Increasing prevalence of asthma diagnosis and symptoms in children is confined to mild symptoms

BACKGROUND: The prevalence of childhood asthma is increasing but few studies have investigated trends in asthma severity. We investigated trends in asthma diagnosis and symptom morbidity between an eight year time period in a paired prevalence study. METHODS: All children in one single school year aged 8-9 years in the city of Sheffield were given a parent respondent questionnaire in 1991 and 1999 based on questions from the International Survey of Asthma and Allergy in Children (ISAAC). Data were obtained regarding the prevalence of asthma and wheeze and current (12 month) prevalences of wheeze attacks, speech limiting wheeze, nocturnal cough and wheeze, and exertional symptoms. RESULTS: The response rates in 1991 and 1999 were 4580/5321 (85.3%) and 5011/6021 (83.2%), respectively. There were significant increases between the two surveys in the prevalence of asthma ever (19.9% v 29.7%, mean difference 11.9%, 95% confidence interval (CI) 10.16 to 13.57, p<0.001), current asthma (10.3% v 13.0%, mean difference 2.7%, 95% CI 1.44 to 4.03, p<0.001), wheeze ever (30.3% v 35.8%, mean difference 5.7%, 95% CI 3.76 to 7.56, p<0.001), wheeze in the previous 12 months (17.0% v 19.4%, mean difference 2.5, 95% CI 0.95 to 4.07, p<0.01), and reporting of medication use (16.9% v 20%, mean difference 3.0%, 95% CI 1.46 to 4.62, p<0.001). There were also significant increases in reported hayfever and eczema diagnoses. CONCLUSIONS: Diagnostic labelling of asthma and lifetime prevalence of wheeze has increased. The current 12 month point prevalence of wheeze has increased but this is confined to occasional symptoms. The increased medication rate may be responsible for the static prevalence of severe asthma symptoms. The significant proportion of children receiving medication but reporting no asthma symptoms identified from our 1999 survey suggests that some children are being inappropriately treated or overtreated.     

Diagnostic and treatment behaviour in children with chronic respiratory symptoms: relationship with socioeconomic factors

BACKGROUND: The prevalence and severity of asthma is believed to increase with increasing socioeconomic deprivation. The relationship between asthma diagnosis, symptoms, diagnostic accuracy, and socioeconomic deprivation as determined by Townsend scores was determined in Sheffield schoolchildren. METHODS: All 6021 schoolchildren aged 8-9 years in one school year in Sheffield were given a parent respondent survey based on International Survey of Asthma and Allergies in Childhood (ISAAC) questions. RESULTS: 5011/6021 (83.2%) questionnaires were returned. Postcode data were available in 4131 replies (82.4%) and were used to assign a composite deprivation score (Townsend score). Scores were divided into five quintiles, with group 1 being least and group 5 being most deprived. A positive trend was observed from group 1 to group 5 for the prevalence of wheeze in the previous 12 months, wheeze attacks >or=4/year, nocturnal wheeze and cough (all p<0.001), cough and/or wheeze "most times" with exertion (p<0.03), current asthma (p<0.001), and significant asthma symptoms (p<0.001). No significant trend was observed for lifetime wheeze or attacks of speech limiting wheeze. There were no significant trends in the prevalence of current asthmatic children without significant symptoms (overdiagnosis) or children with significant asthma symptoms but no current asthma diagnosis (underdiagnosis) across the social groups. There was a significant negative trend in the ratio of asthma medication to asthma diagnosis from least to most deprived groups (p<0.001). CONCLUSIONS: Asthma morbidity and severity increase according to the level of socioeconomic deprivation. This may be due to differences in environment, asthma management, and/or symptom reporting. Diagnostic accuracy does not vary significantly across deprivation groups but children living in areas of least deprivation and taking asthma medication are less likely to be labelled as having asthma, suggesting diagnostic labelling bias.     

Obesity and asthma in 11-12 year old New Zealand children in 1989 and 2000

BACKGROUND: There has been a concurrent increase in the prevalence of obesity and asthma in recent years in New Zealand and other countries. METHODS: Two cross sectional surveys performed in 1989 and 2000 were used to test this association in children of mean age 11.7 years. Body mass index (BMI) was calculated as weight/height2 (kg/m2) and obesity and overweight defined according to an international standard. Standard questions were used to measure the prevalence of asthma symptoms. RESULTS: Significant increases in the prevalence of reported symptoms and disease between 1989 and 2000 were not explained by a concurrent increase in the prevalence of obesity. In 2000, multivariate analysis showed that increasing BMI standard deviation score was significantly associated with current wheeze (p=0.002), inhaled steroid use (p=0.004), and the use of any medication (p=0.001). None of the associations was significantly different for boys or girls. CONCLUSION: There is some evidence for an association of obesity with asthma symptoms and treatment but this does not explain the increasing prevalence of this disease.     

Asthma and atopy in overweight children

BACKGROUND: Obesity may be associated with an increase in asthma and atopy in children. If so, the effect could be due to an effect of obesity on lung volume and thus airway hyperresponsiveness. METHODS: Data from 5993 caucasian children aged 7-12 years from seven epidemiological studies performed in NSW were analysed. Subjects were included if data were available for height, weight, age, skin prick test results to a common panel of aeroallergens, and a measure of airway responsiveness. History of doctor diagnosed asthma, wheeze, cough, and medication use was obtained by questionnaire. Recent asthma was defined as a doctor diagnosis of asthma ever and wheeze in the last 12 months. Body mass index (BMI) percentiles, divided into quintiles per year age, were used as a measure of standardised weight. Dose response ratio (DRR) was used as a measure of airway responsiveness. Airway hyperresponsiveness was defined as a DRR of >/=8.1. Adjusted odds ratios were obtained by logistic regression. RESULTS: After adjusting for atopy, sex, age, smoking and family history, BMI was a significant risk factor for wheeze ever (OR = 1.06, p = 0.007) and cough (OR = 1.08, p = 0.001), but not for recent asthma (OR = 1.02, p = 0.43) or airway hyperresponsiveness (OR = 0.97 p = 0.17). In girls a higher BMI was significantly associated with higher prevalence of atopy (chi(2) trend 7.9, p = 0.005), wheeze ever (chi(2) trend 10.4, p = 0.001), and cough (chi(2) trend 12.3, p<0.001). These were not significant in boys. CONCLUSIONS: Higher BMI is a risk factor for atopy, wheeze ever, and cough in girls only. Higher BMI is not a risk factor for asthma or airway hyperresponsiveness in either boys or girls.     

Association between obesity and asthma in 4-11 year old children in the UK

BACKGROUND: There is evidence of a positive association between asthma and obesity in adults and in children. We investigated, in a large sample of English and Scottish primary school children, whether there is a consistent association between fatness and asthma symptoms in Britain. METHODS: A cross sectional analysis was made of 18 218 children aged 4-11 years who participated in the 1993 or 1994 surveys of the National Study of Health and Growth (NSHG). Children belonged either to English or Scottish representative samples, or an English inner city sample. Asthma attacks in the previous year, occasional wheeze, or persistent wheeze were the symptoms used in the analysis. Body mass index (BMI) and the sum of triceps and subscapular skinfolds converted to standard deviation scores (SDS) were used to assess levels of fatness. RESULTS: A total of 14 908 children (81.8%) were included in the analysis. In the multiple logistic analysis BMI and asthma (asthma attacks or wheeze) were associated in the representative sample (OR for the comparison of the 10th and 90th centiles of BMI 1.28, 95% CI 1.11 to 1.48), but sum of skinfolds was unrelated to asthma symptoms in most analyses. The association between asthma and BMI was stronger in girls than in boys in the inner city sample, but less convincingly in the representative sample. CONCLUSIONS: Levels of obesity are associated with asthma symptoms regardless of ethnicity. The association is more consistent for BMI than for sum of skinfolds, partly because obese children are more advanced in their maturation than other children. There is some evidence that, as in adults, the association is stronger in girls than in boys, but only in the multiethnic inner city sample.     

Evaluation of bronchial responsiveness to exercise in children as an objective measure of asthma in epidemiological surveys.

BACKGROUND: Exercise has been proposed as a useful challenge test for the measurement of bronchial responsiveness in community surveys of the prevalence of childhood asthma. This study aimed to develop a standardised exercise challenge in which the sensitivity to detect asthma was increased by inhalation of dry air. METHODS: Sixty four children aged 12-13 years who had reported wheeze in the past 12 months and 70 control subjects were invited to participate in an exercise challenge at school. Subjects performed eight minutes of cycle exercise while breathing dry air at a workload calculated to produce a minute ventilation of 60% maximum voluntary ventilation during the final three minutes. A fall in forced expiratory volume in one second (FEV1) of 10% or more from baseline was considered a positive test. Data on recent asthma symptoms, asthma morbidity, and use of medication were collected by parent completed questionnaires in those subjects who reported wheeze in the past 12 months. Repeatability of the exercise test was determined in a further 13 children with known asthma. RESULTS: Fifty five children (88%) who reported wheeze in the previous 12 months and 54 control subjects (77%) were studied. Nine subjects in whom baseline FEV1 was less than 75% predicted did not perform the exercise test. Technically unsatisfactory tests were obtained in five subjects. Twenty six (57%) subjects who reported wheeze and three controls (6%) had a positive exercise test, giving a sensitivity of 57% (26 of 46) and specificity of 94% (47 of 50). Estimates of the repeatability of the exercise test showed a mean difference in percentage fall in FEV1 for patients with asthma of 3.08% (95% limits of agreement -7.76% to 13.92%). CONCLUSIONS: Despite attempts to maximise the stimulus to bronchoconstriction in this exercise challenge test, its sensitivity and specificity were not improved in comparison with previous epidemiological studies of the prevalence of asthma.     

Descriptive study of cough, wheeze and school absence in childhood.

BACKGROUND: Respiratory symptoms such as cough and wheeze are associated with significant morbidity, including school absenteeism. METHODS: A respiratory questionnaire was sent to the parents of all 5727 children aged 7-9 years of age registered with 95 general practitioners in the Southampton area to determine (a) the prevalence of asthma, cough and wheeze, (b) the effects of respiratory symptoms on school absenteeism, and (c) the use of anti-asthma medication. RESULTS: A total of 4830 parents replied (response rate 86%). The 12 month prevalence of wheeze in the absence of cough was 5.5%, cough in the absence of wheeze was 10.0%, and 7.6% reported cough and wheeze; 15.2% of children had been diagnosed. Of the 4830 who replied, 12.7% were receiving bronchodilators, 0.6% xanthine derivatives, 1.7% sodium cromoglycate, and 4.1% inhaled corticosteroids. In all, 348 (7.2%) children had missed more than five days of schooling in the preceding year for respiratory symptoms, while 43 children (0.9%) had missed more than 20 days of schooling in the preceding year. Of the children who had missed more than five days of schooling, 43% reported cough and wheeze, 33% cough alone, and 16% wheeze alone in the preceding year. Compared with children who coughed, those who wheezed were significantly more likely to be diagnosed as asthmatic and to be receiving bronchodilators or inhaled corticosteroids. CONCLUSIONS: In this study, cough was the most frequently reported symptom amongst children missing more than five days of schooling per year.     

Factors influencing the relation of infant feeding to asthma and recurrent wheeze in childhood

BACKGROUND: The relationship between infant feeding and childhood asthma is controversial. This study tested the hypothesis that the relation between breast feeding and childhood asthma is altered by the presence of maternal asthma. METHODS: Healthy non-selected newborn infants (n = 1246) were enrolled at birth. Asthma was defined as a physician diagnosis of asthma plus asthma symptoms reported on > or = 2 questionnaires at 6, 9, 11 or 13 years. Recurrent wheeze (> or = 4 episodes in the past year) was reported by questionnaire at seven ages in the first 13 years of life. Duration of exclusive breast feeding was based on prospective physician reports or parental questionnaires completed at 18 months. Atopy was assessed by skin test responses at the age of 6 years. RESULTS: The relationship between breast feeding, asthma, and wheeze differed with the presence or absence of maternal asthma and atopy in the child. After adjusting for confounders, children with asthmatic mothers were significantly more likely to have asthma if they had been exclusively breast fed (OR 8.7, 95% CI 3.4 to 22.2). This relationship was only evident for atopic children and persisted after adjusting for confounders. In contrast, the relation between recurrent wheeze and breast feeding was age dependent. In the first 2 years of life exclusive breast feeding was associated with significantly lower rates of recurrent wheeze (OR 0.45, 95% CI 0.2 to 0.9), regardless of the presence or absence of maternal asthma or atopy in the child. Beginning at the age of 6 years, exclusive breast feeding was unrelated to prevalence of recurrent wheeze, except for children with asthmatic mothers in whom it was associated with a higher odds ratio for wheeze (OR 5.7, 95% CI 2.3 to 14.1), especially if the child was atopic. CONCLUSION: The relationship between breast feeding and asthma or recurrent wheeze varies with the age of the child and the presence or absence of maternal asthma and atopy in the child. While associated with protection against recurrent wheeze early in life, breast feeding is associated with an increased risk of asthma and recurrent wheeze beginning at the age of 6 years, but only for atopic children with asthmatic mothers.     

The home environment and asthma symptoms in childhood: two population based case-control studies 13 years apart

BACKGROUND: Prevalence surveys of asthma and/or wheezing among all children aged between 7 1/2 and 8 1/2 attending state and private schools in the London Borough of Croydon were conducted in February 1978 and February 1991. Two population based case-control studies drawn from the survey responders were used to investigate the association between childhood wheeze and characteristics of the home environment and to assess whether changes in these characteristics between 1978 and 1991 may have contributed to an increase in the population prevalence of wheeze among school children. METHODS: Information on exposure to potential indoor environmental risk factors was obtained from parents by home interview and compared between cases-that is, children with frequent (> or = 5) or in-frequent (1-4) attacks of asthma or wheezing in the past 12 months- and controls, with adjustment for study. Changes in exposure over time were assessed by comparing control groups. RESULTS: Between 1978 and 1991 the population prevalence odds of wheeze increased by 20% (OR 1.20; 95% CI 1.04 to 1.39). Change in parental smoking, gas cooking, pet ownership, and central heating did not appear to explain the rise. Use of non-feather pillows was positively associated with childhood wheeze even after adjusting for other risk factors and after re-coding from non-feather to feather cases thought to have changed pillow in response to symptoms (OR 1.54; 95% CI 1.13 to 2.10). The proportion of control children reportedly using non-feather pillows was 44% in 1978 and 67% in 1991. CONCLUSIONS: Increased use of non-feather pillows was the only domestic indoor exposure studied which appeared to explain a modest rise in prevalence of wheeze from 1978 to 1991. Our analysis attempts to address behavioural change in response to the child's symptoms but an artifact arising from lifelong avoidance of feather bedding in atopic families cannot be entirely discounted.


     

Effect of readmissions on increasing hospital admissions for asthma in children.

BACKGROUND--Previous studies have reported increases in the number of hospital admissions for asthma in children. The aim of the present study was to examine the effect of readmissions on these increased hospital admissions and to investigate gender differences in asthma readmissions. METHODS--The Provincial Government of Saskatchewan provides universal health care to its residents. Hospital admissions data for asthma were obtained from the Saskatchewan Health Department for all 134 hospitals in the province between 1980 and 1989. Age-specific and sex-specific hospital admission rates for asthma were calculated for each calendar year using first admissions and all admissions. The ratio between the number of readmissions and all admissions in a year was defined as the readmission rate for that year. RESULTS--Although rates based on all admissions for asthma were greater than rates based on first admissions, trends and sex differences were similar for the two rates. Despite the higher hospital admission rates for boys aged 10-14 years, girls in this age group had higher readmission rates for asthma from 1981 to 1989 (odds ratio (OR) 1.6 for girls; 95% confidence intervals (CI) 1.3 to 1.9). Similar increases were observed in readmission rates for asthma among children aged 5-9 years from 1985 to 1989 (OR 1.3 for girls; 95% CI 1.1 to 1.5). CONCLUSIONS--Readmissions for asthma do not seem to explain the increasing trend in hospital admissions for asthma in children. In children aged 10-14 years girls had higher hospital readmission rates for asthma than boys, and further studies are required to find factors related to the increased readmissions among girls in this age group.     

Comparative epidemiology of atopic and non-atopic wheeze and diagnosed asthma in a national sample of English adults

BACKGROUND: There is debate as to whether asthma has distinct atopic and non-atopic forms and whether in epidemiological studies asthma cases should be defined by a physician diagnosis or by self-reported asthma symptoms. METHODS: A total of 24,952 people aged 11 and over were surveyed as part of the 1995-6 health surveys for England. Participants were asked if they had experienced wheezing in the past year and if they had ever been given a diagnosis of asthma by a doctor. Serum total IgE and house dust mite (HDM) specific IgE were measured. RESULTS: Wheeze in the past year without an asthma diagnosis was more common in men and older age groups, whereas wheeze with an asthma diagnosis was more common in women and younger people. Both types of wheeze were more common in the lower social classes, among ex-smokers and current smokers, and in urban areas. Thirty two percent of people reporting wheezing and 22% of those with diagnosed asthma had neither raised total IgE nor HDM IgE. Among the non-atopic subjects the prevalence of wheeze rose with age and lower social class, largely due to an increase in wheeze without diagnosed asthma. In contrast, among atopic subjects there was no overall trend with age or social class, but wheeze with diagnosed asthma decreased with age. CONCLUSIONS: Clear epidemiological differences are evident between adult wheeze with and without an asthma diagnosis and between atopic and non-atopic wheeze. Subjects with diagnosed asthma are more likely to be atopic, but the results challenge the premise that adult asthma is almost always associated with some IgE mediated reaction.     

Diet and asthma in Dutch school children (ISAAC-2)

BACKGROUND: The rise in the prevalence of asthma in western societies may be related to changed dietary habits. Epidemiological studies in children have shown inverse associations of asthma related outcomes with intake of fruits, vegetables, dairy and whole grain products, and fish. In contrast to most previous studies, we used both questionnaire and clinical data to define asthma. METHODS: Intake of the abovementioned foods was studied in relation to asthma in 598 Dutch children aged 8-13 years. Dietary intake was estimated using a parent completed semi-quantitative food frequency questionnaire. Current wheeze and current asthma were defined based on questionnaire data. More complex end points were defined using information on bronchial hyperresponsiveness (BHR) and atopic sensitisation as well. Linear associations were studied using logistic regression analysis and odds ratios presented for the highest versus the lowest tertile of intake. In the final models, adjustments were made for maternal educational level, foreign descent, and total energy intake. RESULTS: The intake of whole grain products and of fish was inversely associated with asthma. Adjusted odds ratios for the independent associations with whole grains and fish were 0.46 (95% CI 0.19 to 1.10) and 0.34 (95% CI 0.13 to 0.85) for current asthma and 0.28 (95% CI 0.08 to 0.99) and 0.12 (95% CI 0.02 to 0.66) for atopic asthma with BHR. Similar results were observed for current wheeze and atopic wheeze with BHR. Intake of (citrus) fruits, vegetables, and dairy products showed no clear associations with asthma end points. CONCLUSIONS: Our findings suggest that a high intake of whole grain products and fish may have a protective effect against asthma in children.     

Worldwide trends in the prevalence of asthma symptoms: phase III of the International Study of Asthma and Allergies in Childhood (ISAAC)

BACKGROUND: Phase I of the International Study of Asthma and Allergies in Childhood (ISAAC) was designed to allow worldwide comparisons of the prevalence of asthma symptoms. In phase III the phase I survey was repeated in order to assess changes over time. METHODS: The phase I survey was repeated after an interval of 5-10 years in 106 centres in 56 countries in children aged 13-14 years (n = 304,679) and in 66 centres in 37 countries in children aged 6-7 years (n = 193,404). RESULTS: The mean symptom prevalence of current wheeze in the last 12 months changed slightly from 13.2% to 13.7% in the 13-14 year age group (mean increase of 0.06% per year) and from 11.1% to 11.6% in the 6-7 year age group (mean increase of 0.13% per year). There was also little change in the mean symptom prevalence of severe asthma or the symptom prevalence measured with the asthma video questionnaire. However, the time trends in asthma symptom prevalence showed different regional patterns. In Western Europe, current wheeze decreased by 0.07% per year in children aged 13-14 years but increased by 0.20% per year in children aged 6-7 years. The corresponding findings per year for the other regions in children aged 13-14 years and 6-7 years, respectively, were: Oceania (-0.39% and -0.21%); Latin America (+0.32% and +0.07%); Northern and Eastern Europe (+0.26% and +0.05%); Africa (+0.16% and +0.10%); North America (+0.12% and +0.32%); Eastern Mediterranean (-0.10% and +0.79%); Asia-Pacific (+0.07% and -0.06%); and the Indian subcontinent (+0.02% and +0.06%). There was a particularly marked reduction in current asthma symptom prevalence in English language countries (-0.51% and -0.09%). Similar patterns were observed for symptoms of severe asthma. However, the percentage of children reported to have had asthma at some time in their lives increased by 0.28% per year in the 13-14 year age group and by 0.18% per year in the 6-7 year age group. CONCLUSIONS: These findings indicate that international differences in asthma symptom prevalence have reduced, particularly in the 13-14 year age group, with decreases in prevalence in English speaking countries and Western Europe and increases in prevalence in regions where prevalence was previously low. Although there was little change in the overall prevalence of current wheeze, the percentage of children reported to have had asthma increased significantly, possibly reflecting greater awareness of this condition and/or changes in diagnostic practice. The increases in asthma symptom prevalence in Africa, Latin America and parts of Asia indicate that the global burden of asthma is continuing to rise, but the global prevalence differences are lessening.     

Comparison of the prevalence of asthma among Asian and European children in Southampton.

BACKGROUND: Primary health care workers have reported an impression that asthma is commoner among Asian than European children, and a cross sectional survey was designed to compare the prevalence in Asian and European children. METHODS: The survey was carried out in children aged 7-11 in eight primary schools in Southampton. Four schools contained predominantly children of European ancestry, two contained predominantly Asian children, and two contained a mixture of ethnic groups. Data were collected by means of parent completed questionnaire on recent asthma symptoms, diagnosis, morbidity, and treatment from 759 European and 274 Asian children. RESULTS: The prevalence of reported wheeze in the previous 12 months was higher among European (19.6%) than Asian children (11.9%), as was the prevalence of a night cough (European 64.2%, Asian 42.3%). Although the prevalence of diagnosed asthma was higher in European (12%) than Asian (6.2%) children, a slightly higher proportion of Asian than European children with current wheeze had visited their doctor (European 66.9%, Asian 78.1%, not significant) or been admitted to hospital for wheezing (European 4.8%, Asian 6.5%) in the previous 12 months. CONCLUSIONS: This study failed to demonstrate a higher prevalence of asthma among Asian than European children in Southampton.     

Geographical and socioeconomic variation in the prevalence of asthma symptoms in English and Scottish children.

BACKGROUND: There has been controversy over the relation between poverty and asthma in the community. The aim of this analysis was to disentangle geographical and socioeconomic variation in asthma symptoms. METHODS: The analysis is based on parental reports of symptoms from data collected in 1990 and 1991. Children aged 5-11 years from three populations (English representative sample, Scottish representative sample, and an English inner city sample) were included. Of 17 677 eligible children, between 14 490 (82.0%) and 15 562 (88.0%) children were available for analysis according to symptom group. RESULTS: Wheezy symptoms were less prevalent in the Scottish sample than in the English samples and asthma attacks were most prevalent in the English representative sample. Asthma attacks were less prevalent in inner city areas than in the English representative sample (OR 0.79, 95% CI 0.66 to 0.95), but persistent wheeze and other respiratory symptoms were more prevalent (OR 1.95, 95% CI 1.65 to 2.32 and OR 1.67, 95% CI 1.52 to 1.84, respectively). The prevalence of persistent wheeze was higher in children whose father's social class was low and in those living in areas with a high Townsend score (an index of poverty) than in other children (p<0.001). Of the 14 areas with the highest Townsend score, 13 had an OR above 1 and six had an OR significantly higher than the reference area. CONCLUSIONS: Persistent wheeze is more prevalent in poor areas than in less deprived areas. This may indicate that poverty is associated with severe asthma or that a high percentage of persistent asthma symptoms in inner city areas are unrecognised and untreated.     

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

BACKGROUND: Although many children with asthma may have a remission as they grow and other children who did not have asthma may develop asthma in adult life, knowledge about the factors that influence the onset and prognosis of asthma during adolescence and young adulthood is very limited. METHODS: A cohort of 8-10 year old children (n=718) living in Belmont, New South Wales, Australia were surveyed six times at 2 yearly intervals from 1982 to 1992, and then again 5 years later in 1997. From this cohort, 498 subjects had between three and seven assessments and were included in the analysis. Atopy, airway hyperresponsiveness (AHR), and wheeze in the last 12 months were measured at each survey. Late onset, remission, and persistence were defined based on characteristics at the initial survey and the changes in characteristics at the follow up surveys. RESULTS: The proportion of subjects with late onset atopy (13.7%) and wheeze (12.4%) was greater than the proportion with remission of atopy (3.2%) and wheeze (5.6%). Having atopy at age 8-12 years (OR 2.8, 95% CI 1.5 to 5.1) and having a parental history of asthma (OR 2.0, 95% CI 1.02 to 4.13) were significant risk factors for the onset of wheeze. Having AHR at age 8-12 years was a significant risk factor for the persistence of wheeze (OR 4.3, 95% CI 1.3 to 15.0). Female sex (OR 1.9, 95% CI 1.01 to 3.60) was a significant risk factor for late onset AHR whereas male sex (OR 1.9, 95% CI 1.1 to 2.8) was a significant risk factor for late onset atopy. CONCLUSIONS: The onset of AHR is uncommon during adolescence, but the risk of acquiring atopy and recent wheeze for the first time continues during this period. Atopy, particularly present at the age of 8-10 years, predicts the subsequent onset of wheeze.     

Asthma in preschool children: prevalence and risk factors

BACKGROUND: The prevalence of asthma in children has increased in many countries over recent years. To plan effective interventions to reverse this trend we need a better understanding of the risk factors for asthma in early life. This study was undertaken to measure the prevalence of, and risk factors for, asthma in preschool children. METHODS: Parents of children aged 3-5 years living in two cities (Lismore, n=383; Wagga Wagga, n=591) in New South Wales, Australia were surveyed by questionnaire to ascertain the presence of asthma and various proposed risk factors for asthma in their children. Recent asthma was defined as ever having been diagnosed with asthma and having cough or wheeze in the last 12 months and having used an asthma medication in the last 12 months. Atopy was measured by skin prick tests to six common allergens. RESULTS: The prevalence of recent asthma was 22% in Lismore and 18% in Wagga Wagga. Factors which increased the risk of recent asthma were: atopy (odds ratio (OR) 2.35, 95% CI 1.49 to 3.72), having a parent with a history of asthma (OR 2.05, 95% CI 1.34 to 3.16), having had a serious respiratory infection in the first 2 years of life (OR 1.93, 95% CI 1.25 to 2.99), and a high dietary intake of polyunsaturated fats (OR 2.03, 95% CI 1.15 to 3.60). Breast feeding (OR 0.41, 95% CI 0.22 to 0.74) and having three or more older siblings (OR 0.16, 95% CI 0.04 to 0.71) decreased the risk of recent asthma. CONCLUSIONS: Of the factors tested, those that have the greatest potential to be modified to reduce the risk of asthma are breast feeding and consumption of polyunsaturated fats.     

Can the increase in body mass index explain the rising trend in asthma in children?

BACKGROUND: The reported association between asthma and obesity and the documented rise in each over time have led to suggestions that rising obesity might explain the increase in the prevalence of asthma. Trends in both in British children participating in the National Study of Health and Growth were marked from 1982 to 1994. METHODS: Odd ratios for trends in asthma and symptoms in 8 and 9 year old children were calculated with and without adjustment for body mass index (BMI). RESULTS: In a representative sample of white children the odds ratio per year for asthma was 1.09 (95% CI 1.07 to 1.11) before and after adjustment for BMI for boys and 1.09 (95% CI 1.07 to 1.12) and 1.09 (95% CI 1.05 to 1.12), respectively, for girls. Unadjusted and adjusted odds ratios were also virtually identical for wheeze and "asthma or bronchitis". The lack of effect of adjustment was due to a change in the association between BMI and symptoms with time. CONCLUSIONS: Trends in overweight and obesity do not explain the increase in asthma. The evidence points towards the association between asthma and obesity being of recent origin. This may be explained by obesity being a marker of recent lifestyle differences now associated with both asthma and overweight.     

Trends in the prevalence of asthma in Scottish and English primary school children 1982-92.

BACKGROUND--Some doubts exist as to whether the increase in the prevalence of asthma is real or an artefact. The 10 year trend of asthma up to 1993 in England and Scotland was therefore assessed. METHODS--Information on asthma and bronchitis attacks, occasional wheeze, and persistent wheeze in the last 12 months, was obtained using a self administered questionnaire completed by the parents. Exactly the same questions were asked in 14 study areas in Scotland and 22 study areas in England in 1982 or 1983 and in 1992 or 1993 in 5-11 year old children. RESULTS--The numbers of children with data for all respiratory illness were 5556 (85.2%) and 5801 (87.1%) in England and 3748 (90.4%) and 3738 (90.4%) in Scotland in 1982 and 1992, respectively. There was a significant increase in asthma attacks (approximately three times more in 1992 than in 1982) and occasional wheeze (30-60% more in 1992 than in 1982) in both sexes in England and Scotland. Persistent wheeze also increased in both countries, but the increase was significant only in England (30-40% more in 1992 than in 1982). CONCLUSIONS--The study coincides with others that suggest that the increased prevalence of asthma may be due, in part, to changes in diagnostic behaviour. However, the continuing increase of persistent wheeze in the total sample suggests that part of the increase is real. There was no difference in the increase of persistent wheeze between Scotland and England, but the trend was only significant in England.     

Asthma prevalence in 1973, 1988 and 2003

BACKGROUND: A study was undertaken to see whether the prevalence of asthma has changed since a survey was conducted in 1988, using the same methods that showed an increase during the previous 15 years. METHODS: A survey of 12 year old children was conducted in schools in South Wales where surveys had taken place in 1973 and 1988. The survey comprised a parentally completed questionnaire and an exercise challenge test, performed when no bronchodilator had been recently used. RESULTS: In 1973, 1988, and 2003, questionnaires were obtained for 817, 965 and 1148 children, respectively; the exercise test was performed by 812, 960 and 1019 children, respectively. The prevalence of reported wheeze in the last year rose during each 15 year period (9.8%, 15.2%, 19.7%), with an even steeper rise in reported asthma ever (5.5%, 12.0%, 27.3%). There was a continued increase in wheeze attributed to running, in terms of all children (5.8%, 10.5%, 16.0%) and also as the proportion of those with a history of wheeze (34.1%, 47.0%, 57.3%). The use of inhaled corticosteroids (not available in 1973) increased fourfold between 1988 and 2003. The prevalence of exercise induced bronchoconstriction rose between 1973 and 1988 but had declined by 2003. CONCLUSIONS: The rise in the prevalence of asthmatic symptoms has continued since 1988. This appears to conflict with a reported recent decline, unless asthma prevalence peaked in the 1990s. The decline in exercise induced bronchoconstriction is probably attributable to better control of the disease as more children are now using inhaled corticosteroids as preventive treatment.