International comparison of the prevalence of asthma symptoms and bronchial hyperresponsiveness

Asthma progression and mortality: the role of inhaled corticosteroids

Overall, asthma mortality rates have declined dramatically in the last 30 years, due to improved diagnosis and to better treatment, particularly in the 1990s following the more widespread use of inhaled corticosteroids (ICSs). The impact of ICS on other long-term outcomes, such as lung function decline, is less certain, in part because the factors associated with these outcomes are incompletely understood. The purpose of this review is to evaluate the effect of pharmacological interventions, particularly ICS, on asthma progression and mortality. Furthermore, we review the potential mechanisms of action of pharmacotherapy on asthma progression and mortality, the effects of ICS on long-term changes in lung function, and the role of ICS in various asthma phenotypes.

Overall, there is compelling evidence of the value of ICS in improving asthma control, as measured by improved symptoms, pulmonary function and reduced exacerbations. There is, however, less convincing evidence that ICS prevents the decline in pulmonary function that occurs in some, although not all, patients with asthma. Severe exacerbations are associated with a more rapid decline in pulmonary function, and by reducing the risk of severe exacerbations, it is likely that ICS will, at least partially, prevent this decline. Studies using administrative databases also support an important role for ICS in reducing asthma mortality, but the fact that asthma mortality is, fortunately, an uncommon event makes it highly improbable that this will be demonstrated in prospective trials.

There is compelling evidence of the value of ICS in improving asthma control and indirect evidence that ICS prevents lung function decline by preventing severe exacerbations. Registry-based studies support the role of ICS in reducing asthma mortality.http://bit.ly/2VcNjaz

Remembering the forgotten non-communicable diseases

The forthcoming post-Millennium Development Goals era will bring about new challenges in global health. Low- and middle-income countries will have to contend with a dual burden of infectious and non-communicable diseases (NCDs). Some of these NCDs, such as neoplasms, COPD, cardiovascular diseases and diabetes, cause much health loss worldwide and are already widely recognised as doing so. However, 55% of the global NCD burden arises from other NCDs, which tend to be ignored in terms of premature mortality and quality of life reduction. Here, experts in some of these 'forgotten NCDs' review the clinical impact of these diseases along with the consequences of their ignoring their medical importance, and discuss ways in which they can be given higher global health priority in order to decrease the growing burden of disease and disability.

Time-dependent variation in the responses to the web-based ISAAC questionnaire

BACKGROUND

Epidemiologic studies have shown seasonal variations in responses to the written questionnaire for rhinitis symptoms.

OBJECTIVE

To evaluate whether the timing of data collection affected responses to the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire in a Web-based study.

METHODS

The Web-based ISAAC questionnaires were completed by parents with children 6 to 12 years old using an online research system. The authors conducted surveys of asthma symptoms every month for 1 year and surveys of rhinitis and eczema symptoms every season throughout 1 entire year.

RESULTS

There was a significant fluctuation in the positive responses to questions about wheezing in the past 12 months (P < .001) but not in the positive responses to questions about exercise-induced wheezing in the past 12 months and asthma ever (P = .75 and P = .15, respectively). The positive responses to questions about rhinitis and allergic rhinoconjunctivitis in the past 12 months and pollinosis ever exhibited significant seasonal variations (P = .002, P < .001, and P < .001, respectively). In contrast, there were no significant variations in positive responses regarding eczema in the past 12 months and eczema ever (P = .33 and P = .55, respectively).

CONCLUSION

There were time-dependent fluctuations in responses to the Web-based questionnaire regarding allergic symptoms. Timing of data collection should be taken into account when evaluating prevalence of asthma and rhinitis in children.

Normal variation of bronchial reactivity in nonasthmatics is associated with the level of mite-specific IgE

OBJECTIVE

To investigate association between non-specific bronchial reactivity (NBR) and level of mite specific IgE amongst mite-sensitized non-asthmatic subjects.

METHODS

Subjects attending occupational check-up were assessed for: respiratory symptoms, atopic status (skin prick testing [SPT], total and specific IgE), spirometry and NBR. Individuals without history of respiratory disease (N = 234) were included into analysis.

RESULTS

All subjects had normal spirometry and 99% had normal NBR while 41.8% had detectable specific IgE to mites. Lung function parameters and NBR were significantly lower in mite sensitized subjects. Multiple regression analysis controlling for age, gender, smoking, family history, SPT, IgE, and lung function showed that NBR was significantly associated only with mite specific IgE level (beta = 0.26; 95% CI, 0.05-0.47; p = 0.018).

CONCLUSION

Even in subjects without allergic symptoms, IgE-mediated sensitization does not appear to be all or nothing phenomenon influencing the normal variability of underlying airway reactivity.

Asthma deaths and the athlete

Asthma has recently become more prevalent, more severe, and more deadly. Approximately 4500 individuals die from asthma annually in the United States, an unacceptable number for a condition that can be managed effectively. Sudden death with exercise may result from a variety of causes, including previously unrecognized cardiac conditions. Asthma has also been recognized as a cause of death in association with sports. Recent data indicate those who suffer from mild to moderate asthma are also at risk for asthma fatality. The absolute magnitude of the increase in risk of death from asthma during sports, however, is very small. For this reason, individuals with asthma should not be discouraged from active participation in sports. Rather, this should reinforce the message that asthma is a condition that may be potentially serious, but can, and should be, well controlled with proper management.

Asthma prevalence in European, Maori, and Pacific children in New Zealand: ISAAC study

The International Study of Asthma and Allergies in Childhood (ISAAC) demonstrated that the highest prevalence of asthma in the world is in English-speaking countries, including New Zealand. In this paper, we compare asthma symptom prevalence in the three major ethnic groups (Maori, Pacific, and European) in the six participating centers in New Zealand. Hospital admission rates for asthma are higher among Maori and Pacific children compared to European children. The working hypothesis was that there were important differences in prevalence of asthma symptoms or diagnosis between ethnic groups which might explain these observed differences in asthma morbidity. In each center in 1992-1993, we sampled approximately 3000 children at each of the age brackets 6-7 years and 13-14 years. There were 37592 participants. Maori children had higher rates of diagnosed asthma and reported asthma symptoms than Pacific children in both age groups (diagnosed asthma in 6-7-year-olds: Maori, 31.7%; Pacific, 21.2%; 95% confidence interval on difference (CID), 7.2, 13.8; P < 0.001; 13-14-year-olds: Maori, 24.7%; Pacific, 19.2%; CID 2.5, 8.5; P < 0.001; recent wheeze in 6-7-year-olds: Maori, 27.6%; Pacific, 22.0%; CID, 2.6, 8.6; P < 0.001; 13-14-year-olds: Maori, 30.8%; Pacific, 21.1%; CID, 4.8, 14.5; P < 0.001;). European children had rates intermediate between those of Maori and Pacific children (6-7-year-olds) or similar to those of Maori children (13-14-year-olds), but had the lowest prevalence of night waking with wheeze in both age groups (e.g., 6-7-year-olds: European, 2.6%; Maori, 5.8%; Pacific, 5.7%; European-Maori CID: -4.2, -2.2, P < 0.001; European-Pacific CID: -4.7, -1.7, P < 0.001; Maori-Pacific CID: -1.7, 1.8, P = 1.0). The pattern of differences closely resembled that in a 1985 Auckland study, despite a 1.5-1.7-fold overall increase in prevalence. In conclusion, there are important differences in asthma prevalence among Maori, Pacific, and European children. These differences are small compared to worldwide variation, but their pattern is stable over time. The higher rate of severe asthma symptoms that Maori and Pacific children report may be one reason for the increased asthma morbidity in these groups. Further studies are needed to determine the reasons for these apparent differences in asthma severity.

Asthma and atopy - the price of affluence?

Irrespective of improved knowledge of many aspects of atopic diseases, the unfavorable trends in their prevalence particularly among children could not have been reversed. A growing body of evidence suggests that something may lack from our societal affluence that has the capacity to provide protection against the development of atopic diseases. Much attention during the last years has been devoted to the hygiene hypothesis. This review outlines the impact of environment and lifestyle, particularly from the perspective of the East-West gradient, on the development of atopic diseases, with a special emphasis on the hygiene hypothesis in its broadest sense.

How do Thai children and adolescents describe asthma symptoms?

Prevalence of childhood asthma appears to be increasing worldwide. In Thailand, the prevalence of childhood asthma increased from 4.2% to 13% within the past decade. The last epidemiologic survey in Thailand utilized the International Study of Asthma and Allergies in Childhood (ISAAC) phase I questionnaire translated into Thai language. Language in the questionnaire can affect the reliability and validity of results of the survey. The purpose of this study is to determine common Thai wordings actually used by Thai children and adolescents to describe wheeze, chest tightness, shortness of breath and dyspnea. Sixty asthmatic Thai children, aged 9.2-18 years with asthmatic attacks less than 1 yr prior to the study, and 178 age-matched controls were recruited into the study. Asthmatic children spontaneously expressed their terms describing their asthma symptoms (in Thai) and then answered a preoutlined questionnaire regarding asthma terminology during an interview session after viewing the severe attack scene of the International ISAAC video questionnaire. Controls responded only to the preoutlined questionnaire after viewing the video scene. Of the 60 asthmatic children (38 males and 22 females, mean age 11.9 yr), 75% had their last asthmatic attacks within 2 months prior to the study. Wheeze was referred to as " and '/wi:d/' in 50% and 33% of patients, respectively, and " in 93.8% among controls. Using only the word '/wi:d/' in our previous ISAAC-I survey, as it sounded like the English word 'wheeze', it appears that up to 67% of the cases could have been missed. Dyspnea was referred to as rapid breathing and feeling tired in 78.2% of cases and as rapid and difficult breathing in 76.3% of controls. Chest tightness was referred to as chest discomfort in 65.7%. Shortness of breath was referred to as not being able to catch a breath, too short a breath, not enough breath and feeling suffocated in 88.8%. Local terms for asthma symptoms should be established and validated into each language to obtain reliable epidemiologic data.

[Gain, loss and agreement between respiratory specialists and generalists in the diagnosis of asthma]

OBJECTIVE

To determine and analyze the degree of agreement and disagreement in the diagnosis of bronchial asthma (BA) by respiratory disease specialists and generalists in regional hospital and primary care settings.

MATERIAL AND METHODS

Ninety-six outpatients (16 to 70 years of age) were studied; all had been assigned a diagnosis of BA by the referring physician or by the respiratory disease specialist. We recorded 1) clinical symptoms, determining the initial probability of a diagnosis (IPD)of BA to be high, medium or low; 2) results of spirometry and bronchodilator testing (BDT), peak flow variability and methacholine challenge testing; 3) prick test results, eosinophil levels and total serum IgE levels. Three diagnoses were recorded: the initial diagnosis (ID) by the referring physician to whom follow-up data were unavailable; diagnosis by the respiratory disease specialist based only on clinical symptoms (RSS); and the final diagnosis(FD). To arrive at a FD of BA, it was necessary to have a high or medium IPD and a positive BDT. A Kappa test was used to analyze the degree of agreement among the three diagnoses. Group features associated with greater or lesser agreement were analyzed by chi-square tests and analysis of variance.

RESULTS

Agreement was acceptable between RSS and FD (K = 0.63) but very low between ID and RSS and between ID and FD. In the latter two cases, agreement was greatest for patients diagnosed in hospital and for those with high IgE levels (p < 0.05), with high IPD, longer course of disease and a history of asthma (p < 0.01) (odds ratio =59.8). Diagnostic disagreement occurred mainly for patients for whom a BA diagnosis was gained later, the of under-diagnosis being 39%. The patients involved visited the physician only because they had observed an isolated symptom related to asthma (odds ratio = 119) and to arrive at a diagnosis bronchomotor tests other than BDT were required (p < 0.01).

CONCLUSIONS

a) The degree of agreement for a diagnosis of BA is low. b)The functional profile of patients for whom diagnostic agreement exists differs from that of patients for whom diagnosis is gained through testing. c) In the context of this study, a high rate of under-diagnosis is evident.

Atopy among schoolchildren in northern and southern Sweden in relation to pet ownership and early life events

Studies have suggested a higher prevalence of asthma and allergies in northern, as compared to southern, Scandinavia. The aim of this study was to evaluate regional differences in atopy in relation to pet ownership and certain early life events among schoolchildren (n=2108) aged 10-11 years from Linköping in southern Sweden and Ostersund in northern Sweden. The parents completed a questionnaire, comprising questions on home environment, heredity, socio-economic conditions, and the core questions on symptoms from the International Study of Asthma and Allergies in Childhood. The children were skin-prick tested to eight common inhalant allergens. Information on maternal smoking habits, gestational age, and anthropometric measures were obtained from the Swedish Medical Birth Registry. The prevalence of atopic symptoms and sensitization to pollen were similar in Ostersund and in Linköping. A higher prevalence of sensitization to animal dander among children in Ostersund could be linked to a higher occurrence of pets in the community. Current cat ownership was related to less sensitivity to cat allergen but only in children with an atopic heredity. Ponderal index >30 kg/m3 was related to an increased risk of atopic sensitization, both in Linköping (adjusted odds ratio 2.1; 95% confidence interval 1.1-4.0) and in Ostersund (adjusted odds ratio 2.0; 95% confidence interval 1.1-3.5). Maternal smoking during pregnancy was related to an increased risk of atopic sensitization among children in Linköping, whereas current smoking was associated with a decreased risk of sensitization in Ostersund. In conclusion, we demonstrated that a high occurrence of pets in the community was associated with sensitization, whereas atopic symptoms were essentially unaffected. This study has also suggested an association between body size at birth and atopic sensitization at 10-11 years of age.

Prevalence of asthma symptoms in Latin America: the International Study of Asthma and Allergies in Childhood (ISAAC)

The prevalence of respiratory symptoms indicative of asthma in children from Latin America has been largely ignored. As part of the International Study of Asthma and Allergies in Childhood (ISAAC), 17 centers in 9 different Latin American countries participated in the study, and data from 52,549 written questionnaires (WQ) in children aged 13-14 years and from 36,264 WQ in 6-7 year olds are described here. In children aged 13-14 years, the prevalence of asthma ever ranged from 5.5-28%, and the prevalence of wheezing in the last 12 months from 6.6-27%. In children aged 6-7 years, the prevalence of asthma ever ranged from 4.1-26.9%, and the prevalence of wheezing in the last 12 months ranged from 8.6-32.1%. The lower prevalence in centers with higher levels of atmospheric pollution suggests that chronic inhalation of polluted air in children does not contribute to asthma. Furthermore, the high figures for asthma in a region with a high level of gastrointestinal parasite infestation, and a high burden of acute respiratory infections occurring early in life, suggest that these factors, considered as protective in other regions, do not have the same effect in this region. The present study indicates that the prevalence of asthma and related symptoms in Latin America is as high and variable as described in industrialized or developed regions of the world.

Repeatability of the ISAAC video questionnaire and its accuracy against a clinical diagnosis of asthma

The objective of the study was to evaluate the performance of the International Study of Asthma and Allergies in Childhood (ISAAC) video questionnaire in terms of repeatability and accuracy against a clinical diagnosis of asthma achieved according to the National Heart, Lung and Blood Institute (NHLBI) algorithm. Two hundred and forty-one subjects, aged 13-14 years from two secondary schools in Rome, Italy, were enrolled. Video and written ISAAC questionnaires were completed twice, 3 months apart, by 194 and 190 adolescents, respectively. Two months later, 106 subjects were visited by two physicians blinded to the results of questionnaires. Sixteen subjects were classified as having clinical asthma (CA) at the clinical visit, and eight of them as having clinical active asthma (CAA) on the basis of at least one positive outcome of the NHLBI algorithm. The repeatability of video questionnaire was similar to that of the written questionnaire for items on exercise wheeze and nocturnal cough and, to a lesser degree, for items concerning any wheeze in the past. The video questionnaire showed a worse performance than the written questionnaire for items on asthma attack: K-value (95% CL) = 0.59 (0.37-0.80) for video scene no. 5 and K-value (95% CL) = 0.86 (0.74-0.98) for written question no. 6. The overall accuracy of the video questionnaire, estimated as a positive answer to any video scene, was lower in terms of sensitivity than that of any written question when CA was used as a gold standard (0.50 vs. 0.81, P=0.025) and increased with respect to CAA (0.75 vs. 0.87, P = 0.317). The specificity of any video scene was better than that of any written question, independently from the gold standard used. In conclusion, the video questionnaire showed a fairly good accuracy, although slightly lower than that of the written questionnaire and provided sufficiently reliable results. However, samples of subjects from different geographic areas and cultures should be studied in order to conclusively define the performance of the ISAAC video questionnaire.

The epidemiology of childhood asthma

Variability is the hallmark of childhood asthma. Conceptually defined as variable airflow obstruction, asthma affects individual children through a variety of clinical manifestations. Particular controversy surrounds the nature of wheezing in early infancy and its relationship to atopic asthma of later onset. Asthma prognosis is also highly variable and only to a limited extent predictable by clinical indicators in early childhood. Long-term follow-up studies suggest a complex pattern of remission and relapse as wheezy children are followed through adolescence into adult life. Similarly, the population burden of asthma is highly variable, both over time and between countries. The balance of evidence worldwide suggests a modest but sustained increase in the prevalence of asthma symptoms over the past three decades. Superimposed on this have been larger changes in diagnostic fashion and use of health services for childhood asthma in many countries. There is substantial international variation in the prevalence of asthma symptoms, and marked urban-rural differences have been reported from several African countries. These contrast with the more uniform distribution of the disease within industrialized countries, reflecting its ubiquity in affluent societies.

Prevalence of asthma among young men in a military recruitment office of South Italy

The prevalence of asthma was studied in 3065 male 18 year-olds, examined in a southern Italy (Basilicata) military recruitment office. The disease was evaluated by questionnaires, pulmonary function tests and specialist diagnosis. The point prevalence of asthma was 1.4%. The disturbance was more frequent in high versus a low level of maternal education (OR: 3.70; 95% CI: 2.00-6.88), in high versus a low level of paternal education (OR: 2.71; 95% CI: 1.48-4.98), in urban residence versus rural residence (OR: 3.04; 95% CI: 1.61-5.75), in first-borns versus nonfirst-borns (OR: 2.46; 95% CI: 1.33-4.53). Home environment (dampness, heating, crowding) was not significantly correlated to asthma. This reported prevalence of asthma is low, compared with overall European and Italian data. The higher risk in urban areas and high level of education has been confirmed. The association between asthma and first-borns is interesting and needs further investigation, focusing on maternal issues like the low maternal age and the mother-child interaction.

Cough, cough receptors, and asthma in children

This review discusses current general concepts on cough and the relationship between cough, cough receptor sensitivity, and asthma in children. It presents models of the relationship between cough and bronchoconstriction, and proposes a new model outlining the relationship between cough receptor sensitivity, airway hyperresponsiveness, and the clinical issues of cough, wheeze, and dyspnea in children with and without asthma. Cough is very common in children, with a prevalence of 15-20%. Those with non-specific cough (dry cough in the absence of identifiable respiratory illness) are often treated with a variety of drugs, in particular, medications for asthma and gastroesophageal reflux. However, there is little evidence to use these medications for the sole symptom of cough in children. Clinical studies on cough need to be interpreted in light of inherent methodological problems in studying cough. These methodological problems include the nonrepeatable nature of questions on cough, the unreliability of subjective measurements of cough, the lack of objective measurements to quantify cough severity, and the period effect (spontaneous resolution of cough). Although cough can be troublesome, cough serves as an important function for maintaining normal health of the respiratory system. The importance of cough in maintaining respiratory health is reflected in the development of lung atelactasis/collapse from retained secretions and recurrent pneumonia in clinical situations where the cough reflex is ineffective. The cough reflex is complex and still poorly understood. In this article the simplified cough pathway is presented and involves cough receptors, mediators of sensory nerves and the afferent pathway, the vagus nerve, the cough centre, efferent pathway, and cough effectors.

The International Study of Asthma and Allergies in Childhood (ISAAC). ISAAC Steering Committee

Despite considerable research, the aetiology of asthma and allergic disease remains poorly understood. The International Study of Asthma and Allergies In Childhood (ISAAC), was founded to maximize the value of epidemiological research into asthma and allergic disease by establishing a standardized methodology and facilitating international collaboration. It has achieved its specific aims which are to describe the prevalence and severity of asthma, rhinitis and eczema in children living in different centres and to make comparisons within and between countries; to obtain baseline measures for assessment of future trends in the prevalence and severity of these diseases; and to provide a framework for further aetiological research into genetic, lifestyle, environmental and medical care factors affecting these diseases. The ISAAC design comprises three phases. Phase One used simple core written questionnaires for two age groups, and was completed in 156 collaborating centres in 56 countries and a total of 721 601 children participated. In the 13-14 years age group 155 centres from 56 countries participated, of which 99 centres completed a video questionnaire. For the 6-7 years age group there were 91 collaborating centres in 38 countries. ISAAC Phase One has demonstrated a large variation in the prevalence of asthma symptoms in children throughout the world including hitherto unstudied populations. It is likely that environmental factors were responsible for major differences between countries. The results provide a framework for studies between populations in contrasting environments which are likely to yield new clues about the aetiology of asthma. ISAAC Phase Two will investigate possible aetiological factors, particularly those suggested by the findings of Phase One. ISAAC Phase Three will be a repetition of Phase One in the year 2000 to assess trends in prevalence.

Comparison between two districts of the effects of an air pollution intervention on bronchial responsiveness in primary school children in Hong Kong

STUDY OBJECTIVE

This study examined the impact on children's respiratory health of a government air quality intervention that restricted the sulphur content of fuels to 0.5% from July 1990 onwards.

DESIGN/SETTING/PARTICIPANTS

This study examined the changes, one and two years after the introduction of the intervention, in airway hyperreactivity of non-asthmatic and non-wheezing, primary 4, 5, and 6, school children aged 9-12 years living in a polluted district compared with those in a less polluted district. Bronchial hyperreactivity (BHR)(a 20% decrease in FEV1 provoked by a cumulative dose of histamine less than 7.8 mumol) and bronchial reactivity slope (BR slope) (percentage change in logarithmic scale in FEV1 per unit dose of histamine) were used to estimate responses to a histamine challenge. The between districts differences after the intervention were studied to assess the effectiveness of the intervention.

MAIN RESULTS

In cohorts, comparing measurements made before the intervention and one year afterwards, both BHR and BR slope declined from 29% to 16% (p = 0.026) and from 48 to 39 (p = 0.075) respectively in the polluted district; and from 21% to 10% (p = 0.001) and 42 to 36 (p > 0.100) in the less polluted district. Comparing measurements made in 1991 (one year after intervention) with those in 1992 (two years after intervention), only the polluted district showed a significant decline from 28% to 12% (p = 0.016) and from 46 to 35 (p = 0.014), for BHR and BR slope respectively, with a greater decline in both responses (p = 0.018 and 0.073) than in the less polluted district.

CONCLUSION

Bronchial hyperresponsiveness tests can be used to support the evaluation of an air quality intervention. The demonstrated reduction in bronchial hyperresponsiveness is an indication of the effectiveness of the intervention.

Optical illusions from visual data analysis: example of the New Zealand asthma mortality epidemic

The abundance of health-related statistics routinely collected worldwide invites their misuse from haphazard associations between secular trends of these data. This misuse is often compounded by assessing these associations simply on the basis of a visual inspection of the data. The visual approach to data analysis, known to have several pitfalls, is particularly tempting in the context of asthma where it has often been used. For example, the epidemic of asthma deaths that occurred in New Zealand during the last two decades has been imputed to fenoterol, a medication for asthma, on the basis of a visual assessment of ecological data. The simultaneity of time trends in the asthma death rate and fenoterol market share in that country formed an important part of the statistical basis of the evidence. We verified whether the results of such visual analyses are corroborated by more objective quantitative statistical methods of analysis. We reanalyzed these same data, namely the time trend data of New Zealand asthma death rates, fenoterol market share, sales of beta-agonists and inhaled corticosteroids, measured yearly for the 16-year span 1976-1991, using Poisson weighted loglinear regression. We found that the protective effect of inhaled corticosteroids (rate ratio 0.5 per canister per month; 95% confidence interval 0.4 to 0.7; p = 0.0001) was more closely associated with changes in asthma mortality than either fenoterol (RR 2.7 per canister per month; 95% CI: 0.9 to 7.5; p = 0.06) or all beta-agonists combined (RR 1.6; 95% CI: 0.8 to 3.0; p = .19). We conclude from this quantitative analysis that these ecological asthma mortality data provide evidence of a stronger association with inhaled corticosteroids, little used in New Zealand at the onset of the epidemic but used abundantly at its termination, than with fenoterol. This conclusion is diametrically opposite to that found by the visual approach. The quantitative analysis demonstrates that the visual approach to the analysis of ecological data, although seemingly convincing, can be misleading by creating an optical illusion. This purely visual approach to data analysis may thus have serious implications when the resulting scientific information is used to make vital public health and policy decisions.

Chronic respiratory symptoms, skin test results, and lung function as predictors of peak flow variability

We examined how chronic respiratory symptoms, reported in a questionnaire, and results of skin prick tests and spirometry predicted variability in peak expiratory flow (PEF) among 6-12-yr-old children (n = 1,854). After characterization with skin tests and spirometry, children were followed for 2-3 mo during the winter of 1993-1994. Peak expiratory flow was measured daily in the morning and evenings. Children with asthmatic symptoms (wheeze and/or attacks of shortness of breath with wheeze in the past 12 mo and/or ever doctor diagnosed asthma) had a greater variation in PEF than children with dry nocturnal cough as their only chronic respiratory symptom. Similarly, doctor-diagnosed asthma was associated with a greater variation in PEF, also among children with asthmatic symptoms. Peak flow variability increased with an increasing number of symptoms reported in the questionnaire. Atopy, positive skin test reactions to house dust mite and cat and lowered level (as % of predicted) in FEV1 and in MMEF were also associated with an increased variation in PEF. All the differences were observed in both diurnal and day-to-day variation in PEF. In conclusion, chronic respiratory symptoms reported in a questionnaire, spirometric lung function and skin prick test results among asthmatic children predicted variation in PEF measured during a 2-3 mo follow-up. The difference in morning PEF coefficient of variation (CV) between children with asthmatic symptoms and children with cough only was somewhat bigger in girls than in boys. The effect of atopy on morning PEF CV was somewhat bigger in young than in older children.

Prevalence of childhood asthma in Istanbul, Turkey

In order to determine the asthma prevalence in 6-12-year-old schoolchildren in Istanbul, we issued 2350 questionnaires, according to ISAAC criteria, in six randomly selected city primary schools to be completed at home by parents. A total of 2232 of the questionnaires were completed, an overall response rate of 94.9%, and 2216 questionnaires were taken into consideration. The prevalence of asthma was found to be 9.8% and wheezing 15.1%. To investigate the effect of socioeconomic status on the prevalence of asthma, we evaluated the heating system at home, the place of residence, the educational levels of the mother and father, the number of people living in the house, the sharing of bedrooms, and the annual family income. In conclusion, the prevalence of childhood asthma was not affected by any of these factors. Atopic family history, food allergy, eczema, and frequent otitis media and sinusitis attacks were evaluated and found to be significant in asthma prevalence.

Deaths from asthma in Italy (1974-1988): is there a relationship with changing pharmacological approaches?

In this article we consider the relationship between asthma mortality rates, obtained from the Italian National Institute of Statistics (ISTAT), and the doses of all antiasthmatic drugs except systemic steroids sold in Italy in the years 1974-1988. The total asthma mortality rate showed three different trends: it decreased slowly until 1978 (period A); increased 10-fold from 1979 to 1985, rising from 0.30 to 4.17/100,000 (period B); and remained stable until 1988 (period C). More than half of the deaths in 1988 occurred in people 75 years of age or more. Men died more in the older age groups, while the mortality of women prevailed in the 35- to 54-year age group. In the 5- to 34-year age group the rate rose from 0.01 in 1978 to 0.21 /100,000 in 1986. Coding changes due to the 9th revision of the International Classification of Disease, adopted in Italy in 1979, probably increased the number of deaths being attributed to asthma in case of contemporary mention of bronchitis, a common diagnosis in older men, which showed the greatest increase in mortality. Increased prevalence and awareness of asthma may also have played a role. Although international comparisons strongly suggest undertreatment of asthma in Italy, the doses of anti-asthma drugs sold in Italy grew from 276 to 1,080 million from 1974 to 1985. During period B xanthine sales rose sevenfold and grew from 6.5 to 23.3% of the total doses, along with a twofold increase in beta 2-agonist and cromolyn sales. Period C was characterized by stable total doses (1155 million in 1988), with increases only in antiinflammatory and preventive drug sales. The increase in asthma deaths in Italy has been striking despite the contemporary rise in sales of all antiasthma drugs, particularly of beta 2-agonist metered aerosols and xanthine tablets. The increase in antiinflammatory and preventive drug sales may have contributed to the stabilization of asthma deaths during period C.

Prevalence and impact of chronic childhood conditions in Auckland, New Zealand

OBJECTIVE

To establish the prevalence of specific chronic conditions of childhood in the Auckland area and to quantify resource use by these children.

METHODOLOGY

Estimates were made from available registry data and published data sources of the population of children with selected chronic conditions resident in the Auckland Area Health Board area. Resource use data were extracted for admissions to Auckland public hospitals and from providers of community based technology services.

RESULTS

The largest community prevalence groups are those with asthma, intellectual handicap, congenital heart disease and epilepsy. Children aged 0-14 with chronic conditions accounted for at least 14,340 hospital days stay in Auckland in 1992 at an estimated minimum cost of $7.9 million. Over 200 children are dependent on technological aids at home.

CONCLUSIONS

There are sparse data on the numbers and needs of children with chronic conditions in the population. A non-categorical approach which crosses disease entities may be the best method of meeting common needs.

Problems of measuring asthma prevalence

This review considers the issues involved in measuring the community prevalence of asthma, particularly in the context of international comparisons. We argue that there is no gold standard definition for measuring asthma prevalence, and discuss the currently available methods of case ascertainment. Prevalence studies, if they are to be generalizable, need to involve large sample sizes with high response rates. This necessitates methods that are simple, inexpensive and practicable, but also as sensitive and specific for asthma as possible. We discuss some of the issues that are specific to comparisons of asthma prevalence between diverse populations, and suggest that large surveys using written or video questionnaires of self reported symptoms validated in all of the target populations are the method of choice.

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.

Prevalence of asthma at school age: a clinical population-based study in eastern Finland

A questionnaire aimed at screening and identifying patients with asthmatic symptoms was sent to the parents of 2011 children aged 7 to 12 years; 1633 (81%) returned the questionnaire. A clinical examination was given to 165 symptomatic and 82 non-symptomatic children. The children were classified into three groups: 1, clinical asthma (n = 43); 2, other symptoms from lower airways (OSLA) (n = 34); 3, healthy children (n = 170). The prevalences of asthma and OSLA in the whole source population (n = 1633) were then estimated based on these figures. The lifetime prevalence of asthma was 4.0%. All children with asthma were either symptomatic or on continuous maintenance therapy during the preceding 12 months. The lifetime prevalence of OSLA was 5.0%, with 3.0% being symptomatic during the preceding 12 months. Asthma was more common in boys (5.0%) than in girls (2.8%). The respective figures for OSLA were 6.2 and 3.7%. The occurrence of asthma as well as respiratory symptoms suggestive of asthma was more common than previously observed in this area.

The prevalence of asthma and respiratory symptoms among young adults: is it increasing in Australia?

The objective of this study was to determine the prevalence of self-reported asthma and respiratory symptoms among young adults and whether there had been any change since a previous survey. A cross-sectional postal community survey was conducted in three parliamentary electorates in the inner South East region of Melbourne, Australia. A total of 4500 individuals aged between 20 and 44 years were randomly selected from the electoral roll. After three mailings and telephone follow-up, an adjusted response rate of 79% was achieved. No intervention was performed. Self-reported asthma and respiratory symptoms were recorded from the European Community Respiratory Health Survey screening questionnaire. Respondents were most likely to report nasal allergies (41%), nocturnal cough (28.6%), and wheeze in the last 12 months (28.1%). Nocturnal cough was more common in females than males. The prevalence of wheeze, nocturnal chest tightness, and use of asthma medications decreased with age. An attack of asthma in the last 12 months was reported by 9.7% of young adults, and this fell to 8.2% after correction for nonresponse bias. The prevalence of current asthma had not increased significantly since a previous postal survey in 1990. However the prevalence of nocturnal chest tightness, nocturnal cough, and use of asthma medications had increased significantly over a 2-year period. Further research is required to investigate why asthma is so prevalent in Australia and why some features are increasing in prevalence.

Major reduction in asthma morbidity and continued reduction in asthma mortality in New Zealand: what lessons have been learned?

Increasing financial barriers to primary health care against a background of social and economic decline are likely to have contributed to asthma morbidity and mortality in New Zealand. Although there would not have been a sufficient increase in asthma prevalence to have accounted for the threefold increase in mortality rates, whether or not there was an increase in asthma severity in the late 1970s remains open to debate. Misuse or poor use of newly available and potent bronchodilator medications by those with the most severe asthma may simply have contributed to further delays in obtaining appropriate care and therefore to an increase in frequency of severe attacks in the community. Despite substantial increases in the use of bronchodilator therapy in New Zealand, there was no immediate improvement in indices of either asthma morbidity or mortality. The initial reduction in mortality rates in the 1980s happened at a time when first admissions for asthma were still increasing and seems to be best explained by an improvement in utilisation of hospital services (which were free until 1992) rather than a reduction in asthma severity. However, the recent reductions in all measures of asthma morbidity and further reduction in asthma mortality since 1989 does now suggest a reduction in asthma severity and would be best explained by the substantial increase in medium and high dose inhaled corticosteroid use, and to the endorsement of the current management strategies for asthma which are being promoted internationally and which were given considerable publicity in New Zealand in 1989 and 1990. Whilst sales of inhaled beta agonists were higher in 1991 than 1989, this may not reflect their pattern of use by individual patients since the need for an increase in inhaled beta agonist treatment has been accepted as indicating a lack of control and the need for either starting or increasing the dose of inhaled steroid treatment.

An integrated environmental asthma model

Asthma is a significant public health problem in many communities. Symptoms of asthma occur as a direct or indirect result of many contributing factors, including influences from the natural and built environments, human behavior, and the adequacy of techniques used in its management. A model is presented to integrate many of these contributing factors, highlighting the characteristics of the atmosphere, i.e., climate, irritants, and allergens. The model stresses the need for investigators to heed the many contributing triggers and influences, including possible synergistic mechanisms, in this disease.

Prevalence, severity and medical management of asthma in European school children in 1985 and 1991

This present study, conducted in 1991, examined trends in the prevalence, severity and medical management of asthma in European school children by repeating the protocol of a study performed in 1985, using the same schools and questionnaire. One thousand, nine hundred and one children in 1991 were compared with 1084 children in 1985. The prevalence of respiratory symptoms increased significantly by approximately one-third, although the increase in the diagnostic label 'asthma' did not increase significantly. Asthma severity indices (> 12 asthma attacks in the last 12 months and symptoms in the last month) were not significantly increased, except for night cough in the last month (1985 7.0%, 1991 9.9%, P = 0.008). In 1991, children with wheeze in the last 12 months were more likely to be diagnosed as having asthma and treated with bronchodilators and prophylactic drugs than in 1985. We conclude that the prevalence of asthma symptoms has increased from 1985 to 1991, but the two indices of severity of asthma are mostly unchanged. Diagnosis of asthma in children with symptoms has improved but asthma still appears underrecognized. Drug treatment of asthma has increased.

The beta 2-agonist controversy. Observations, explanations and relationship to asthma epidemiology

Links between frequent use of inhaled beta 2-agonists and morbidity and mortality from asthma appear probable. Two mortality epidemics followed the marketing of potent inhaled adrenergic agents. Case-control studies in New Zealand linked mortality with prescription of fenoterol, especially in severe asthma. A Saskatchewan case-control study confirmed an association of mortality with fenoterol, and also with frequent use of salbutamol (albuterol). Cardiac effects of beta 2-agonists do not cause mortality, but frequent use of these agents may increase the chronic severity of asthma, hence increasing the number of asthmatic patients at risk of death in an acute attack. Frequent use of beta 2-agonists may reduce lung function, increasing airway responsiveness, and impair control of asthma, despite use of inhaled corticosteroids. Mechanisms for this effect may include tachyphylaxis to nonbronchodilator effects, increased responsiveness to allergen, interaction with corticosteroid receptors, altered mucociliary function, differential effects of enantiomers, and masking of symptoms by beta 2-agonist use. The withdrawal of fenoterol from New Zealand in 1990 was associated with a substantial decline in morbidity and mortality. Overall, the evidence suggests that frequent use of inhaled beta 2-agonists has a deleterious effect on the control of asthma. Epidemics of mortality are explained by an increase in chronic severity of asthma following introduction of more potent beta 2-agonists. While beta 2-agonists remain essential for relief of breakthrough symptoms, long term use, particularly with high doses of potent agents, appears to be detrimental.

Bronchial responsiveness in children exposed to atmospheric pollution in Hong Kong

Bronchial responsiveness was studied by histamine challenge in 423 school children with mean (SEM) age of 10.85 (0.05) years living in two districts of Hong Kong with contrasting levels of air pollution. Differences between districts of residence were observed, with a higher prevalence of bronchial hyperreactivity (BHR) in children living in the more polluted district (chi 2 = 7.74, df = 3, p = 0.052). Bronchial hyperreactivity was defined as a 20 percent or greater drop in FEV1. The district effect remained after exclusion of children with a history of wheeze and those diagnosed asthmatic for prevalence of BHR (chi 2 = 8.93, df = 3, p = 0.030) and for degree of bronchial reactivity (BR) after adjustment for other socioeconomic factors and smoking in the home (z = 1.97, p = 0.049). Bronchial reactivity was defined as the percentage drop in FEV1 per cumulative histamine dose from postsaline to end dose. The results demonstrate that studies on bronchial responsiveness can be used to assess the effects of air quality on the respiratory health of children and will be employed to measure the impact of new air quality control measures in Hong Kong.

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)

Grading asthma severity: using the APS component of the Apache II system

OBJECTIVE

Measurement of severity is fundamental to the description and comparison of case series, treatment regimens and disease outcomes. This study examines the Acute Physiology Score (APS) as a severity measure of an acute "life-threatening" asthma attack.

DESIGN

The APS in the emergency department (ED) and ICU, demographic, treatment and outcome variables were prospectively studied. Relationships between severity, treatment and progress were investigated. In addition, patients were stratified according to ED APS and differences between the participating hospitals were examined.

SETTING

Emergency Departments and Intensive Care Units of two New Zealand hospitals.

PATIENTS

64 admissions to the ICUs following an acute episode of asthma.

INTERVENTIONS

Standard management of acute asthma as practised at the two participating hospitals.

MEASUREMENTS AND RESULTS

Both the treatment delivered (intravenous salbutamol, sodium bicarbonate and IPPV) and the rate of improvement as defined by change in APS between the ED and the ICU were found to be strongly related to ED APS. Similarly, the length of stay in the ICU correlated with the ICU APS. Stratification on the basis of ED APS allowed small but significant differences in patient physiologic derangement, dose of salbutamol, use of IPPV and incidence of complications to be detected between patients at the two hospitals.

CONCLUSION

This prospective study involving two hospitals validates the APS as a method for measuring the severity of an acute asthma attack. It demonstrates how correction for severity can be used to compare treatment and outcome variables in different case series.

Ontogeny of epithelial modulation of airway smooth muscle function in the guinea pig

The purpose of this study was to investigate the ontogeny of guinea pig airway smooth muscle (ASM) responses and the epithelial modulation of these responses. Paired tracheal rings from fetal, newborn, and adult guinea pigs were studied. One of each pair was denuded of airway epithelium (AE) by gentle rubbing. Isometric tension was measured in rings mounted in organ baths filled with Krebs' solution. Cumulative dose-response curves were generated by adding either acetylcholine (ACh) or histamine over a concentration range of 10(-8)-10(-4) M. Significant agent-specific, age-related differences in maximal contraction were seen for both ACh and histamine in intact tissues (Ach: for fetus 66.7 +/- 6.2 x 10(-2) g/mg wet wt, for newborn 51.4 +/- 6.2, for adult 29.3 +/- 2.6; histamine: for fetus 46.1 +/- 5.1, for newborn 72.9 +/- 6.0, for adult 25.3 +/- 3.2). Similar differences in sensitivity to both agents were observed (EC50 with ACh: for fetus 0.80 +/- 0.11 x 10(-6) M; for newborn 0.85 +/- 0.26 x 10(-6) M; for adult 1.7 +/- 0.20 x 10(-6) M; EC50 with histamine; for fetus 1.88 +/- 0.50 x 10(-6) M; for newborn 1.34 +/- 0.16 x 10(-6) M; for adult 3.78 +/- 0.75 x 10(-6) M). Removal of AE caused a significant decrease in maximal responses to ACh in fetal tissue, a smaller, insignificant one for newborn and a nonsignificant alteration for adult tissues. Age-related sensitivity difference was abolished with removal of AE to ACh but not to histamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Risk factors for increased airway responsiveness to methacholine challenge among laboratory animal workers

As a first step in a prospective study of the incidence of asthma to laboratory animals, a group of 364 adults 18 to 48 yr of age who were beginning employment with laboratory animals were evaluated in terms of their past history, health status, allergy, and airway responsiveness to methacholine. At entry to the study, 269 had previous occupational contact with animals, 109 had chest symptoms in the previous year, 168 had a history of allergic symptoms to laboratory animals (any with asthmatic responses were systematically excluded), and 118 had positive immediate skin tests (29 had positive skin tests to laboratory animals). When defined as a PD20FEV1 of 80 breath units or less, 18.4% of these young adults had methacholine hyperresponsiveness (HRA). Significant risk factors for HRA were found to be younger age, female sex, lower educational level, a history of allergic symptoms to laboratory animals, and a history of chest symptoms. Positive skin tests to laboratory animals were present in 8% of workers; this was not a significant risk factor for HRA although positive skin tests to pollen and household allergens were. Previous work experience was a risk factor, especially among those with allergic symptoms, and a trend toward self-selection was suggested in that the rate of HRA was lowest in workers with more than 2 yr of experience or with two or more previous jobs with laboratory animals.

Toward a definition of asthma for epidemiology

Because there is no "gold standard" for defining asthma for epidemiology, we have defined current asthma as bronchial hyperresponsiveness (BHR) plus recent wheeze (in the 12 months prior to study). To describe the characteristics of groups categorized by these measurements, we studied two samples of children aged 7 to 12 yr: 210 from a population sample and 142 self-identified asthmatics. Bronchial responsiveness to histamine was measured by the rapid method, respiratory symptom history, and asthma medication use by self-administered questionnaire to parents and atopy by skin prick tests to 14 allergens. Children recorded daily Airflometer readings and symptom scores for 2 wk. Children with current asthma had more severe bronchial responsiveness, greater Airflometer variability, more symptoms, more atopy (particularly to house dust mites), and used more asthma medication than children with BHR or recent wheeze alone. Children with BHR, but not with recent wheeze, were intermediate between the current asthma and normal groups in terms of bronchial responsiveness, Airflometer variability, and atopy. Children with recent wheeze and normal responsiveness differed from the normal group only in symptoms and medication use. Our definition of current asthma discriminates a group of children that is clearly different in terms of both clinical features and physiologic measures. As such, it is the most useful definition to date for measuring the prevalence of clinically important asthma in populations.

Reliability of a respiratory history questionnaire and effect of mode of administration on classification of asthma in children

Because there is no consensus definition of asthma for epidemiology, we have examined the reliability of a questionnaire and the effect of its mode of administration on classification of asthma in children. A symptom history questionnaire was parent self-administered and then readministered within three months by a nurse. The questions of diagnosed asthma, cumulative wheeze, and recent wheeze (wheeze in the previous 12 months) were more repeatable than questions of night cough, but 7 percent of children changed diagnosed asthma category, 13 percent changed cumulative wheeze category, and 9 percent changed recent wheeze category at second questionnaire. Because the numbers who changed from symptom positive to negative roughly equalled the changes from negative to positive, prevalence estimates were not affected. Methods of measuring asthma with greater precision are urgently needed. Because of reporting bias, epidemiologic information collected by current questionnaires should be treated with some caution.

Asthma morbidity in Australia: an epidemiological study

OBJECTIVE

To examine the prevalence and management of asthma in adults and children in a population sample in eastern Australia.

SETTING

A random sample of children from 33 primary schools in Sydney, Melbourne, Brisbane, and the Upper Hunter Valley (New South Wales), and their parents.

DESIGN

A cross-sectional analytic survey of 8753 primary school children aged between 5 and 12 years, and their parents (n = 13,945 adults). Asthma prevalence and management practices were determined by parental responses to a questionnaire, and spirometry was performed in children with "probable asthma".

RESULTS

Of 8753 children whose parents responded, the prevalence of current wheeze was 19.5% and diagnosed asthma was 17.1%. Of the children with "probable asthma", 30% had their lung function measured in the previous year, and 6% possessed both a peak flow meter and an action plan for their asthma. Undertreatment was likely, as preventive asthma medications (inhaled corticosteroids or sodium cromoglycate) were used regularly by only 25.5% of these children and by 44.3% of children who had asthma symptoms more than twice per week. Children with the diagnosis of asthma reported higher rates of preventive medication use and ventilatory function measurement than children with frequent symptoms without the diagnosis. In the 13,945 adults, the reported prevalence of asthma was 7%, of whom 39% were using preventive medications, 34% had their ventilatory function assessed in the previous year, and 7% had both a peak flow meter and an asthma action plan.

CONCLUSIONS

The study illustrated the gap between the current level of asthma management in the community and the standards set by the Thoracic Society of Australia and New Zealand. Undertreatment and suboptimal management of asthma remain important problems in Australia.

Lung function, bronchial reactivity, atopic status, and dust exposure in Lancashire cotton mill operatives

A total of 645 cotton mill operatives were administered a respiratory questionnaire. Of these, 85 (13.2%) complained of one or more work-related respiratory symptoms: 23 (3.6%) had byssinosis and the remaining 62 had symptoms not conforming to byssinosis (nonbyssinotic symptomatics, NBS). All byssinotic, 56 NBS, and 84 matched asymptomatic operatives underwent pulmonary function testing (FEV1 and FVC), skin testing to common allergens, and histamine bronchial challenge. Work area and personal breathing zone cotton dust concentrations were assessed, and a cumulative cotton dust exposure index was calculated for each individual. Byssinotic, NBS, and asymptomatic operatives all had reduced FEV1; observed mean liters (95% CI); predicted mean: byssinosis, 2.36 (2.09 to 2.63), 3.02; NBS, 2.94 (2.71 to 3.17), 3.29; and asymptomatic, 3.12 (2.95 to 3.29), 3.31. Only byssinotic subjects had evidence of impaired FVC: 3.31 (2.97 to 3.65), 3.69. The majority of byssinotic operatives (18 of 23) had bronchial hyperreactivity (BHR) in comparison with 21 of 56 NBS and 14 of 84 asymptomatic operatives. Mean log PD20 (95% CI) values were significantly lower in the byssinotic group -0.72 (-1.42, -0.02) than in NBS 0.57 (0.08, 1.06) and asymptomatic subjects 0.57 (-0.26, 1.39). The distribution of atopy did not differ significantly between groups, and lung function did not differ significantly between atopic and nonatopic subjects. The cumulative cotton dust exposure index was the only dust parameter to be significantly greater in those with BHR (mean mg-yr/m3 [95% CI] 14.13 [13.1 to 15.1]) than those with normal reactivity [5.35 (3.9 to 6.8)].

Relation of dose-response slope to respiratory symptoms in a population of Australian schoolchildren

To describe bronchial responsiveness in populations, the dose-response slope (DRS), which is the linear slope of the dose-response curve, may be a more useful measure of severity than the provoking dose that causes a 20% fall in FEV1 (PD20 FEV1). To examine the distribution of DRS measurements and their relation to respiratory symptoms in children, we have analyzed data collected during a population study designed to measure the prevalence of bronchial hyper-responsiveness and respiratory symptoms. In this study, respiratory symptom history was measured by a self-administered questionnaire to parents and bronchial responsiveness was measured using the rapid inhalation method. Of 1,217 children studied, DRS values were obtained for 1,203 children who had technically satisfactory bronchial challenge data. In asymptomatic children, DRS values were distributed symmetrically on a logarithmic scale. The geometric mean DRS was reliable measure of the central position of the curve, and 1.96 standard deviations only slightly underestimated the 95% interval. In children with recent wheeze, the distribution was skewed toward larger DRS values. Mean DRS values were significantly different between groups determined according to symptom frequency. It appears that DRS values are more useful than PD20 FEV1 values in epidemiologic studies of respiratory illness in children because a value that relates well to symptom history can be calculated for the entire sample. The major advantages are that the measurement more clearly discriminates between symptom severity groups and that a value that represents abnormal responsiveness can be calculated.

Repeatability of histamine bronchial challenge and comparability with methacholine bronchial challenge in a population of Australian schoolchildren

To measure the repeatability of the bronchial challenge test and the comparability of histamine and methacholine as provoking agents, we studied a population sample of children and conducted histamine bronchial challenge tests on each of 3 consecutive days followed by a methacholine bronchial challenge on the fourth day. Bronchial responsiveness was measured using the rapid inhalation method. A total of 393 children had satisfactory bronchial challenge data for all 4 days. The measurements derived from the dose-response curve were the PD20 FEV1, which was measured as the provoking dose causing a 20% fall in FEV1, and the dose-response slope (DRS), which was measured as the percentage fall in FEV1 at final dose/total dose administered. Children who had a PD20 FEV1 were categorized as having bronchial hyperresponsiveness (BHR). The percentage of children with BHR each day was between 7 and 11. One-third of the children with BHR reacted only to histamine or methacholine. The within-subject range for histamine PD20 FEV1 values compared with methacholine suggested that histamine and methacholine are not directly comparable bronchial challenge agents. The dose-response slope values, which could be obtained for all children, had slightly better repeatability than PD20 FEV1 values. Because DRS values obtain data for the entire sample, have good repeatability, and are equally repeatable in children with normal responsiveness or bronchial hyperresponsiveness, they should prove more useful than PD20 FEV1 values for measuring bronchial responsiveness in populations.

Exercise but not methacholine differentiates asthma from chronic lung disease in children

Bronchial provocation challenges with exercise and methacholine were performed on the same day or within a short interval in 52 children with asthma, 22 with other types of chronic lung disease (including cystic fibrosis), and 19 control subjects with no evidence of chronic lung disease. There were no significant differences in the baseline lung function before the two types of challenge in the individual groups and differences between the patients with asthma and with chronic lung disease were minor. When the mean -2 SD of the methacholine response of the control group was taken as the lower limit of normal, 49/52 (94%) patients with asthma and 18/22 (82%) with chronic lung disease responded abnormally. In contrast, with the mean +2 SD of the exercise response of the control group as the upper limit of normal, 41/52 (79%) asthmatic patients responded but none of those with chronic lung disease. Thus the response to the two types of challenge helps to distinguish asthma from other types of chronic lung disease in children.

Prevalence of asthma among 12 year old children in New Zealand and South Wales: a comparative survey

A survey of 12 year old schoolchildren was carried out in New Zealand and South Wales, the same questionnaire and exercise provocation test being used. The prevalence of a history of asthma at any time was higher in New Zealand (147/873, 17%) than in South Wales (116/965, 12%). The New Zealand children were also more likely than the Welsh children to have a history of "wheeze ever" (27% versus 22%), and wheeze brought on by running (15% versus 10.5%). The sex ratio of asthmatic and wheezy children was very similar in the two countries. A history of hospital admission for chest trouble was twice as common in New Zealand as in South Wales. An exercise test produced a fall in peak expiratory flow rate of 15% or more in more New Zealand children (12.2%) than Welsh children (7.7%). These results suggest that the prevalence of childhood asthma is higher in New Zealand than in South Wales.

Prevalence of asthma in Melbourne schoolchildren: changes over 26 years

OBJECTIVES

To determine the prevalence of asthma in the past 12 months in Melbourne schoolchildren aged 7, 12, and 15 years and to compare the prevalence of a history of asthma with that of 26 years ago.

DESIGN

A questionnaire on respiratory symptoms was distributed to children for completion by parents and return to the school. Subjects were selected by a stratified cluster design.

SETTING

Government and non-government schools in the greater Melbourne area, Australia.

SUBJECTS

10,981 children. Parents completed questionnaires for 3324 children aged 7, 2899 aged 12, and 2968 aged 15. The overall response rate was 90%.

MAIN OUTCOME MEASURES

History of wheeze or asthma in the past 12 months and in lifetime.

RESULTS

The prevalences of wheeze in the past 12 months were 23.1%, 21.7%, and 18.6% for 7, 12, and 15 year olds respectively. A history of wheeze was more common in boys than in girls at age 7 (443/1711 v 324/1614) and 12 (418/1767 v 322/1718) but not at age 15. Overall, 78% (1548) of those reporting wheeze also reported a history of asthma and 83% (1611) had used a bronchodilator. The prevalence of a history of asthma among 7 year olds was 46% compared with 19.1% in the 1964 survey, an increase of 141%.

CONCLUSIONS

The current prevalence of asthma in Melbourne schoolchildren is high and has risen substantially over the past 26 years.

Analysis of bronchial reactivity in epidemiological studies

The measurement of bronchial reactivity in epidemiological studies has the advantage of quantifying an objective physiological feature of asthma. Bronchial reactivity was developed in a clinical setting and has been conventionally expressed as the dose of agonist producing a 20% fall in FEV1 (PD20). As PD20 can be estimated for less than 20% of subjects in general community surveys with the doses of agonist that are usually given, data from most subjects must be censored. Thus PD20 alone is a poor index of bronchial reactivity for epidemiological studies. Data from 809 aluminium smelter workers were used to evaluate alternative methods of analysing bronchial reactivity. Dose-response relationships were analysed by four methods: (1) PD20 by the conventional method of interpolating the dose on a logarithmic scale between the last two measurements of FEV1; (2) PD20 (with allowance for extrapolation), estimated by fitting an exponential curve to the dose-response data; (3) the linear regression slope between dose and FEV1 when significant; (4) the dose-response slope obtained in all subjects as the % change in FEV1 from baseline in response to total dose. When each of these measures was related to symptoms, diagnosis, and treatment of asthma, all differentiated between "asthmatic" and "non-asthmatic" subjects. The dose-response slope (method 4) had the advantages of simplicity and no censored data, and was shown to be clinically relevant. It is suggested that the dose-response slope should be used for the analysis of bronchial reactivity in epidemiological studies.