J. K. Peat

Changing prevalence of asthma in Australian children.

Abstract Objective : To investigate whether prevalence of asthma in children increased in 10 years. Design : Serial cross sectional studies of two populations of children by means of standard protocol. Setting : Two towns in New South Wales: Belmont (coastal and humid) and Wagga Wagga (inland and dry). Subjects : Children aged 8-10 years: 718 in Belmont and 769 in Wagga Wagga in 1982; 873 in Belmont and 795 in Wagga Wagga in 1992. Main outcome measures : History of respiratory illness recorded by parents in self administered questionnaire; airway hyperresponsiveness by histamine inhalation test; atopy by skin prick tests; counts of house dust mites in domestic dust. Results : Prevalence of wheeze in previous 12 months increased in Belmont, from 10.4% (75/718) in 1982 to 27.6% (240/873) in 1992 (P<0.001), and in Wagga Wagga, from 15.5% (119/769) to 23.1% (183/795) (P<0.001). The prevalence of airway hyperresponsiveness increased twofold in Belmont to 19.8% (173/873) (P<0.001) and 1.4-fold in Wagga Wagga to 18.1% (P<0.05). The prevalence of airway hyperresponsiveness increased mainly in atopic children only, but the prevalence of atopy was unchanged (about 28.5% in Belmont and about 32.5% in Wagga Wagga). Numbers of house dust mites increased 5.5-fold in Belmont and 4.5-fold in Wagga Wagga. Conclusions : We suggest that exposure to higher allergen levels has increased airway abnormalities in atopic children or that mechanisms that protected airways of earlier generations of children have been altered by new environmental fators.

Obesity is a risk for asthma and wheeze but not airway hyperresponsiveness

BACKGROUND A study was undertaken to assess whether the recent increases in prevalence of both asthma and obesity are linked and to determine if obesity is a risk factor for diagnosed asthma, symptoms, use of asthma medication, or airway hyperresponsiveness. METHODS Data from 1971 white adults aged 17–73 years from three large epidemiological studies performed in NSW were pooled. Doctor diagnosis of asthma ever, history of wheeze, and medication use in the previous 12 months were obtained by questionnaire. Body mass index (BMI) in kg/m2 was used as a measure of obesity. Airway hyperresponsiveness (AHR) was defined as dose of <3.9 μmol histamine required to provoke a fall in forced expiratory volume in one second (FEV1) of 20% or more (PD20FEV1). Adjusted odds ratios (OR) were obtained by logistic regression. RESULTS After adjusting for atopy, age, sex, smoking history, and family history, severe obesity was a significant risk factor for recent asthma (OR 2.04, p=0.048), wheeze in the previous 12 months (OR 2.6, p=0.001), and medication use in the previous 12 months (OR 2.83, p=0.005), but not for AHR (OR 0.87, p=0.78). FEV1 and forced vital capacity (FVC) were significantly reduced in the group with severe obesity, but FEV1/FVC ratio, peak expiratory flow (PEF), and mid forced expiratory flow (FEF25–75) were not different from the group with normal BMI. The underweight group (BMI <18.5 kg/m2) had increased symptoms of shortness of breath, increased airway responsiveness, and reduced FEV1, FVC, PEF, and FEF25–75 with similar use of asthma medication as subjects in the normal weight range. CONCLUSIONS Although subjects with severe obesity reported more wheeze and shortness of breath which may suggest a diagnosis of asthma, their levels of atopy, airway hyperresponsiveness, and airway obstruction did not support the suggestion of a higher prevalence of asthma in this group. The underweight group appears to have more significant respiratory problems with a higher prevalence of symptoms, reduced lung function, and increased airway responsiveness without an increase in medication usage. This group needs further investigation.

Effects of damp and mould in the home on respiratory health: a review of the literature

This review examines whether there is a direct or indirect relation between damp or mould in the home and respiratory health. Home dampness is thought to have health consequences because it has the potential to increase the proliferation of house‐dust mites and moulds, both of which are allergenic. The results from the many studies conducted to investigate whether damp and mould are associated with health outcomes are diffecult to compare because the methods of measuring exposures and helth outcomes have not been standardized. However, the studies that have been conducted in children are probably the most reliable because the confounding effects of active smoking or occupational exposures are absent, and because the presence of symptoms of cough and wheeze have been consistently investigated in many studies. The increased risk of children having these symptoms if the home has damp or mould is fairly small with an odds ratio that is generally in the range 1.5–3.5, these estimates being statistically significant when the sample size has been large enough. This range is consistent with the measured effects of other environmental exposures which are considered important to helth, such as environmental tobacco smoke or outdoor air pollutants. The potential benefits or reducing mould in the home have not been investigated, and the few studies that have investigated health improvement as a result of increasing ventilation or reducing damp in order to reduce house‐dust mite levels suggest that this intervention is expensive, requires a large commitment, and is unlikely to be successful in the long term. This implies that houses need to be specifically designed for primary prevention of respiratory problems associated with indoor allergen proliferation rather than using post hoc procedures to improve indoor climate and reduce allergen load as a secondary or tertiary preventive strategy.

Longitudinal changes in atopy during a 4-year period: Relation to bronchial hyperresponsiveness and respiratory symptoms in a population sample of Australian schoolchildren

A total of 380 schoolchildren living in Belmont, New South Wales, a coastal town where the predominant aeroallergens are house dust mites, were studied on three occasions at 2-year intervals. At each study, atopy was measured by skin prick tests to 13 allergens, bronchial responsiveness was measured by histamine inhalation test, and respiratory illness history was assessed by a self-administered questionnaire to parents. The age of the group was 8 to 10 years at enrollment. We found that skin wheals less than 4 mm were not associated with respiratory or allergic illness, and therefore, we defined atopy as the presence of a skin wheal of greater than or equal to 4 mm. In the sample, 24% of the children were atopic at 8 to 10 years (early-onset atopy), and an additional 15% became atopic during the study (late-onset atopy). Both early- and late-onset atopy had a close association with hay fever. Late-onset atopy was strongly associated with inconsistent reporting of symptoms. Early-onset atopy was an important risk factor for bronchial hyperresponsiveness (BHR), diagnosed asthma, and continuing symptoms of wheeze, and was a particularly important risk factor for BHR with current wheeze in late childhood years. We conclude that atopy acquired at an early age is an important predictive factor for respiratory symptoms occurring with BHR and continuing into late childhood.

Prevalence of bronchial hyperresponsiveness and asthma in a rural adult population.

The prevalence of bronchial hyperresponsiveness in adult populations is not known. To document its prevalence and distribution and to determine the factors associated with it, a random sample of the adult population of Busselton, Western Australia, was studied. Spirometric function, bronchial responsiveness to histamine, and atopic responses to skin prick tests were measured. Respiratory symptoms were determined by questionnaire. Data were obtained from 916 subjects. Of these, 876 underwent a histamine inhalation test and bronchial hyperresponsiveness to histamine (defined as a dose of histamine provoking a 20% fall in FEV1 equal to or less than 3.9 mumol) was found in 10.5%. Another 40 subjects with poor lung function were tested with a bronchodilator and 12 were found to have bronchial hyperresponsiveness (defined as a greater than 15% increase in FEV1), making the total prevalence of bronchial hyperresponsiveness 11.4%. The prevalence of current asthma, defined as bronchial hyperresponsiveness plus symptoms consistent with asthma in the last 12 months, was 5.9%. The distribution of bronchial hyperresponsiveness in the studied population was continuous. There was a significant association between it and respiratory symptoms, atopy, smoking, and abnormal lung function (p less than 0.001 for all associations). There was no association with age, sex, or recent respiratory tract infection.

Bronchial hyperresponsiveness in two populations of Australian schoolchildren. I. Relation to respiratory symptoms and diagnosed asthma

In order to explore the relationship between bronchial hyperresponsiveness (BHR) to inhaled histamine, respiratory symptoms and diagnosed asthma in children, we undertook a cross‐sectional study of 2363 Australian schoolchildren aged 8–11 years. The methods used included a self‐administered questionnaire to parents, which was shown to have a high degree of repeatability, and a histamine inhalation test to measure bronchial responsiveness (BR). The study showed that 17.9% of children had BHR, defined as a 20% fall in FEV1 at a provoking dose of histamine (PD20 FEV1) of less than 7.8 μmol. The distribution of PD20 FEV1 appeared to be continuous. Most children with PD20 FEV1 values < 1.0μmol had symptoms of asthma. However, 6.7% of children had BHR without symptoms or a previous diagnosis of asthma and 5.6% had had a diagnosis of asthma but had no BHR. Although there was a good association between BHR and respiratory symptoms, questionnaire data of wheeze and diagnosed asthma do not reflect accurately the level of BHR in the community. We conclude that cross‐sectional studies of BR to identify children with BHR probably do not reflect the prevalence of asthma in populations of children. However, the strong association between BHR and symptoms, particularly in children with severe and moderate BHR, suggests that measurements of BR in populations are useful for defining a group of children whose airways behave differently from those of the majority. Prospective studies are needed to define the level of BHR that is associated with important sequelae.

Importance of house dust mite and Alternaria allergens in childhood asthma: an epidemiological study in two climatic regions of Australia

The relation of house dust mite allergen levels to asthma and allergy was examined in two population samples of children aged 8–11 years in northern New South Wales. We studied 805 children in Lismore (a hot, humid, coastal region) and 770 in Moree/ Narrabri (a hot, dry inland region). Respiratory symptoms were measured by questionnaire, bronchial hyperresponsiveness (BHR) by histamine inhalation test, and allergy by skin‐prick tests. Current asthma was defined as the presence of both wheeze in last 12 months and BHR. Der p I levels were measured in dust from the bed and floors in the homes of 57 randomly selected children in the coastal region and of 74 inland children. Der p I levels were significantly higher by the coast (83.0 vs 11.2 μg/g, P < 0.001). House dust mite sensitivity was of similar prevalence in both regions (28.6 vs 26.4%, n.s.) but Alternaria sensitivity was higher inland (4.0 vs 15.2%P < 0.001). Bronchial responsiveness was more severe in coastal children sensitized to house dust mites and in inland children who were sensitized to Alternaria. The adjusted odds ratios for current asthma in children sensitized to house dust mites were 21.3 (95% CI 10.5, 43.2) by the coast and 2.7 (95% CI 1.3, 5.4) inland, and in children sensitized to Alternaria were 3.4 (95% CI 1.3, 9.1) in the coastal region and 5.6 (95% CI 3.1, 10.1 inland. These studies suggest that high house dust mite allergen levels in a humid, subtropical region act to significantly increase bronchial responsiveness in sensitized children, and that Alternaria allergens have a similar but less potent action in a dry, rural region.

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 andhaving cough or wheeze in the last 12 monthsand 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.

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 (χ2 trend 7.9, p = 0.005), wheeze ever (χ2 trend 10.4, p = 0.001), and cough (χ2 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.

Effect of peer led programme for asthma education in adolescents: cluster randomised controlled trial

Abstract Objective: To determine the effect of a peer led programme for asthma education on quality of life and related morbidity in adolescents with asthma. Design: Cluster randomised controlled trial. Setting: Six high schools in rural Australia. Participants: 272 students with recent wheeze, recruited from a cohort of 1515 students from two school years (mean age 12.5 and 15.5 years); 251 (92.3%) completed the study. Intervention: A structured education programme for peers comprising three steps (the “Triple A Program”). Main outcome measures: Quality of life, school absenteeism, asthma attacks, and lung function. Results: When adjusted for year and sex, mean total quality of life scores showed significant improvement in the intervention than control group. Clinically important improvement in quality of life (>0.5 units) occurred in 25% of students with asthma in the intervention group compared with 12% in the control group (P=0.01). The number needed to treat was 8 (95% confidence interval 4.5 to 35.7). The effect of the intervention was greatest in students in year 10 and in females. Significant improvements occurred in the activities domain (41% v 28%) and in the emotions domain (39% v 19%) in males in the intervention group. School absenteeism significantly decreased in the intervention group only. Asthma attacks at school increased in the control group only. Conclusion: The triple A programme leads to a clinically relevant improvement in quality of life and related morbidity in students with asthma. Wider dissemination of this programme in schools could play an important part in reducing the burden of asthma in adolescents