EVIPNet Americas: Overcoming barriers to integrate scientific evidence and health policies in the Americas

In response to the challenges created by the COVID-19 pandemic to the role of evidence in policymaking, the World Health Organization (WHO) in collaboration with the Pan American Health Organization (PAHO) convened the first Global Evidence-to-Policy (E2P) Summit.This summit brought together different stakeholders from all WHO Regions to identify common challenges, share lessons learned, and provide recommendations to support evidence-informed decisionmaking as a catalyst for policy and societal changes

Effect of Tricalcium Phosphate and Calcium Sucrose Phosphate on the Inhibition of Streptococcus mutans: An In Vivo Study.

AIM: To determine the efficacy of tricalcium phosphate (TCP) and calcium sucrose phosphate (CSP) on the inhibition of Streptococcus mutans (SM). MATERIALS AND METHODS: Thirty healthy children between 13 and 18 years of age were divided into two groups of 15 each; Group I receiving TCP-containing cream and Group II receiving calcium sucrose phosphate-containing cream. On the first day of the study, 30 minutes after breakfast, baseline plaque samples were taken from the buccal surface of first mandibular permanent molar using a sterile wedge which was immediately transferred to sterile container containing 1 mL of saline, and were subjected to microbiological examination. On the following days, both the creams were applied to the respective groups. On the 16th day, plaque samples were collected from the same site, and colony forming units were recorded using agar plate as a culture medium. RESULTS: The mean of S. mutans count before application of TCP-containing paste was 16.27 cfu per mL and before calcium sucrose phosphate-containing paste was 15.33 cfu per mL. The mean after application of TCP-containing paste and calcium sucrose phosphate-containing paste was 3.53 and 9.87 cfu per mL, respectively. And, there was a statistically significant difference found within the groups. CONCLUSION: Both TCP and CSP have an inhibitory effect on S. mutans. CLINICAL SIGNIFICANCE: This can be an effective preventive tool for children with high caries risk and even for special child. Both TCP and CSP deposit the mineral reservoir in plaque and saliva; it may help resist the future cariogenic challenges.

The cost-effectiveness of removing television advertising of high-fat and/or high-sugar food and beverages to Australian children.

OBJECTIVE: To model the health benefits and cost-effectiveness of banning television (TV) advertisements in Australia for energy-dense, nutrient-poor food and beverages during children's peak viewing times. METHODS: Benefits were modelled as changes in body mass index (BMI) and disability-adjusted life years (DALYs) saved. Intervention costs (AUD$) were compared with future health-care cost offsets from reduced prevalence of obesity-related health conditions. Changes in BMI were assumed to be maintained through to adulthood. The comparator was current practice, the reference year was 2001, and the discount rate for costs and benefits was 3%. The impact of the withdrawal of non-core food and beverage advertisements on children's actual food consumption was drawn from the best available evidence (a randomized controlled trial of advertisement exposure and food consumption). Supporting evidence was found in ecological relationships between TV advertising and childhood obesity, and from the effects of marketing bans on other products. A Working Group of stakeholders provided input into decisions surrounding the modelling assumptions and second-stage filters of 'strength of evidence', 'equity', 'acceptability to stakeholders', 'feasibility of implementation', 'sustainability' and 'side-effects'. RESULTS: The intervention had a gross incremental cost-effectiveness ratio of AUD$ 3.70 (95% uncertainty interval (UI) $2.40, $7.70) per DALY. Total DALYs saved were 37 000 (95% UI 16,000, 59,000). When the present value of potential savings in future health-care costs was considered (AUD$ 300m (95% UI $130m, $480m), the intervention was 'dominant', because it resulted in both a health gain and a cost offset compared with current practice. CONCLUSIONS: Although recognizing the limitations of the available evidence, restricting TV food advertising to children would be one of the most cost-effective population-based interventions available to governments today. Despite its economic credentials from a public health perspective, the initiative is strongly opposed by food and advertising industries and is under review by the current Australian government.

A new approach to assessing the health benefit from obesity interventions in children and adolescents: the assessing cost-effectiveness in obesity project.

OBJECTIVE: To report on a new modelling approach developed for the assessing cost-effectiveness in obesity (ACE-Obesity) project and the likely population health benefit and strength of evidence for 13 potential obesity prevention interventions in children and adolescents in Australia. METHODS: We used the best available evidence, including evidence from non-traditional epidemiological study designs, to determine the health benefits as body mass index (BMI) units saved and disability-adjusted life years (DALYs) saved. We developed new methods to model the impact of behaviours on BMI post-intervention where this was not measured and the impacts on DALYs over the child's lifetime (on the assumption that changes in BMI were maintained into adulthood). A working group of stakeholders provided input into decisions on the selection of interventions, the assumptions for modelling and the strength of the evidence. RESULTS: The likely health benefit varied considerably, as did the strength of the evidence from which that health benefit was calculated. The greatest health benefit is likely to be achieved by the 'Reduction of TV advertising of high fat and/or high sugar foods and drinks to children', 'Laparoscopic adjustable gastric banding' and the 'multi-faceted school-based programme with an active physical education component' interventions. CONCLUSIONS: The use of consistent methods and common health outcome measures enables valid comparison of the potential impact of interventions, but comparisons must take into account the strength of the evidence used. Other considerations, including cost-effectiveness and acceptability to stakeholders, will be presented in future ACE-Obesity papers. Information gaps identified include the need for new and more effective initiatives for the prevention of overweight and obesity and for better evaluations of public health interventions.

Implementation of evidence based guidelines for paediatric asthma management in a teaching hospital.

AIMS: To evaluate a systematic approach to the development and implementation of evidence based asthma management guidelines. METHODS: Comparative study of children (2-18 years) with acute asthma; a control cohort (cohort 1) was recruited before implementation of the guidelines and two cohorts were recruited after implementation (cohorts 2 and 3). RESULTS: There was no difference in the proportion of patients who reattended in the six months following initial presentation for cohort 1 (21.5%), cohort 2 (27.8%), or cohort 3 (25.4%) and no difference in readmission rates (11.4%, 11.3%, 11.0% respectively). There was no difference in measures of asthma morbidity between the cohorts at 3 and 6 months across three domains: interval symptoms, exercise limitation, and bronchodilator use. Of those who did not have a management plan before presentation, one was provided to 46.9% of cohort 1, 74.8% of cohort 2, and 81.1% of cohort 3. There was no difference comparing cohort 2 or cohort 3 with cohort 1 regarding quality of life for either the subjects or their parents. CONCLUSIONS: Implementation of our evidence based guidelines was associated with the improved provision of asthma management plans, but there was no effect on reattendance or readmission to hospital, asthma morbidity, or quality of life. Future efforts to improve asthma management should target specific components of asthma care.

Trends and geographic variations in hospital admissions for asthma in Victoria. Opportunities for targeted interventions.

OBJECTIVE: To describe variations in rates of hospital admissions for asthma in Victoria as health indicators of quality of primary care services and access. DESIGN: Routine analyses of age and sex standardised admission rates of asthma in rural and metropolitan Victoria from 1993-1994 to 1999-2000. RESULTS: There were 10,079 admissions for asthma, with an average of 2.71 bed days in 1999-2000. The admission rate for asthma decreased from 3.1/1000 (95% CI: 3.1-3.2) in 1993-1994 to 2.2/1000 (2.1-2.2) in 1999-2000, with a 37% reduction in rural regions and 26% in metropolitan regions. Sixteen primary care partnerships (small areas), 13 of them rural, had significantly higher admission rates than the Victorian average. CONCLUSION: Although asthma hospital admission rates are falling faster in rural than metropolitan areas, rural areas still have higher admission rates with significant variation between small areas.

Asthma in children: gaps between current management and best practice.

OBJECTIVES: To determine the extent to which steps three to six of the Australian six-step asthma management plan are being implemented in the community and to identify barriers to the adoption of best practice asthma management. METHODS: A cross-sectional descriptive study was conducted at the Royal Children's Hospital and Sunshine Hospital, Melbourne. Two hundred and thirty-one 2-5-year old children who visited the emergency department for asthma were enrolled in the study. Main outcome measures were frequency of asthma management practices and barriers, as measured by parent-completed questionnaire. RESULTS: Gaps: 51% of parents do not feel they have enough information about asthma triggers, more than 60% of children with persistent or frequent episodic asthma are not using regular preventive medication, 48% do not have a written action plan, 39% have not had their asthma reviewed in the last 6 months, and 38% of parents do not feel that they have enough information about their child's asthma. Areas where current practice was close to best practice: 83% of doctors had talked to parents about what causes or 'triggers' their child's asthma, less than 1% of children are using puffers without a spacer, 83% of parents who had an action plan used it for the current visit to the emergency department. CONCLUSIONS: Large gaps still exist between current management and best practice in this group of emergency department attenders. Improvements in asthma management could be achieved if the child's asthma doctor requested review visits for asthma, provided an action plan and followed best practice in relation to asthma medications.

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.

Interventions for educating children who have attended the emergency room for asthma.

BACKGROUND: Asthma is one of the most common reasons for paediatric admissions to hospital, with substantial cost to the community. There is some evidence to suggest that many hospital admissions could be prevented with effective education about asthma and its management. OBJECTIVES: To conduct a systematic review of the literature in order to identify whether asthma education leads to improved health outcomes in children who have attended the emergency department for asthma. SEARCH STRATEGY: We searched the Cochrane Airways Group trials register, including Medline, Embase, and Cinahl databases, and reference lists of trials and review articles. SELECTION CRITERIA: Randomised controlled trials or controlled clinical trials of asthma education for children who had attended the emergency department for asthma, with or without hospitalisation, within the previous 12 months. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed trial quality and extracted data. Study authors were contacted for additional information. MAIN RESULTS: Eight trials involving 1407 patients were included, in all the education was provided by nurses or researchers. Compared to control (usual care or lower intensity education) education did not reduce subsequent emergency department (ED) visits [4 trials; relative risk (RR)= 0.87, 95% confidence interval (CI) 0.37 to 2.08], hospital admissions [5 trials; RR=0.74, 95% CI 0.38 to 1.46] and unscheduled doctor visits [5 trials; RR= 0.74, 95% CI 0.49 to 1.12). Each analysis showed evidence of heterogeneity among the studies (P<0.01). Subgroup analyses by the overall difference in scale of intervention between treatment and control groups (comprehensive programme versus information only) or the timing of the intervention/recruitment (early versus delayed) gave similar results to the main analysis and still revealed significant heterogeneity between trials. REVIEWER'S CONCLUSIONS: On the basis of the published trials, there is no firm evidence to support the use of asthma education for children who have attended the emergency department for asthma as a means of reducing subsequent ED visits, hospital admissions or unscheduled doctor visits. Some trials appeared to show clear evidence of benefit, but reasons for differences between these and the negative studies is not clear. More research is required

Daycare attendance before the age of two protects against atopy in preschool age children.

Early attendance at daycare has been shown to protect against atopy, as defined by a positive skin prick test. One proposed hypothesis for this association is that early exposure to other children protects against atopy by facilitating the spread of infections among children. An alternative hypothesis is that children attending daycare centers have less atopy due to lower levels of exposure to indoor allergens. Our aim was to determine whether attendance at daycare before age 2 years protects against atopy in Australian preschool age children and to test the two alternative hypotheses, as well as a number of potential confounding factors. We conducted a cross-sectional study of children aged 3-5 years living in one humid coastal city (Lismore, n = 286) and one dry, inland city (Wagga Wagga, n = 364) in New South Wales, Australia, in 1995. Atopy was assessed by skin prick tests to six common allergens. Daycare attendance and other possible risk factors for atopy were measured by a parent-completed questionnaire. Children who attended daycare before age 2 years had a reduced risk of atopy at 3-5 years. The greatest effect was seen in children who attended a daycare center (odds ratio (OR), 0.26; 95% CI, 0.14-0.50) rather than family daycare (OR, 0.66; 95% CI, 0.41-1.04). The results of this study do not support either of the proposed hypotheses, nor can the effect be explained by any of the other potential confounders measured. Further work is needed to determine the exposure that is responsible for the protective effect of daycare attendance on atopy.

Public health and preventive healthcare in children: current practices of Victorian GPs and barriers to participation.

OBJECTIVES: To assess general practitioners' attitudes to and involvement in child public health activities and identify barriers affecting their participation. DESIGN: Cross-sectional written questionnaire survey of a representative sample of actively practising GPs. SETTING: General practices in the State of Victoria. PARTICIPANTS: 840 GPs returned questionnaires (65% response rate), and, of these, 792 (94%) saw children 0-12 years. MAIN OUTCOME MEASURES: Attitudes to and involvement in public health promotion; predictive factors for GPs' involvement. RESULTS: The odds of GPs' involvement in child public health issues were increased by being female (odds ratio [OR], 1.88), receiving basic medical qualifications outside Australia (OR, 1.55), attending continuing education and postgraduate training (OR, 1.60), and having confidence in dealing with newborns and infants (OR, 1.93) and preschool children (OR, 2.94) (both P < 0.05). Older GPs, compared with younger GPs, had significantly lower odds of involvement (P < 0.01). After adjustment, GPs had higher odds of involvement if they agreed it was important for them to take part in health promotion, or in screening and surveillance (OR, 2.76 and 1.94, respectively; P < or = 0.05); and lower odds if they agreed that screening and surveillance should be mainly done by maternal and child health nurses (OR, 0.60). The most common barriers to involvement were insufficient time, inadequate financial reimbursement for long consultations, inappropriateness of raising these issues in children presenting with illness, and lack of community resources. CONCLUSIONS: Increasing GPs' involvement in child public health will require attention to barriers (time, remuneration and perceived appropriateness), continuing education and changes in workforce composition and patterns.

Asthma and other atopic diseases in Australian children. Australian arm of the International Study of Asthma and Allergy in Childhood.

OBJECTIVE: To determine the prevalence of asthma, eczema and allergic rhinitis in Australian schoolchildren using the protocol of the International Study of Asthma and Allergy in Childhood (ISAAC). DESIGN: Questionnaire-based survey. SETTING: Melbourne, Sydney, Adelaide (in winter-spring, 1993) and Perth (in winter-spring, 1994). SUBJECTS: All children in school years 1 and 2 (ages 6-7 years) or in year 8 (ages 13-14 years), attending a random sample of 272 schools, stratified by age and city. MAIN OUTCOME MEASURES: Parent-reported (for 6-7 year olds) or self-reported (for 13-14 year olds) symptoms of atopic disease in the previous 12 months, or ever; treatment of asthma; and country of birth. RESULTS: 10,914 questionnaires were completed for 6-7 year olds and 12,280 for 13-14 year olds (84% and 94% response rates, respectively). Prevalence of wheeze in the past 12 months was 24.6% for the 6-7 year olds and 29.4% for the 13-14 year olds, and, among 6-7 year olds, was significantly higher in boys (27.4%) than girls (21.7%). Children born in Australia were more likely to report current wheeze than those born elsewhere (6-7 year olds: odds ratio [OR], 1.82; 95% confidence interval [CI] 1.55-2.15; and 13-14 year olds: OR, 1.88; 95% CI, 1.68-2.11). Prevalences of current eczema and allergic rhinitis were 10.9% and 12.0%, respectively, for the 6-7 year olds, and 9.7% and 19.6%, respectively, for the 13-14 year olds. Asthma, eczema and rhinitis coexisted in 1.8% of 6-7 year olds and 2.8% of 13-14 year olds. CONCLUSION: This study provides evidence that asthma prevalence in Australian schoolchildren is continuing to increase and is higher among Australian-born children than among those born elsewhere. Asthma, eczema and allergic rhinitis coexist to a lesser extent than expected. These results form the basis for future Australian and international comparisons.

Factors that affect normal lung function in white Australian adults.

STUDY OBJECTIVE: To classify abnormal lung function in epidemiologic studies, we first calculated "normal" values using data from Australian white adults. We then examined the effects of airway hyperresponsiveness (AHR), respiratory symptoms, current and past asthma, and current smoking on spirometric function. METHODS: A large random sample of 1,527 adults aged 18 to 73 years was studied. We measured respiratory symptoms and smoking history by questionnaire and AHR by histamine inhalation test. RESULTS: Data from 729 "normal" subjects (asymptomatic nonsmokers without AHR) were used to obtain regression models for FVC, FEV1, peak expiratory flow rate, and forced expiratory flow between 25% and 75% of FVC. The R2 values were 0.76, 0.74, 0.58, and 0.29, respectively. The presence of AHR reduced FVC by 0.1 L and FEV1 by 0.2 L, on average. Subjects with asthma-related symptoms had a mean reduction in FVC of 0.1 L for both genders and in FEV1 of 0.08 L for women and 0.2 L for men. Current asthma reduced FVC by 0.3 L, on average, and FEV1 by 0.5 L for women and 0.6 L for men. The FEV1 was reduced by 0.002 L per cigarette smoked daily. CONCLUSION: Recent symptoms, AHR, and current smoking were all important predictors of reduced lung function.

Consumption of oily fish and childhood asthma risk.

OBJECTIVE: To investigate the association between diet and airway disease in children in the light of epidemiological studies suggesting that consumption of fish more than once a week reduces the risk of developing airway hyperresponsiveness (AHR). DESIGN: Diet was assessed by a detailed food frequency questionnaire and airway disease by respiratory symptoms or airway responsiveness to exercise. METHODS: A questionnaire, containing questions about the frequency of eating more than 200 foods, was sent to the parents of 574 children in whom we had measured recent wheeze (by questionnaire), AHR (by exercise) and atopy (by skin prick tests) six months before this study. We defined current asthma as the presence of both recent wheeze and AHR. RESULTS: Response rate to the questionnaire was 81.5% (n=468.) After adjusting for confounders such as sex, ethnicity, country of birth, atopy, respiratory infection in the first two years of life and a parental history of asthma or smoking, children who ate fresh, oily fish (>2% fat) had a significantly reduced risk of current asthma (odds ratio, 0.26; 95% confidence interval, 0.09-0.72; P<0.01). No other food groups or nutrients were significantly associated with either an increased or reduced risk of current asthma. CONCLUSION: These data suggest that consumption of oily fish may protect against asthma in childhood.

House dust mite allergens. A major risk factor for childhood asthma in Australia.

If house dust mite allergen (Der p I) is an important cause of asthma, there should be a direct relationship between level of exposure to this allergen and asthma severity. To examine this, we studied six large random samples of children in different regions of New South Wales, Australia. We measured recent wheeze by questionnaire, airway hyperresponsiveness (AHR) by histamine inhalation test and sensitization to house dust mites by skin prick tests. Current asthma was defined as the presence of recent wheeze and AHR. We measured Der p I levels in the beds of approximately 80 children in each region. In regions where Der p I levels were high, more children were sensitized to house dust mites, and these children had significantly more AHR and recent wheeze. After adjusting for sensitization to other allergens, we found that the risk of house dust mite-sensitized children having current asthma doubled with every doubling of Der p I level. There was a modest correlation between AHR and Der p I exposure in individuals (r = 0.23, p < 0.03). These data suggest that house dust mite allergens are an important cause of childhood asthma and that reducing exposure to these allergens could have a large public health benefit in terms of asthma prevention.

Prevalence and severity of childhood asthma and allergic sensitisation in seven climatic regions of New South Wales.

OBJECTIVE: To compare the prevalence and severity of asthma and of allergic sensitisation in children in different regions. We hypothesised that regions with different standardised hospital admission rates would have different prevalences of childhood asthma and that diverse climates would result in a range of sensitisations to different allergens. DESIGN AND SETTING: We studied large random population samples of children in seven regions in New South Wales (NSW) in 1991-1993. Hospitalisation rates were obtained from NSW Department of Health data. PARTICIPANTS: 6394 children aged 8-11 years. OUTCOME MEASURES: History of respiratory symptoms by self-administered questionnaire; airway hyperresponsiveness by histamine inhalation test; and sensitisation to allergens by skin-prick tests. RESULTS: Children in all regions had a high prevalence of recent wheeze (22%-27%), of diagnosed asthma (24%-38%) and of use of asthma medications (22%-30%), but no region was consistently higher or lower for all measurements. The prevalence of current asthma in children living in three coastal regions (where sensitisation to house-dust mites was high) and in the far west (where sensitisation to alternaria was high) was 12%-13%, which was significantly higher than the prevalence of 7%-10% in children living in three inland regions (where sensitisation to these allergens was lower) (P < 0.01). CONCLUSIONS: We found significant variations in the prevalence and severity of childhood asthma in NSW. The prevalence of hospitalisations, diagnosed asthma, recent symptoms and medication use may relate to different regional diagnostic patterns, whereas current asthma prevalence may relate to different levels of allergic sensitisation.

An exercise challenge for epidemiological studies of childhood asthma: validity and repeatability.

We assessed the validity, repeatability and practicality of a standardized exercise challenge protocol for measuring airway responsiveness in epidemiological studies of asthma in children aged 8-11 yrs. The construct validity of the exercise challenge was assessed by comparing response to exercise with other measures of asthma, i.e. wheeze frequency, diagnosed asthma, asthma medication use, atopy and urgent doctor visits (n = 802), and by comparison with response to histamine challenge (n = 201). Repeatability was assessed by comparison of responsiveness to two exercise challenges within 3 days (n = 113), and practicality was assessed by measurement of consent, compliance and throughput rates (n = 802). There was a significant relationship between frequency of wheeze attacks and % fall in forced expiratory volume in one second (FEV1) to exercise. The correlation (r) between % fall in FEV1 to exercise challenge and dose-response ratio to histamine challenge was 0.59. The repeatability of the exercise challenge was +/- 12% fall in FEV1. Consent and compliance rates for exercise challenge were 78 and 99%, respectively, and the mean throughput rate was 45 children per school day for a team of seven researchers. In conclusion, this exercise challenge was found to have good validity and to be reliable and practical. Thus, this challenge could be used as a standardized epidemiological tool to investigate the prevalence, aetiology and mechanisms of asthma.

Effect of passive smoking, asthma, and respiratory infection on lung function in Australian children.

We have calculated normal standards for lung function of Australian children and have estimated the effects on lung function of passive smoking, current asthma, past asthma, and a current respiratory infection. Three cross-sectional samples of children in school years 3-5 (aged 8-11 years) were studied. The 2765 children were from two rural regions of NSW and from the city of Sydney. Details of passive smoking and respiratory illness were collected by a questionnaire sent to parents. Forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), peak expiratory flow rate (PEFR), and forced mid-expiratory flow rate (FEF25-75%) were used as measures of lung function. Airway responsiveness was assessed by histamine inhalation test. Data from 1278 "normal" children were used in regression analysis to calculate prediction models for lung function. Passive smoking was associated with reduced FEV1, PEFR, and FEF25-75%. Children with current asthma had reduced FEV1 and FEF25-75% and children with past asthma had reduced FEF25-75%. Children with a current respiratory infection had reduced FVC, FEV1, PEFR, and FEF25-75%. The effects of these deficits on the future lung function of these children is not known but is likely to be important.

An exercise challenge protocol for epidemiological studies of asthma in children: comparison with histamine challenge.

We investigated whether an exercise challenge protocol is suitable for measuring bronchial responsiveness in epidemiological studies of asthma in children, and determined its comparability with histamine challenge. The exercise challenge was 6 minutes of outdoor, free-range running at 85-90% of maximum heart rate, measured by heart rate monitor. Nose clips were worn. Distance run was measured to estimate oxygen consumption. Water content of the inspired air was < 10 mg H2O.l-1. Histamine challenge was by the rapid method. We used questionnaires to measure respiratory symptoms and skin prick tests to measure atopy. A total of 96 children aged 8-11 years were studied. Bronchial hyperresponsiveness (BHR) to exercise challenge was defined as a fall in forced expiratory volume in one second (FEV1) of 13% of greater. Eleven children had a positive response to exercise challenge and 11 to histamine challenge but 12 responded to one challenge and not to the other. The correlation coefficient between the two tests was 0.65 (p = 0.0001). Exercise challenge thus proved to be a practical epidemiological tool for objective measurements of bronchial responsiveness in children. In this sample, some children responded to one challenge and not to the other which suggests that the two challenges identify different abnormalities of the airways.

Prevalence of asthma in adults in Busselton, Western Australia.

OBJECTIVE: To estimate whether the prevalence of asthma in adults increased over a nine year interval. DESIGN: Serial cross sectional studies of the population with a protocol that included both subjective and objective measurements. SETTING: Busselton, Western Australia. SUBJECTS: A random sample of 553 subjects aged 18-55 years in 1981, and of 1028 subjects aged 18-55 years in 1990. MAIN OUTCOME MEASURES: Respiratory symptoms measured by self administered questionnaire, bronchial responsiveness measured by bronchial challenge with histamine, and allergy measured by skin prick tests. RESULTS: Symptoms with increased prevalence were those with significant association with allergy in this population. Recent wheeze increased from 17.5% to 28.8% (p < 0.001) and diagnosed asthma increased from 9.0% to 16.3% (p < 0.001). The increase was greatest in subjects less than 30 years old. The prevalence of shortness of breath coming on at rest and of hay fever also increased significantly, but the prevalence of shortness of breath on exertion, chronic cough, bronchial hyperresponsiveness, current asthma (defined as recent wheeze plus bronchial hyperresponsiveness), and allergy did not increase. The severity of bronchial responsiveness did not change significantly in any symptom group. CONCLUSIONS: Young adults showed a significant increase in reporting of symptoms related to allergy but not in the prevalence of current asthma. The increase in symptoms may be due to increased awareness of asthma in this community, to changed treatment patterns, or to increased exposures to allergens.