Asthma from birth to age 23: incidence and relation to prior and concurrent atopic disease

Residential exposure to volatile organic compounds and asthma

We critically analysed the literature concerning exposure to volatile organic compounds and asthma. Observational studies have consistently found a relation between volatile organic compounds and indicators of asthma, such as symptoms, peak flows, and objectively measured bronchial reactivity. In contrast, interventional studies have generally failed to find a relation between exposure to residential levels of formaldehyde and other volatile organic compounds and asthma. One hypothesis to explain the discrepancy in findings between interventional and observational studies is that the effect size is small requiring relatively large numbers of study subjects, common in observational studies but often not feasible in interventional studies. Another hypothesis is that longer duration of exposure is important, a common circumstance in observational studies where the home environment is the exposure setting. In contrast, duration of exposure in interventional studies is usually of minutes-to-hours in a chamber. Finally, the observed association in observational studies could be confounded by a factor which is a determinant of asthma and is also associated with exposure to volatile organic compounds.

Sex differences among children 2-13 years of age presenting at the emergency department with acute asthma

Hospitalization rates for asthma have been reported to be higher in males than females in children under age 15, but it is not clear whether this disparity reflects gender differences in prevalence, severity, or treatment. We performed a prospective cohort study as part of the Emergency Medicine Network. Patients aged 2-13 years who presented to the emergency department (ED) with acute asthma underwent a structured interview in the ED and another by telephone 2 weeks later. Of 1,602 patients, 61% (95% CI, 59-64%) were boys. Girls were slightly older than boys, although no material differences existed in acute presentation, chronic asthma characteristics, ED treatment, or ED course. There was no difference in admission rates for boys or girls (20% vs. 22%; P = 0.48). This finding persisted when adjusting for other factors in a multivariate logistic regression model. No sex differences were observed for relapse or ongoing exacerbation on univariate or multivariate analysis. These data suggest that asthma is not inherently more severe in boys with asthma compared to girls, and that the increased rate of hospitalizations in boys under age 13 is due to differences in prevalence, not severity.

Association between polymorphisms in serine protease inhibitor, kazal type 5 and asthma phenotypes in a large German population sample

BACKGROUND

Atopic diseases are characterized by immunoglobulin E (IgE)-mediated immune responses towards common allergens, many of which are proteases. Recently it has been suggested that a proteinase inhibitor gene, SPINK5, which is located on chromosome 5q31, may play a role in the pathogenesis of atopic diseases.

OBJECTIVE

We investigated the association between the polymorphism G1258A leading to a putative amino acid change (Glu420Lys) in serine protease inhibitor, kazal type 5 (SPINK5) and phenotypes of atopic diseases in a large general population sample of German children.

METHODS

Parental questionnaires were used and children underwent skin prick testing, pulmonary function testing and bronchial challenge. Blood was collected for serum IgE measurements and DNA extraction. In total, 1161 children were genotyped for the SPINK5 Glu420Lys polymorphism and association studies were performed.

RESULTS

A significant association between SPINK5 420Lys and the development of asthma was observed (OR 1.77; 95%CI: 1.02-3.06, P=0.041 for 420Lys homocygotes). Atopic carriers of SPINK5 420Lys showed an increased risk for asthma and asthma symptoms (OR 2.06; 95%CI: 1.01-4.20, P=0.047). When children with a combination of asthma and atopic dermatitis were compared with normal controls, the SPINK5 420Lys genotype was more prevalent in the disease group (OR 4.56; 95%CI: 1.370-15.12, P=0.007). No association between SPINK5 420Lys genotypes and total serum IgE levels, skin prick test (SPT) reactivity or atopic dermatitis was observed.

CONCLUSION

These results suggest that SPINK5 Glu420Lys polymorphism may be associated with certain asthma phenotypes characterized by the concomitant expression of asthma and atopic dermatitis or SPT reactivity.

Characteristics and outcome for admissions to adult, general critical care units with acute severe asthma: a secondary analysis of the ICNARC Case Mix Programme Database

INTRODUCTION

This report describes the case mix, outcome and activity (duration of intensive care unit [ICU] and hospital stay, inter-hospital transfer, and readmissions to the ICU) for admissions to ICUs for acute severe asthma, and investigates the effect of case mix factors on outcome.

METHODS

We conducted a secondary analysis of data from a high-quality clinical database (the Intensive Care National Audit and Research Centre [ICNARC] Case Mix Programme Database) of 129,647 admissions to 128 adult, general critical care units across England, Wales and Northern Ireland over the period 1995-2001.

RESULTS

Asthma accounted for 2152 (1.7%) admissions, and in 57% mechanical ventilation was employed during the first 24 hours in the ICU. A total of 147 (7.1%) patients died in intensive care and 199 (9.8%) died before discharge from hospital. The mean age was 43.6 years, and the ratio of women to men was 2:1. Median length of stay was 1.5 days in the ICU and 8 days in hospital. Older age, female sex, having received cardiopulmonary resuscitation (CPR) within 24 hours before admission, having suffered a neurological insult during the first 24 hours in the ICU, higher heart rate, and hypercapnia were associated with greater risk for in-hospital death after adjusting for Acute Physiology and Chronic Health Evaluation II score. CPR before admission, neurological insult, hypoxaemia and hypercapnia were associated with receipt of mechanical ventilation after adjusting for Acute Physiology and Chronic Health Evaluation II score.

CONCLUSION

ICU admission for asthma is relatively uncommon but remains associated with appreciable in-hospital mortality. The greatest determinant of poor hospital survival in asthma patients was receipt of CPR within 24 hours before admission to ICU. Clinical management of these patients should be directed at preventing cardiac arrest before admission.

The relationship of sex to asthma prevalence, health care utilization, and medications in a large managed care organization

BACKGROUND

Age-related sex differences in asthma hospitalizations and emergency department (ED) visits have been reported, but relationships of these differences to disease prevalence and outpatient management have not been defined.

OBJECTIVE

To define the relationships of sex to asthma-related health care utilization and medications, accounting for age-related differences in asthma prevalence.

METHODS

Computerized data from Southern California Kaiser-Permanente were used to identify asthmatic patients, aged 2 to 64 years, enrolled continuously during 1999 and 2000. Age-specific asthma prevalence in 1999 was calculated to identify ages of male or female predominance. Males and females were compared with regard to asthma-related health care utilization outcomes (outpatient clinic visits, ED visits, and hospitalizations) and medication use (beta-agonists, inhaled steroids, and oral steroids). Hospitalizations, ED visits, and oral steroid use were considered markers of disease severity.

RESULTS

Of the 60,694 subjects, the female-male prevalence ratio was approximately 35:65 at each age between 2 and 13 years, it was inverse (65:35) between the ages of 23 and 64 years, and prevalences were relatively similar at the ages of 14 to 22 years. In patients aged 2 to 13 years, most utilization and medication variables were significantly greater in males (P < .01). Females aged 14 to 22 years had more outpatient and ED visits and used more oral steroids than males. In patients aged 23 to 64 years, all utilization variables were significantly greater in females, except beta-agonist use and mean inhaled steroid dispensings.

CONCLUSIONS

Asthma utilization and severity appear greater in males aged 2 to 13 years, somewhat greater in females aged 14 to 22 years, and definitely greater in females aged 23 to 64 years. The mechanisms for these striking sex differences merit further investigation.

Longitudinal follow-up of the changing gender ratio in asthma from childhood to adulthood: role of delayed manifestation in girls

Boys suffer more often from asthma than girls, while in adults the gender ratio is reversed. It is not clear when exactly this change occurs and by what mechanism. From a cohort of all 5030 German 4th grade pupils (age 10 years) in Munich, 274 children with current asthma were identified (164 males, 110 females) through a questionnaire, and skin prick tests were performed. These subjects were re-evaluated at ages 14 and 20 years with a questionnaire. A random sample (n = 1000) of all 3538 German children without current asthma at age 10 was also re-evaluated at age 20 (controls). At age 20, only 24.5% (21 males, eight females) of the initial asthma group still had symptoms, and their gender ratio remained male dominated. In the controls, 4.8% (48/1000) had current asthma at age 20 and these were predominantly female: 6.4% (31/485) of control girls vs. 3.3% (17/515) of boys (p = 0.022). Half of the new asthma cases had had no symptoms or diagnoses until age 10, and atopy at age 10 was not associated with subsequent asthma in these. Asthma at age 10 has no better prognosis in boys than in girls, and the mechanism of the changing gender ratio appears to be late incidence of asthma among girls. Because the latter constitute a considerable part of adult asthma cases, it appears important to further explore this asthma phenotype and the risk factors associated with it.

Retrospective evaluation of epidermal skin prick tests in patients living in Aegean region

Sensitization to aeroallergens of Aegean region is not well decumented. In this study we evaluated the epidermal skin prick test results of the patients who applied to allergy outpatient department retrospectively. Epidermal skin prick test of the 5055 patients were evaluated. Of these patients 2638 (52 %) were female, 2417 (48 %) male, 1213 (24 %) adult and 3842 (76 %) pediatric patient, 1163 (23 %) patients were allergic rhinitis, 2477 (49 %) were bronchial asthma, 505 (10 %) were allergic rhinitis with bronchial asthma, 556 (11 %) were chronic urticaria, 253 (5 %) were wheezy infant and 101 (2 %) patients were atopic dermatitis, 2932 (58 %) had atopy history in their first and second degree relatives. Patients were aged between 3.5 months and 79 years (mean 14.1 3.2 years and median 11 years). In epidermal skin prick tests sensitization to house dust mites (D. farinae, D. pteroniyssinus), pollens (grass, cereals and trees), moulds, animal danders, foods (especially in early childhood) and cockroach were evaluated. Our data indicate that allergens that may be the cause of the high prevalence of allergic diseases in Izmir are probably produced by pollens and mites.

Therapeutic implications of sex differences in asthma and atopy

Clear sex differences exist in asthma and atopy with a preponderance of boys before puberty. There is a reversal of this sex ratio during puberty with girls having more asthma and atopy throughout the reproductive years. Elucidating the reasons for the switch in the sex ratio should provide fresh insights into asthma and atopy with a real prospect of novel therapies for these troublesome diseases. The challenge is to match the epidemiology and physiology with the accumulating scientific knowledge on gender differences in immune responses. Hormonal changes have been implicated in the reversal of the sex ratio. Testosterone is an immunosuppressant and is likely to be protective, while female sex steroids are proinflammatory and will increase the susceptibility to atopy. Modified so as to be non-virilising/feminising, sex steroids could therefore play a useful part in modulating the immunological and inflammatory processes that underlie asthma and other allergic disorders, complementing the currently used glucocorticoid derived steroids.

Natural history of asthma

For some children, asthma is a disease whose symptoms seem to remit with time. Numerous children, however, develop disease that is persistent throughout their lifetimes and is associated with more severe symptoms, increased airway reactivity, and loss of lung function. These children typically have a family history of asthma and demonstrate increased airways reactivity and atopy in childhood. A clearer picture of the natural history of asthma in the developing child has been derived from the results of several longitudinal studies. Although some questions have been clarified, several questions still remain. Now that the incidence and severity of asthma seem to be increasing, children born in the last 10 years may experience more severe disease or a different pathophysiology than those born 30 to 40 years ago. New cohort studies are needed to assess this possibility. Additional investigations into the genetics of asthma causation will help elucidate the different phenotypic expressions of this complex disease. Once these different phenotypic groups can be identified early in life, further studies can be performed to explore the impact of therapeutic intervention on the severity of asthma symptoms and loss of lung function.

Introduction to nasal and pulmonary allergy cascade

The early phase of an IgE-dependent allergic reaction is followed by the activation of a complex network of inflammatory phenomena - T lymphocytes, cytokines, mediators, and adhesion molecules - that mediate late and ongoing allergic symptoms. The kinetics of respiratory inflammation following allergen exposure involve the migration of inflammatory cells to the mucosa within about 30 min, increased inflammatory infiltration over the following hours, and then slow subsidence. A relationship between asthma and allergic rhinitis is supported by epidemiological, histological, physiological, and immunopathological data, and by the response of asthma symptoms in rhinitic patients to intranasal corticosteroids and antihistamines. For example, there is no morphological difference between the bronchial inflammatory response following allergen-specific challenge in patients suffering from asthma alone or rhinitis alone. It is the allergen dose that makes the difference in the airway response to allergen in allergic rhinitis and asthma. Recognition of the relationship between asthma and allergic rhinitis has led to the introduction of new diagnostic terminology and treatment recommendations: 1) patients with persistent rhinitis should be evaluated for asthma; 2) patients with persistent asthma should be evaluated for rhinitis; and 3) a strategy should combine the treatment of upper and lower airways in terms of efficacy and safety.

Advances in allergy management

Our understanding of the pathophysiology of allergy has moved to the molecular level, while study of epidemiology and genetics has revealed risks of developing allergies based on environmental and genetic profiles, and pharmacoeconomic data have enabled accurate measurement of the immense burden of allergic disease. These advances in allergy research have affected its management, particularly the search for new antiallergy therapies. New therapies should intervene in the systemic allergy inflammatory cascade and provide clinical efficacy that extends to multiple allergic disease states. In addition, these new therapies should present no additional safety issues, offer improvements over existing therapies, and have an impact on disease-impaired quality of life. In vitro studies show that desloratadine, a new, once-daily, nonsedating, selective histamine H1-receptor antagonist, blocks the systemic allergy cascade at multiple points. Desloratadine 5 mg once daily relieves the symptoms of chronic idiopathic urticaria and of both seasonal (SAR) and perennial allergic rhinitis. In patients with concomitant asthma and SAR, asthma symptoms are relieved and beta2-agonist medication use is decreased by desloratadine. Unlike many other second-generation histamine H1-receptor antagonists, desloratadine provides the added benefit of efficacy against nasal obstruction in SAR. Desloratadine improves quality of life by decreasing the impact of allergic symptoms on sleep and on daily activities.

Response to montelukast among subgroups of children aged 2 to 14 years with asthma

BACKGROUND

Determining who responds to asthma therapies, particularly leukotriene modifiers, continues to be explored.

OBJECTIVE

We sought to identify patient characteristics predictive of response to montelukast.

METHODS

We used data from 2 clinical trials in which children with asthma received either montelukast or placebo. Symptoms, beta-agonist use, and unanticipated health resource use caused by asthma were recorded in validated daily diaries for children 2 to 5 (n = 689) and 6 to 14 (n = 336) years old. We defined primary end points of days without asthma in 2- to 5-year-old patients (24 hours without symptoms, beta-agonist use, or asthma attack) and change in percent predicted FEV(1) in 6- to 14-year-old children. Asthma attack was defined by the use of rescue oral corticosteroids or by an unscheduled visit to a medical provider. Patients were grouped according to baseline characteristics, such as family history of asthma, personal history of allergy, frequency of asthma symptoms, eosinophilia, and concomitant use of inhaled corticosteroids or cromolyn. We examined the stratum-specific effects of montelukast on the percentage of days without asthma, change in percent predicted FEV(1), asthma attack, and a variety of secondary symptom and FEV(1) end points.

RESULTS

We did not identify characteristics that predicted response to montelukast in either preschool or 6- to 14-year-old children. These findings were consistent across all symptom and FEV(1) outcomes. There was also no differential response to montelukast in either age group when asthma attack was the outcome.

CONCLUSION

The patient characteristics studied do not appear to provide an indication of who will benefit most from treatment with montelukast.

Different sensitization profile for asthma, rhinitis, and eczema among 7-8-year-old children: report from the Obstructive Lung Disease in Northern Sweden studies

Sensitization to different airborne allergens in relation to asthma, rhinitis, and eczema has been studied. A cross-sectional study was performed among 7-8-year-old children living in northern Sweden. The ISAAC-questionnaire with additional questions were sent to the parents, and 3431 (97%) participated. Two-thirds of the children were invited to undergo a skin test with 10 common airborne allergens, and 2148 (88%) participated. The prevalence rates of all three diseases were significantly higher among the children who were sensitized to any of the tested allergens. Among asthmatics, 40% were sensitized to cat, 34% to dog, 28% to horse, 23% to birch and 16% to timothy. The corresponding figures for rhinitis were: cat 49%, dog 33%, horse 37%, birch 46%, timothy 32%; and for eczema: cat 29%, dog 21%, horse 15%, birch 20%, and timothy 11%. Only a few children were sensitized to mites or moulds. The main risk factors for all three diseases were type-1 allergy and a family history of the disease. Independently from other risk factors, sensitization to dog (OR 2.4) and horse (OR 2.2) were significant risk factors for asthma. Sensitization to birch (OR 6.0), horse (OR 4.1), and timothy (OR 2.8) were significant risk factors for rhinitis, while birch (OR 2.4), dog (OR 2.0) and cat (OR 1.6) were significant risk factors for eczema. Despite a large over-lapping of the diseases the pattern of sensitization was different for asthma, rhinitis and eczema. Sensitization to cat was most common among all children, but sensitization to dog and horse was associated with the highest risk for asthma, and sensitization to birch showed the highest risk for rhinitis and eczema. The different risk factor pattern for the often coexisting diseases; asthma, rhinitis, and eczema, may indicate differences in the etiology.

The impact of estrogen and progesterone on asthma

OBJECTIVE

This paper describes evidence of a positive effect of both endogenous and exogenous estrogen and progesterone on lung function across the life span in women.

DATA SOURCES

Articles were identified using the keywords asthma, pulmonary function, menarche, menopause, estrogen, progesterone, hormone replacement therapy, oral contraceptives, and menstrual cycle from years 1966 to 2001 in MEDLINE. Additional studies were identified from article reference lists.

STUDY SELECTION

Relevant, peer-reviewed original research articles in the English language were selected.

RESULTS

Estrogen and/or progesterone may alter pulmonary function and asthma. Premenopausal women experience decreases in pulmonary function and increases in asthma exacerbations and hospitalizations during the premenstrual and menstrual phases. Oral contraceptives and hormone replacement therapy are associated with improved pulmonary function and decrease in asthma exacerbation. Some asthmatic patients experience improved pulmonary function and reduced asthma medication requirement during pregnancy.

CONCLUSIONS

Estrogen and progesterone modify airway responsiveness. Further research is needed to elucidate the clinical relevance of estrogen and progesterone in the pathophysiology and therapy of asthma.

Incidence rates and risk factors for asthma among school children: a 2-year follow-up report from the obstructive lung disease in Northern Sweden (OLIN) studies

Studies of incidence of asthma are still limited. A longitudinal study of asthma in school children was started in 1996 in Northern Sweden. The incidence of asthma and the associated risk factors have been studied over a 2 years period. The study started with a parental questionnaire, the ISAAC questionnaire with additional questions, and a skin-prick test. The cohort, 3,525 children, 7 and 8 years old at start, was followed after 1 and 2 years by using the same questions, Each year responded 97%. The cumulative incidence of physician-diagnosed asthma was 1.7%, 0.9/1,000/year the first year, and 0.8/1,000/year the second year. The cumulative incidence of wheezing was 6.3%, and of frequent or daily users of asthma medicines 2.1%. Significant risk factors for incident asthma were a positive skin test, OR 5.64 (3.10-10.25); rhinitis,OR 3.53 (1.80-6.90); eczema, OR 2.19 (1.26-3.82); a family history of asthma, OR 2.83 (1.75-4.56); low birth weight, OR 3.38 (1.61-754); respiratory infections, OR 2.12 (1.24-3.63); male gender, OR 1.71 (1.06-2.81); and a smoking mother OR 2.00 (1.07-3.73). In summary the incidence of asthma during 2 years after age 7 was high, almost 1/100/year. Allergy was the most important risk factor, but other factors were influential.

High prevalence of current asthma and active smoking effect among the elderly

BACKGROUND

Although asthma is a common cause of morbidity in adults, relatively few objectively measured population studies of asthma prevalence in adult populations have been conducted.

OBJECTIVE

To evaluate the prevalence of asthma, based on both a questionnaire and methacholine bronchial provocation test, and to determine the risk factors of asthma prevalence in an adult population.

METHODS

A total of 2,467 adults, who were randomly selected from metropolitan urban, non-metropolitan urban and rural areas, responded to the modified ISAAC questionnaire, and underwent methacholine bronchial provocation tests and skin prick tests to locally common aeroallergens.

RESULTS

The prevalence of current asthma based on the questionnaire and the methacholine challenge was 2.0% in adults younger than 40, 3.8% in 40- to 54-year-olds, 7.7% in 55- to 64-year-olds and 12.7% in those aged 65 or higher. For subjects of 55-64 years, active smoking was found to be significantly related with the prevalence of current asthma and bronchial hyper-responsiveness, although smoking was positively associated with percentage predictive value of forced expiratory volume of 1 s (FEV1).

CONCLUSION

The prevalence of current asthma is common among the elderly, and active smoking may play an important role in the development of asthma and bronchial hyper-responsiveness among the elderly.

Effect of cat and dog ownership on sensitization and development of asthma among preteenage children

An inverse relationship has been proposed between exposure to high quantities of cat allergen at home and both asthma and cat allergy. First- and second-grade children from Luleå, Kiruna, and Piteå, Sweden participated in an asthma questionnaire study (n = 3,431) and incidence was evaluated over the next 3 years. Skin testing was performed on the children in Luleå and Kiruna (n = 2,149). The strongest risk factor for incident cases of asthma was Type 1 allergy (relative risk [RR], 4.9 [2.9-8.4]), followed by a family history of asthma (RR, 2.83 [1.8-4.5]). Living with a cat was inversely related both to having a positive skin test to cat (RR, 0.62 [0.47-0.83]) and incidence of physician-diagnosed asthma (RR, 0.49 [0.28-0.83]). This effect on incident asthma was most pronounced among the children with a family history of asthma (RR, 0.25 [0.08-0.80]). The evidence also suggests that many of the children exposed to cats at home can develop an immune response that does not include immunoglobulin E. Weaker protective trends were seen with dog ownership. The traditional thinking that not owning cats can provide protection against developing allergy and asthma among those with a family history of allergy needs to be re-evaluated. In a community where cat sensitization was strongly associated with asthma, owning a cat was protective against both prevalent and incident asthma.

The importance of maximal airway response to methacholine in the prediction of asthma development in patients with allergic rhinitis

BACKGROUND

Allergic rhinitis is a known predictor and correlate of asthma incidence. However, it is not clear which patients with allergic rhinitis are at greater risk of the development of asthma.

OBJECTIVE

The aim of this study was to investigate whether airway hypersensitivity and/or increased maximal response on the dose-response curve to methacholine would predict the development of asthma in subjects with allergic rhinitis.

METHODS

One hundred and forty-one children with allergic rhinitis were prospectively studied for 7 years. At the initiation of the study, bronchial provocation test with methacholine using a stepwise increasing concentration technique was performed to measure PC(20) (provocative concentration causing a 20% fall in FEV(1)) and maximal response. Each subject was evaluated at least every 6 months and details of asthmatic symptoms or signs experienced during the intervening period were taken.

RESULTS

Twenty of 122 subjects available for the follow-up developed asthma. Nine (19.6%) of 46 hypersensitive (PC(20) < 18 mg/mL) subjects developed asthma, compared with 11 (14.5%) of 76 normosensitive subjects (P = 0.462). Eight (32%) of 25 subjects without maximal response plateau developed asthma, compared with 12 (12.4%) of 97 subjects with maximal response plateau (P = 0.018). Score test for trend revealed a significant association between the level of maximal response (P = 0.007), but not the degree of methacholine PC(20) (P = 0.123), and the future development of asthma.

CONCLUSION

An increased maximal airway response to methacholine is shown to be a better predictor for the future development of asthma in patients with allergic rhinitis, than airway hypersensitivity to methacholine.

Different slopes for different folks: socioeconomic and racial/ethnic disparities in asthma and hay fever among 173,859 U.S. men and women

Although allergic diseases such as asthma and hay fever are a major cause of morbidity in industrialized countries, most studies have focused on patterns of prevalence among children and adolescents, with relatively few studies on variations in prevalence by race/ethnicity and socioeconomic position among adults. Our study examined racial/ethnic and socioeconomic patterns in the prevalence of asthma overall, asthma with hay fever, asthma without hay fever, and hay fever overall, in a population of 173,859 women and men in a large prepaid health plan in northern California. Using education as a measure of socioeconomic position, we found evidence of a positive gradient for asthma with hay fever with increasing level of education but an inverse gradient for asthma without hay fever. Hay fever was also strongly associated with education. Compared with their White counterparts, Black women and men were more likely to report asthma without hay fever, and Black women were less likely to have asthma with hay fever. Asian men were also more likely to report asthma with hay fever, and Asian women and men were much more likely to have hay fever. Racial/ethnic disparities in prevalence of allergic diseases were largely independent of education. We discuss implications for understanding these social inequalities in allergic disease risk in relation to possible differences in exposure to allergens and determinants of immunologic susceptibility and suggest directions for future research.

Epidemiology of asthma and recurrent wheeze in childhood

To summarize, wheeze is common throughout childhood, although it decreases as children age. However, the characteristics of wheeze, its relations with asthma, and its risk factors all change with age. Longitudinal studies have shown that "transient early wheezing" predominates during the first years of life. The principal risks for this type of wheezing are largely mechanical, relating to small airways, and infectious, relating to the risk of becoming infected with respiratory viruses. Associated with passive exposure to cigarette smoke, exposure to other children, and not being breastfed, this form of wheezing was unrelated to increased airway liability or atopy in the child. For the majority of children, particularly those with low lung function at birth, wheezing with early LRIs is a benign condition, not associated with subsequent wheeze or risk for asthma. During the middle part of the first decade of life, wheezing appears to reflect a mix of infectious and allergic wheezing. By 6 yr of age, some children have already wheezed persistently. This group is more likely to have high total IgE levels, to be skin-test positive, and to be given a diagnosis of asthma. Further, their immunologic response to their early LRIs was consistent with a Th2 bias: persistent wheezers produced high levels of IgE, and did not demonstrate the normal pattern of decreased eosinophils. Nevertheless, the children who wheeze in middle childhood are a mixed group, with some being less allergic. Thus, although markers of allergy become increasingly important predictors of wheezing for the group as a whole, wheezing in middle childhood is not associated with later methacholine hyperresponsiveness (42). Finally, persistent allergic wheezing, usually associated with a diagnosis of asthma, predominates by the end of the first decade of life. Wheezing at this age is associated with methacholine responsiveness, peak-flow variability, and markers of atopy, such as total IgE and allergy skin-test response. Although children who wheezed early in life are more likely to wheeze later, early wheeze does not increase the risk of atopy, suggesting that early LRIs are markers of increased risk rather than causes. The gender differences in wheeze disappear, with boys becoming less likely to wheeze and to have asthma, whereas both conditions appear to increase in girls. Finally, some of the risk factors for early LRIs, such as exposure to other children in infancy, appear to be associated with protection from later allergic wheezing. Clearly, asthma and wheeze during childhood are complex entities, presenting with different characteristics at different ages, and implicating varied and changing causes. Genetic factors are important determinants of the intermediate phenotypes. However, environmental factors operating at different developmental stages also appear to influence the development of asthma. Additional research regarding these relationships is essential, both to elucidate possible causal mechanisms and to provide insight into the primary prevention of asthma.

Risk factors for onset and remission of atopy, wheeze, and airway hyperresponsiveness

BACKGROUND

Although many children with asthma may have a remission as they grow and other children who did not have asthma may develop asthma in adult life, knowledge about the factors that influence the onset and prognosis of asthma during adolescence and young adulthood is very limited.

METHODS

A cohort of 8-10 year old children (n=718) living in Belmont, New South Wales, Australia were surveyed six times at 2 yearly intervals from 1982 to 1992, and then again 5 years later in 1997. From this cohort, 498 subjects had between three and seven assessments and were included in the analysis. Atopy, airway hyperresponsiveness (AHR), and wheeze in the last 12 months were measured at each survey. Late onset, remission, and persistence were defined based on characteristics at the initial survey and the changes in characteristics at the follow up surveys.

RESULTS

The proportion of subjects with late onset atopy (13.7%) and wheeze (12.4%) was greater than the proportion with remission of atopy (3.2%) and wheeze (5.6%). Having atopy at age 8-12 years (OR 2.8, 95% CI 1.5 to 5.1) and having a parental history of asthma (OR 2.0, 95% CI 1.02 to 4.13) were significant risk factors for the onset of wheeze. Having AHR at age 8-12 years was a significant risk factor for the persistence of wheeze (OR 4.3, 95% CI 1.3 to 15.0). Female sex (OR 1.9, 95% CI 1.01 to 3.60) was a significant risk factor for late onset AHR whereas male sex (OR 1.9, 95% CI 1.1 to 2.8) was a significant risk factor for late onset atopy.

CONCLUSIONS

The onset of AHR is uncommon during adolescence, but the risk of acquiring atopy and recent wheeze for the first time continues during this period. Atopy, particularly present at the age of 8-10 years, predicts the subsequent onset of wheeze.

Incidence of asthma and its determinants among adults in Spain

The objective was to measure the incidence of asthma and its determinants in Spain, where the prevalence of asthma is low to medium. A follow-up of subjects participating in the European Community Respiratory Health Survey (ECRHS) was conducted in 1998- 1999 (n = 1,640, 85% of those eligible). Subjects were randomly selected from the general population and were 20 to 44 yr old in 1991-1993. Time of follow-up was on average 6.75 yr (range, 5.3 to 7.9 yr). Asthma was defined as reporting ever having had asthma. The incidence of asthma was 5.53 (95% confidence interval, 4.28- 7.16) per 1,000 person-years (6.88 in females, 4.04 in males). Incidence was highest in subjects who at the baseline survey had bronchial hyperresponsiveness (incidence rate ratio [IRR], 3.85), in those with positive IgE against timothy grass (IRR, 3.16), and in females (IRR, 1.80). These results persisted after adjusting for respiratory symptoms at baseline. There was no significant association (p < 0.2) with high total serum IgE, atopy defined by reactivity to any allergen, smoking, occupational exposure, or maternal asthma. A sensitivity analysis using four definitions of population at risk yielded incidence rates varying from 5.53 to 1.50. In this population of subjects without self-reported asthma or asthma-type symptoms at baseline, bronchial hyperresponsiveness and IgE reactivity to grass appeared as the main determinants of new asthma.

Prevalence of bronchial asthma and association with environmental tobacco smoke exposure in adolescent school children in Chandigarh, north India

Prevalence of asthma and its association with environmental tobacco smoke (ETS) exposure were examined among adolescent schoolchildren in Chandigarh, India. Using a previously standardized questionnaire, data from 9090 students in the 9- to 20-year age range were analyzed. There were 4367 (48%) boys, in whom the observed prevalence of asthma was 2.6%. Among 4723 (52%) girls, asthma was present in 90 (1.9%) students. Presence of one or more respiratory symptoms was reported by 31% students. More students with asthma had either parents or other family members smoking at home as compared to nonasthmatics (41% vs. 28%, p<0.0001). The odds ratio for being asthmatic for patients exposed to ETS compared to those not exposed to ETS was 1.78 (95% confidence interval 1.33-2.31). ETS was also positively associated with prevalence of all the respiratory symptoms, with odds ratios varying between 1.6 and 2.25.

Incidence of physician-diagnosed asthma in adults--a real incidence or a result of increased awareness? Report from The Obstructive Lung Disease in Northern Sweden Studies

Only limited data are available about the incidence of asthma based on longitudinal prospective studies. Further, the results from different studies on incidence vary considerably depending on the age composition of the cohorts under study, the used methods and the criteria for disease. Also among adults high incidence rates have been reported during recent years. The aim of this study was to examine to what extent the incidence of physician-diagnosed asthma could be explained by a real incidence of the disease, and to what extend by an increased diagnostic activity or altered diagnostic praxis. Another aim was to study risk factors for asthma based on incident cases. Three cross-sectional surveys have been performed in the same population sample living in the northern-most province of Sweden, Norrbotten. The first survey was performed in 1986, and 5698 subjects, 86% of those invited, responded to a postal questionnaire. Of these, 4754 subjects (83%) participated at the third survey in 1996. After exclusion of all subjects who had reported that they had asthma in 1986, or had been classified as having asthma in 1986, 68 men and 98 women (P=0.02) reported in 1996 that they had been diagnosed as having asthma by a physician. Thus, the cumulative incidence for the 10-year period was 3.2% among men and 4.5% among women. After correction for subjects who already in 1986 had reported symptoms common in asthma, or had been classified as having chronic bronchitis, 97 subjects with incident asthma remained, which corresponded to an annual incidence rate among men of 1.7 and among women of 2.9/1000 persons year(-1) (P=0.1). Clinical examinations confirmed asthma in a large majority of these 97 subjects. Significant risk factors were family history of asthma, both ex- and current smoking, and female sex. The socio-economic groups manual workers and assistant non-manual employees were associated with incident asthma, although not significantly. The increasing prevalence of asthma among adults during recent 10-20 years may to a considerable extent be explained by an increased diagnostic activity or altered diagnostic praxis. Use of different methods when measuring incidence may in part explain the extremely diverging incidence rates of asthma found in different studies.

Increased incidence of asthmalike symptoms in girls who become overweight or obese during the school years

The possibility of a causal relationship is suggested by recent concomitant increases in the prevalence of obesity and asthma. In a general population sample, prevalence and incidence of asthma symptoms, skin tests, and body mass index (BMI) were ascertained at mean ages of 6.3 (n = 688) and 10.9 (n = 600) yr. Lung function, bronchodilator responsiveness, and daily peak flow variability were measured at 11 yr of age. There was no association between BMI at age 6 and wheezing prevalence at any age. Females, but not males, who were overweight or obese at 11 yr of age were more likely to have current wheezing at ages 11 and 13 but not at ages 6 or 8. This effect was strongest among females beginning puberty before the age of 11. Females who became overweight or obese between 6 and 11 yr of age were 7 times more likely to develop new asthma symptoms at age 11 or 13 (p = 0.0002); at age 11 their peak flow variability and bronchodilator responsiveness were significantly more likely to be increased. In females, becoming overweight or obese between 6 and 11 yr of age increases the risk of developing new asthma symptoms and increased bronchial responsiveness during the early adolescent period.

Puberty and prognosis of asthma and bronchial hyper-reactivity

It is a commonly held view that pediatric asthma frequently abates during puberty. However, little data are available that associate the stage of puberty with the prognosis of asthma and bronchial hyper-reactivity (BHR). In this study, 155 children with active asthma at 10 years of age (60 girls [38.70%], 95 boys [61.3%]) were followed-up until they reached 14 years of age. The stage of puberty was assessed by parental questionnaire; in addition, serum 3-alpha-androstanediolglucuronide, as an endocrinological marker for peripheral androgen status, was measured in 107 subjects. Persistence of asthma was determined via questionnaire, lung function testing, and bronchial provocation (hyperventilation of cold, dry air). At 14 years of age, 73.3% of girls were reported to have had menarche and 40.8% of boys a voice change, and only 35.5% of the subjects had experienced acute asthma symptoms during the last 12 months, with an almost unchanged gender ratio (19 girls [34.5%], 36 boys [65.5%]) vs. that recorded at 10 years of age. The level of androstanediolglucuronide was higher in the children who reported puberty (mean+/-SD): 3.03+/-2.13 nmol/l vs. 1.89+/-1.26 nmol/l, p = 0.003. No statistically significant relationship was found between the reported signs of late puberty and loss of asthma or BHR. Likewise, no significant association was found between asthma persistence and the level of androstanediolglucuronide (2.39+/-1.75 nmol/l vs. 2.44+/-1.82 nmol/l, p = 0.84), or BHR and the level of androstanediolglucuronide (3.02+/-1.97 nmol/l vs. 2.28+/-1.67 nmol/l, p = 0.13), at 14 years of age, in girls or boys. At 14 years of age, no change in the gender ratio of children with active asthma had occurred. These results may indicate that the change in gender predominance of asthma through the second decade of life is not caused by increased loss of established asthma in boys between 10 and 14 years of age.

Definition of respiratory symptoms and disease in early childhood in large prospective birth cohort studies that predict the development of asthma

We have reviewed the prospective value of early respiratory symptoms for determining the risk of development of asthma later in life by using data from studies based on the general population, hospital population, and general practices. Although "wheezing" in infancy generally has a good prognosis, it is an important risk factor for the development of asthma later in life. The prognostic value of "coughing" and "shortness of breath" in infancy for the later development of asthma is less clear. Despite the fact that no internationally accepted criteria for the definition of asthma in early childhood are available, many studies have been performed on this topic. We also investigated the outcome variables that were used to describe respiratory symptoms and disease in early childhood in the publications of nine large prospective birth cohort studies on the development of asthma. From seven of these studies, we reviewed the original questionnaires. We found that various studies used different outcome variables, but the data actually collected were similar. This is an important observation because it implies that comparisons between studies can be markedly improved by data sharing among investigators.

Incidence and remission of asthma in schoolchildren: report from the obstructive lung disease in northern Sweden studies

OBJECTIVE

An increasing prevalence of asthma has been reported worldwide as well as in Sweden. In 1996, the prevalence of asthma and type 1 allergy was investigated in a cohort of 3525 children 7 and 8 years old in 3 areas of northern Sweden. The aim of the present study was to estimate the incidence of asthma and to identify risk factors for incident cases over 1 year.

METHODS

The study started with a parental questionnaire, the International Study of Asthma and Allergies in Childhood questionnaire with additional questions, a skin prick test, and a validation study. The cohort was followed up after 1 year with the same questions. The response rate to the questionnaire was 97% in 1996, and 3339 children (97%) participated both in 1996 and 1997.

RESULTS

The incidence of physician-diagnosed asthma was 0.9/100/year; of wheezing, 3.8/100/year; and of new frequent or daily users of asthma medicines, 1.1/100/year. There was no difference by sex. The risk factor pattern based on incident cases of asthma was different from that based on prevalent cases. Significant risk factors for incident asthma were a positive skin test (odds ratio [OR]: 9.3; 95% confidence interval [CI]: 3.8-22.7); low birth weight (OR: 7.4; 95% CI: 2.2-24.5); and family history of asthma (OR: 2.6; 95% CI: 1.1-6.3). Having or having had pets at home was associated with a decreased risk for asthma and wheezing based on prevalent cases, although it was associated with an increased risk for incidence of wheezing (OR: 2.9; 95% CI: 1.3-6.2). Remission of asthma, which was reported by 10% of the children with current asthma during 1 year, was associated with a negative skin test.

CONCLUSION

The incidence of asthma at the age of 8 years was high, but remission was also common. Important risk factors for the development of asthma at this age were type 1 allergy, low birth weight, and family history of asthma. Furthermore, the results suggest that in a region where sensitivity to domestic animals is a strong risk factor for asthma, the presence of pets in the home may have different effects in early childhood compared with later in childhood.

Problems and possibilities in understanding the natural history of asthma

In early life, asthma symptoms can occur intermittently or may not be severe enough to limit normal activities, which makes it difficult for the clinician to make reliable predictions and administer therapy with some precision. In the case of pediatric asthma, the identification of children who will experience the development of a clinically important illness that will impair their quality of life can be a complex process. The usual methods for describing this information include the prognostic statistics of sensitivity, specificity, likelihood ratio, and positive predictive value. The sensitivity, specificity, and likelihood ratio of various early markers of asthma have been calculated from several cohort studies.

Issues and unmet needs in pediatric asthma

Asthma is common and becoming more so in childhood. Although mild asthma may incur low average annual costs per child, these estimates need to be viewed in the context of the very large numbers of affected individuals. Whereas asthma and wheezing illness in childhood had in the past been broadly subdivided into asthma (often associated with atopy) and wheezy bronchitis (wheeze only, with associated upper respiratory tract infection), this distinction was lost during the 1970s in view of the demonstrated underdiagnosis and undertreatment of symptomatic school-age children. The acceptance of asthma as a chronic inflammatory disease and evidence for airway remodeling and progressive deterioration in airway function in association with symptoms and atopy have led to earlier use of topical steroids at higher starting doses delivered by improved age-appropriate devices. Treating all children as if they were destined to become atopic asthmatics and at risk of airway remodeling may not be rational, particularly in those whose symptoms will subsequently resolve. However, there are as yet no screening tests which can clearly identify individuals at risk of long-term chronic airway inflammation and airway remodeling. The large number of infants and young children with current symptoms suggestive of asthma and in whom resolution is likely in the majority poses problems for the clinician in deciding the best initial therapy. There is an urgent need to develop simple and reliable measures that can identify the early manifestations of atopic airway sensitisation and to establish the place of early intervention with nonsteroidal drugs, including leukotriene antigonists.

Prevalence of asthma, allergic rhinitis, and eczema in 13- to 14-year-old children in Kuwait: an ISAAC study. International Study of Asthma and Allergies in Childhood

OBJECTIVES

To determine the prevalence of asthma and allergic diseases in 13 to 14 years old children in Kuwait.

DESIGN

Supervised self-administered written and video questionnaires of the international study of asthma and allergies in childhood (ISAAC).

SUBJECTS

Students at third and fourth years from 40 intermediate level schools chosen randomly from across Kuwait.

RESULTS

3,110 students were surveyed. The prevalence rates (95% CI) in the written questionnaire for wheeze ever, current wheeze (within the last 12 months), and physician diagnosis of asthma are 25.9% (24.5 to 27.4), 16.1% (15.8 to 17.4), and 16.8% (15.5 to 18.1) respectively. The prevalence rates (95% CI) for symptoms of allergic rhinitis (AR) ever, current symptoms of allergic rhinitis (AR), and diagnosis of AR are 43.9% (42.2 to 45.6), 30.7% (29.1 to 32.4) and 17.1% (14.8 to 18.4) respectively. The prevalence rates (95% CI) for itchy rash ever, current itchy rash, and diagnosis of eczema are 17.5% (16.2 to 18.8), 12.6% (11.4 to 13.8), and 11.3% (10.2 to 12.4) respectively. The prevalence of wheeze ever, wheeze during the last year, and physician diagnosis of asthma are higher in males compared with females, P < .01. In multiple logistic regression: male gender (OR 1.6, 95% CI, 1.3 to 2.0) and diagnosis of AR (OR 1.7, 95% CI, 1.4 to 2.2) were associated with the physician diagnosis of asthma even after controlling for symptoms of asthma.

CONCLUSION

This is the first study on the prevalence of allergic diseases in Kuwait and it shows that children in Kuwait have a moderate prevalence of asthma, AR, and eczema compared with other countries where the ISAAC study is done. The prevalence of asthma is higher in boys compared with girls.

Regressive logistic modeling of familial aggregation for asthma in 7,394 population-based nuclear families

The aim of this population-based study was to determine whether asthma aggregates in families, and if so, whether aggregation was consistent with environmental and/or genetic etiologies. Data were from 7,394 nuclear families (41,506 individuals) from the 1968 Tasmanian Asthma Survey, in which all Tasmanian schoolchildren born in 1961 were surveyed by respiratory questionnaire completed by their parents. Similar data were obtained for parents and siblings of probands. For a child, having ever had asthma was predicted by a parent or sibling having ever had asthma; odds ratio (OR) = 3.13 (95% confidence interval [CI] 2.82-3.48) for mother, 2.99 (2.69-3.32) for father, and 3.47 (3.23-3.72) for a sibling. Regressive logistic modeling showed that, in addition to parent-offspring effects, the data were consistent with the existence of an unmeasured factor shared by siblings, evident in 15% (SE 2%) of families and associated with a conditional OR of 9.68 (8.27-11.32). Familial aggregation was best described by a general oligogenic model with non-Mendelian transmission probabilities. Of the Mendelian models, a codominant model with an allele frequency of 16% (SE 0.3%) was preferred. Under a dominant model there was evidence for additional parent-offspring and sibling effects of similar magnitude. It is unlikely that there is one major loci influencing asthma susceptibility; the overall effects of asthma genes in the population are more likely to be inherited codominantly, at least for the majority of loci of major etiological importance. The role of environmental factors in explaining part of familial aggregation for asthma cannot be ruled out, as major triggers of asthma attacks are familial.

Asthma from childhood to adulthood: course and outcome of lung function

Lung function (FEV1 before and after bronchodilatation) was studied prospectively over five visits in 55 asthmatic children (28 boys) from childhood to adulthood (age 30). At the last follow-up recordings were made at rest, after cold air challenge (CACh), and after bronchodilatation. Results were related to clinical asthma scoring and to sensitization to furred animals, as described in a companion paper. Lung function outcome was shown to be influenced by initial FEV1 (% predicted) and gender, but not by initial asthma severity or sensitization. FEV1 (% predicted) was higher in females than in males over the first two follow-ups, but the reverse was found over the subsequent visits. It deteriorated from childhood to adulthood in the females but improved in the males. In adulthood the females (for height 170 cm) had a steeper normalized annual fall in post-bronchodilator FEV1 than the males (55 +/- 38 vs. 25 +/- 36 ml; P = 0.006). The degree of bronchial hyperresponsiveness was associated significantly with asthma severity and the extent of sensitization to furred animals, but not with gender. The results indicate a better lung function outcome for asthmatic boys than for girls, confirming trends seen in clinical asthma severity. In adulthood the extent of sensitization to relevant perennial inhaled allergens significantly influences airway responsiveness and asthma severity, but not lung function.

Asthma from childhood to adulthood: asthma severity, allergies, sensitization, living conditions, gender influence and social consequences

The course of asthma severity, clinical allergies, allergic sensitization, changes in living conditions and social outcome were studied prospectively over five follow-up visits from the mean age of 9 to 30 years in a cohort of 28 boys and 27 girls, selected randomly among asthmatic children attending a paediatric outpatient unit. Asthma severity improved from childhood to adulthood, judged by symptom and medication scores and by the number of hospital admissions, but only nine subjects (16%) had been free from symptoms and medication over the last year of follow-up. After adolescence, asthma continued to improve among the males but not among the females. This difference could not be explained by gender differences in the course of clinical allergies or sensitization (skin-prick-tests and RAST) to common inhaled allergens, or by differences in environmental or social conditions. Sensitization to relevant perennial inhaled allergens correlated with asthma severity during adulthood. In general, clinical allergies and sensitization to inhaled allergens adopted during childhood persisted into adulthood. Approximately 10% of the subjects never adopted a clinical allergy or a positive allergy test. The social outcome was good.

Association between plasma CC16 levels, the A38G polymorphism, and asthma

The effect of the A38G polymorphism on Clara cell secretory protein (CC16) gene expression and asthma was investigated by measuring plasma CC16 levels in 100 asthmatic and nonasthmatic children. Restriction digestion determined the A38G genotype and plasma CC16 levels were analyzed using a sensitive latex immunoassay. Asthmatics had lower mean plasma CC16 levels adjusted for age and gender (7.96 microg/L; 95% confidence interval [CI] = 6.79 to 9.31) than nonasthmatic subjects (9.98 microg/L; 95% CI = 8.83 to 11.26) (p = 0. 006). Similarly adjusted, mean plasma CC16 levels were also lower in 38A/38A (6.79 microg/L; 95% CI = 4.56 to 9.02) than 38G/38G subjects (10.01 microg/L; 95% CI = 7.90 to 12.12; p = 0.003). The odds ratio for asthma diagnosis of 38A/38A subjects was 4.78 (95% CI = 1.08 to 21.18; p = 0.04) compared with 38G/38G subjects. However, this was reduced when corrected from plasma CC16 level, suggesting that the odds of asthma was largely mediated through altered plasma CC16 levels. The 38A sequence was associated with reduced plasma CC16 levels and individuals with lower plasma CC16 levels were more likely to have asthma. This provides further evidence for a significant role of the CC16 gene, 38A allele in the development of asthma.

Prevalence and severity of asthma, rhinitis, and atopic eczema: the north east study

Using the international study of asthma and allergies in childhood (ISAAC) questionnaire, 3000 children aged 6-7 years from various schools in the north east of England were studied. In this population, the lifetime prevalence rates of various symptoms and diagnoses were: wheezing, 29.6%; atopic eczema, 27.8%; rhinitis, 23. 1%; and self reported asthma, 22.7%. Rhinitis was reported by 44% and 40% of boys and girls with asthma, respectively. Atopic eczema was reported by 46% of both boys and girls with asthma. The prevalence rates of reported asthma, and of symptoms suggestive of asthma, were higher than those reported from studies conducted on UK children in 1992.

Hay fever, eczema, and wheeze: a nationwide UK study (ISAAC, international study of asthma and allergies in childhood)

OBJECTIVES

To describe the prevalence of atopic symptoms in children throughout the UK.

METHOD

A questionnaire survey of 12-14 year olds throughout England, Wales, Scotland, and the Scottish Islands using the international study of asthma and allergies in childhood (ISAAC) protocol.

RESULTS

A total of 27 507 (86%) children took part. Recent rhinoconjunctivitis was reported by 18.2%, with 6.2% reporting symptoms between March and September; 16.4% reported itchy flexural rash in the past 12 months. The prevalence of atopic symptoms was higher in girls and subjects born within the UK. The prevalence of severe wheeze was highest in subjects reporting perennial rhinoconjunctivitis, as opposed to summertime only symptoms. Winter rhinoconjunctivitis was associated with severe wheeze and severe flexural rash. One or more current symptoms were reported by 47.6% of all children and 4% reported all three symptoms.

CONCLUSION

In general, geographical variations were small but the prevalence of symptoms was significantly higher in Scotland and northern England. The study demonstrates the importance of atopic diseases both in their own right and in association with asthma.

Prevalence of asthma, rhinitis and eczema among children in 2 Canadian cities: the International Study of Asthma and Allergies in Childhood

BACKGROUND

Wide variations in the prevalence of asthma, rhinitis and eczema have been reported between regions within Canada and between different countries. The International Study of Asthma and Allergies in Childhood (ISAAC) was developed to provide a standardized tool and methodology to ascertain the prevalence of asthma and allergies in different regions. Comparisons of prevalence rates across geographic regions and at different times may help to identify factors that contribute to the development of these conditions in individuals.

METHODS

Two Canadian centres, Hamilton and Saskatoon, participated in the ISAAC. A standard questionnaire was distributed through schools and completed by 13- and 14-year-old children and by the parents of 6- and 7-year-old children. Prevalence rates and 95% confidence intervals were calculated for asthma, wheezing, rhinitis and eczema.

RESULTS

The overall response rates were 75.1% among the children 6 and 7 years old and 68.6% among those 13 and 14 years old. Among the younger children, the lifetime prevalence of asthma was 17.2% in Hamilton and 11.2% in Saskatoon; the corresponding rates among the older children were 19.2% and 12.2% respectively. The prevalence of wheezing in the 12 months before the survey in the younger group was 20.1% in Hamilton and 14.1% in Saskatoon; in the older group it was 30.6% and 24.0% respectively. The prevalence of rhinitis in the 12 months before the survey was 28.6% in Hamilton and 22.6% in Saskatoon in the younger group and 45.8% and 33.8% respectively in the older group. The prevalence of eczema was slightly higher in Saskatoon in both age groups.

INTERPRETATION

High prevalence rates of asthma, rhinitis and eczema exist among school children in Hamilton and Saskatoon, similar to rates in other Western countries. Further studies are required to determine the factors associated with the high rates in the 2 regions and possible reasons for the higher rates in Hamilton.