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 37 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 life4.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 coughing4.
As of 2011, 235-330million people world are affected by asthma, and approximately 250,000-345,000people die per year from the disease 16 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 affluent16. Low and middle income countries make up more than 80% of the mortality12.
Risk factors in childhood
Phenotypes
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 wheezing32. Only transient wheezing in early infancy has been well characterized, with decreased airflow rates on pulmonary function testing at birth32, onset of wheezing within the first year and resolution by mind-childhood is with no lasting effects on pulmonary function.
Breasting
The influence of breastfeeding on the risk of childhood atopy and asthma remains controversial. Some studies have shown protection 336 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 45.
Lung function
Decrease airway caliber in infancy has been reported as risk factor for wheezing32, perhaps related to prenatal and postnatal exposure to environmental tobacco smoke 29.The presence of airway decreased with caliber has been associated with increased bronchial responsiveness and increased symptoms of wheezing32.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 years31.
Family structure
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 phenotypes40. 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’ infection40 .
Socio-economic status
Children of parents with lower socio-economic status have greater morbidity from asthma17, but finding with respect to the prevalence of asthma mixed27, 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 asthma11. 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 infancy24, 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 asthma45.
Exposure to environmental tobacco smoke
Postnatal exposure to environmental tobacco smoke, especially from maternal smoking, has been consistently associated with respiratory symptoms of wheezing41. Exposure to environmental tobacco smoke also consistently worsens asthma symptoms and is a risk factor for severe asthma11.
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 inconsistent31. 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 asthma8. Before age 12, boys have more severe asthma than girls, with high rates of admission to hospital21. 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 adolescence10.
Occupational asthma
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 others2.
Symptoms of asthma
Asthma is characterized by recurrent episode of wheezing, shortness of breath, chest tightness and coughing16. 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 air5. Some people with asthma rarely experience symptoms, usually in response to triggers, whereas others have marked and persistent symptoms16.
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 asthma22. 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 asthma14. 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 bronchodilators23. Spirometry is the preferred objective measure to assess for the reversible air way obstruction45, (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 hospital39.
Avoidance of relevant allergens or irritants is an important components of asthma management 33 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 39. 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.