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A general pattern of factors influencing development of asthma seems to be emerging, including family allergy history/ asthma genetics, smoking, diet, obesity, and inactivity, all of which seem to influence the development of asthma and disease outcomes (Table bellow).

Many clinical or area studies have reported substantially higher rates of asthma prevalence, hospitalization, and mortality among racial and ethnic minorities. However, asthma is also most common among low socioeconomic groups, regardless of race. While black children have higher rates of asthma than white children, most studies have found that black race is not a significant correlate of asthma after controlling for location of residence and socioeconomic status (SES). The basis for the effects of poverty and urban residence on asthma prevalence is not known. One potential asthma factor is allergen exposure and allergen sensitization are common in urban environments. Black children in inner city Atlanta are exposed to high levels of dust mites and cockroach allergen, and a high proportion of the children with asthma were sensitized to these allergens. Litonjua and colleagues also concluded that a large proportion of racial/ethnic differences in asthma prevalence can be explained by factors related to income, area of residence, and level of education.

Asthma Factors that Influence Disease Development and Severity

Income is a determinant of access to health care, and frequently, the quantity and quality of health care available. Persons who have low income, regardless of race or ethnicity, are more likely to be uninsured, to encounter delays or be denied care, to rely on hospital clinics in emergency departments for health services, and to receive substandard care. The usual socioeconomic indicators, education and personal or household income, serve only as surrogates for more complicated correlates of individuals within populations and multiple asthma factors that can impact both on prevalence of asthma and adverse outcomes from the disease.

Studies from Germany comparing the populations of East and West Germany have shown the prevalence of hay fever and asthma as significantly higher in West German children, suggesting that asthma environmental factors explain the difference in prevalence in these ethnically similar populations. Early exposure to infections (as with being in a day-care environment early in life) or exposure to endotoxin (as with growing up on a farm with close exposure to the farm animals) are associated with a decreased prevalence of asthma. In contrast, growing up in an urban environment or generally with an increased standard of living are associated with an increased prevalence of asthma. Such correlates are also present for atopic disorders other than asthma. In fact, Strachan, who noted that prevalence of hay fever was inversely related to family size, was the first to recognize the importance of early exposures on atopic disease. In the USA, asthma is more prevalent in African-Americans and Puerto Ricans. These findings are not explained by the observations on the role of social class in European studies. Given the ethnic differences between African-Americans and whites, these studies may represent gene-by-environment interaction producing varied phenotypic outcomes.

Avoidance of any one of the individual risk factors associated with childhood asthma has not been successful in preventing its development. The purpose of this study was to determine the effectiveness of a multifaceted intervention programme for the primary prevention of asthma in high-risk infants at 7 years of age. Five hundred and forty-five high-risk infants with an immediate family history of asthma and allergies were prospectively randomized into intervention and control groups pre-natally. (more…)

The geographical variation in the prevalence of asthma in children does not coincide with variations in air pollution levels. The increase in the prevalence of asthma and allergies seen over the last decades was paralleled by a decrease in emissions of SO2 and particles from coal combustion, and an increase of emissions from motor vehicle traffic. There is a growing number of studies suggesting that increased exposure to traffic exhausts, particularly diesel exhausts, may be a risk factor for the new onset of asthma. (more…)

There is increasing evidence relating body mass index to the prevalence of asthma and incidence of asthma in children and adults, males, and more consistently, in adolescent females. It is unlikely that the association is attributable to reverse causation, i.e. that asthma and obesity because of exercise-induced asthma symptoms. Rather, weight gain can antedate the development of asthma. Weight reduction among asthmatic patients can also result in improvements of lung function. (more…)

Asthma is a complex syndrome rather than a single disease entity. Different phenotypes with varying prognosis and determinants have been described, particularly over childhood years 2 and will be discussed in detail in the following. For example, transient early wheezing is characterized by the occurrence of wheezing in infants up to the age of 2 to 3 years which disappears thereafter. The main predictor of these wheezing illnesses is premorbid reduced lung function before the manifestation of any wheeze. These decrements in pulmonary function are in part determined by passive smoke exposure in utero 4 and result in symptoms of airway obstruction when infants get infected with respiratory viruses. (more…)

According to the National Survey of Children in the United States, the prevalence of asthma was 15% (last 12 months), that of hay fever was 12.4%, of skin allergy 9.8% and digestive/ food allergy 3.6%. Overall, every fourth child is affected (25.4%). Regarding the diagnosis of asthma in children, the prevalence, for instance in Germany, rose from 1.25% to 2.21% between 1951–1952 and 1964–1965. For the last 10 years there has been dispute about whether the increase in asthma and allergy has come to a halt. However, the observation period is too short to draw any conclusion. A study of adults went beyond this simple dispute and investigated age and cohort effects for immunoglobulin E (IgE) sensitization from 1992 to 1998–2002. (more…)

The symptoms of asthma occur together with variations in the diameter of medium- size airways such that it is increasingly difficult to exhale. Narrowing of the airways can occur because of smooth muscle contraction, edema or swelling of the wall, or increased mucus in the airways. However, it is increasingly clear that the pathologic event underlying most cases of asthma is acute inflammation of the airway walls. (more…)

During recent decades there has been extensive epidemiological research to explore the increasing prevalence of asthma and allergy in childhood. The worldwide variations in the prevalence of these diseases necessitate regional rapport. Furthermore, time-trend analyses with comparable methods are important in order to monitor the rapidly changing prevalence of these atopic diseases. Three cross sectional questionnaire-based studies of asthma and allergy in school children were conducted in the counties of Troms and Finnmark in northern Norway in 1985, 1995 and 2000. (more…)

There have been concurrent increases in the prevalence of obesity and asthma in recent years in New Zealand and other countries. Two cross-sectional surveys performed in 1989 and 2000 were used to test this association in children of mean age 11.7 years. BMI was calculated as weight/height 2 (kg/m 2 ) and obesity and overweight defined according to an international standard. Standard questions were used to measure the prevalence of asthma symptoms. (more…)

Epidemiological studies of farm children are of international interest because farm children are less often atopic disorders, have less allergic disease, and often have less asthma pain than do non-farm children—findings consistent with the hygiene hypothesis. The investigators studied a cohort of rural Iowa children to determine the association between farm and other environmental risk factors with four asthma outcomes: (more…)