The Impact of Asthma and Allergic Diseases on Schoolchildren: Are They at Increased Risk of Absenteeism and Poor School Performance?

1.1 Asthma and allergic diseases in children Asthma is the most common chronic illness of childhood in both developed and developing countries and there is a wide concensus that asthma and allergies have become more prevalent among children (Robertson et al., 2004). Among children, higher prevalence rates of asthma have been found in industrialized western countries than in developing countries in Asia and Africa (Beasley et al., 2000). In some western countries, the prevalence of asthma and allergies has reached alarming proportions, affecting more than one-third of the children within the general population (Khaldi et al., 2005). It appears that differences in asthma prevalence between population groups are due to differential exposure to environmental factors: genetic variations alone could not account for the risk in the prevalence of disease over a few decades. Allergen exposure in early life appears to correlate with sensitization and expression of asthma and atopy. Lifestyle factors including diet and ambient air pollution may be disease modifiers (Shapiro & Stout, 2002). Air pollution has a positive and significant effect on asthma exacerbation. A cohort study on asthma and exposure to ozone reported that pollution has been associated with new onset asthma as well as other respiratory diseases (McConnell et al., 2002). Urban atmospheric pollution has a well known impact on acute and chronic respiratory disease. The United Nations estimated that over 600 million people in urban areas worldwide were exposed to dangerous levels of traffic generated air pollutants (Cacciola et al., 2002). There is substantial epidemiological evidence indicating a link between respiratory and cardiovascular morbidity and outdoor air pollution levels (Bener et al., 2009).