International Study of Asthma and Allergies in Childhood (ISAAC): rationale and methods

Asthma prevalence among Alaska Native and nonnative residents younger than 20 years enrolled in Medicaid

BACKGROUND

No study of childhood asthma prevalence in Alaska or among Alaska Natives has been conducted.

OBJECTIVE

To determine asthma prevalence among Alaska Medicaid enrollees younger than 20 years, with an emphasis on Alaska Natives, the state's largest minority and predominant rural citizens.

METHODS

A master database was obtained that included all children enrolled in Medicaid during July 1998 through June 1999. Physician, pharmacy, and hospital claims files for International Classification of Diseases codes 493.0x to 493.9x were linked to this master database. Asthma was defined as any asthma-related care or medication claim.

RESULTS

Asthma prevalence among the study population was 6.9%. Alaska Natives had a lower asthma prevalence than nonnatives (risk ratio [RR], 0.70; 95% confidence interval [CI], 0.66-0.75), but among the subgroup of children residing in the state's major urban center, Alaska Natives had a higher prevalence. Overall, 0.22% of the study population experienced an asthma-related hospitalization, with Alaska Natives having a higher risk of hospitalization than nonnatives (RR, 1.6; 95% CI, 1.2-2.3). Among hospitalized children, Alaska Natives were less likely to have received a long-term control medication (RR, 0.54; 95% CI, 0.33-0.88).

CONCLUSIONS

Compared with nonnatives, Alaska Natives have a lower risk of asthma but only among nonurban residents. The increased risk of hospitalization among Alaska Natives may be related to underuse of long-term control medications.

Risk factors for asthma in school children from Ciudad Juarez, Chihuahua

Asthma and allergic rhinitis were analyzed in a random sample of school children (n=6174) residing in Ciudad Juarez, Chihuahua, Mexico. The International Study of Asthma and Allergies in Childhood methodology was applied through a standardized questionnaire. The sample was obtained with a bietapic design. Cumulative prevalence of asthma and wheezing was 6.8% (95% CI 6.2, 7.4) and 20% (95% of CI 19.7, 21.8) respectively; the prevalence of rhinitis was 5.0% (95% CI 4.5, 5.6). Family history of asthma odds ratio (OR) 2.33 (95% CI 1.78-3.05), respiratory infection after birth (OR) 3.44 (95% CI 2.76-4.29), and exposure to environmental tobacco (OR) 1.35 (95% CI 1.06-1.68) were the strongest risk factors for asthma and allergic rhinitis. The multifactorial etiology of asthma and allergic rhinitis was confirmed, as well as the importance of early exposure to environmental factors.

Wheezing, allergy, and parasite infection in children in urban and rural Ethiopia

Epidemiological studies in developing countries suggest that intestinal parasite infection may reduce the risk of asthma. Because this evidence is all derived from adults and older children, we have investigated the relation between parasite infection, wheezing, and allergen skin sensitization in nested case-control studies drawn from a survey of 7,155 children aged 1 to 4 years living in urban and rural areas of Jimma, Ethiopia. Infection with parasites was common, predominantly with Trichuris (54%), Ascaris (38%), and hookworm (10%). Wheezing in the past year was significantly more prevalent in urban (4.4%) than rural children (2.0%), and was less prevalent in those infected with Ascaris (age, sex, and urban/rural adjusted odds ratio, 0.5; 95% confidence interval, 0.3 to 0.9), particularly in relation to high-intensity infection. Similar, although nonsignificant, associations were found for hookworm (adjusted odds ratio, 0.6; 95% confidence interval, 0.2 to 1.8), but there was no suggestion of any relation to Trichuris infection. Dermatophagoides pteronyssinus and cockroach (Blattella germanica) skin sensitization was more prevalent in rural than urban children, and was unrelated to wheeze. We conclude that Ascaris and possibly hookworm infection protects against wheeze in young Ethiopian children, and that this effect is not mediated by inhibition of allergen sensitization.

Development and validation of school-based asthma and allergy screening instruments for parents and students

BACKGROUND

The increasing morbidity attributable to asthma among school-aged children suggests the potential utility of school-based asthma screening programs.

OBJECTIVE

We report our efforts to develop and validate culturally sensitive and clinically useful screening questionnaires (parent and child versions) for asthma and allergies among urban US school children.

METHODS

Instrument development was accomplished through literature review, expert medical and child developmental input, focus group feedback, and a rigorous trial of the instruments in a public school setting. Questionnaires were distributed to 2,800 children and their families in an urban public school system (grades kindergarten through 6). Validity was evaluated by blinded comparison of results against a standardized clinical evaluation in 107 children, with final designations determined by an expert panel.

RESULTS

Questionnaires pertaining to 2,083 children were returned (participation rate of 74%). A moderate level of agreement was observed between parent and student questionnaire responses (r values = 0.36 to 0.50; P values < 0.001). The highest frequency of asthma-like symptoms was reported for African-American boys and the lowest for Caucasian girls. The items from the parent questionnaire that best predicted asthma were "breathing problems" (occurring rarely or more; odds ratio 12.8; 95% confidence interval, 4.5 to 36.1) and "problems coughing" (sometimes or more; odds ratio 9.7; 95% confidence interval, 3.6 to 26.5). Considering the presence of cough (sometimes or more) and/or breathing problem (rarely or more) yielded a sensitivity of 80%; a specificity of 75%, a positive predictive value of 50%, and a negative predictive value of 92%. Similar levels of prediction were observed for the items "trouble breathing" and "noisy breathing" as directly reported by the students. Allergic rhinitis was best predicted by report of a runny/stuffy no se (sometimes or more; sensitivity of 83%, specificity of 61%). Allergic conjunctivitis was best predicted by "itchy eyes."

CONCLUSIONS

Administration of a school-based questionnaire is feasible, with a high response rate and excellent internal consistency. A high sensitivity and acceptable specificity was achieved by using one to two questions for asthma, allergic rhinitis, and allergic conjunctivitis. Among the children in grades 2 or above, comparable levels of prediction could be achieved with the student or parent version.

Household exposure factors, asthma, and school absenteeism in a predominantly Hispanic community

The Passaic Asthma Reduction Effort (PARE) used an asthma symptom and household exposure factor questionnaire to screen 4634 elementary school children over a 4-year period in Passaic, New Jersey. During the first year, an additional 240 preschool children were also screened. Overall, 16% of the school children were reported by their parents to have been diagnosed with asthma. In all, 30% of responding families claimed to have at least one family member diagnosed with asthma and this was five times more likely if the target child had asthma. Exposures consistently associated with childhood asthma diagnosis included environmental tobacco smoke (ETS), presence of dampness/mold, roaches, and furry pets in the home. Diagnosis of asthma was primarily associated with all six symptoms used in the PARE questionnaire, and secondarily with environmental factors. Puerto Rican and black children had the highest asthma prevalence (26% and 33%), while Mexican children had the lowest (7%). Use of medications and school absenteeism among asthmatic children were associated with wheeze and night cough, but not with any specific environmental exposure. Increased school absenteeism by children undiagnosed with asthma was associated with ETS and dampness/mold in the home. Differences in asthma diagnosis and absenteeism in response to environmental factors were found across ethnic subgroups. Getting asthmatic children on medical management protocols and providing families with education about environmental risk reduction should aid in reducing morbidity in this ethnically complex population. Such coordinated efforts offer the promise of reducing school absenteeism.

Results of an inner-city school-based asthma and allergy screening pilot study: a combined approach using written questionnaires and step testing

BACKGROUND

A questionnaire alone may not be an adequate screening tool for asthma.

OBJECTIVE

To determine whether an asthma questionnaire used in combination with an exercise step test is better than a questionnaire alone in screening for asthma in children and to evaluate the validity of a rhinitis questionnaire in determining atopy.

METHODS

The International Study of Asthma and Allergies in Childhood (ISAAC) asthma core questionnaire was used to screen for asthma in 307 inner-city first through third graders. All children who had scores consistent with a diagnosis of asthma underwent step testing, as did a subset of children who had negative overall scores. All children who had inconsistent asthma scores and step test results underwent methacholine challenge testing. The same 307 children underwent rhinitis screening and children who had one or more positive responses on the ISAAC rhinitis questionnaire underwent skin testing as did a subset of children who had all negative responses.

RESULTS

Three hundred of 307 asthma and rhinitis questionnaires were returned. Twenty-eight children (9%) had global asthma scores that were considered to be positive (5 or above). Twenty-four of these children underwent step testing as did 34 randomly selected children who had negative global asthma scores. Thirty-one (91%) of the 34 children who had negative global asthma scores had negative step tests. Similarly, 20 of 24 children (83%) of the children who had positive global asthma scores had negative step tests. Only 4 children who had positive global asthma scores were step test-positive or had reversible airway obstruction at baseline. Using a positive methacholine challenge as the gold standard for establishing bronchial hyperresponsiveness, the global asthma score derived from the eight-item ISAAC asthma questionnaire yielded a sensitivity of 64%, a specificity of 11%, a positive predictive value of 47%, and a negative predictive value of 20%. Comparing the six-item ISAAC rhinitis questionnaire results to the gold standard, skin test reactivity, the questionnaire yielded a sensitivity of 76%, a specificity of 21%, a positive predictive value of 56%, and a negative predictive value of 40%.

CONCLUSIONS

Step testing was not useful as a screening tool for asthma. In addition, the ISAAC asthma questionnaire may not be a good asthma screening tool for inner-city pediatric populations, especially if the form is self-administered. Investigators should first validate both the ISAAC asthma and rhinitis screening questionnaires in the particular population to be studied before widespread asthma and allergy screening efforts are initiated using these tools.

Gender differences in asthma prevalence may depend on how asthma is defined

BACKGROUND

Asthma may be defined either as wheeze within the previous 12 months (current wheeze) doctor-diagnosed asthma (DDA), or current wheeze plus confirmed airway hyperresponsiveness (AHR).

AIMS

We wanted to estimate asthma prevalence in randomly selected adolescents based on different criteria for asthma diagnosis, study gender differences in reported asthma-like symptoms vs DDA, and relate our findings to measurements of AHR, levels of exhaled nitric oxide (ENO) and total IgE.

METHODS

As part of the health survey of North-Trøndelag (HUNT), 8571 adolescents aged 13-19 years were investigated with an interview on allergic and respiratory symptoms (phase I study). Of these, 401 subjects who reported wheeze within the previous 12 months (current wheeze) and 213 non-symptomatic controls were randomly selected and investigated with allergy screening, methacholine bronchoprovocation test and measurements of ENO (phase II study).

RESULTS

In the phase I study prevalence of current wheeze was 26% (30% in girls and 23% in boys, P < 0.01). Prevalence of DDA was 10.8% (10.5% in girls and 11% in boys). Among subjects with current wheeze, the likelihood of having DDA was reduced in girls compared to boys, odds ratio (95% CI) 0.82 (0.68-0.98) which was partly explained by a longer history of wheeze among boys. In the phase II study, although more girls than boys with current wheeze had AHR (62% versus 50%, P < 0.02) more boys than girls reported DDA (44% vs. 32%, P < 0.02). Of the objective parameters, increased levels of ENO most strongly increased the risk of having DDA.

CONCLUSIONS

When asthma is defined as DDA, there is a risk of underestimating the prevalence of asthma, especially among girls.

Schistosoma mansoni infection is associated with a reduced course of asthma

BACKGROUND

Helminthic infections decrease skin reactivity to indoor allergens, but data on whether they influence asthma severity are lacking.

OBJECTIVE

This study evaluated the course of asthma in patients with and without Schistosoma mansoni infection.

METHODS

Asthmatic subjects were enrolled from 3 low-socioeconomic areas: a rural area endemic for schistosomiasis (group 1) in addition to a rural area (group 2) and a slum area (group 3), both of which were not endemic for schistosomiasis. A questionnaire on the basis of the International Study of Asthma and Allergies in Childhood study was applied in these 3 areas, and from each area, 21 age- and sex-matched asthmatic subjects were selected for a prospective 1-year study. Pulmonary function tests, skin prick tests with indoor allergens, stool examinations, and serum evaluations were performed in these subjects. Every 3 months, the subjects were evaluated for asthma exacerbation through physical examination, and a questionnaire regarding asthma symptoms and use of antiasthma medicine was administered.

RESULTS

The prevalence of S mansoni infection was greater in group 1 compared with in groups 2 and 3 (P <.0001), whereas the frequency of other helminth and protozoa infections was similar among the 3 groups. The frequency of positive skin test responses to indoor allergens was less (19.0%) in group 1 subjects relative to those in group 2 (76.2%) and group 3 (57.1%; P <.001). The frequencies of symptoms, use of antiasthma drugs, and pulmonary abnormal findings at physical examination were less in group 1 subjects than in group 2 and 3 subjects (P =.0001).

CONCLUSION

Our results suggest that S mansoni infection is associated with a milder course of asthma.

Increased serum IL-10/IL-12 ratio in wheezing infants

To investigate the association between various serum markers and atopic symptoms in the first year of life, and to evaluate the prognostic value of these markers for the development of wheezing and skin rash in the second year of life. Data of 86 children on the development of wheezing and skin rash in the first 2 years of life were collected prospectively, making use of parental completed questionnaires, weekly symptom cards, structured interview and physical examination. Serum markers (IL-10, IL-12, IL-13, eotaxin, sE-selectin, sICAM-1, sIL-2R) and total and specific IgE were determined at age 1. Children who developed wheezing in the first year of life had lower serum levels of IL-12 than children without symptoms (median 40.3 pg/ml vs. 49.0 pg/ml, p = 0.01) and a higher serum IL-10/IL-12 ratio (0.41 vs. 0.31, p = 0.001) at age 1. The IL-10/IL-12 ratio increased with an increasing number of wheezing episodes. Levels of sE-selectin in children with wheezing and in children with itchy skin rash in the first year of life were higher than in symptom free children (6.1 ng/ml and 5.9 ng/ml vs. 4.9 ng/ml, p = 0.01 and p = 0.03, respectively). Children who developed wheezing in the second year of life already had increased sICAM-1 levels at age 1. Children who developed wheezing in the first year of life showed a serum cytokine response that is skewed towards a T-helper 2 profile, with lower IL-12 levels and an increased IL-10/IL-12 ratio. Children who developed wheezing in the second year of life had elevated sICAM-1 levels at age 1. Follow-up of the children is needed to evaluate the prognostic value of various serum markers for the development of allergic disease in later childhood.

Applicability of interrupter resistance measurements using the MicroRint in daily practice

This study was performed to evaluate the applicability of a simple device (MicroRint) for measuring airway resistance, to derive normal values and to compare values with maximal expiratory flow volume (MEFV) parameters in asthmatic and healthy children. Repetitive R(int) measurements were performed in 125 healthy children and 107 asthmatic children (age range 0.8-16.8 years). In 42 asthmatic patients R(int) and MEFV values were compared and in 29 asthmatic children bronchodilation testing was performed. Successful R(int) measurements were possible in 91% of the children. The mean coefficient of variation of repeated measurements was 7.1 (+/-6.1)%. R(int) values of healthy children showed a significant curvilinear correlation with age (r=-0.80, P < 0.001) and height (r=-0.81, P < 0.001). In asthmatic and healthy children R(int) values were comparable. A significant inverse correlation was found between R(int) and MEFV values (for FEV1 and R(int) r=-0.80, P < 0.001). After bronchodilation there was a significant increase in FEV1 and decrease in R(int), but changes between the two parameters did not correlate. In conclusion, the interrupter technique is feasible and repeatable in children and has a significant correlation with other parameters of airway caliber. Baseline values do not discriminate healthy from asthmatic children.

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.

Atopic manifestations, breast-feeding protection and the adverse effect of DDE

Despite the numerous studies on the possible protective effect of breast feeding against the onset of atopic manifestations during childhood, this issue remains controversial. As part of an environmental epidemiological study, we investigated whether different blood concentrations of dichlorodiphenyl-dichloroethylene (DDE) modified the protective effect of breast feeding against atopic manifestations in 338 children. DDE concentration, duration of breast feeding and manifestation of atopic disorders were measured in 1994-95 at age 7-8 years. Information gathered on asthma, atopic eczema and hay fever was based on questionnaire data. We measured the total serum concentration of immunoglobulin E (IgE) and specific IgE levels against inhalant allergens. In 1997, we also determined bronchial hyper-reactivity with a hypertonic saline challenge test. To estimate odds ratios from our cross-sectional analysis, we applied logistic regressions, controlling for confounders. Breast feeding had a protective effect on the two asthma variables (e.g.> 12 weeks breast feeding for doctor-diagnosed asthma, OR = 0.32 [95% CI 0.11, 0.87]; for 'ever' asthma, OR = 0.13 [95% CI 0.02, 0.68]), but not on bronchial hyper-reactivity, hay fever, atopic eczema or the two IgE variables. The protective effect became stronger in children with DDE blood levels below the median of 0.29 micro g/L (e.g. doctor-diagnosed asthma,> 12 weeks breast feeding, OR = 0.24 [95% CI 0.06, 0.95]). Also, for specific IgE against inhalant allergens, the association gained statistical significance. For children with a DDE concentration of 0.29 micro g/L and higher, breast feeding did not show a significant protective effect. Our results suggest that contaminants such as DDE may modify the protective effect and may have contributed to inconsistent findings on the protective effect of breast feeding in previous studies. We recommend determining levels of breast milk contaminants in children when assessing the impact of breast feeding on atopic manifestations.

Does heredity modify the association between farming and allergy in children?

AIM

It has been suggested that living on a farm decreases the risk of childhood allergy, especially if farming involves livestock. The aim of this study was to examine the association between farming and allergy in children, and the influence of atopic heredity in this association.

METHODS

The cross-sectional data of the 7981 children aged 13-14 y who participated in the Finnish ISAAC study between the years 1994 and 1995 were used to evaluate the association between farming and allergy.

RESULTS

Living on a farm was associated with a decreased risk of current symptoms of allergic rhinoconjunctivitis among all children (aOR 0.79; 95% CI 0.63, 0.99), and with a decreased risk of hay fever, especially among those children with a parental history of hayfever (aOR 0.60; 95% CI 0.40-0.89, p = 0.072 for interaction). The children of farmers with a history of hay fever also had a decreased risk of current wheeze (aOR 0.38; 95% CI 0.12-1.24, p = 0.040 for interaction). No significant association was found between farming and either asthma or eczema. Children living on a farm with livestock had the lowest risk of allergic rhinoconjunctivitis (aOR 0.69), followed by those living on a farm without livestock (aOR 0.89) compared with the non-farming children (p-value for trend 0.024).

CONCLUSION

Our results support the recent findings on a decreased risk of allergy among the children living on farms. A possible differential effect of parental history of hay fever on the relation of farming environment and the risk of allergic symptoms warrant further investigation.

Nutrition and respiratory health in children in six Central and Eastern European countries

BACKGROUND

The results of studies on the effect of nutrition on respiratory diseases are inconsistent. The role of nutrition in children's respiratory health was therefore analysed within the cross sectional Central European Study on Air Pollution and Respiratory Health (CESAR).

METHOD

A total of 20 271 children aged 7-11 were surveyed in six European countries. Respiratory health and food intake were assessed using questionnaires. Associations between four symptoms and nutritional factors were evaluated using logistic regression, controlling for area plus other potential confounders.

RESULTS

All symptoms showed initial associations with nutritional factors. Low consumption of fish and of summer and winter fruit were the most consistent predictors. In a fully adjusted model low fish intake remained a significant independent predictor of persistent cough (OR=1.18; 95% CI 1.04 to 1.34), wheeze ever (OR=1.14; 95% CI 1.03 to 1.25) and current wheeze (OR=1.21; 95% CI 1.06 to 1.39) and a weaker predictor of winter cough (OR=1.10; 95% CI 0.99 to 1.23). Low summer fruit intake was a predictor of winter cough (OR=1.40; 95% CI 1.10 to 1.79) and persistent cough (OR=1.35; 95% CI 1.01 to 1.82). Low winter fruit intake was associated with winter cough (OR=1.28; 95% CI 1.09 to 1.51). Associations between symptoms and vegetable intake were inconsistent. Low summer intake was significantly associated with winter cough (OR=1.23; 95% CI 1.03 to 1.47) but, overall, winter intake had inverse associations with both coughs. Associations between winter vegetable intake and wheeze varied considerably between countries.

CONCLUSION

A number of associations were found between respiratory symptoms and low intake of fish, fruit and vegetables in children. Low fish intake was the most consistent predictor of poor respiratory health. Fruit and vegetable intake showed stronger associations with cough than with wheeze.

Association of CCR5Delta32 with reduced risk of childhood but not adult asthma

BACKGROUND

A number of potential candidate genes have been implicated in the pathogenesis of asthma. A 32 base pair deletion in the CCR5 gene renders this chemokine receptor non-functioning and has been shown to be associated with a reduced prevalence of asthma in childhood. The mechanism may be related to impairment of pathogen entry into cells and modified host inflammatory response. We sought to determine the influence of the CCR5Delta32 mutation on asthma and allergy in the transition from childhood to adulthood.

METHODS

627 individuals first studied as part of a whole population schoolchildren cohort in 1989 when aged 8-12 years were followed up 10 years later for respiratory and allergy symptoms and laboratory markers of atopy. CCR5Delta32 status was also characterised and the association with childhood and adulthood symptoms determined.

RESULTS

The follow up sample was representative of the original cohort except for a slightly greater prevalence of symptomatic individuals. As children, none who were homozygous for the CCR5Delta32 mutation had a current physician's diagnosis of asthma. In multivariate analysis and controlling for known confounders, the protective effect of carrying the allele in childhood was highly significant (OR 0.31, 95% CI 0.14 to 0.72, p=0.006). There was no protective association with "current asthma" as classified in adulthood within the same population. Subjective or laboratory markers of atopy in childhood or adulthood were not associated with the CCR5Delta32 mutation. Methacholine bronchial hyperresponsiveness in adulthood was also unrelated to gene carrier status.

CONCLUSIONS

In a population with a high allelic frequency for the CCR5Delta32 mutation, a significant protection against childhood asthma is evident which is independent of atopy. This protection is lost in the transition between childhood and early adulthood. The contribution of different genetic candidates to the expression of asthma may change with advancing maturity and confound the interpretation of association and linkage studies unless age is taken into account.

A relatively high prevalence and severity of asthma, allergic rhinitis and atopic eczema in schoolchildren in the Sultanate of Oman

OBJECTIVES

Although asthma, allergic rhinitis and eczema are among the most common chronic diseases in children worldwide, there is very limited information about the burden of these conditions in Oman. The aim of this study was to determine the prevalence and severity of symptoms of asthma, allergic rhinitis and eczema in Omani schoolchildren using the International Study of Asthma and Allergies in Childhood (ISAAC) Phase I questionnaire.

METHODS

An Arabic version of the ISAAC Phase I questionnaire was completed by parents of 3893 children aged 6-7 years and self-completed by 3174 children aged 13-14 years, randomly selected from a nationwide sample of public schools.

RESULTS

The prevalence rates of reported diagnoses of asthma, allergic rhinitis and eczema were higher in older children (20.7%, 10.5% and 14.4% compared with 10.5%, 7.4% and 7.5%, respectively, in young children). In young children, 277 were current wheezers and of these 40.8% had sleep-disturbing wheeze at least once a week and 45.1% had speech-limiting wheeze during the past year. Similarly, 283 older children were current wheezers, and of these 30.0% had sleep-disturbing wheeze at least once a week and 37.5% had speech-limiting wheeze during the past year. Exercise-induced wheeze was higher in older children (19.2% vs 6.9%; P < 0.001). Allergic rhinitis and eczema were also associated with significant sleep disturbance and limitation of activity in both age groups.

CONCLUSION

Allergic conditions in Omani schoolchildren are common and associated with significant morbidity. Further research is required to identify the local risk factors for allergy to allow better understanding and management of these conditions.

Perception of dyspnea during exercise-induced bronchoconstriction

After strenuous physical exercise, many subjects show a significant bronchoconstriction and report dyspnea. Despite this clinical condition being a commonly encountered situation during daily life, which may be responsible for substantial disability there is little information on the relationship between the perception of dyspnea and exercise-induced bronchoconstriction (EIB) after a standardized exercise challenge. For these reasons, we evaluated 200 consecutive outpatients (median age 13 years, ranging from 5 to 56 years) referred to our laboratory to perform an exercise test out of suspicion of EIB. On exercise challenge, perception of dyspnea was rated on a modified bipolar Borg scale immediately before each FEV1 measurement. Sixty-nine (35%) subjects had a positive exercise challenge, defined as a decrease of at least 20% in FEV1 from baseline. Both the onset and the decay of dyspnea preceded those of bronchoconstriction. Overall, the rating of dyspnea in the laboratory was well related with the reports of exercise-related symptoms. Similarly, 36 of 77 (47%) asthmatics with a history of exertional symptoms and 24 of 65 patients (40%) without a history had a positive challenge. Asthmatics reporting exertional symptoms perceived a greater magnitude of dyspnea after exercise independently from the degree of bronchoconstriction. Overall, dyspnea was significantly but loosely correlated to the magnitude of decrease in FEV1, being also influenced by age, gender and BMI.

CONCLUSIONS

We conclude that dyspnea recorded in the laboratory after exercise test is related to exertional symptoms reported during real life, but not completely related to EIB. The rating of dyspnea is a well-suited model to study naturally occurring exercise-induced dyspnea and a useful tool to enlarge the results of an exercise challenge.

Volcanic ash and respiratory symptoms in children on the island of Montserrat, British West Indies

BACKGROUND

In July 1995 the volcano on the West Indian island of Montserrat erupted after being inactive for several hundred years. Since then, clouds of ash have been released intermittently from the volcano. Some of this ash is <10 micro m in diameter and therefore respirable. Concerns were raised that the particles might cause respiratory problems.

AIMS

To evaluate whether ashfalls had any effect on the respiratory health of children in Montserrat.

METHODS

A survey of asthma diagnoses, respiratory symptoms, exercise induced bronchoconstriction (EIB), and current and previous exposure to volcanic ash was carried out in schools in Montserrat during February 1998.

RESULTS

Questionnaire information was available for nearly 80% of the 443 children on the school rolls. The prevalence of wheeze symptoms in the previous 12 months was 18% in children aged 12 years and under and 16% in children aged 13 years and over. In children aged 12 and under, the prevalence of wheeze was greater in those who had ever been heavily or moderately exposed to volcanic ash compared with the group who had only ever been exposed to low levels (wheeze in last 12 months: odds ratio (OR) 4.30; wheeze ever: OR 3.45). The prevalence of EIB in 8-12 year olds was about four times higher in those who were currently heavily exposed to volcanic ash (OR 3.85) compared to those currently exposed to low levels.

CONCLUSIONS

Volcanic ash emissions adversely affected the respiratory health of Montserrat children. The findings emphasise the need to limit exposures of children to volcanic ash and ensure the appropriate management of respiratory symptoms.

Relationship between exhaled NO, respiratory symptoms, lung function, bronchial hyperresponsiveness, and blood eosinophilia in school children

BACKGROUND

Exhaled nitric oxide (eNO) may serve as a non-invasive marker of airway inflammation but its relationship with other commonly used measures has not been evaluated.

METHODS

Levels of eNO in a sample of 450 children aged 7-12 years out of a total sample of 2504 school children living in different urban areas near motorways were determined. The aim of this cross-sectional study was to explore the relationship between eNO, impairment of lung function (PEF, FVC, FEV(1) and MMEF), bronchial hyperresponsiveness (BHR), and blood eosinophilia in children with and without atopy as assessed by skin prick testing.

RESULTS

Regression analysis showed that wheezing and nasal discharge and conjunctivitis that had occurred during the previous 12 months were positively associated with eNO levels in atopic children (relative increase of 1.48 and 1.41, respectively; p<0.05) but not in non-atopic children. Similarly, BHR and the number of blood eosinophils per ml were positively associated with eNO levels in atopic children (relative increase of 1.55 and 2.29, respectively; p<0.05) but not in non-atopic children. The lung function indices PEF, FVC, FEV(1) and MMEF were not associated with eNO levels.

CONCLUSIONS

In addition to conventional lung function tests and symptom questionnaires, eNO is a suitable measure of airway inflammation and its application may reinforce the power of epidemiological surveys on respiratory health.

Lack of agreement in classification of the severity of acute asthma between emergency physician assessment and classification using the National Asthma Council Australia guidelines (1998)

AIMS

To determine the level of agreement in classification of the severity of acute asthma at presentation to the emergency department, between emergency physician global assessment and severity classification according to the National Asthma Council Guidelines, Australia 1998 (NACG).

METHODS

Prospective observational study in emergency departments throughout Australia, participating in the Asthma Snapshot 2000 project. Patients between the ages of one and 60 years presenting to participating emergency departments with acute asthma between 21 August and 3 September 2000 were included. Data collected were emergency physician global assessment of asthma severity and severity classification according to the National Asthma Council Guidelines and disposition.

RESULTS

Five hundred and five subjects had completed data for emergency physician assessment of severity and for calculation of severity classification according to the National Asthma Council Guidelines. Weighted kappa for agreement in classification was 0.48 (95% confidence interval: 0.40, 0.56). Emergency physicians assess asthma as less severe compared to the National Asthma Council Guidelines assessment.

CONCLUSIONS

Agreement between physician assessment of severity of acute asthma and severity classification according to National Asthma Council Guidelines is only moderate. This may have implications in treatment and disposition. This also suggests that emergency physicians may be using other methods to classify acute asthma than the National Asthma Council Guidelines classification.

The relationship between exhaled nitric oxide and allergic sensitization in a random sample of school children

BACKGROUND

Exhaled nitric oxide (NO) has been proposed as novel a non-invasive marker of airway inflammation.

OBJECTIVE

The level of exhaled NO was determined in a random sample of school children (7-12 years old) with the aim of investigating the relationship between exhaled NO and sensitization to common allergens.

RESULTS

In the 450 children tested by skin prick tests (SPT), the prevalence of sensitization was 29.5% (overall), 21.9% (sensitization to indoor allergens), and 15.0% (sensitization to outdoor allergens). Regression analysis showed that levels of exhaled nitric oxide were closely associated with various measures of sensitization to aeroallergens. Sensitization to indoor allergens was associated with higher levels of exhaled NO (eNO) than sensitization to outdoor allergens when assessed by IgE but not when assessed by SPT. Children with reported wheeze in the past 12 months had much stronger associations between sensitization and eNO than children without wheeze.

CONCLUSION

We conclude that allergic sensitization is strongly associated with increased levels of exhaled NO, especially in children with wheeze.

Smoking among adolescents in Muenster, Germany: increase in prevalence (1995-2000) and relation to tobacco advertising

BACKGROUND

Understanding patterns and trends of smoking among youths is of major importance for the assessment of the burden of smoking in the society and efforts to decrease it.

OBJECTIVE

The aims were to determine the prevalence and trends of smoking among adolescents in Muenster, Germany, and to assess its relation to youths' awareness of tobacco advertisement.

DESIGN

Information on smoking habits was collected during two school-based surveys (1994/1995 and 1999/2000) of 12- to 15-year-old adolescents (3934 students in 1994/5 and 4028 students in 1999/2000) in Muenster, Germany. In addition, in 1994/1995 information about youths' awareness and appreciation of tobacco advertisement was collected.

RESULTS

During the 5-year period, the prevalence of current smoking increased from 21.3 to 28.3%, and daily smoking increased from 10.0 to 14.2%. Among girls, daily smoking increased by 62% during this period. Almost all participants (94%) in 1994/1995 knew a tobacco brand, and appreciation of tobacco advertisement was strongly associated with the frequency of smoking.

CONCLUSION

Smoking is increasing among adolescents in Germany especially among girls. These data are a cause of concern and call for efforts to reverse these trends, which should include a ban on tobacco advertisement in Germany.

Family history as a predictor of asthma risk

Asthma, one of the most important chronic diseases of children, disproportionately affects minority and low-income children. Many environmental risk factors for asthma have been identified, including animal, mite, and other allergens; cigarette smoke; and air pollutants. Genetics also play an important causative role, as indicated by familial aggregation and the identification of candidate genes and chromosomal regions linked to asthma risk. Using a positive family history of asthma to identify children at increased risk could provide a basis for targeted prevention efforts, aimed at reducing exposure to environmental risk factors. To assess the predictive value of family history as an indicator of risk for childhood asthma, we reviewed population-based studies that evaluated family history of asthma and atopic disease in children with asthma. Our search identified 33 studies from all geographic regions of the world for review. The studies varied in definitions of positive family history and asthma phenotype and used study populations with asthma prevalence ranging from 2% to 26%. Nevertheless, family history of asthma in one or more first-degree relatives was consistently identified as a risk factor for asthma. In ten studies, sensitivity and predictive value of a positive family history of asthma could be calculated: sensitivity ranged from 4% to 43%, positive predictive value from 11% to 37%, and negative predictive value from 86% to 97%. Although a positive family history predicts an increased risk of asthma, it identifies a minority of children at risk. Positive family history may have utility in targeting some individual prevention efforts, but the low positive predictive value limits its value as a means to direct environmental remediation efforts.

Geographical variations of asthma and asthma symptoms among schoolchildren aged 5 to 8 years and 12 to 15 years in Palestine: the International Study of Asthma and Allergies in Childhood (ISAAC)

BACKGROUND

Many studies demonstrated the existence of geographic differences, within and between countries, in the prevalence of asthma, rhinitis, and eczema. However, in Palestine, there are no comprehensive Palestinian data to compare with those from other regional and international centers.

OBJECTIVE

To describe the prevalence of asthma and asthma symptoms in schoolchildren in two districts (Ramallah and North Gaza) in Palestine.

METHODS

After a two-stage stratified systematic sampling, approximately 14,500 schoolchildren, from the first and second grades of elementary school (ages 5 to 8 years) and eighth and ninth school grades (ages 12 to 15 years), were invited to participate in a survey using International Study of Asthma and Allergies in Childhood phase III questionnaires and protocols.

RESULTS

In general, younger children were reported to have a higher 12-month wheezing prevalence rate than older children (9.6 and 7.2%, respectively), and more physician-diagnosed asthma (8.4 and 5.9%, respectively). However, nocturnal cough and exercise-related wheezing were higher in the older age group compared with younger children. Younger children living in North Gaza district showed slightly higher prevalence rates for asthma and asthma symptoms, but older children had higher rates in Ramallah district. After adjustment using logistic regression analysis, male sex, living in inland areas, and younger age were shown to predict 12-month wheezing and physician-diagnosed asthma.

CONCLUSIONS

Palestinian children have asthma symptoms rates that are similar to several countries in the Mediterranean region such as Spain and Turkey, but still lower than other Middle East countries such as Saudi Arabia and Israel.

Interferon-gamma levels in nasopharyngeal secretions of infants with respiratory syncytial virus and other respiratory viral infections

Respiratory syncytial virus (RSV) infection, one of the most common causes of hospitalization of children in developed countries, has been implicated as a cause of asthma. We aimed to characterize the cytokine profile in nasopharyngeal aspirates (NPAs) taken from infants during upper respiratory tract infection to investigate whether RSV induced a unique immune response as compared with other viruses. Additionally, we sought to determine whether this profile was influenced by the infants' atopic status. A prospective birth cohort of babies at high risk of atopy was recruited. Ratios of a T-helper 1 (Th1) cytokine, interferon gamma (IFN-gamma) and a T-helper 2 (Th2)-like cytokine, interleukin-10 (IL-10), in NPAs were determined during episodes of respiratory tract infections in the first year. The viral aetiology of the respiratory tract infections was determined using polymerase chain reaction (PCR), culture and immunofluorescence. Atopic status was ascertained at 1 year of age using skin prick tests. Participants were recruited antenatally and subsequently followed in the community. Sixty babies with one or both parents atopic were enrolled into the study. IFN-gamma : IL-10 ratios in NPAs during upper respiratory tract infections and their correlation with viral aetiology and atopic status were the main outcome measures. The mean IFN-gamma : IL-10 ratio was significantly lower (due to lower IFN-gamma) during RSV infections than during infections with other viruses (P = 0.035). The cytokine ratio, however, did not differ between infants with or without wheeze during URTIs (P = 0.44), or between infants who were atopic or non-atopic (P = 0.49). This study suggests that RSV is associated with lower IFN-gamma production in young babies, regardless of their atopic status, compared to upper respiratory tract infections where either another virus is detected or where no viral identification is made.

Allergen sensitization and allergen exposure in Greenlander Inuit residing in Denmark and Greenland

The aim of this study was to estimate the prevalence of allergic sensitization and possible risk factors in a genetically homogenous Inuit population living under widely differing climatic and cultural conditions. A written questionnaire and skin prick test for 10 aeroallergens were obtained from 1119 adult Greenlanders residing in Denmark, Nuuk (main city in Southern Greenland) and Uummannaq (rural settlement in Northern Greenland). Allergen exposure was assessed by pollen counts, questions on pet keeping and counts of house dust mites in dust samples. The overall prevalence of at least one positive skin prick test was 22.8% in Denmark, 10.6% in Nuuk, and 6.4% in Uummannaq. In Denmark, the total birch pollen counts were 40-1000 times higher compared to Nuuk, whereas the grass pollen count was 13-30 times higher in Denmark compared to Nuuk. Dogs were held indoor with a similar frequency in Denmark and Nuuk, but much less frequently in Uummannaq. In Denmark, house dust mites were found in 72% of house holds (>10/0.1 g dust). Less than 15% of households in Greenland had measurable levels of house dust mites. The prevalence of sensitization to aeroallergens in Inuit Greenlanders differed significantly between Denmark, Nuuk and Uummannaq. These findings correlated with the observed differences in population allergen exposure in the three regions. Furthermore, differences in lifestyle factors such as educational level, stress and ethnic self-identification seemed to be associated with the risk of allergic sensitization in Greenland.

Early respiratory and skin symptoms in relation to ethnic background: the importance of socioeconomic status; the PIAMA study

AIMS

To evaluate ethnic differences in the prevalence of respiratory and skin symptoms in the first two years of life.

METHODS

A total of 4146 children participated in the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) study. Parents completed questionnaires on respiratory and skin symptoms, ethnic background, and other potential confounders during pregnancy, and at 3 months, 1 year, and 2 years of age.

RESULTS

In the first year, "non-Dutch" children (compared with "Dutch" children) had a higher prevalence of runny nose with itchy/watery eyes (11.0% versus 5.0%). In the second year, a higher prevalence of wheeze at least once (26.7% versus 18.5%), night cough without a cold (24.6% versus 15.5%), runny nose without a cold (34.1% versus 21.3%), and runny nose with itchy/watery eyes (13.7% versus 4.6%) was found. Adjustment for various confounders, especially adjustment for socioeconomic factors, reduced most associations between ethnicity and respiratory symptoms. Only runny nose with itchy/watery eyes in the second year of life was independently associated with non-Dutch ethnicity (adjusted odds ratio 2.89, 95% CI 1.3-6.4).

CONCLUSIONS

Non-Dutch children more often had respiratory symptoms in the first two years of life than Dutch children. This could largely be explained by differences in socioeconomic status. Follow up of the cohort will determine whether this higher prevalence of respiratory symptoms in children with non-Dutch ethnicity represents an increased risk of developing allergic disease rather than non-specific or infection related respiratory symptoms.

Present status on the genetic studies of asthma

Asthma, one of the most common chronic diseases, is a complex and heterogeneous disorder. The results of genome screens for asthma-related traits in 11 different populations identified at least 18 regions of the genome that probably house asthma/atopy genes. The most consistently replicated regions are on chromosomes 2q, 5q, 6p, 12q and 13q. Positional cloning projects are ongoing in laboratories around the world to identify the asthma susceptibility loci in these regions. In addition, many candidate genes have been associated with asthma phenotypes, such as the genes in the IL-4/IL-13 pathway.

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.

Respiratory symptoms and dust exposure among male workers in small-scale wood industries in Tanzania

Few studies have assessed respiratory symptoms and dust exposure levels in small-scale wood industry workers in Africa. We interviewed 546 workers exposed to wood dust and 565 control subjects using a respiratory health questionnaire. Inhalable dust measurements were collected for 106 workers. The dust exposure was high, and job title-based geometric mean exposure levels ranged from 2.9 to 22.8 mg/m3. Prevalence of respiratory symptoms in the previous 12 months was significantly higher in the exposed group compared with the nonexposed office workers. Allergy and sensitivity symptoms were reported regularly in the exposed group with Odds ratios and 95% confidence intervals (CIs) varying from 2.4 (95% CI = 1.8-3.1) for low- and 2.7 (1.8-4.0) for high-exposure groups compared with controls. We conclude that working in the small-scale wood industry in Tanzania is associated with an increased prevalence of respiratory symptoms.

Nasal cellularity in 183 unselected schoolchildren aged 9 to 11 years

OBJECTIVE

Although rhinitis is extremely frequent in children, methods for assessing the severity of nasal inflammation produce results with wide variability and hence weak clinical significance. We designed this epidemiologic investigation to define the clinical usefulness of assessing nasal cellularity in children.

METHODS

We studied 183 of 203 eligible unselected schoolchildren who were aged 9 to 11 years and whose parents gave informed consent and completed a questionnaire on the history of atopic and respiratory symptoms. In all children, nasal swabs were obtained from both nostrils and eluted in saline and slides were prepared from cytospin preparations for staining and white cell counts. Children also underwent determination of nasal volume, skin prick tests with 7 common local allergens, flow volume curves, and nitric oxide measurement in expired air. Blood samples were drawn for the measurement of total immunoglobulin E, eosinophil percentage, and detection of Chlamydia pneumoniae antibodies. C pneumoniae DNA was also sought in eluates from nasal swabs. The percentage, standard deviations, and percentiles of the various nasal white cell populations were determined.

RESULTS

No correlation of the percentage of these cells was found with the history of allergies or respiratory disease or with functional or laboratory finding. Repeat nasal swabs obtained 1 month after the initial examination in 31 children (20 with neutrophils higher and 11 lower than 14%) in 77.4% of the cases confirmed the previous (high or normal) result. Twelve of the 16 eligible children with persistently high nasal neutrophil counts completed a 15-day cycle of intranasal flunisolide therapy (200 micro g twice a day). Therapy significantly reduced nasal neutrophil percentage and increased nasal volume.

CONCLUSIONS

Increased nasal neutrophils, although related neither to the clinical history nor to laboratory variables, are a common important finding in children. A 15-day cycle of intranasal flunisolide is sufficient to restore normal nasal neutrophilia.

Farm residence and exposures and the risk of allergic diseases in New Zealand children

BACKGROUND

Studies in Europe have reported a reduced prevalence of allergy in farmers' children. We aimed to determine if there is a similar reduction in allergy among New Zealand farm children.

METHODS

Two hundred and ninety-three children participated (60%) aged 7-10 years, from selected schools in small towns and the surrounding rural area. Skin prick tests (SPT) to eight common allergens were performed. Parents completed questionnaires about allergic and infectious diseases, place of residence, exposure to animals, and diet, and they provided dust from the living-room floor. Endotoxin was measured using an Limulus amoebocyte lysate (LAL) assay and Der p 1 using enzyme-linked immunoassay (ELISA).

RESULTS

Current farm abode was found to increase the risk of having symptoms associated with allergy, but not SPT positivity. Independent inverse associations were found for early-life exposures: at least weekly consumption of yoghurt with hayfever (odds ratio (OR) = 0.3, 95% confidence intervals (CI) 0.1-0.7) and allergic rhinitis (OR = 0.3, 95% CI 0.2-0.7); any unpasteurized milk consumption with atopic eczema/dermatitis syndrome (AEDS) (OR = 0.2, 95% CI 0.1-0.8); cats inside or outside with hayfever (OR = 0.4, 95% CI 0.1-1.0) and AEDS (OR = 0.4, 95% CI 0.2-0.8); dogs inside or outside with asthma (OR = 0.4, 95% CI 0.2-0.8); and pigs with SPT positivity (OR = 0.2, 95% CI 0.1-0.9).

CONCLUSIONS

Despite finding a protective effect of early-life animal exposures, we found a greater prevalence of allergic disease on farms.

Atopic disorders in ankylosing spondylitis and rheumatoid arthritis

BACKGROUND

The prevalence of atopic disorders in ankylosing spondylitis (AS) is unknown. AS and rheumatoid arthritis (RA) exhibit divergent T helper (Th) cell cytokine patterns.

OBJECTIVE

To test the hypothesis that Th2 polarised atopic disorders may be decreased in Th1 polarised RA but increased in AS, which is characterised by an impaired Th1 cytokine pattern, by assessing the prevalence of atopic disorders in AS and RA.

METHODS

2008 subjects (380 patients with AS, 728 patients with RA, 900 controls) from Berlin, Germany, were considered in this cross sectional study. A questionnaire incorporating questions from the European Community Respiratory Health Service (ECRHS) and the International Study of Asthma and Allergies in Childhood (ISAAC) protocol was mailed to all subjects. Disease severity was assessed by the modified Health Assessment Questionnaire (mHAQ).

RESULTS

1271 (63.3%) people responded to the questionnaire. The prevalence of any atopic disorder was 24.6% (61/248) in patients with AS, 20.7% (111/536) in controls, and 13.1% (64/487) in patients with RA (p=0.0009 for AS v RA; p=0.001 for controls v RA). Hay fever was reported by 40/248 (16.1%) patients with AS, 82/536 (15.3%) controls, and 42/487 (8.6%) patients with RA (p=0.002 for AS v RA; p=0.001 for controls v RA). Atopic dermatitis was reported by 19/248 (7.7%) patients with AS, 26/536 (4.9%) controls, and 14/487 (2.9%) patients with RA (p=0.003 for AS v RA), and asthma by 18/248 (7.3%) patients with AS, 35/536 (6.5%) controls, and 21/487 (4.3%) patients with RA. The differences were related neither to age nor to drugs. Disease severity was less in atopic patients with RA who had the atopic disorder before the onset of RA (median mHAQ 0.75) than in patients in whom RA preceded the atopic disorder (median mHAQ 1.75; p=0.027).

CONCLUSIONS

Atopic disorders are decreased in RA but only slightly and non-significantly increased in AS. This may imply that atopy confers some protection from RA but only little if any susceptibility to AS. It may further indicate that the cytokine deviation towards an impaired Th1 pattern in AS is less strong than the cytokine deviation towards Th1 in RA, a finding which may affect future therapeutic approaches.

A parent completed questionnaire to describe the patterns of wheezing and other respiratory symptoms in infants and preschool children

AIM

To develop a standardised and validated respiratory symptom questionnaire for use in epidemiological or follow up studies in infants and preschool children.

METHODOLOGY

After initial design and development, the questionnaire was administered to two cohorts of subjects, one recruited from a respiratory clinic and the other from a postnatal ward. The two cohorts then repeated the questionnaire, two weeks apart. The qualities of the questionnaire were assessed.

RESULTS

Response rate to the initial questionnaire was 100% for the clinic based cohort and 64% for postnatally recruited families (total number of subjects 114). Questions showed good to moderate short term reliability (weighted kappa scores 0.47-0.7; average correct classification rates 0.74-0.91). Four domain concept scores showed excellent internal consistency (Cronbach alpha scores 0.87-0.95). Using principal component factor analysis, four new domains were devised showing acceptable construct validity and internal consistency. Criterion validity was assessed using a respiratory physician based diagnosis of asthma (RPBDA) as the gold standard for comparison. All eight scales in the questionnaire could significantly distinguish between infants with RPBDA and well or mildly symptomatic subjects.

CONCLUSION

We have developed a practical, acceptable questionnaire with eight concept domains for use in infants and preschool children. The questionnaire has strong construct validity and internal consistency with good short term reliability of questions. More detailed study of criterion validity and the responsiveness of the questionnaire is required using a larger population and including children with the different phenotypes of wheezy illness.

Gender differences in the impact of adolescent smoking on lung function and respiratory symptoms. the Nord-Trøndelag Health Study, Norway, 1995-1997

Girls take up smoking at least as frequently as boys. Few studies have focused on gender differences in the impact of adolescent smoking. We evaluated the sex-specific effect of adolescent smoking on respiratory symptoms and lung function. All students in junior high and high schools in Nord-Trøndelag County Norway, 1995-97, were invited to participate in a cross-sectional study. Information on smoking habits and respiratory symptoms was obtained by self-administered questionnaires. Spirometry was performed in accordance with ATS standards. Eight-thousand-three-hundred and five students (83%) completed both questionnaire and spirometry. Among 6811 students aged 13-18 years (50.3% girls) with no history of asthma, 2993 (43.9%) reported never smoking, 665 (98%) reported occasional smoking, and 667 (9.9%) reported daily smoking (mean initiation age: 13.9 years). More boys than girls were heavy smokers. In all smoking categories, smokers reported a higher prevalence of respiratory symptoms than nonsmokers; symptoms increased with smoke burden. Girls reported more symptoms compared to boys with comparable smoke burden. A dose-response relation between smoking and reduced lung function was found only in girls. Girls were more vulnerable than boys to the impact of smoking on respiratory symptoms and lung function.

Environmental exposure to endotoxin and its relation to asthma in school-age children

BACKGROUND

In early life, the innate immune system can recognize both viable and nonviable parts of microorganisms. Immune activation may direct the immune response, thus conferring tolerance to allergens such as animal dander or tree and grass pollen.

METHODS

Parents of children who were 6 to 13 years of age and were living in rural areas of Germany, Austria, or Switzerland where there were both farming and nonfarming households completed a standardized questionnaire on asthma and hay fever. Blood samples were obtained from the children and tested for atopic sensitization; peripheral-blood leukocytes were also harvested from the samples for testing. The levels of endotoxin in the bedding used by these children were examined in relation to clinical findings and to the cytokine-production profiles of peripheral-blood leukocytes that had been stimulated with lipopolysaccharide and staphylococcal enterotoxin B. Complete data were available for 812 children.

RESULTS

Endotoxin levels in samples of dust from the child's mattress were inversely related to the occurrence of hay fever, atopic asthma, and atopic sensitization. Nonatopic wheeze was not significantly associated with the endotoxin level. Cytokine production by leukocytes (production of tumor necrosis factor alpha, interferon-gamma, interleukin-10, and interleukin-12) was inversely related to the endotoxin level in the bedding, indicating a marked down-regulation of immune responses in exposed children.

CONCLUSIONS

A subject's environmental exposure to endotoxin may have a crucial role in the development of tolerance to ubiquitous allergens found in natural environments.

How should a birth cohort study be organised? Experience from the German MAS cohort study

Birth cohort studies offer the opportunity to study average risks, rates and occurrence times of disease longitudinally from birth. The effect of genetic and environmental factors and their interactions can be studied. Furthermore, quantity and duration of exposure to environmental agents can be evaluated prospectively. However, prospective birth cohort studies are expensive, labour intensive and take many years to complete. Loss of subjects over time as well as recall bias complicate the interpretation of observations. This paper summarises the potential pitfalls of such studies and discusses the experience of the German Multicentre Allergy Study (MAS), which began in 1990 in five German cities and included 1314 newborns for the study of the natural course of atopic diseases.

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.

Issues in identifying asthma and estimating prevalence in an urban school population

This article first presents salient issues related to identifying children in urban schools who might benefit from asthma services. It discusses a brief questionnaire for identifying cases and problems in estimating asthma prevalence. Subsequently, results of case detection in 14 urban schools are presented and discussed in light of these issues. The questionnaire was employed with parents of 4,653 African-American children in Detroit. Results suggest that determining number, type, and frequency of symptoms may be necessary to ascertain prevalence of asthma. Using only number and type produced a rate of asthma of 25%. Adding frequency provided a more conservative estimate of 19%. About 9% of children exhibiting symptoms of asthma had no physician diagnosis. Only 25% with symptoms reflecting mild persistent, 35% with moderate persistent, and 26% with severe persistent disease had prescriptions for anti-inflammatory medicine. Further, 23% of children with asthma-like symptoms had no prescription for asthma medicine of any type.

CONCLUSIONS

(1) low-cost procedures can be used in schools to identify children with suspected undiagnosed and undertreated asthma; (2) prevalence estimates for asthma in the group of urban school children studied are among the highest in the United States; and (3) asthma is undertreated in this sample.

The development of childhood asthma: lessons from the German Multicentre Allergy Study (MAS)

Epidemiological surveys have indicated that there has been a notable increase in the prevalence of both asthma and other allergic symptoms in children and young adults. Since it seems unlikely that genetic factors would contribute to the rising trend, environmental factors might play a major part in the development of childhood asthma. In a prospective birth-cohort study, we assessed the relevance of different exposures such as mite and cat allergen exposure, environmental tobacco smoke (ETS) exposure, early infectious diseases and vaccinations for the development of childhood asthma up to the age of 10 years. Data up to 7 years of age have been evaluated. Of 1314 newborn infants enrolled in five German cities in 1990, follow-up data at age 7 years were available for 939 children (72%). Assessments included repeated measurements of specific IgE to food and inhalant allergens, measurement of indoor allergen exposure at 6 months, 18 months and 3 years of age and yearly interviews by a paediatrician. At age 7 years, pulmonary function was tested and bronchial responsiveness was determined in 645 children. At age 7, the prevalence of wheezing in the past 12 months was 10% (94 out of 938), and 6.1% (57 out of 939) parents reported a doctor's diagnosis of asthma in their children. Sensitisation to indoor allergens was associated with asthma, wheeze and increased bronchial responsiveness. However, no relationship between early indoor allergen exposure and the prevalence of asthma, wheeze and bronchial responsiveness was seen. During the first 3 years of life, intra-uterine tobacco and consistent ETS exposure have an adjuvant effect on allergic sensitisation that is transient and restricted to children with a genetic predisposition for allergy. Children sensitised to any allergen early in life and sensitised to inhalant allergens by the age of 7 years were at a significantly increased risk of being asthmatic at this age (odds ratio (OR) = 10.12; 95% confidence interval (CI) = 3.81-26.88). Children with repeated episodes (> or =2) of runny nose before the age of 1 year were less likely to develop asthma by the age of 7 years (OR = 0.52; 95% CI = 0.29-0.92). Our data do not support the hypothesis that exposure to environmental allergens directly causes asthma in childhood but that induction of specific IgE responses and the development of childhood asthma are determined by independent factors. Indoor allergen avoidance is recommended as first line treatment in secondary and tertiary prevention; however, conclusions should be drawn with caution about the possible effect of primary preventative measures. Since allergic asthma seems to be a Th2-disease, immunomodulating factors such as early childhood infections, LPS-exposure or other factors influencing gene-environment interaction and individual susceptibility seem to be relevant for the development of childhood asthma.

Upper respiratory symptoms associated with aging of the ventilation system in artificially ventilated offices in São Paulo, Brazil

BACKGROUND

The increase of work-related respiratory complaints in artificially ventilated buildings has multiple causes, and the role of allergen exposure and symptoms is still controversial.

STUDY OBJECTIVES

To analyze the risk factors and the association of work-related symptoms with allergen exposure and different conditions of the same air conditioning system in São Paulo, Brazil.

DESIGN

Workers were classified according to characteristics of the air conditioning system: the first group (group 1) with ventilation machinery and ducts with > 20 years of use, the second group (group 2) with ventilation machinery with > 20 years of use and ventilation ducts with < 2 years of use, and the third group (group 3) with ventilation machinery and ducts with < 2 years of use. Logistic regression was performed to check the associations between air conditioning groups, allergen exposure (fungi, mites, animal dander, and cockroach), and symptoms.

RESULTS

There was a higher prevalence of building-related worsening of respiratory symptoms (p = 0.004; odds ratio [OR], 8.53) and symptoms of rhinoconjunctivitis (p = 0.01; OR, 8.49) in group 1. There was a lower relative humidity (p = 0.05) and nonsignificant lower temperature in group 1, when compared to the other groups. The viable mold spores totals were higher outdoors than in the indoor samples (n = 45, p = 0.017). There were higher levels of Der p 1 in group 2 (p = 0.032). All allergen levels were considered low.

CONCLUSION

There was a strong association of building-related upper-airway symptoms with places having ventilation systems with > 20 years of use.

Placebo-controlled trial of house dust mite-impermeable mattress covers: effect on symptoms in early childhood

We investigated the effect of house dust mite (HDM)-allergen avoidance on the development of respiratory symptoms, atopic dermatitis, and atopic sensitization by performing a double blind, placebo-controlled trial. In total, 1,282 allergic pregnant women were selected (416 received HDM allergen-impermeable mattress covers for the parents' and child's mattress in the third trimester of pregnancy [active], 394 received placebo covers, 472 received no intervention). Data on allergen exposure, clinical symptoms, and immunoglobulin E were collected prospectively. The prevalence of night cough without a cold in the second year of life was lower in the group with active covers compared with the group with placebo covers (adjusted odds ratio 0.65; 95% confidence interval 0.4-1.0). No effect of the intervention was seen on other respiratory symptoms, atopic dermatitis, and total and specific immunoglobulin E. It can be concluded that application of HDM-impermeable mattress covers on the child's and parents' beds reduced night cough, but not other respiratory symptoms, atopic dermatitis, and atopic sensitization in the first 2 years of life. Follow-up will determine the long-term effect of the intervention on the development of atopic disease.

Prevalence of asthma and asthma-like symptoms in inner-city elementary schoolchildren

American inner-city children are disproportionately affected by asthma. During the 1999-2000 school year, we conducted a survey of 6 Bronx, New York City elementary schools to assess the prevalence of asthma and asthma-like symptoms as reported by parents. Children with probable asthma had symptoms within the last 12 months and parents who indicated that their child had asthma. Children with possible asthma had symptoms within the last 12 months but lacked a diagnosis.Overall, 74% (4,775/6,433) of parents returned completed surveys, identifying 20% (949/4,775) of children as probable asthmatics, and 12% (589/4,775) as possible asthmatics. In multivariate analyses, probable asthma was associated with: Puerto Rican, Black, and white race/ethnicity, male gender, having health insurance, and registration at the poorest school. Possible asthma was associated with lack of health insurance and female gender, but was not associated with any specific race/ethnicity. Our findings support the effectiveness of school-based surveys to identify children at high risk for asthma. The challenge remains to engage children and families in appropriate follow-up care and to manage their illness, either through the use of school-based health centers or stronger links to community services.

Parents' accounts of wheeze and asthma related symptoms: a qualitative study

AIMS

To examine parents' accounts of how they recognise and judge respiratory symptoms in children, and to investigate their interpretations of respiratory survey questions about wheeze, shortness of breath, and cough.

METHODS

Qualitative study using semistructured interviews. Data were analysed using the constant comparative method. Nineteen parents of children aged under 6 years were recruited from a cohort of parents who had responded to an earlier respiratory symptom survey and from one general practice.

RESULTS

Parents judged respiratory symptoms using a range of cues, including changes in the sound of breathing and changes in appearance and behaviour. Experiential resources and contextual factors played an important role in parents' judgements. Interpretations of questions about respiratory symptoms were varied, particularly in relation to the terms "attacks of wheeze" and "shortness of breath". Parents' descriptions of wheeze differed from descriptions of the sound of wheeze used in some survey questionnaires. Parents drew fine distinctions between different "types" of cough and identified a distinct "asthma" cough.

CONCLUSIONS

Attention needs to be given to the complexity of reporting respiratory symptoms in children and to the importance of contextual factors in parents' judgements. We suggest that questions which require parents to report on children's internal feelings or states be avoided. Consideration should be given to providing parents with explicit direction on what cues to attend to or ignore in reporting symptoms, and to clarifying some questions that are currently used in clinical practice and in surveys.

Natural history of hay fever and pollen sensitization, and doctors' diagnosis of hay fever and pollen asthma in German schoolchildren

BACKGROUND

In order to prevent pollen asthma by immunotherapy it is mandatory to know the best time to initiate it. Children with hay fever complaints are at considerable risk of developing pollen asthma. Population-based data on their natural history is urgently needed.

METHODS

A longitudinal cohort study was conducted over four years in six rural towns in Baden-Württemberg, Germany. A questionnaire with questions taken from the International Study of Asthma and Allergies in childhood (ISAAC) was filled in every spring and autumn. Hay fever complaints, asthma defining symptoms and new doctors' diagnosis of hay fever and asthma were recorded. Additionally a skin prick test with pollen allergens was performed every autumn.

RESULTS

In 1996, 19.7% of 1101 elementary school children (age: 8.1-9.9 years (5-95%)) were found to be sensitized to pollen and 8.7% had already been diagnosed as having hay fever. In a pooled analysis of 2478 children-summers, children with positive pollen sensitization had a significantly higher risk of developing hay fever symptoms (2.63; 2.17-3.10 odds ratio (OR); 95% confidence interval (CI)) and of being diagnosed as suffering from hay fever (7.88; 4.70-13.20). Furthermore, although their OR for the development of asthma symptoms during the pollen season was 3.88 (2.48-6.07 CI), it was only 0.69 (0.24-2.01 CI) for doctors' diagnosis of pollen asthma.

CONCLUSION

Children of elementary school age with pollen sensitization and a history of hay fever are at considerable risk of getting pollen asthma, but they are not quickly diagnosed as such. Specific immunotherapy might be a means of preventing asthma completely in such a situation. Our data helps to estimate the sample size for intervention studies of this kind.

Prevention of sensitization to house dust mite by allergen avoidance in school age children: a randomized controlled study

BACKGROUND

Sensitization to dust mites predisposes to asthma and allergic rhinitis, and prevention of this sensitization might reduce the rising prevalence of these disorders.

OBJECTIVE

To test the effectiveness of dust mite avoidance measures on the development of sensitization to dust mites in children.

METHODS

As part of a multicentre study (Study of Prevention of Allergy in Children of Europe), 242 children, aged 5-7 years, in three European countries (United Kingdom, Greece and Lithuania), were randomized to prophylactic group (n = 127) and control group (n = 115). At randomization these children were required to have a family history of atopy and positive skin test to an aeroallergen but not to house dust mite. Children in the prophylactic group were provided with dust mite impermeable mattress covers and advice on environmental measures to reduce exposure to dust-mite allergen. Control group children were given non-specific advice. After 12 months a standardized questionnaire was completed and skin prick tests were performed.

RESULTS

Ten children in the prophylactic group and 19 in the control group were lost to follow-up. Three of 117 (2.56%) children in the prophylactic group and nine of 96 (9.38%) in the control group developed sensitization to dust mites. Logistic regression analysis confirmed an independent effect of prophylactic measures (adjusted odds ratio (OR): 0.14, 95% confidence interval (CI): 0.03-0.79, P = 0.03). Fifteen children need to be treated to prevent sensitization in one child.

CONCLUSION

Dust mite sensitization can be reduced in school age children with simple mite avoidance measures.