the airways (most especially the bronchus, bronchi and bronchioles), which subsequently results in increased contractability of the surrounding smooth muscles. This among other factors leads to bouts of narrowing of the airway and the classic symptoms of wheezing. The narrowing is typically reversible with or without treatment. Occasionally the airways themselves change. Typical changes in the airways include an increase inDiagnosis
While asthma is a well-recognized condition, there is not one universal agreed upon definition. It is defined by the Global Initiative for Asthma as "a chronic inflammatory disorder of the airways in which many cells and cellular elements play a role. The chronic inflammation is associated with airway hyper-responsiveness that leads to recurrent episodes of wheezing, breathlessness, chest tightness and coughing particularly at night or in the early morning. These episodes are usually associated with widespread but variable airflow obstruction within the lung that is often reversible either spontaneously or with treatment". There is currently no precise test for the diagnosis, which is typically based on the pattern of symptoms and response to therapy over time. Asthma may be suspected if there is a history of recurrent wheezing, coughing or difficulty breathing and these symptoms occur or worsen due to exercise, viral infections, allergens or air pollution. Spirometry is then used to confirm the diagnosis. In children under the age of six the diagnosis is more difficult as they are too young for spirometry.Spirometry
Spirometry is recommended to aid in diagnosis and management. It is the single best test for asthma. If the FEV1 measured by this technique improves more than 12% and increases by at least 200 milliliters following administration of a bronchodilator such asOthers
The methacholine challenge test, methacholine challenge involves the inhalation of increasing concentrations of a substance that causes airway narrowing in those predisposed. If negative it means that a person does not have asthma; if positive, however, it is not specific for the disease. Other supportive evidence includes: a ≥20% difference in peak expiratory flow rate on at least three days in a week for at least two weeks, a ≥20% improvement of peak flow following treatment with either salbutamol, inhaled corticosteroids or prednisone, or a ≥20% decrease in peak flow following exposure to a trigger. Testing peak expiratory flow is more variable than spirometry, however, and thus not recommended for routine diagnosis. It may be useful for daily self-monitoring in those with moderate to severe disease and for checking the effectiveness of new medications. It may also be helpful in guiding treatment in those with acute exacerbations.Classification
Asthma is clinically classified according to the frequency of symptoms, forced expiratory volume in one second (spirometry, FEV1), and peak expiratory flow rate. Asthma may also be classified as atopic (extrinsic) or non-atopic (intrinsic), based on whether symptoms are precipitated by allergens (atopic) or not (non-atopic). While asthma is classified based on severity, at the moment there is no clear method for classifying different subgroups of asthma beyond this system. Finding ways to identify subgroups that respond well to different types of treatments is a current critical goal of asthma research. Although asthma is a chronic obstructive lung disease, obstructive condition, it is not considered as a part of chronic obstructive pulmonary disease, as this term refers specifically to combinations of disease that are irreversible such as bronchiectasis and Pneumatosis#Lungs, emphysema. Unlike these diseases, the airway obstruction in asthma is usually reversible; however, if left untreated, the chronic inflammation from asthma can lead the lungs to become irreversibly obstructed due to airway remodeling. In contrast to emphysema, asthma affects the bronchi, not the Pulmonary alveolus, alveoli. The combination of asthma with a component of irreversible airways obstruction has been termed the asthma-chronic obstructive disease (COPD) overlap syndrome (ACOS). Compared to other people with "pure" asthma or COPD, people with ACOS exhibit increased morbidity, mortality and possibly more comorbidities.Asthma exacerbation
An acute asthma exacerbation is commonly referred to as an ''asthma attack''. The classic symptoms areExercise-induced
Exercise can trigger bronchoconstriction both in people with or without asthma. It occurs in most people with asthma and up to 20% of people without asthma. Exercise-induced bronchoconstriction is common in professional athletes. The highest rates are among cyclists (up to 45%), swimmers, and cross-country skiers. While it may occur with any weather conditions, it is more common when it is dry and cold. Inhaled beta2-agonists do not appear to improve athletic performance among those without asthma, however, oral doses may improve endurance and strength.Occupational
Asthma as a result of (or worsened by) workplace exposures is a commonly reported occupational disease. Many cases, however, are not reported or recognized as such. It is estimated that 5–25% of asthma cases in adults are work-related. A few hundred different agents have been implicated, with the most common being: isocyanates, grain and wood dust, colophony, soldering flux, latex, animals, and aldehydes. The employment associated with the highest risk of problems include: those who spray paint, bakers and those who process food, nurses, chemical workers, those who work with animals, welders, hairdressers and timber workers.Aspirin-induced asthma
Aspirin-exacerbated respiratory disease (AERD), also known asAlcohol-induced asthma
Alcohol may worsen asthmatic symptoms in up to a third of people. This may be even more common in some ethnic groups such as the Japanese people, Japanese and those with aspirin-induced asthma. Other studies have found improvement in asthmatic symptoms from alcohol.Non-atopic asthma
Non-atopic asthma, also known as intrinsic or non-allergic, makes up between 10 and 33% of cases. There is negative skin test to common inhalant allergens. Often it starts later in life, and women are more commonly affected than men. Usual treatments may not work as well. The concept that "non-atopic" is synonymous with "non-allergic" is called into question by epidemiological data that the prevalence of asthma is closely related to the serum IgE level standardized for age and sex (P<0.0001), indicating that asthma is almost always associated with some sort of IgE-related reaction and therefore has an allergic basis, although not all the allergic stimuli that cause asthma appear to have been included in the battery of aeroallergens studied (the "missing antigen(s)" hypothesis). For example, an updated systematic review and meta-analysis of population-attributable risk (PAR) of ''Chlamydia pneumoniae'' biomarkers in chronic asthma found that the PAR for ''C. pneumoniae''-specific IgE was 47%.Infectious asthma
When queried, asthma patients may report that their first asthma symptoms began after an acute lower respiratory tract illness. This type of history has been labelled the "infectious asthma" (IA) syndrome, or as "asthma associated with infection" (AAWI) to distinguish infection-associated asthma initiation from the well known association of respiratory infections with asthma exacerbations. Reported prevalences of IA for adults range from around 40% in a primary care practice to 70% in a specialty practice treating mainly severe asthma patients. The true population prevalence of IA in adult-onset asthma is unknown because clinicians are not trained to elicit this type of history routinely, and recollection in child-onset asthma is challenging.Differential diagnosis
Many other conditions can cause symptoms similar to those of asthma. In children, symptoms may be due to other upper airway diseases such asPrevention
The evidence for the effectiveness of measures to prevent the development of asthma is weak. The World Health Organization recommends decreasing risk factors such as tobacco smoke, air pollution, chemical irritants including perfume, and the number of lower respiratory infections. Other efforts that show promise include: limiting smoke exposure Uterus, in utero, breastfeeding, and increased exposure to daycare or large families, but none are well supported enough to be recommended for this indication. Early pet exposure may be useful. Results from exposure to pets at other times are inconclusive and it is only recommended that pets be removed from the home if a person has allergic symptoms to said pet. Dietary restrictions during pregnancy or when breast feeding have not been found to be effective at preventing asthma in children and are not recommended. Omega-3 consumption, mediterranean diet and anti-oxidants have been suggested by some studies that might help preventing crisis but the evidence is still inconclusive. Reducing or eliminating compounds known to sensitive people from the work place may be effective. It is not clear if annual influenza vaccines, influenza vaccinations affects the risk of exacerbations. Immunization, however, is recommended by the World Health Organization. Smoking bans are effective in decreasing exacerbations of asthma.Management
While there is no cure for asthma, symptoms can typically be improved. The most effective treatment for asthma is identifying triggers, such as Health effects of tobacco smoking, cigarette smoke, pets, or aspirin-induced asthma, aspirin, and eliminating exposure to them. If trigger avoidance is insufficient, the use of medication is recommended. Pharmaceutical drugs are selected based on, among other things, the severity of illness and the frequency of symptoms. Specific medications for asthma are broadly classified into fast-acting and long-acting categories. The medications listed below have demonstrated efficacy in improving asthma symptoms, however "real world" use-effectiveness is limited as around half of people with asthma worldwide remain sub-optimally controlled, even when treated. People with asthma may remain sub-optimally controlled either because optimum doses of asthma medications do not work (called "refractory" asthma) or because individuals are either unable (e.g. inability to afford treatment, poor inhaler technique) or unwilling (e.g., wish to avoid side effects of corticosteroids) to take optimum doses of prescribed asthma medications (called "difficult to treat" asthma). In practice, it is not possible to distinguish "refractory" from "difficult to treat" categories for patients who have never taken optimum doses of asthma medications. A related issue is that the asthma efficacy trials upon which the pharmacological treatment guidelines are based have systematically excluded the majority of people with asthma. For example, asthma efficacy treatment trials always exclude otherwise eligible people who smoke, and smoking blunts the efficacy of inhaled corticosteroids, the mainstay of asthma control management. Bronchodilators are recommended for short-term relief of symptoms. In those with occasional attacks, no other medication is needed. If mild persistent disease is present (more than two attacks a week), low-dose inhaled corticosteroids or alternatively, a leukotriene antagonist or a mast cell stabilizer by mouth is recommended. For those who have daily attacks, a higher dose of inhaled corticosteroids is used. In a moderate or severe exacerbation, corticosteroids by mouth are added to these treatments. People with asthma have higher rates of anxiety,Lifestyle modification
Avoidance of triggers is a key component of improving control and preventing attacks. The most common triggers includeMedications
Medications used to treat asthma are divided into two general classes: quick-relief medications used to treat acute symptoms; and long-term control medications used to prevent further exacerbation. Antibiotics are generally not needed for sudden worsening of symptoms or for treating asthma at any time.Medications of asthma exacerbations
Long–term control
Delivery methods
Medications are typically provided as metered-dose inhalers (MDIs) in combination with an asthma spacer or as a dry powder inhaler. The spacer is a plastic cylinder that mixes the medication with air, making it easier to receive a full dose of the drug. A nebulizer may also be used. Nebulizers and spacers are equally effective in those with mild to moderate symptoms. However, insufficient evidence is available to determine whether a difference exists in those with severe disease. For delivering short-acting beta-agonists in acute asthma in children, spacers may have advantages compared to nebulisers, but children with life-threatening asthma have not been studied. There is no strong evidence for the use of intravenous LABA for adults or children who have acute asthma. There is insufficient evidence to directly compare the effectiveness of a metered-dose inhaler attached to a homemade spacer compared to commercially available spacer for treating children with asthma.Adverse effects
Long-term use of inhaled corticosteroids at conventional doses carries a minor risk of adverse effects. Risks include oral candidiasis, thrush, the development of cataracts, and a slightly slowed rate of growth. Rinsing the mouth after the use of inhaled steroids can decrease the risk of thrush. Higher doses of inhaled steroids may result in lower bone mineral density.Others
Inflammation in the lungs can be estimated by the level of exhaled nitric oxide. The use of exhaled nitric oxide levels (FeNO) to guide asthma medication dosing may have small benefits for preventing asthma attacks but the potential benefits are not strong enough for this approach to be universally recommended as a method to guide asthma therapy in adults or children. When asthma is unresponsive to usual medications, other options are available for both emergency management and prevention of flareups. Additional options include: * Humidified Oxygen to alleviate hypoxia (medical), hypoxia if oxygen saturation, saturations fall below 92%. * Corticosteroid by mouth are recommended with five days of prednisone being the same 2 days of dexamethasone. One review recommended a seven-day course of steroids. * Magnesium sulfate intravenous treatment increases bronchodilation when used in addition to other treatment in moderate severe acute asthma attacks. In adults intravenous treatment results in a reduction of hospital admissions. Low levels of evidence suggest that inhaled (nebulised) magnesium sulfate may have a small benefit for treating acute asthma in adults. Overall, high quality evidence do not indicate a large benefit for combining magnesium sulfate with standard inhaled treatments for adults with asthma. * Heliox, a mixture of helium and oxygen, may also be considered in severe unresponsive cases. * Intravenous salbutamol is not supported by available evidence and is thus used only in extreme cases. * Methylxanthines (such as theophylline) were once widely used, but do not add significantly to the effects of inhaled beta-agonists. Their use in acute exacerbations is controversial. * The dissociative anesthetic ketamine is theoretically useful if intubation and mechanical ventilation is needed in people who are approaching respiratory arrest; however, there is no evidence from clinical trials to support this. * For those with severe persistent asthma not controlled by inhaled corticosteroids and LABAs, bronchial thermoplasty may be an option. It involves the delivery of controlled thermal energy to the airway wall during a series of bronchoscopy, bronchoscopies. While it may increase exacerbation frequency in the first few months it appears to decrease the subsequent rate. Effects beyond one year are unknown. * Monoclonal antibody injections such as mepolizumab, dupilumab, or omalizumab may be useful in those with poorly controlled atopic asthma. However, as of 2019 these medications are expensive and their use is therefore reserved for those with severe symptoms to achieve cost-effectiveness. Monoclonal antibodies targeting Interleukin 5, interleukin-5 (IL-5) or its receptor (IL-5R), including mepolizumab, reslizumab or benralizumab, in addition to standard care in severe asthma is effective in reducing the rate of asthma exacerbations. There is limited evidence for improved health-related quality of life and lung function. * Evidence suggests that sublingual immunotherapy in those with bothAlternative medicine
Many people with asthma, like those with other chronic disorders, use alternative medicine, alternative treatments; surveys show that roughly 50% use some form of unconventional therapy. There is little data to support the effectiveness of most of these therapies. Evidence is insufficient to support the usage of vitamin C or vitamin E for controlling asthma. There is tentative support for use of vitamin C in exercise induced bronchospasm. Fish oil dietary supplements (marine n-3 fatty acids) and reducing dietary sodium do not appear to help improve asthma control. In people with mild to moderate asthma, treatment with vitamin D supplementation may reduce the risk of asthma exacerbations, however, it is not clear if this is only helpful for people who have low vitamin D levels to begin with (low baseline vitamin D). There is no strong evidence to suggest that vitamin D supplements improve day-to-day asthma symptoms or a person's lung function. There is no strong evidence to suggest that adults with asthma should avoid foods that contain monosodium glutamate (MSG). There have not been enough high-quality studies performed to determine if children with asthma should avoid eating food that contains MSG. Acupuncture is not recommended for the treatment as there is insufficient evidence to support its use. Air ionisers show no evidence that they improve asthma symptoms or benefit lung function; this applied equally to positive and negative ion generators. Manual therapies, including osteopathy, osteopathic, chiropractic, physical therapy, physiotherapeutic and respiratory therapy, respiratory therapeutic maneuvers, have insufficient evidence to support their use in treating asthma. The Buteyko breathing technique for controlling hyperventilation may result in a reduction in medication use; however, the technique does not have any effect on lung function. Thus an expert panel felt that evidence was insufficient to support its use. There is no clear evidence that breathing exercises are effective for treating children with asthma.Prognosis
The prognosis for asthma is generally good, especially for children with mild disease. Mortality has decreased over the last few decades due to better recognition and improvement in care. In 2010 the death rate was 170 per million for males and 90 per million for females. Rates vary between countries by 100 fold. Globally it causes moderate or severe disability in 19.4 million people as of 2004 (16 million of which are in low and middle income countries). Of asthma diagnosed during childhood, half of cases will no longer carry the diagnosis after a decade. Airway remodeling is observed, but it is unknown whether these represent harmful or beneficial changes. Early treatment with corticosteroids seems to prevent or ameliorates a decline in lung function. Asthma in children also has negative effects on quality of life of their parents.Epidemiology
Economics
From 2000 to 2010, the average cost per asthma-related hospital stay in the United States for children remained relatively stable at about $3,600, whereas the average cost per asthma-related hospital stay for adults increased from $5,200 to $6,600. In 2010, Medicaid was the most frequent primary payer among children and adults aged 18–44 years in the United States; private insurance was the second most frequent payer. Among both children and adults in the lowest income communities in the United States there is a higher rate of hospital stays for asthma in 2010 than those in the highest income communities.History
Notes
References
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* {{Good article Asthma, Chronic lower respiratory diseases Human diseases and disorders Respiratory therapy Wikipedia emergency medicine articles ready to translate Steroid-responsive inflammatory conditions Wikipedia medicine articles ready to translate (full)