Prevalence of bronchial asthma among schoolchildren in a Swedish district

Time trend for the prevalence of asthma among school children in a Swedish district in 1985-2005

AIM

To assess the temporal trend for asthma and asthma-like symptoms over a period of 20 years.

METHOD

Repeated cross-sectional surveys with identical study design were carried out among all school children (7-16 years) in a well-defined area in Sweden in 1985, 1995 and 2005.

RESULTS

In 2005, the parents of 1110 out of 7825 children (14.2%) answered yes to a screening question on asthmatic symptoms. Of these, 783 out of 1110 (70.5%) replied to a postal questionnaire with detailed questions concerning symptoms and asthma management. The rate of affirmative response to the screening question was unchanged between 1995 and 2005. However, the percentage of children with wheezing or three or more asthma-like symptoms decreased, whereas the percentage of children with physician-diagnosed asthma increased steadily since 1985. The number of reported symptoms was closely associated with the number of days with physical restriction. The annual sale of inhaled steroids from local pharmacies was stable between 1995 and 2005.

CONCLUSION

The increase in asthmatic symptoms in school children has peaked. Reduced severity of symptoms and divergent trends for wheezing and physician-diagnosed asthma suggest an increased awareness of asthma with improved management of the symptoms. However, differences in trends between allergic and nonallergic asthma could not be excluded.

Prevalence, severity and determinants of asthma in Danish five-year-olds

BACKGROUND

The prevalence of asthma and wheeze is increasing.

AIM

To study the annual and cumulative prevalence of asthma and wheeze in 5-y-old Danish children.

METHODS

We obtained data on 3052 (82.0% of eligible) Danish children by a postal parental questionnaire including ISAAC questions regarding respiratory symptoms and our own questions on sociodemography and tobacco exposure.

RESULTS

"Wheeze ever" was reported in 38.3%, "doctor-diagnosed asthma ever" in 10.5%, "childhood bronchitis ever" in 30.0%, "current wheeze" (<12 mo) in 19.7%, and being "severe" (>3 episodes) in 3.9% of the children. Current wheeze was associated with male gender (OR 1.63, 95% CI 1.35-1.96), low parental post-primary education (OR 1.29, 95% CI 1.02-1.63 for <3 y vs > or =3 y) and current maternal smoking (OR 1.69, 95% CI 1.39-2.04). "Severe current wheeze" was recognized as asthma in six and childhood bronchitis in three of 10 cases. Nearly all diagnosed asthmatics had suffered wheeze, two-thirds recently.

CONCLUSION

We found a high prevalence of asthma and wheeze in Danish late-preschool children, associated with male gender, current maternal tobacco smoking and low parental post-primary education. The majority of children with current wheeze had an early onset, and severe early symptoms tended to persist. Used with consideration, the label "childhood bronchitis" seems purposeful.

New ventilation systems at select schools in Sweden--effects on asthma and exposure

The air-exchange rate is often low in schools. The authors studied the possible impact of improving school ventilation on health and exposure of pupils. Questionnaire data on allergies, asthma, and asthmatic symptoms were obtained in 1993 and 1995 for 1,476 primary- and secondary-school pupils in 39 randomly selected schools. Various exposure factors were measured in 1993 and 1995 in approximately 100 classrooms. In 12% of the classrooms, new ventilation systems were installed between 1993 and 1995; the subsequent air-exchange rate increased and the relative humidity and concentration of several airborne pollutants were reduced compared with classrooms in nonimproved buildings. The reporting of at least one asthmatic symptom and the reporting of more asthmatic symptoms in 1995 than in 1993 were less common among the 143 pupils who attended schools with new ventilation systems.

Risk factors for development of bronchial asthma in children in Delhi

BACKGROUND

Information on the magnitude of the problem of childhood asthma in India and the factors influencing its occurrence is inadequate.

OBJECTIVE

To measure the prevalence of asthma in schoolchildren in Delhi and study the factors determining its occurrence.

METHODS

A questionnaire-based study carried out in nine randomly selected schools in Delhi. The age range was 5 to 17 years. The questionnaires were distributed to all the children (n = 21,367) for answering by either parent. The key questions relate to complaints of recurrent wheezing in the past, during the immediate last 1-year, and also wheezing exclusively induced by exercise or colds. In all, 19,456 questionnaires were received back (response rate 91%). Out of these, 18,955 were complete and analyzed.

RESULTS

The prevalence of current asthma was 11.9% while past asthma was reported by 3.4% of children. Exclusive exercise-induced asthma was reported by 2.1% while that associated with colds by 2.4% of children. Boys had a significantly higher prevalence of current asthma as compared with girls (12.8% and 10.7%, respectively). Multiple logistic regression analysis showed that male sex, a positive family history of atopic disorders, and the presence of smokers in the family were significant factors influencing the development of asthma while economic class, air pollution (total suspended particulates), and type of domestic kitchen fuel were not.

CONCLUSIONS

The prevalence of current asthma in children in Delhi is 11.9%. Significant risk factors for its development are male sex, a positive family history of atopic disorders, and the presence of smokers in the family.

Different pattern of risk factors for atopic and nonatopic asthma among children--report from the Obstructive Lung Disease in Northern Sweden Study

BACKGROUND

A cross-sectional study was performed among 78-year-old schoolchildren during the winter of 1996 in three municipalities in the most northern province of Sweden, Norrbotten. The study was the starting point of a longitudinal study of asthma, rhinitis, eczema, and type-1 allergy, and provided data on prevalence and risk factors for these conditions. The aim of the present study was to validate the classification of asthma based on a parental questionnaire, and to examine risk factors for atopic and nonatopic asthma.

METHODS

The ISAAC questionnaire with additional questions was distributed by the schools to the parents. The response rate was 97%, and 3431 completed questionnaires were returned. The children in Kiruna and Luleå were also invited to be skin tested, and 2149 (88%) were tested with 10 common airborne allergens. A structured interview was administered by pediatricians in stratified samples of the children to test the validity of the diagnosis of asthma based on the questionnaire.

RESULTS

After the validation study, the prevalence of "ever asthma" was estimated to be 8.0%. The specificity of the question, "Has your child been diagnosed as having asthma by a physician?", was high, >99%, while the sensitivity was around 70%. The strongest risk factor for "ever asthma" was a positive skin test (OR 3.9). Risk factors for asthma in the asthmatics who were not sensitized were family history of asthma, OR 3.6; breast-feeding less than 3 months, OR 1.8; past or present dampness at home, OR 1.8; smoking mother, OR 1.7; and male sex, OR 1.6. Among the sensitized asthmatics, only a family history of asthma was a significant risk factor (OR 3.0), while breast-feeding less than 3 months was not associated with an increased risk (OR 1.0). A synergistic effect between genetic and environmental factors was found especially in the nonatopic asthmatics; the children with a family history of asthma who had a smoking mother and past or present dampness at home had an OR for "ever asthma" of 13.

CONCLUSIONS

Different risk-factor patterns were found for asthma and type-1 allergy. In addition, the risk factors for atopic or allergic asthma diverged from those for nonatopic asthma.

Prevalence of bronchial asthma in schoolchildren in Delhi

There is a paucity of information on the prevalence of asthma in children in India. Some evidence suggests that asthma is less common in developing than in the developed countries. The present study was carried out to estimate its current magnitude in children in Delhi. The questionnaire-based study was carried out in two randomly selected schools in Delhi. All the children were eligible. The age range was 4-17 years. The questionnaires were distributed to all the children present (n = 2867) to be answered by either parent. The key questions were related to complaints of recurrent wheezing in the past, in the last 1 year, and also wheezing exclusively induced by exercise or colds. In all, 2609 questionnaires were completed and returned (response rate 91%). There was a slight excess of males (54%). The prevalence of current asthma was 11.6% and past asthma was reported by 4.1% of children, giving a cumulative prevalence of 15.7%. Exclusive exercise-induced asthma was 2.8% and that associated with colds, 2.3%. The current prevalence of all wheezing was thus 16.7% and cumulative prevalence was 20.8%. While there was no sex-related difference in prevalence, wheezers were the highest in the 9-13 year age group. A significant association was found between the prevalence of wheezing and a family history of asthma (odds ratio 3.65) and presence of smokers in the family (odds ratio 1.62). When both the above factors combined, the odds ratio for risk of asthma was 4.58. There was no significant association with any economic class. Only 11% of asthmatics had been labeled so by their physicians. The prevalence of bronchial asthma and wheezing in children in Delhi is quite high and comparable to that reported from several developed countries. A positive family history of asthma and presence of smokers in the family emerged as significant risk factors.

Bayesian estimation of asthma prevalence, and comparison of exercise and questionnaire diagnostics in the absence of a gold standard

PURPOSE

To estimate the sensitivities, specificities, and predictive values of exercise challenge and questionnaire, when these tests are used to diagnose asthma in children.

METHODS

Participants were children, predominantly aged 6 to 12 years, selected from three primary school grades among 18 different schools in Montreal. Of 1111 participants, 989 successfully completed a six-minute free running test at school and returned a respiratory questionnaire. A total of 952 children had complete information that could be used for analysis. A history of wheezing in the past year in conjunction with a past diagnosis of asthma defined current asthma by questionnaire. Exercise responsiveness was defined as a > or = 10% fall in FEV1 after a six-minute free run. As there is no perfectly accurate diagnostic test for asthma, we analyzed the data using a previously published Bayesian method that allows for the estimation of test properties when no gold standard test is available.

RESULTS

Current asthma by questionnaire was found to have significantly higher specificity (94.9%, 95% credible interval (CI): 93.2-96.5 versus 82.6%, 95% CI: 79.9-85.1) and positive predictive value (53.8%, 95% CI: 41.0-66.7 versus 19.2%, 95% CI: 12.3-27.8) in comparison to exercise challenge. While there was no statistically significant difference between the two tests with respect to sensitivity and negative predictive values, the estimates were higher for current asthma (64.4%, 95% CI: 50.9-76.6 and 96.7%, 95% CI: 94.6-98.1, respectively) in comparison to exercise challenge (51.3%, 95% CI: 37.8-64.5 and 95.4%, 95% CI: 93.2-97.1, respectively). Agreement between the two diagnostic methods was poor and the combined use of the two tests did not significantly improve the likelihood of correctly identifying children with asthma.

CONCLUSIONS

Our findings support the view that exercise testing adds little to a well designed questionnaire in identifying subjects with asthma in community based studies.

Sensitization to dust mites as a dominant risk factor for asthma among adolescents living in central Virginia. Multiple regression analysis of a population-based study

Factors influencing asthma were investigated in a population of school children in central Virginia. A survey of 1,054 children in two middle schools (one urban and one suburban) identified 135 students with symptoms suggestive of asthma. Eighty-eight symptomatic children and 123 control subjects were randomly selected for further evaluation by skin testing using common indoor and outdoor allergens; serum assays for total IgE and specific IgE; dust samples assayed for mite (Der p 1 Der f 1), cat (Fel d 1), and cockroach (Bla g 2) allergens; and provocation with histamine to test for bronchial hyperreactivity. Forty-eight of the children with symptoms responded to < or = 3.9 mumol of histamine and were considered to have asthma. Marginal analysis identified elevated total IgE and dust mite, cat, and cockroach sensitization as significant risk factors for asthma. Using multiple regression, only dust mite sensitization was independently associated with asthma (odds ratio = 6.6; p < 0.0001). Dust from 81% of the houses contained high levels of mite allergen (> 2 micrograms/g), while approximately 40% of the children were exposed to cat and 17% were exposed to cockroach allergen. In this population, there was no significant association between asthma and race, socioeconomic status, home smoking, sensitization to outdoor allergens, or allergen concentration in the child's home. In an area where there is a high prevalence of asthma and most houses contain high concentrations of dust mite allergen, sensitization to this allergen is the dominant risk factor for asthma defined as symptomatic bronchial hyperreactivity

Genes, environments, and sex: factors of importance in atopic diseases in 7-9-year-old Swedish twins

Various atopic manifestations among adults have been shown to be influenced mainly by genetic factors. With the increase in prevalence of atopic diseases in recent years, especially among children, a great deal of attention has been given to environmental causes. In a study of 1480 Swedish twin pairs, 7-9 years old, we examined the importance of genetic and environmental factors in asthma, hay fever, eczema, and urticaria. Structural equation model fitting showed 33-76% of the variation in liability to the diseases to be due to genetic effects. Shared environmental effects were also important for hay fever and urticaria in both sexes and for eczema among girls. The clustering of atopic disease in families was almost entirely due to a common set of genes, but each disease manifestation also seemed to have specific genes of importance. Investigation of unlike-sex twins showed that boys had a higher cumulative incidence of asthma and hay fever than girls, whereas girls had a higher incidence of eczema. Thus, it may be concluded that although genetic factors are of major importance in atopic manifestation in children, both environmental and sex-related factors play a role.

Factors associated with asthma in school children

To investigate the factors associated with asthma in school children, a case-control study of 203 asthmatic and 203 non-asthmatic children (103 males and 100 females in each group) aged 6 to 18 years, was organized during the period September 1992 to May 1993 in Al Ain city, United Arab Emirates. Cases comprised known asthmatic children who were regularly receiving medication for asthma and were confirmed as asthmatics by a physician. Cases and controls were matched by age and sex. A questionnaire was used to obtain information about respiratory illnesses (pneumonia, bronchitis, bronchiolitis, sinusitis and croup); atopy (allergic rhinitis and atopic dermatitis) and familial allergic diseases (parental asthma and atopy). Information about socioeconomic status and limitations to children as a result of asthma were also obtained. Logistic regression analysis showed that bronchitis, atopy (allergic rhinitis and atopic dermatitis), croup, parental asthma and parental atopic dermatitis were significant risk factors for childhood asthma after adjusting for other confounding covariates. The model also showed that parental asthma (p < 0.0001) is much more influential than parental atopic dermatitis (p = 0.01) as a risk factor for asthma. Although pneumonia and sinusitis were significant risk factors when analyzed univariately, they were not significant after adjusting for other covariates. Bronchiolitis, smoking and socioeconomic status were beyond the reach of statistical significance as risk factors to asthma in our sample.

Increase of asthma, allergic rhinitis and eczema in Swedish schoolchildren between 1979 and 1991

BACKGROUND

A previous study has shown a twofold increase in prevalence of asthma and allergic rhinitis (AR) in Swedish recruits during the 1970s. The increase was higher in more northerly colder regions.

OBJECTIVES

To follow up the previously found trend to increasing prevalences with time as well as the climatic variations within the country.

METHODS

The prevalences of asthma, allergic rhinitis and eczema were assessed using two questionnaire studies, 12 years apart (1979 and 1991) with identical questions about the diseases. The study comprised representative samples of children from the Göteborg area on the south-western coast (in 1979: 7-year-olds, n = 4255, in 1991: 7-year-olds, n = 1649) and in Kiruna, a mining town in the northernmost inland mountains (in 1979: 7-year-olds, n = 427, in 1991: 7-9-year-olds, n = 832). In 1991 there was also a personal interview and a skin-prick test (SPT) on subsamples.

RESULTS

The prevalence of all these diseases present over the last year had roughly doubled over the 12-year period. On both occasions, most symptoms were more prevalent in the northern area. In 1991, the prevalence of one or more symptoms in Göteborg was 23.8% and 32.5% and in Kiruna 29.9% and 44.8% in the questionnaire and the interview, respectively.

CONCLUSION

Asthma, AR and eczema increase continuously in prevalence in Sweden and the climatic distribution of the prevalences suggests possible major risk factors to be found in a closed indoor climate.

Cat (Fel d I), dog (Can f I), and cockroach allergens in homes of asthmatic children from three climatic zones in Sweden

We have investigated the levels of cat (Fel d I), dog (Can f I), and cockroach (Per a I) allergens in dust from bedrooms, living rooms, kitchens, and bathrooms from 123 homes of asthmatic children in three zones of Sweden with varying climates. Absolute indoor humidity (AIH), relative humidity (RH), rate of ventilation in air changes per hour (ach), and number of airborne particles were also measured. Fel d I, Can f I, and Per a I allergen contents were determined by mab ELISA, and the levels were related to various environmental factors. The major cat allergen, Fel d I, was detected in all homes, and the concentrations varied between 16 ng and 28,000 ng/g fine dust. The dog allergen, Can f I, was detected in 85% of the homes, and the levels varied from 60 ng to 866,000 ng/g dust. Cockroach allergen was detected in only one home (40 ng/g). Fel d I and Can f I allergens were equally distributed geographically. Dust from living rooms contained significantly higher (P < 0.05) concentrations of both Fel d I and Can f I allergens than dust from bedrooms, kitchens, and bathrooms. The levels tended to be higher in homes with poor ventilation (< 0.5 ach) and in homes with wall-to-wall carpets. Significantly higher (P < 0.01) numbers of airborne particles were found in homes with high humidity (i.e., AIH > or = 7 g/kg or RH > or = 45%).(ABSTRACT TRUNCATED AT 250 WORDS)

International comparison of asthma prevalence in children: Australia, Switzerland, Chile

The aim of the study was to determine if the prevalence of symptoms suggestive of asthma in school-age children was similar in three countries with differing language and culture. To answer this question, we used the same instrument, translated appropriately, for schoolchildren in Melbourne, Australia, St. Gallen, Switzerland, and La Serena, Chile. A three page respiratory symptoms questionnaire was issued to schools for distribution to children for completion by parents and return to the school. Three age groups were selected for study, based on the average age of the school grade. Grades were used with average ages of 7, 12, and 15 years, respectively. A total of 26,628 questionnaires were issued to parents (Australia, 10,981; Switzerland, 4,464; Chile, 11,183). The response rates for each country were 89% for Australia, 97.5% for Switzerland, and 71% for Chile. The prevalence of wheezing in the last 12 months for 7 year olds was 23.1% in Melbourne, 7.4% in St. Gallen, and 26.5% in La Serena; for 12 year olds it was 20.9% in Melbourne, 6.0% in St. Gallen, and 21.1% in La Serena; for 15 year olds it was 18.6% in Melbourne, 4.5% in St. Gallen, and 17.7% in La Serene. A history of wheezing was more common in boys than girls at age 7 in Melbourne and St. Gallen, but not La Serena. This difference was less at age 12 and was not seen at age 15. Among those who had reported wheezing in the last 12 months, bronchodilator use was reported by 83% (1,611/1,948) from Melbourne, 46% (118/259) from St. Gallen, and 47% (538/1,140) from La Serena.(ABSTRACT TRUNCATED AT 250 WORDS)

Neonatal IgE levels and three different blood sampling techniques

Comparison was made of IgE and IgA levels in aspirated and gravity-collected cord blood (CB) from the umbilical vein and in capillary blood samples collected on the 4-5th day of life among 21 infants with atopic heredity. The IgA levels, but not the IgE levels, were significantly (p < 0.001) lower at days 4-5 of life than at delivery. Further, there were significantly (p < 0.05) more infants with decreasing IgA levels (20/21; 95%) than IgE levels (9/15; 60% of those with detectable IgE, i.e., > or = 0.125 kU/l). These observations, together with the highly significant correlation observed between IgE in aspirated CB samples and at 4-5 days of age, suggest active IgE synthesis during the prenatal and postnatal periods. Contamination of CB with maternal blood, defined as an increased CBIgA level (> or = 14.1 micrograms/ml), was found in 3 (14%) CB samples, all of which were gravity-collected. Of 4 CB samples (gravity-collected) with elevated IgE (i.e., > or = 0.9 kU/l), 2 had suspected maternal contamination. Therefore, aspiration of CB or capillary collection at 4-5 days of age should be preferred for allergy prediction. If gravity collection is used, contamination should be investigated by determining IgA in all CB samples with IgE concentrations exceeding the cut-off point.

Atopy and environmental factors in upper respiratory infections: an epidemiological survey on 2304 school children

Upper respiratory infections (URI) during the first years of life are mostly viral in origin. However, a number of observations suggest the influence of both predisposing and triggering factors. Atopy in particular seems to play an important role as do environmental factors. Many children with early symptoms such as blocked or runny nose are likely to become skin-positive later in life to antigens such as, e.g., D. pteronissinus. A standardized questionnaire was administered to 2304 schoolchildren in order to ascertain the URI frequency and to correlate it with family and environmental factors and with results of prick tests for main allergens in our climate (D. pteronissinus and Grasses). Results showed a wide overlapping of URI and lower respiratory illnesses (in particular, asthma), which are widely distributed in the families of patients. Passive smoking and the quality of housing are the main triggering environmental factors. In our sample, skin positivity for D. pteronissinus and Grasses largely exceeds the symptomatic portion of the whole population. It is therefore suggested that many asymptomatic children are "at risk" for allergic respiratory illness. The highest incidence of winter rhinitis in skin-negative subjects (71.7%) and the skin positivity for D. pteronissinus in patients with perennial symptoms, suggest the importance of both atopy and viral infections in the occurrence of URI. Nasal troubles are most frequent in asthmatic subjects and may be considered the actual additional symptom in asthma.

Increasing incidence of childhood coeliac disease in Sweden. Results of a national study

A survey of the incidence of coeliac disease was carried out by asking all 43 paediatric departments in Sweden to report the number of children born between 1978 and 1987 in whom coeliac disease had been diagnosed. Thirty-four departments representing a population of 7.18 million reported 1944 cases of coeliac disease among 804,935 children born between 1978 and 1987. The cumulative incidence of coeliac disease was 1.7 per 1000 live births in children born between 1978 and 1982 and doubled to 3.5 per 1000 live births in children born after 1982. The highest incidence was found in the southern and south-eastern regions of the country. The observed increase may have been influenced by changes in infant feeding practices such as the postponed age of introduction of gluten from four to six months of age and an increase in gluten content of proprietary baby foods.

Natural history of bronchial asthma in childhood. A prospective study from birth up to 12-14 years of age

In a cohort of 1654 consecutively born children followed from birth, the cumulated incidence of asthma up to 11 years was 5.3% and the prevalence 3% between 10 and 11 years of age. The asthma début was prior to 1.5 years in 1/3 and before 3 years in 1/2 of the children. Among 59 children examined at 11.5-14.5 years of age, 16 (27%) had no prevalent asthma. On the other hand, inadequate medication was found in 13, undiagnosed chest deformity in four, and wheezing in seven children. All 54 tested children including those with no prevalent asthma had a PC20 histamine less than 8 mg/ml. Tread mill test gave a significant reaction in 15 children. Animal danders and pollens were the most common allergens giving reactions at skin prick test. Compared to one earlier Swedish study an increase in mite sensitivity was found. Cord-blood IgE concentration and a positive immediate family history of atopic disease had no predictive value for the severity of asthma at this follow-up. A new total asthma score including number of days with functional impact of asthma during the last year and present medication was used for group comparisons. Children with a high score at 11.5-14.5 years had more exercise-induced asthma, more concomitant allergic diseases, earlier asthma start, more chest deformity, hyperreactivity both on tread mill and histamine challenge tests, elevated IgE, positive Phadiatop and more reactions at skin prick test, especially to animals and mites. Bronchial asthma was found more often in children born during August through October, possibly due to unsuitable indoor climate and more virus infections during their first 6 months of life. The severity of the asthma was, however, not influenced by the month of birth. No significant differences were found between boys and girls regarding the age at début, asthma severity at follow-up, or bronchial histamine threshold levels.

Asthma in schoolchildren. Factors influencing morbidity in a Swedish survey

In a survey of asthma among schoolchildren, a questionnaire was sent to the parents of 10,527 children aged 7-16 years. A group of 420 children with asthma was thereafter identified. Their asthma symptoms had caused little absence from school (none in the past 6 months in 60% of the group, and greater than 5 days in only 13%). During the preceding year 40% of the group had had more than 10 days of restricted physical activity due to asthma. Severe symptoms due to undertreatment were uncommon. Although 68 children were receiving no medication, most of them appeared to have only mild symptoms, and the parents requested aerosol inhaler in only ten cases. Symptoms at school were usually related to sporting activities. In 40% of the total asthma group the symptoms were unknown to the school health service before the survey. Dissatisfaction with the service was expressed by 24% of the parents of asthmatic children.