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.2. Risk factors
1. Wheezing rhinovirus illnesses
Virus-induced wheezing episodes in infancy often precede the development of asthma. Researchers at the the Department of Pediatrics, University of Wisconsin-Madison, showed that Nearly 90% (26 of 30) of children who wheezed with RV in Year 3 had asthma at 6 years of age.From birth to age 3 years, wheezing with respiratory syncytial virus (RSV) (odds ratio [OR], 2.6), rhinovirus (RV) (OR, 9.8), or both RV and RSV (OR , 10) was associated with increased asthma risk at age 6 years. In Year 1, both RV wheezing (OR, 2.8) and aeroallergen sensitization (OR, 3.6) independently increased asthma risk at age 6 years. By age 3 years, wheezing with RV (OR, 25.6) was more strongly associated with asthma at age 6 years than aeroallergen sensitization (OR, 3.4)(17).
2. Airflow obstruction
Asthma and family history of allergic rhinitis are important risk factors associated with airflow. according to the Department of Pediatrics, Lerdsin General Hospitalobstruction(18).
If you are women, you are at increased risk to develop asthma. According to the study by the Department of Woman and Child Health, Karolinska Institutet, in adolescence, the pattern changes and onset of wheeze is more prevalent in females than males. Asthma, after childhood, is more severe in females than in males, and is underdiagnosed and undertreated in female adolescents(19).
Researchers at the Departments of Family Medicine and Pediatrics, University of Pittsburgh, suggested that stress, whether at the individual (i.e. epigenetics, perceived stress), family (i.e. prenatal maternal stress, early-life exposure, or intimate partner violence) or community (i.e. neighborhood violence; neighborhood disadvantage) level, influences asthma and asthma morbidity(20).
a study by National Taiwan University, showed that GSTP1, INSIG2 and IL4Ra may influence the lifetime asthma susceptibility through gene-gene interactions in schoolchildren. Home dampness combined with each one of the genes STAT6, IL13 and ADRB2 could raise the asthma risk(21). Other suggested that rs17880588 showed a significant association with asthma in the Saudi population due to the association of between asthma and 5 single-nucleotide polymorphisms (SNPs) in the interleukin 17 (IL17) gene. Levels of IL17A and IL17F were significantly upregulated in the asthma patients(22).
6. Airway inflammation and hyperreactivity
People with Air way hyperreactivity are at increased risk to develop asthma as a result of the immune system over response to allergan. Some study suggested that epidermal growth factor receptor (EGFR) signaling, especially in the airway epithelium, plays an important role in mediating AHR and remodeling in a chronic allergic asthma model(23).
5. Atopy and viral infection
Atopy – such as eczema, allergic rhinitis, allergic conjunctivitis and virual infection are associated with higher risk to asthma development. According to the study by The University of Western Australia, suggested that underlying this bipartite process (Viral infections occurring against a background of allergic sensitization to aeroallergens as a uniquely potent risk factor for the expression of acute severe asthma-like symptoms and for the ensuing development of asthma that can persist through childhood and into adulthood) are a series of interactions between antiviral and atopic inflammatory pathways that are mediated by local activation of myeloid cell populations in the airway mucosa and the parallel programming and recruitment of their replacements from bone marrow(24).
6. Family history
Family history of asthma in one or more first-degree relatives was consistently identified as a risk factor for asthma. But although a positive family history predicts an increased risk of asthma, it identifies a minority of children at risk. Positive family history may have utility in targeting some individual prevention efforts, but the low positive predictive value limits its value as a means to direct environmental remediation efforts, according to the study the Department of Medical History and Ethics, University of Washington(25).
7. Smoke during Pregnancy
Smoking and severe asthma exacerbations in pregnancy are risk factors for low birth weight babies.
During pregnancy, asthma exacerbations are more common and more severe in current smokers than never smokers. The risk of effects of maternal asthma on the fetus may be greater among smokers(26).
8. Low birth weight
There is a strong independent association between low birth weight and asthma. For 1988 national birth cohort, an estimated 4000 excess asthma cases were attributable to birth weight less than 2500 g(27).
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