Asthma is a chronic disease of airways; that is widely characterized by an increased responsiveness to a large variety of stimuli, airway inflammation and obstruction. It is the most common respiratory disorder disease in developed and developing countries. The study was aimed to assess the factors that contribute for the cause of asthma disease in Ambo town and cross-sectional survey was conducted to gather information from March to April 2022. 30 respondents were selected using purposive sampling technique for interview and data collections. According to the study the more affected age group were 22-32(53%) and the major risk factor for the disease was air pollution (53%). The pollution is due to domestic wastes that are discharged to the environment. Therefore, the government and extension health workers should aware the community about the risk factors of asthma and proper waste disposal mechanisms.
Academic Editor: Jong In Kim, Korea, Republic of
Checked for plagiarism: Yes
Review by: Single-blind
Copyright © 2023 Damtew Bekele, et al.
The authors have declared that no competing interests exist.
Background of the Study
Asthma is a chronic inflammatory disease of air ways. The chronic inflammation is associated with air way hyper-pensiveness or an exaggerated air way narrowing response to, such as allergens and exercise, that lead to recurrent symptom such as wheezing, dyspnea (shortness of breath), chest tightness and coughing. Symptoms episodes are generally associated with a wide spread, but variable, air flow obstruction within lungs that is usually reversible either spontaneously or with appropriated asthma treatment. It is generally accepted that there are both allergic and non-allergic forms of asthma disease (GINA, 2009).
The prevalence of asthma varies widely around the world, probably because of gene-by-environment interaction. Parental risk factors for asthma may include maternal smoking, diet and nutrition, stress, use of antibiotics, and delivery by cesarean section. Childhood risk factor for asthma may include allergic sensitization, environmental tobacco smoking, exposure to animals, breastfeeding decreased lung function in infancy, family size and structure, socio-economic status, antibiotics and functions, sex and gender. Occupational exposure constitutes a common risk factors adult asthma (Padmaja et al., 2009).
Several factors have been proposed to account of the cause of asthma disease and increase the prevalence (Jorge and Mazza, 2011). It is agreed that genetic changes in population would be too slow to account. Environmental factors have been a key role agenesis of asthma disease. Among the environmental determinant exposure to allergens such as house dust mite, grass pollen, cockroach and animal dander (Bourdin et al., 2009).
Moreover, in developing country like Ethiopia, the effect of this disease is more serious (Yemaneberhan et al., 2000). According to the latest data published in 2017 asthma death in Ethiopia reached in 6.269 or 0.99% of total death. The age adjusted death rate is 11.98 per 100,000 of population ranks Ethiopia in the world (WHO, 2017). Particularly, southwestern is a place where several peoples are affected by asthma. Therefore, this study aimed to assess the risk factors that contribute for the cause of this disease. No research can be found that focuses on the factors that contribute for asthma disease in Ambo town.
Statement of the Problem
Asthma is the worldwide problem affecting more than 230 million people around the globe. It is the most common respiratory disease in developing and developed countries. Furthermore, asthma disease can affect all aged group of people in Ethiopia (Yemanehberhan et al., 2011). It is also one of the diseases observed in Ambo Town. Several factors have been proposed to account for the risk factor impact and difficulty, even environmental factor play a key role. The main issue to do this study is the higher prevalence and the lack of awareness of the risk factor impact and difficulty in this study area. Therefore, this study aimed to assess the risk factors impact and difficulty for asthma in Ambo town.). So, this study was attempted to answer the following questions:
What are the factors that contribute for the cause of asthma disease?
What is the effect of the asthma disease?
How the symptoms of asthma disease are identified from other respiratory disease?
What is the main factor for the prevalence of asthma disease?
How the environment could be one of the major factors for the cause of asthma diseases?
To assess the factors that can contribute for the cause of asthma disease in Ambo town.
To identify the risk factor of asthma disease in Ambo town, Oromia, Ethiopia.
To determine the impacts of asthma on the asthma patients in Ambo town.
To identify the difficulties of asthma patients in Ambo town, Oromia, Ethiopia.
Significance of the Study
Asthma is the worldwide problem affecting more than 230 million people around the globe. The findings of this study may provide certain information about the risk factors that aggravate asthma. The findings of this study also give awareness about the risk factors impact and difficulty and effect of asthma and the study may serve as reference data for those who want to conduct further studies on the area risk factors of asthma.
Limitation of study
The research was conducted to Some Asthma patients of Ambo town. A questioner was distributed to 60 respondents living in ambo town of them only 30 respondents are found to have asthma. The data was collected from 17 respondents from school and 13 respondents from hospital who are patients. Since the study design is a cross sectional descriptive which studies are carried out at one time point or a short period which may recall bias
Epidemiology of Asthma
Asthma is a chronic disease characterized by recurrent attack of breathlessness and wheezing. According to WHO estimates 235 million people suffer from asthma. It occurs in all countries regardless of development. Over 80% of asthma diseases occur in low and lower middle income countries.
Asthma remain the most common chronic respiratory disease (Ottawa and Ontario, 2007) affecting approximately 10% of the population. Although, asthma is often believed to be disorder localized to the lungs, current evidence indicate that it may represent a component of symptoms air way disease involving the entire respiratory tract, and this is supported by the fact that asthma frequently allergic rhinitis. Poor asthma control contributes to unnecessary morbidity, limitation to daily activities and impairment in overall quality of life (Bourdin etal.,2009).The chronic inflammation associated with air way hyper responsiveness (an exaggerated air narrowing response to triggers such as allergens and exercise), dyspnea (shortness of the breath), chest tightness and coughing(Bourdin etal.,2009).
As of 2011, 235-330million people world are affected by asthma, and approximately 250,000-345,000people die per year from the disease (GINA, 2011; Lozano, 2012). Rates vary between 1and 18% (GINA, 2011).It is more common in developed than developing country. One thus sees lower rates in Asia, Eastern Europe and Africa. Within developed countries it is more common in those who are economically disadvantaged while in contrast in developing countries it is more common in the affluent(GINA,2011). Low and middle income countries make up more than 80% of the mortality (Fanta, 2009).
Risk factors for asthma
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% (Elward etal., 2010).
Genome-wide linkage studies and case -control studies have identified 18 genomic regions and more than 100 genes associated with allergy and asthma in 11 different population. In particular, there are consistently replicated regions on the long arms of chromosomes 2, 5, 6, 12 and 13. Association studies of unrelated individuals have also identified more than 100 genes associated with allergy and asthma, 79 of which have been replicated in at least one further study (Ober and Hoffjan, 2006)
Prenatal risk factors
Risk factors in the prenatal period are multi-factorial. Assessment is complicated by the variety of wheezing conditions that may occur in infancy childhood, only some of which evolve to classical asthma.
Prenatal tobacco smoke
Prenatal maternal smoking has been consistently associated with early childhood wheezing (GINA, 2011; British Guideline, 2009) and there is a dose- response relation between exposure and decreased airway caliber in early life (Boulet etal., 2011; GINA, 2011).Prenatal maternal smoking is also associated with increased risks of food allergy (George and Renald, 2005), cytokine responses in the cord blood and concentration of nitric oxide in exhaled air in newborn (Frey u etal., 2004).
Diet and nutrient
Observational studies examining prenatal nutrient level or dietary intervention and the subsequent development of atopic disease have focused on foods with anti -inflammatory properties (e.g. Omega -3 fatty acids) and anti-oxidants such as vitamin E and zinc. Higher intake of fish or fish oil during pregnancy is associated with lower risk of atopic disease (specifically eczema and atopic wheeze) up to age 6 years. Similarly, higher prenatal vitamin E and zinc levels have been associated with lower risk of development of wheeze up to 5 year (Litonjua etal., 2006; Willers etal., 2007).
A number of animal model have suggested that prenatal maternal stress acts through regulations of offspring's hypothalamic-pituitary-adrenal axis to decrease cortisol levels, which may affect the development of an allergic phenotype. Although there is a correlation between caregiver stress early in the infant's life and higher level of immune -globulin E in the infant and early wheezing (Wright etal., 2004; Lin etal., 2004), no studies to data have shown an association with asthma (Kozyrskyj etal., 2007).
Risk factors in childhood
Although some 50% of preschool children have wheezing, only 10%-15% have diagnosis of "true” asthma by the time they reach school age (Sears etal., 2003). Commonly described phenotypes in early infancy and children are transient wheezing, non-atopic wheezing, late-onset wheezing and persistent wheezing (Martinez etal., 2005). Only transient wheezing in early infancy has been well characterized, with decreased airflow rates on pulmonary function testing at birth (Martinez etal., 2005), onset of wheezing within the first year and resolution by mind-childhood is with no lasting effects on pulmonary function.
The influence of breastfeeding on the risk of childhood atopy and asthma remains controversial. Some studies have shown protection (Bergman etal., 2002; oddy, 2000) where as others have reported higher rates of allergy and asthma among breastfed children. A meta-analysis and several individual studies showed that exclusive breastfeeding for at least 3 months was associated with lower rates of asthma between 2 and 5 years of age, a greatest effect occur among those with a parental history of atopy. One of the difficulties in interpreting the data lies in differentiating viral-associated wheeze in childhood from developments of atopic asthma. Breastfeeding was associated with a higher risk of atopic asthma in later childhood, with the greatest influence occurring among those with maternal history of atopy (Sears etal., 2002; Wright etal., 2000).
Decrease airway caliber in infancy has been reported as risk factor for wheezing (Martinz etal., 2005), perhaps related to prenatal and postnatal exposure to environmental tobacco smoke (Lodrup , 2002).The presence of airway decreased with caliber has been associated with increased bronchial responsiveness and increased symptoms of wheezing (Martinz etal., 2005). Several studies have suggested an association between reduced airway function in the first weeks of life and asthma in later life (Young etal., 2000).
Children with wheezing (and diagnosed asthma) persisting to adulthood have a fixed decrement in lung function as early as age 7 or 9 years (Sears etal., 2003 ) Recent studies of preschool children have documented abnormal lung function in children with persistent wheezing as young as age 3 years (Lowe etal., 2005).
Family size and the number and order of sibling may affect the risk of development of asthma. The hygiene hypothesis posits that exposure of an infant to a substantial number of infections and many types of bacteria stimulate the developing immune system toward non-asthmatic phenotypes (Schaub etal., 2006). This may be exemplified in the real world by large family size, whereby later-born children in large families would be expected to be at lower risks of asthma than first- born children, because of exposure to their older sibling’ infection(Schaub etal., 2006) .
Children of parents with lower socio-economic status have greater morbidity from asthma (Halfon and Newacheck, 2001), but finding with respect to the prevalence of asthma mixed (Lintonjua etal., 2000), such result may depend both on how socio-economic status measured and on the specific outcome examined. Some studies have reported association of lower socio-economic status with greater airway obstruction and symptoms but not with a diagnosis of asthma (Erzen etal., 2003). Whether socio-economic status is as relevant to the incidence of allergy and asthma as it is the expression, severity and managements of this disease remains unclear. Parental stress has also been prospectively associated with wheezing in infancy (Kozyrskyj etal., 2007), and family difficulties have been linked to asthma. Children whose caregivers report high level of stress and who have difficulties parenting are at greater risk for asthma (Wright etal., 2004).
Exposure to environmental tobacco smoke
Postnatal exposure to environmental tobacco smoke, especially from maternal smoking, has been consistently associated with respiratory symptoms of wheezing (Tariq etal., 2000). Exposure to environmental tobacco smoke also consistently worsens asthma symptoms and is a risk factor for severe asthma (Erzen etal., 2003).
Exposure to animal
Although several studies have demonstrated a lower risk of developments of atopy and asthma with exposure to farm animals in early life, the findings of studies of the influence of exposure to domestic cats and dogs have been inconsistent (Simpson and custovic, 2005). In some studies, exposure to cats was associated with greater risk of allergic sensitization 1, whereas other studies showed lower risk. Exposure to dogs may be protective not only against the development of specific sensitization to do allergen 1 but also against other sensitization (e.g., to house dust mite) and asthma.
Sex and gender
Sex affects the development of asthma in a time development manner. Until age 13- years, the incidence and prevalence of asthma is greater among boys than among girls (de Marco etal., 2000). Greater incidence of asthma among adolescent and young adult female and a greater proportion of male with remission of asthma (de Marko etal., 2002). Before age 12, boys have more severe asthma than girls, with high rates of admission to hospital (Kao etal., 2001). In contrast, adult female have more severe asthma than males, with more hospital admission. In childhood, airway hyper-responsiveness is more common and more sever among males; however, airway hyper-responsiveness increase in females during adolescence (Ernst etal., 2002).
Asthma related to workplace exposure has been documented in many occupational settings. Commonly associated occupations and exposures include car painting (isocyanates), hair-dressing (various chemicals), domestic and commercial cleaning (cleaning solutions), healthcare professions (latex) and baking (flour dust), among many others (Barkley etal., 2008).
Symptoms of asthma
Asthma is characterized by recurrent episode of wheezing, shortness of breath, chest tightness and coughing (GINA, 2011). Symptoms by recurrent episodes of wheezing, shortness of breath, chest tightness and coughing (are usually worse at night in the early morning or in response to exercise or cold air (British Guide line, 2009). Some people with asthma rarely experience symptoms, usually in response to triggers, whereas others have marked and persistent symptoms (GINA, 2011).
Diagnosis of asthma
The diagnosis of asthma should be suspected in patient with recurrent cough, wheeze, chest tightness and shortness of the breath such variable symptoms occur upon exposure to allegiance or irritant, that worsen at night and that respond to appropriate asthma therapy are strongly suggestive of asthma (Kaplan etal., 2009). Alternative cause susceptive asthma symptoms should be excluded such as chronic obstructive pulmonary disease, bronchitis, chronic sinusitis gastro esophageal reflux disease, recurrent respiratory infection and heart disease.
A positive family history of asthma or other atopic disease and/or personal history of atopic disorder particularly allergic rhinitis, can also be helpful in identifying patient with asthma (Frew etal., 2010). Exposure to agents encountered in the work environment can also cause asthma. The diagnosis of asthma in young children is often more difficult since episodic wheezing and cough are common and spirometry is a reliable in patients under 6 years of age.
A useful method of confirming a diagnosis in young children is a trial treatment with short acting bronchodilators (Kim and Mazza, 2011). Spirometry is the preferred objective measure to assess for the reversible air way obstruction (Yemanehberhan etal., 2000), (i.e. rapid improvement in lung function after enation of rapid acting bronchodilators and confirm a diagnosis of asthma). During spirometer the patient is instructed to take the deepest breath possible and then to exhale as hard as fully as possible into the mouth piece the spirometry.
Control and treatment
Asthma is a long term disease that has no cure. The asthma treatment is to control the disease. It is controlled by prevent chronic and troublesome symptoms, such as coughing and shortness of breath, reduce your need for quick-relief medicine, help you maintain good lung function, let you maintain your normal activity level and sleep through the night and prevent asthma attacks that could result in an emergency room visit of hospital (WHO, 2014).
Avoidance of relevant allergens or irritants is an important components of asthma management (Mengistu and Balcha, 1998) patients allergic to house dust mite should be instructed to use allergen impermeable covers for bedding and keep the relative humidity in the home below 50% (to inhibit mite growth). According to the recent estimates, asthma affects 300million people (Peter Costa, 2007). Although people of all age suffer from the disease, it most often starts childhood, especially children who have low birth weight, who are exposed to tobacco smoke and are raised in a low income environment.
Asthma in Ethiopia
According to the latest data published in 2017 asthma death in Ethiopia reached in 6.269 or 0.99% of total death. The age adjusted death rate is 11.98 per 100,000 of population ranks Ethiopia in the world (WHO, 2017).
Materials And Methods
Description of Study Area
Ambo town is the ancient of historian place which is situated in central administrative zone of Oromia regional state in the West Shewa tip of the Ethiopian plateau at 8059N latitude and 37051’ E longitude of 2101m above sea level. Geographically Ambo is located west shewa and zone of Oromia region west of Addis Ababa. Regarding to the climatic condition it is conductive for all activities which is “Weynadega” with mean annual temperature ranges between 9.30c and 29.80c whereas the mean annual rainfall range between 85.8ml and 428ml. The total population growth of Ambo town in 2007E.C was 48,171 of these population 23,537 were female and 24,634 were males. (2007 Population and housing census of Ambo town)
Ambo is known for its mineral water, which is bottled outside of the town; it is reportedly the most popular brand in Ethiopia. Ambo is also the location of a research station of the Ethiopian institution of Agricultural research; initiated in 1977, this station hosts research in protecting major crops in Ethiopia.
Study Population and study design
A cross-sectional study design was used to assess on the factors that contribute for asthma disease in Ambo Town. This study was conducted from March to May in 2022. The research was conducted to Some Asthma patients of Ambo town. A questioner was distributed to 60 respondents living in ambo town of them only 30 respondents are found to have asthma. The data was collected from 17 respondents from school and 13 respondents from hospital who are patients.
Sample Size and Sampling Technique
Non-probability purposive sampling technique was used to determine the sample size. The sample size for this study was 60 respondents of them 30 respondents was asthma patients ≥11 years old and the other 30 was excluded patient who do not have asthma. The sample size was determined using Yamane’s (1967) formula (considering a confidence level of 95% and accepting the margin error of 5%).
The total number of Ambo town population was 48171. Applying the formul (Yamane’s, 1967), the sample size for the Ambo town was 220. But the researcher was selected 60 respondents due to delimitation of time and budget.
Where: n = sample size; N = Population; e = Margin error (5%).
Data Collection Method
Data collection method was employed to the people in Addis ketema primary school and Ambo referral hospital asthma patients. The data was collected by using semi-structured questionnaire. During data collection the cause of Asthma and the impact was asked. The questionnaire was originally prepared with English and interpreted to Amharic language. Data collection was carried out for about 15 days. Data Analysis
In order to evaluate the reliability of information during the interview, informants are contacted at least two times for the same ideas to check the validity of the information recorded. If the ideas of the informants contradicted with the original information, it will be rejected since it is considered as unreliable. The collected data was analyzed by using statistical tool Microsoft Excel and the result was presented in the form of tables and figures summarizing them into percentage and frequency.
Gathering data was carried out with full consent of respondents. By respecting their beliefs and culture of the respondents was informed about the objectives of the study and their agreement was take before assure that the information providers was confidential and use only for the purpose of research.
Table 1 indicate the Socio-demographic characteristics of the study respondents Out of 30 study respondents 13 (43%) were male and 17 (57%) female, the age group from 22-32 years were the most affected 16 (53%) and least affected were age group from 33-43 years 3 (10%), based on the occupation students were the most affected 16 (53%) and least affected was driver 1 (3%).Table 1. Socio-demographic characteristics of the study respondents in Ambo town in 2022.
Table 2 indicate the risk factor that contribute for Cause of asthma According to respondents factors that contribute for the cause of asthma were air pollution 53%,cold air 17%, tobacco smoke 10%, dust mite 10%, other 10%.Table 2. Risk factors that contribute for cause of asthma in Ambo town in 2022.
Table 3 indicates symptoms of asthma experienced by the respondents. Out of 30 respondents 17 (53%) experienced cough or sneeze and 6 (20%) chest tightness. The least symptom experienced by the respondents was itching of nose and wheeze both are accounts 7%.Table 3. The symptoms of asthma experienced by the respondents in Ambo town in 2022.
|Cough or sneeze||17||53|
|Shortness of breath||5||17|
|Itching of nose||1||3|
Table 4. Depicts the mechanisms the respondent removed solid waste. 67% respondent removes solid waste by discarding away from environment. 23% of the respondents remove their solid waste through accumulating and using it as fertilizer, 10% of respondents remove solid by burning.Table 4. Methods of removing solid waste in Ambo town in 2022.
|Discarding far away from environment||6||14||20||67%|
|Accumulating and using as fertilizer||5||2||7||23|
Table 5 indicates the period of difficulties of asthma by respondents. As shown in the table, the asthmatic patients feel difficulties during the rainy season (50%) and 17% feel difficulty during warm season. 23% feel difficulty in the night and 10% in the morning.Table 5. Period of difficulties of asthma in Ambo town in 2022.
Even though the most affected age group was (22-32) or 16 (67%) out of total respondents, the next most affected group was (11-21) which was seven (23%) out of total 30 respondents. Age group the least affected was (33-43) that was three (10%) but According to Peter, 2007 study estimation, asthma affects peoples of all age group even though it most often starts at childhood.
The most affected sex was female 17 (57%) and the least was male 13 (43%). In the case of the occupation of the respondents, 16 (53%) were student and the driver were the least affected (3%).comparatively opposite result was investigated by de Marco in 2000 and 2002, His result indicate Sex affects the development of asthma in a time development manner. Until age 13- years, the incidence and prevalence of asthma is greater among boys than among girls. Greater incidence of asthma among adolescent and young adult female and a greater proportion of male with remission of asthma.
When we see the risk factors for asthma (Table 2), air pollution accounts 16(53%), , dust mite 4 (13%), cold air 4 (13%), tobacco smoke 3 (10%) other 3 (10%) similarly Bourdin 2009 study indicate, Environmental pollution has been a key role in genesis of asthma.
The findings of this study has shown symptoms of asthma experienced by the respondents such as coughing and sneezing (57%), chest tightness (20%) shortness of breath (17%), and wheezing (3%) but some have itching nose (3%), similarly The finding of Global Initiative for Asthma, 2009 study indicate the symptoms of asthma are wheezing, shortness of breath, chest tightness and coughing. In addition to these four symptoms, this study the respondents experienced additionally itching of nose as a symptom.
The method of removing domestic solid waste was through burning, discarding away from the environment and accumulating and using as fertilizers later. As shown in table (4) 3 (10%) remove wastes by burning, discard away from the environment 20 (67%) and 7 (23%) accumulate and use as fertilizers, reversely the recent stud's indicate the burning of waste is the main cause for respiratory disorder, this indicate the misunderstanding most of the respondent and they are used improper waste removing way of method.
According to this study the asthmatic patients feel difficulty of pain during the night 11 (36%) during rain nine (30%), in morning 8(27%) and only 2(7%) feel difficult during warm time. comparatively the estimation of the British Guide line, at 2009 indicate less frequent difficulties of asthma usually worsen at night and in early morning or in response to exercise or cold air.
1 In this study physiological impact was shown to be the significant that 15 (50%) respondents were affected physiologically whereas 9(30%) and 6 (20%) were affected economically and socially, respectively (figure 1) similar with the study of Jorge and Mazza, 2011, they estimate that in their study “In addition to its health impact, asthma has other different impacts such as social, economic psychological impacts”. Finally, the inexistence of significant associations between some socio-demographic or socioeconomic factors and OHIP can be attributed to the participants' small number included in the study. Future studies on socioeconomic factors for quality of life including oral cavity are needed (Kim and Kim, 2016).
Conclusions And Recommendations
In general, this study concluded by using non-probability purposive sampling technique and semi structured data collection methods, the data was analyzed by using statistical tool like Microsoft Excel indicate that the risk factors, impact and difficulty of asthma in the study area were, air pollution, dust mite, cold air, tobacco smoke Beside this asthma has economic, psychological and social impacts on the patients and the period of difficulty are during night, rain, morning and warm time.
The society should properly remove the domestic wastes.
The health sector should work with the society towards prevention and control of asthma by giving awareness on better environmental protection, stopping smoking tobacco and reducing indoor and outdoor air pollution and occupational exposures.
It is suggested that further work be conducted, especially studies with a larger sample size, to analyze more broadly the situation of asthma in the Keble also in a wide range.
- 1.Almqvist C, A C Egmar, Hedlin G. (2003) Direct and indirect exposure to pets-risk of sensitization and asthma in 4 years in a birth cohort. Clin Exp Allergy;. 33, 1190-7.
- 2.Bakerly N D, Moore V C, Vellore A D. (2008) Fifteen year trends in occupational asthma: data from the shield surveillance scheme. , Occup Med (Lond) 58, 169-74.
- 3.R L Bergmann, T L Diepgen, Keuss O. (2002) Breast feeding duration is risk factors for atopic eczema. Clin Exp Allergy ;. 32.
- 4.Bourdin A, Gras D, Vchier I, Chanez P. (2009) Upper air way Allergic rhinitis and asthma. United disease through epithelial cells. 64, 999-1004.
- 6.Burke W, Fesinmeyer M, Reed K. (2003) Family history as a predictor of asthma risk. , Am J prev med; 24, 160-9.
- 8.R De Marco, Locatelli F, Cerveri I. (2002) Incidence and remission of asthma: a retrospective study on the nature history of asthma in Italy. , J Allergy clin Immunology: 110, 228-35.
- 9.R De Marco, Locatelli F, Sunyer. (2002) Difference in incidence reported asthma related to age in men and women. , Am J Respire Crit Care Med; 162, 68-74.
- 10.Ernst P, Ghezzo H, Becklake M R. (2002) Risk factor for bronchial hyper-responsiveness in late childhood and early adolescence.Eur. , Respir J 20, 635-9.
- 11.Erzen D, Carriere K C, Dik N. (2003) Income level and asthma prevalence and care patterns. Care med 155:. 1060-5.
- 13.Fitz Gerald JM, Zimmerman S Bouletph, Chapman K R. (2006) control and a cause remain sub optimal: The reality of asthma control study,13:. 253-259.
- 15.Frey U, Kuehhni C, Roiha H. (2004) Maternal atoic disease modified effects of prenatal risk factors on exhaled nitric oxide in infants. 170, 260-5.
- 17.Halfon N, Newacheck P W. (2001) Childhood asthma and poverty: differential impacts and utilization of health services. 91, 56-61.
- 19.J I Kim, Kim G. (2016) Country-Level Socioeconomic Indicators Associated with Healthy Life Expectancy: Income, Urbanization, Schooling, and Internet Users: 2000–2012. Social Indicators Research;. 129, 391-402.
- 20.Jedrychowski W, Galas A, Whyatt R. (2006) The prenatal use of antibiotics and the development of allergic disease in one years old infants. A preliminary study. , Int J occup Med Environ Health 19, 70-6.
- 21.Kao C C, See L C, Yan D C. (2001) Time trends and seasonal variation in hospital admission for childhood asthma in Taiwan from. to
- 24.Kozyrskyj A L, Becker AB Ernst. (2007) Increased risk of childhood asthma from antibiotic use in early life. 131, 1753-9.
- 26.Lin Y C, Web H J, Lee Y L. (2004) Are maternal psychosocial factors associated with cord immunoglobulin E in addition to family atopic history and mother immunoglobulin E?. 34, 548-5.
- 27.Litonijua A A, Carey V J, Eiss S T. (2000) Race, socioeconomic factors, and area of residence are associated with asthma prevalence.
- 28.Litonjua A A, Rifas-Shiman S L, Np Ly.Maternal antioxidant intake in pregnancy and wheezing illnesses in children at 2 y of age. , Am J clin Nutr 84, 903-11.
- 29.Lodrup Carlsen KC. (2002) The Environment and childhood Asthma (ECA). Study in Oslo: ECA-1 and ECA-2. Pediatr Allergy Immunol 13, 29-31.
- 30.Lougheed M D, Lamiere C, Dell S D, Ducherme F M. (2010) Canadian thoracic society of asthma management continuum, consensus summary for children six years of age and over,and adult,17:. 15-24.
- 31.Lowe L A, Simpson A, Woodcock A. (2005) Wheeze phenotypes and lung function in preschool children. , Am J Respir Care Med 171, 231-7.
- 32.Martinez F D, Wright A L, Taussing L M. (2005) Asthma and wheezing in the first six years of life. , The Group Health Medical Association. N Engl J Med 332, 133-8.
- 35.Ober C, Hoffjan S.Asthma genetics (2006). The long and widing road to gene discovery. , Genes Immun 2006, 95-00.
- 37.Ottawa.Ontraio (2007).Life and breath: Respiratory disease in Canada. Public health agency of Canada.
- 39.Costa Peter. (2007) Asthma and respiratory disease. National asthma council. World Health Organization.
- 41.Tarqi S M, Hakim E A.and Matthews SM (2000).Influence of smoking on asthma symptoms and allergen sensitization in early childhood.
- 42.Willers S M, Devereux G, Craig L C. (2007) Maternal food consumption during pregnancy and asthma, respiratory and atopic symptoms in 5-year-old children.
- 44.Wright A L, Holberg C J, Tsaussing L M. (2000) Maternal asthma status alters relation of infant feeding to asthma in childhood.