Tuesday, 26 November 2013

Asthma (Respiratory Disease) – The Causes

Respiratory Disease is defined as medical conditions which affect the breathing organ and tissues including Inflammatory lung disease, Obstructive lung diseases, Restrictive lung diseases, Respiratory tract infections, trachea, bronchi, bronchioles, alveoli, the nerves and  muscles breathing , etc,.
I. Asthma 
Asthma is a chronic inflammatory disease affecting the air way of the lung with recurring symptoms, such as wheezing, chest tightness, shortness of breath, and coughing. The disease affects people of all ages, and mostly starts during childhood. In the study of 463,801 children aged 13-14 years in 155 collaborating centres in 56 countries. Children self-reported, through one-page questionnaires, symptoms of these three atopic disorders. In 99 centres in 42 countries, a video asthma questionnaire was also used for 304,796 children, found that for asthma symptoms, the highest 12-month prevalences were from centres in the UK, Australia, New Zealand, and Republic of Ireland, followed by most centres in North, Central, and South America; the lowest prevalences were from centres in several Eastern European countries, Indonesia, Greece, China, Taiwan, Uzbekistan, India, and Ethiopia(1). In the United States, approximately, asthma affects 25 million people, 7 million of them are children.
B.1. Causes
1. Smoking and second hand smoke
Smoking is considered as one of major cause of lung diseases, including asthma. According to the study by Texas Tech University Health Science Center, Airway mucosal permeability is increased in smokers, which could lead to increased clearance of inhaled corticosteroids from the airways. Smokers also have decreased histone deacetylase activity, which is necessary for corticosteroids to fully suppress cytokine production, and can lead to corticosteroid resistance. The study also indicated that In asthmatic patients who smoke, disease control is poorer than in asthmatic nonsmokers. Of all forms of SHS, maternal exposure seems to have the largest impact on asthma by increasing the frequency and severity of the disease and decreasing lung function. Asthmatic children exposed to multiple household smokers face an increased risk for respiratory illness-related absences from school, and these effects persist during adolescence but weaken during adulthood(6).
2. Allergies
People who are sufferred from alergies are most likely to develop asthma. The allergic march is a progression of atopic disease from eczema to asthma, and then to allergic rhinoconjunctivitis. It appears to be caused by a regional allergic response with breakdown of the local epithelial barrier that initiates systemic allergic inflammation. Genetic and environmental factors predispose to developing the allergic march, according to the study by Department of Surgery, Cape Cod Hospital, Hyannis(7). Other indicated that Allergen exposure contributes to the risk of asthma exacerbations, but other precipitating factors, such as viruses, can interact and increase the risk. According to the study by hôpitaux universitaires de Strasbourg, deteriorating asthma can be related to increased exposure to allergens, particularly allergens from house dust mite, cockroach, cat, rodent, mold or pollen. Several studies have demonstrated that sensitization to respiratory allergens and allergen exposure increases the risk of exacerbation of asthma. When asthma exacerbations are work-related, occupational allergens may be implicated(8).
3. Occupational and environmental exposures
Occupational and exposure history may increase the risk of respiratory problems. According to a report by Dr, Hoy RF., there is a case of a man, 23 years of age and previously well, presents with 2 months of cough, shortness of breath and weight loss. Occupational and exposure history identifies him as commencing work at a mushroom farm 12 months ago where he is exposed to dust from the mixing of mushroom compost. He is not required to use respiratory protection at work. His cough and chest tightness usually start in the afternoon at work and persist into the evening. Some of the effects of exposures may be immediate, whereas others such as asbestos-related lung disease may not present for many decades. Airborne contaminants may be the primary cause of respiratory disease or can exacerbate pre-existing respiratory conditions such as asthma and chronic obstructive pulmonary disease(9).
4. Obesity
Obesity is defined as a medical condition of excess body fat has accumulated overtime, while overweight is a condition of excess body weight relatively to the height. According to the Body Mass Index(BMI), a BMI between 25 to 29.9 is considered over weight, while a BMI of over 30 is an indication of obesity. According to the statistic, 68% of American population are either overweight or obese. In the study to to examine the relationship between central obesity and asthma outcomes in a group of Iranian asthma patients, researchers showed that there is a significant association of WHR-based central obesity with forced expiratory volume in 1 s (FEV(1)) (β = -9.04; p-value = .044) and forced vital capacity (FVC) (β = -10.52; p-value = .012). Logistic regression analysis showed a significant increased risk of asthma attacks in 3 months with Asian WC-based central obesity [odds ratio (OR) = 6.31, 95% confidence interval (CI): 1.16-34.41]; emergency room (ER) visits with NIH WC-based (OR = 5.15, 95% CI: 1.36-19.55) and Asian WC-based (OR = 18.72, 95% CI: 1.92-182.63) central obesity; and hospitalization in 1 year with NIH WC-based (OR = 5.28, 95% CI: 1.28-21.84) and Asian WC-based (OR = 12.39, 95% CI: 1.29-119.53) central obesity(10).
Some study suggested that asthma in the obese patient might be more responsive to leukotriene modifiers, orchestrated by leptin and/or adiponectin derived from adipose tissue, than to inhaled corticosteroids, possibly reflecting differences in the underlying airway inflammation in obese vs. non-obese asthmatics(11).
5. Exercise-Induced Asthma
Vigorous exercise can cause a narrowing of the airways in  asthma patient.There is a report of  a 44-year-old man with a history of seasonal allergic rhinitis but no asthma, who reported difficulty breathing when playing tennis and a 45-year-old woman who presented with persistent, generally well-controlled asthma, who was now experiencing bouts of coughing and wheezing during exercise. EIB is a frequently encountered problem among patients presenting to primary care specialists. Affected patients should be made aware of the importance of proactive treatment with a short-acting beta agonist before initiating any exercise(12).
6. Gastroesophageal reflux disease (GERD)
Gastroesophageal reflux disease (GERD), also known as gastro-oesophageal reflux disease (GORD), gastric reflux disease, or acid reflux disease, is defined as a chronic condition of liquid stomach acid refluxing back up from the stomach into the esophagus, causing heartburn. According to the study of “Updated guidelines for the diagnosis and treatment of gastroesophageal reflux disease.” by DeVault KR, Castell DO; American College of Gastroenterology, GERD is defined as symptoms or mucosal damage produced by the abnormal reflux of gastric contents into the esophagus. It is considered as one the causes of asthma. There is a report of  an 11-year-old boy who was referred to a pediatric respiratory clinic for asthma that was not responsive to inhaled medications. The child presented with a one-year history of dyspnea on exertion, cough and wheeze. He also complained of chronic dyspepsia. The presence of GI symptoms, in addition to abnormalities on chest radiograph and spirometry, suggested the presence of achalasia(13).
7.  Sinusitis
Sinusitis is defined as a condition of inflammation of the paranasal sinuses of which can develop headache as a result of exposure to a cold or flu virus, or an allergic reaction to pollen, mold, dust or smoke, etc..Sinusitisaffects 37 million people each year. Some researchers suggested that there is a close relationship between allergic rhinitis and asthma, food allergy, and atopic dermatitis. Rhinitis and sinusitis often coexist and are commonly referred to with the term rhinosinusitis. These conditions are also linked in the so-called atopic march, which is the sequential appearance of atopic manifestations starting with atopic dermatitis and later followed by food allergy, allergic rhinitis, and asthma(14).
8.  Upper Respiratory Infections
upper respiratory viral infections are strongly associated in time with hospital admissions for asthma in children and adults. Rhinoviruses were the major pathogen implicated, and the majority of viral infections and asthma admissions occurred during school attendance, according to the study by the Department of Medical Statistics and Computing, University of Southampton(15).
9. Irregular Mentruation
Irregular menstruation are associated with asthma. In the study of a total of 8588 women (response rate 77%) participated in an 8 year follow up postal questionnaire study of participants of the ECRHS stage I in Denmark, Estonia, Iceland, Norway, and Sweden. Only non-pregnant women not taking exogenous sex hormones were included in the analyses (n = 6137), showed that Irregular menstruation was associated with asthma (OR 1.54 (95% CI 1.11 to 2.13)), asthma symptoms (OR 1.47 (95% CI 1.16 to 1.86)), hay fever (OR 1.29 (95% CI 1.05 to 1.57)), and asthma preceded by hay fever (OR 1.95 (95% CI 1.30 to 2.96)) among women aged 26-42 years(16).
10. Sulphite additives
Topical, oral or parenteral exposure to sulphites (mainly from the consumption of foods and drinks that contain these additives) has been reported to induce a range of adverse clinical effects in sensitive individuals, ranging from dermatitis, urticaria, flushing, hypotension, abdominal pain and diarrhoea to life-threatening anaphylactic and asthmatic reactions(16a).
11. Cold air
Endurance athletes show an increased prevalence of airway hyperresponsiveness. In the study of a total, 64 elite athletes (32 swimmers and 32 cold-air athletes), 32 mild asthmatic subjects and 32 healthy controls underwent allergy skin prick testing, methacholine challenge and induced sputum analysis found that there is a significant airway inflammation only in competitive athletes with airway hyperresponsiveness. However, the majority of elite athletes showed evidence of bronchial epithelial damage that could possibly contribute to the development of airway hyperresponsiveness(17a).
11. Etc.
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(1) http://www.ncbi.nlm.nih.gov/pubmed/9643741
(6) http://www.ncbi.nlm.nih.gov/pubmed/21551404
(7) http://www.ncbi.nlm.nih.gov/pubmed/21621060
(8) http://www.ncbi.nlm.nih.gov/pubmed/22742468
(9) http://www.ncbi.nlm.nih.gov/pubmed/23145415
(10) http://www.ncbi.nlm.nih.gov/pubmed/23215875
(11) http://www.ncbi.nlm.nih.gov/pubmed/23258582
(12) http://www.ncbi.nlm.nih.gov/pubmed/22162931
(13) http://www.ncbi.nlm.nih.gov/pubmed/21499591
(14) http://www.ncbi.nlm.nih.gov/pubmed/21737039
(15) http://www.ncbi.nlm.nih.gov/pubmed/8810601
(16) http://www.ncbi.nlm.nih.gov/pubmed/15923242
(16a) http://www.ncbi.nlm.nih.gov/pubmed/19775253
(17a) http://www.ncbi.nlm.nih.gov/pubmed/19129276

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