Asymptomatic bronchial hyperreactivity and the development of asthma and other respiratory tract illnesses in children

Exercise-Induced Bronchoconstriction in Children: State of the Art from Diagnosis to Treatment

Exercise-induced bronchoconstriction (EIB) is a common clinical entity in people with asthma. EIB is characterized by postexercise airway obstruction that results in symptoms such as coughing, dyspnea, wheezing, chest tightness, and increased fatigue. The underlying mechanism of EIB is not completely understood. "Osmotic theory" and "thermal or vascular theory" have been proposed. Initial assessment must include a specific work-up to exclude alternative diagnoses like exercise-induced laryngeal obstruction (EILO), cardiac disease, or physical deconditioning. Detailed medical history and clinical examination must be followed by basal spirometry and exercise challenge test. The standardized treadmill running (TR) test, a controlled and standardized method to assess bronchial response to exercise, is the most adopted exercise challenge test for children aged at least 8 years. In the TR test, the goal is to reach the target heart rate in a short period and maintain it for at least 6 min. The test is then followed by spirometry at specific time points (5, 10, 15, and 30 min after exercise). In addition, bronchoprovocation tests like dry air hyperpnea (exercise and eucapnic voluntary hyperpnea) or osmotic aerosols (inhaled mannitol) can be considered when the diagnosis is uncertain. Treatment options include both pharmacological and behavioral approaches. Considering medications, the use of short-acting beta-agonists (SABA) just before exercise is the commonest option strategy, but daily inhaled corticosteroids (ICS) can also be considered, especially when EIB is not controlled with SABA only or when the patients practice physical activity very often. Among the behavioral approaches, warm-up before exercise, breathing through the nose or face mask, and avoiding polluted environments are all recommended strategies to reduce EIB risk. This review summarizes the latest evidence published over the last 10 years on the pathogenesis, diagnosis using spirometry and indirect bronchoprovocation tests, and treatment strategies, including SABA and ICS, of EIB. A specific focus has been placed on EIB management in young athletes, since this condition can not only prevent them from practicing regular physical activity but also competitive sports.

Profiles and characteristics of bronchial responsiveness in general 7-year-old children

BACKGROUND

Although bronchial responsiveness (BR) is usually categorized as normal or hyperresponsive to aid the diagnosis of asthma, it exists on a continuous spectrum, not in a dichotomous manner. We aimed to evaluate the distribution profile of BR in a general population of 7-year-olds.

METHODS

In 2015, 7-year-old Korean children from a nationwide birth cohort study visited regional study hospitals for skin prick test, standard spirometry, and bronchial provocation to establish reference values for the general population. Their BR degrees were categorized into five ordered groups: hyperresponsive BRs were classified into group 1 (provocative concentration (PC) of methacholine causing a 20% fall in forced expiratory volume in 1 second [FEV1], PC20 of <4 mg/mL) and group 2 (PC20 of ≥4 mg/mL and <16 mg/mL), and nonresponsive BRs were categorized into group 3 (final FEV1 percentage fall after inhaling 16 mg/mL of methacholine [FEV1%fall] of >15% and ≤20%), group 4 (FEV1%fall of >10% and ≤15%), and group 5 (FEV1%fall of ≤10%).

RESULTS

In total, 559 subjects finished all tests reliably. Groups 1 and 2 comprised 10.0% and 15.7% of the total population, respectively. Groups 3, 4, and 5 comprised 14.7%, 18.4%, and 41.1%, respectively. As the group number increased, the proportion of those with recent wheezing and those with indoor allergen sensitization decreased (P for trend = 0.001 and P for trend < 0.001, respectively), and the baseline FEV1/FVC increased (P for trend < 0.001) CONCLUSION: BR of the 7-year-olds in the general population, while showing a wide distribution across phenotypes, is associated with allergic symptoms, negatively correlated with baseline lung function and positively correlated with indoor allergen sensitization.

Exercise-induced bronchoconstriction: prevalence, pathophysiology, patient impact, diagnosis and management

Exercise-induced bronchoconstriction (EIB) can occur in individuals with and without asthma, and is prevalent among athletes of all levels. In patients with asthma, symptoms of EIB significantly increase the proportion reporting feelings of fearfulness, frustration, isolation, depression and embarrassment compared with those without symptoms. EIB can also prevent patients with asthma from participating in exercise and negatively impact their quality of life. Diagnosis of EIB is based on symptoms and spirometry or bronchial provocation tests; owing to low awareness of EIB and lack of simple, standardised diagnostic methods, under-diagnosis and mis-diagnosis of EIB are common. To improve the rates of diagnosis of EIB in primary care, validated and widely accepted symptom-based questionnaires are needed that can accurately replicate the current diagnostic standards (forced expiratory volume in 1 s reductions observed following exercise or bronchoprovocation challenge) in patients with and without asthma. In patients without asthma, EIB can be managed by various non-pharmacological methods and the use of pre-exercise short-acting β2-agonists (SABAs). In patients with asthma, EIB is often associated with poor asthma control but can also occur in individuals who have good control when not exercising. Inhaled corticosteroids are recommended when asthma control is suboptimal; however, pre-exercise SABAs are also widely used and are recommended as the first-line therapy. This review describes the burden, key features, diagnosis and current treatment approaches for EIB in patients with and without asthma and serves as a call to action for family physicians to be aware of EIB and consider it as a potential diagnosis.

Clinical phenotypes of bronchial hyperresponsiveness in school-aged children

BACKGROUND

Bronchial hyperresponsiveness (BHR), one of the key features of asthma, has a diverse natural course in school-aged children, but studies on BHR phenotypes are lacking.

OBJECTIVE

To classify BHR phenotypes according to onset age and persistence in children and investigate the characteristics and factors associated with each phenotype in a longitudinal study.

METHODS

This study analyzed 1,305 elementary school children from the Children's Health and Environmental Research (CHEER) study, a 4-year, prospective, follow-up study with 2-year intervals starting at a mean age of 7years. Total serum IgE levels and blood eosinophil counts were measured, and allergy workup, including methacholine challenge tests with the International Study of Asthma and Allergies in Childhood questionnaire, was performed at each survey.

RESULTS

The 4 BHR phenotypes were classified as non-BHR (n = 942 [72.2%]), early-onset transient BHR (n = 201 [15.4%]), late-onset BHR (n = 87 [6.7%]), and early-onset persistent BHR (n = 75 [5.7%]). Early-onset persistent BHR is characterized by an increased eosinophil count, total serum IgE level, sensitization rate, decreased lung function, and increased risk of newly diagnosed asthma during follow-up (adjusted odds ratio, 3.89; 95% confidence interval, 1.70-8.88). The 2 early-onset phenotypes were associated with peripheral airway dysfunction. The late-onset BHR phenotype was related to increased risks of allergic rhinitis symptoms at baseline and later sensitization against inhalant allergens.

CONCLUSION

The early-onset persistent BHR phenotype in school-aged children is associated with high atopic burden and increased risk of newly diagnosed asthma, whereas the late-onset BHR phenotype related with later sensitization and allergic rhinitis symptoms. Diverse BHR phenotypes in children have specific characteristics that require targeted follow-ups.

Independent and combined effects of airway remodelling and allergy on airway responsiveness

Airway remodelling and allergic inflammation are key features of airway hyperresponsiveness (AHR) in asthma; however, their interrelationships are unclear. The present study investigated the separate and combined effects of increased airway smooth muscle (ASM) layer thickness and allergy on AHR. We integrated a protocol of ovalbumin (OVA)-induced allergy into a non-inflammatory mouse model of ASM remodelling induced by conditional and airway-specific expression of transforming growth factor-α (TGF-α) in early growth response-1 (Egr-1)-deficient transgenic mice, which produced thickening of the ASM layer following ingestion of doxycycline. Mice were sensitised to OVA and assigned to one of four treatment groups: Allergy - normal chow diet and OVA challenge; Remodelling - doxycycline in chow and saline challenge; Allergy and Remodelling - doxycycline in chow and OVA challenge; and Control - normal chow diet and saline challenge. Airway responsiveness to methacholine (MCh) and histology were assessed. Compared with the Control group, airway responsiveness to MCh was increased in the Allergy group, independent of changes in wall structure, whereas airway responsiveness in the Remodelling group was increased independent of exposure to aeroallergen. The combined effects of allergy and remodelling on airway responsiveness were greater than either of them alone. There was a positive relationship between the thickness of the ASM layer with airway responsiveness, which was shifted upward in the presence of allergy. These findings support allergy and airway remodelling as independent causes of variable and excessive airway narrowing.

The association between reflux esophagitis and airway hyper-reactivity in patients with gastro-esophageal reflux

BACKGROUND

The association of gastro-esophageal reflux (GER) with a wide variety of pulmonary disorders was recognized. We aimed to evaluate the effect of GER-induced esophagitis on airway hyper-reactivity (AHR) in patients and the response to treatment.

MATERIALS AND METHODS

In this cohort study, 30 patients attending the gastrointestinal clinic of a university hospital with acid reflux symptoms were included. All patients were evaluated endoscopically and divided into case group with esophagitis and control group without any evidence of esophagitis. Spirometry and methacholine test were done in all patients before and after treatment of GER with pantoprazole 40 mg daily for six months.

RESULTS

There was a significant difference in the rate of positive methacholine test between the cases (40%) and the controls (6.7%) prior to anti-acid therapy (P < 0.0001). After six months of treatment, the frequency of positive methacholine test diminished from 40 to 13.3% in the case group (P < 0.05) but did not change in the controls (P = 0.15).

CONCLUSION

The presence of esophagitis due to GER would increase the AHR and treatment with pantoperazole would decrease AHR in patients with proved esophagitis and no previous history of asthma after six months.

Pathogenesis of exercise-induced bronchoconstriction

This article presents the various potential mechanisms responsible for the development of exercise-induced bronchoconstriction (EIB). Although the etiology of EIB is multifactorial, and the physiologic processes involved may vary between individuals (especially between those with and without asthma), drying of the small airways with an associated inflammatory response seems prerequisite for EIB. Dysregulated repair processes following exercise-induced airway epithelial injury may also serve as basis for EIB development/progression.

Local and systemic immunological parameters associated with remission of asthma symptoms in children

The immunological and clinical parameters that are associated with asthma remission are poorly understood. The cytokine and local mediator changes associated with the resolution of asthma symptoms were examined in three groups of subjects 12-18 years of age (n = 15 in each group): (a) continuing asthma group (CA) who had persistent symptoms since early childhood, (b) an age, sex and atopic status-matched group who had persistent symptoms in early childhood but in whom these had resolved (RA), and (c) a non-atopic, non-asthmatic control group. Clinical parameters, sputum cell counts, peripheral blood mononuclear cell (PBMC) cytokine production and activation marker expression were determined. All of the CA had methacholine airway hyperresponsiveness compared with only half of the RA subjects. The CA showed elevated numbers of eosinophils and increased ECP and IL-5 in sputum, which were not observed in the RA. PBMC cytokine studies revealed increased production of the type 1 cytokines IL-12, IFN-γ and TNF-α in the CA group compared with the RA group, under a range of activation conditions, however, the production of IL-4 and IL-5 were unchanged. These findings suggest that decreased type 1 cytokine expression as well as decreased eosinophilic inflammation is associated with the resolution of asthma symptoms.

Does bronchial hyperresponsiveness in childhood predict active asthma in adolescence?

RATIONALE

Bronchial hyperresponsiveness (BHR) is an important, but not specific, asthma characteristic.

OBJECTIVES

We aimed to assess the predictive value of BHR tested by methacholine and exercise challenge at age 10 years for active asthma 6 years later.

METHODS

From a Norwegian birth cohort, 530 children underwent methacholine challenge and exercise-induced bronchoconstriction (EIB) test (n = 478) at 10 years and structured interview and clinical examination at age 16 years. The methacholine dose causing 20% reduction in FEV(1) (PD(20)) and the reduction in FEV(1) (%) after a standardized treadmill test were used for BHR assessment. Active asthma was defined with at least two criteria positive: doctor's diagnosis of asthma, symptoms of asthma, and/or treatment for asthma in the last year.

MEASUREMENTS AND MAIN RESULTS

PD(20) and EIB at 10 years of age increased the risk of asthma (β = 0.94 [95% confidence interval (CI), 0.92-0.96] per μmol methacholine and β = 1.10 [95% CI, 1.06-1.15] per %, respectively). Separately the tests explained 10 and 7%, respectively, and together 14% of the variation in active asthma 6 years later. The predicted probability for active asthma at the age of 16 years increased with decreasing PD(20) and increasing EIB. The area under the curve (receiver operating characteristic curves) was larger for PD(20) (0.69; 95% CI, 0.62-0.75) than for EIB (0.60; 95% CI, 0.53-0.67).

CONCLUSIONS

BHR at 10 years was a significant but modest predictor of active asthma 6 years later, with methacholine challenge being superior to exercise test.

Assessment of the association between atopic conditions and tympanostomy tube placement in children

This study assesses the relationship between otitis media and atopic conditions in children by comparing the incidence of tympanostomy tube placement between children with and without atopic conditions: asthma, allergic rhinitis, and atopic dermatitis. Study subjects were a cohort of 323 healthy children who participated in a study of vaccine response. All episodes of tympanostomy tube placement and physician diagnoses of allergic rhinitis and atopic dermatitis were collected through comprehensive medical record review. Asthma status was ascertained through application of established criteria. We compared incidence rates of tympanostomy tube placement between children with and without atopic conditions. We fitted data to a Poisson regression model to calculate relative risk ratios (RRs) and their corresponding 95% confidence intervals (95% CI). Three subjects were excluded who did not have parental authorization for using records for research. Of the remaining 320 subjects, 170 (53%) were male subjects, 268 (94%) were white, 124 (39%) were asthmatic patients, and 20 (6%) had tympanostomy tube placement. Children with asthma before the index date of tympanostomy tube placement were more likely to have tympanostomy tube placement compared with those without asthma (RR, 19.33; 95% CI, 11.41; 32.75; p < 0.001). We found a similar association between asthma ever (before or after index date) and the incidence of tympanostomy tube placement (RR, 1.53; 95% CI, 0.93-2.53; p = 0.095). This was true for children with allergic rhinitis compared with those without allergic rhinitis (RR, 1.70; 95% CI, 1.01-2.86; p = 0.007). Atopic dermatitis was not associated with the incidence of tympanostomy tube placement. Asthma or allergic rhinitis may be unrecognized risk factors for recurrent or persistent otitis media. However, given the small sample size of the study, a cohort study with a larger sample size is necessary.

Bronchial hyperresponsiveness decreases through childhood

Limited knowledge exists about development of bronchial hyperresponsiveness (BHR) through adolescence. We aimed to assess changes in and risk factors for BHR in adolescence. From a Norwegian birth cohort 517 subjects underwent clinical examinations, structured interviews and methacholine challenges at age 10 and 16. BHR was divided into four categories: no BHR (cumulative methacholine dose required to reduce FEV(1) by 20% (PD(20)) >16 μmol), borderline BHR (PD(20) ≤16 and >8 μmol), mild to moderate BHR (PD(20) ≤8 and >1 μmol), and severe BHR (PD(20) ≤ 1 μmol). Logistic regression analysis was used to assess risk factors and possible confounders. The number of children with PD(20) ≤ 8 decreased from 172 (33%) to 79 (15%) from age 10-16 (p < 0.001). Most children (n = 295, 57%) remained in the same BHR (category) from age 10-16 (50% with no BHR), whereas the majority 182 (82%) of the 222 children who changed BHR category, had decreased severity at age 16. PD(20) ≤ 8 at age 10 was the major risk factor for PD(20) ≤ 8 6 years later (odds ratio 6.3), without significant confounding effect (>25% change) of gender, active rhinitis, active asthma, height, FEV(1)/FVC, or allergic sensitization. BHR decreased overall in severity through adolescence, was stable for the majority of children and only a minority (8%) had increased BHR from age 10 to 16. Mild to moderate and severe BHR at age 10 were major risk factors for PD(20) ≤ 8 at 16 years and not modified by asthma or body size.

Exercise-induced asthma in children

Exercise-induced bronchoconstriction affects 40-90% of people with asthma, compared with 3-15% of the general population. Exercise-induced asthma (EIA) is diagnosed on the basis of subjective symptoms of airflow obstruction during and after exercise, objective measures of airflow obstruction and the exclusion of alternative diagnoses. Although the pathogenesis of EIA has not been fully elucidated, two major theories have been proposed: the airway rewarming theory and the hyperosmolarity theory. Increasing evidence suggests that airway inflammation plays a major role in the pathogenesis of EIA. In this article, we review the prevalence, pathogenesis, methods for diagnosis and treatment of EIA, as well as the responsiveness of children and adolescents to EIA therapies.

Early daycare is associated with an increase in airway symptoms in early childhood but is no protection against asthma or atopy at 8 years

RATIONALE

Daycare exposes young children to more infections early in life and may thereby prevent the development of asthma and allergy.

OBJECTIVES

To prospectively study the effect of daycare on the development of asthma and allergic sensitization during the first 8 years of life.

METHODS

In the Prevention and Incidence of Asthma and Mite Allergy birth cohort 3,963 newborn children were followed prospectively for 8 years. Daycare use and respiratory health were assessed yearly by questionnaires. At 8 years, sensitization to airborne allergens and airway responsiveness were measured. Daycare was defined as early (aged 0-2 yr), late (aged 2-4 yr), or none (no daycare before age 4 yr). Associations of daycare and/or older siblings with asthma symptoms (wheezing, shortness of breath, and inhaled steroids taken in the last year), airway responsiveness, and allergic sensitization were assessed in a longitudinal repeated-event analysis.

MEASUREMENTS AND MAIN RESULTS

Children with early daycare had more wheezing in the first years of life, but less wheezing and steroid use between 4 and 8 years of age. At the age of 8 years, early daycare was not protective for asthma symptoms (adjusted odds ratio [aOR], 0.99; 95% confidence interval [CI], 0.74-1.32), allergic sensitization (aOR 0.86; 95% CI, 0.63-1.18), or airway hyperresponsiveness (aOR, 0.80; 95% CI, 0.57-1.14). The transient reduction in airway symptoms between age 4 and 8 years was only observed in children without older siblings.

CONCLUSION

Early daycare is associated with an increase in airway symptoms until the age of 4 years, and fewer symptoms between the ages of 4 and 8 years. We found no protection against asthma symptoms, hyperresponsiveness, or allergic sensitization at the age of 8 years.

Infant swimming practice, pulmonary epithelium integrity, and the risk of allergic and respiratory diseases later in childhood

OBJECTIVE

Irritant gases and aerosols contaminating the air of indoor swimming pools can affect the lung epithelium and increase asthma risk in children. We evaluated the impact of infant swimming practice on allergic status and respiratory health later in childhood.

METHODS

Clara cell protein, surfactant-associated protein D, and total and aeroallergen-specific immunoglobulin E were measured in the serum of 341 schoolchildren aged 10 to 13 years, among whom 43 had followed an infant swimming program. Asthma was defined as doctor-diagnosed asthma and/or positive exercise-induced bronchoconstriction (15% decrease in postexercise forced expiratory volume).

RESULTS

There were no significant differences between the infant swimming group and the other children regarding the levels of exhaled nitric oxide and total or aeroallergen-specific serum immunoglobulin E. Children who swam as infants showed, by contrast, a significant decrease of serum Clara cell protein and of the serum Clara cell protein/surfactant-associated protein D ratio integrating Clara cell damage and permeability changes of the lung epithelial barrier. These effects were associated with higher risks of asthma and of recurrent bronchitis. Passive exposure to tobacco alone had no effect on these outcomes but seemed to interact with infant swimming practice to increase the risk of asthma or of recurrent bronchitis.

CONCLUSIONS

Our data suggest that infant swimming practice in chlorinated indoor swimming pools is associated with airways changes that, along with other factors, seem to predispose children to the development of asthma and recurrent bronchitis.

How does exercise cause asthma attacks?

PURPOSE OF REVIEW

To remind readers that evaporative water loss from the airway surface is the stimulus for exercise-induced bronchoconstriction. To emphasize that recruitment of the peripheral airways determines severity of exercise-induced bronchoconstriction. To draw attention to the potential for injury of the epithelium and for plasma exudation to contribute to the pathogenesis of exercise-induced bronchoconstriction in athletes. To emphasize that many inflammatory mediators are involved in exercise-induced bronchoconstriction and that some are found in both asthmatic and healthy subjects.

RECENT FINDINGS

That inflammatory mediators are released into the airways in response to exercise and can be measured by inducing sputum (histamine, cysteinyl leukotrienes) or collecting condensate from exhaled air (cysteinyl leukotrienes and adenosine). The concentration of mediators was reduced in response to a combination of loratadine and montelukast. Exercise is a stimulus for upregulating the genes coding for the 5-lipoxygenase pathway in healthy subjects.

SUMMARY

Dehydration of the airways results in release of mediators. The likely source of these mediators is the mast cell. Epithelial injury occurs in exercise-induced bronchoconstriction. The process of repair may contribute to the development of airway hyperresponsiveness in healthy subjects. Measuring the airway response to exercise, or a surrogate for exercise, as an indicator of airway hyperresponsiveness is warranted in patients with symptoms of asthma.

Vocational and working career of asthmatic adolescents is only slightly affected

INTRODUCTION

The aim of this study was to investigate whether teenagers and adolescents (10-22 years) with asthma or asymptomatic bronchial hyperresponsiveness, were more likely to experience vocational or professional career limitations in the future, as compared to non-asthmatic contemporaries.

METHODS

Data were used from a 14-year follow-up study in general practice, investigating the relationship between respiratory health in childhood and adolescence. At follow-up, the respiratory health status and information about career limitations were obtained.

RESULTS

There were no statistical significant differences between asthmatics (n=52) and non-asthmatics (n=154) in the proportion currently employed subjects, or contract type. Most examined career limitations were infrequently reported in both groups, but seemed to occur slightly more frequent among asthmatics. Asthmatics seemed to have an increased risk for limitations in daily activities both attributable to their respiratory health (OR=2.6, 95% CI [1.0; 7.0]) and all-cause (OR=1.8, 95% CI [0.9; 3.3]), and for absence from work all-cause (OR=1.7, 95% CI [0.9; 3.3]). However, the differences were in most cases in the magnitude of only a few days per year. Neither lung function nor bronchial hyperresponsiveness did predict absence from work, or limitations in daily activities.

CONCLUSION

Asthmatic young adults seem to experience somewhat more limitations in their vocational and professional careers. Nonetheless, the majority of the young asthmatics seem to be only slightly limited in their careers. In non-asthmatic young adults the presence of asymptomatic bronchial hyperresponsiveness does not seem to lead to career limitations.

Impulse Oscillometry

OBJECTIVES

To generate reference equations in North American children to be used for assessing respiratory function through the forced oscillation (Rfo) technique, and to determine the changes in oscillatory resistance, reactance, and resonant frequency (Fres) in relation to age, body height, and weight.

DESIGN/SETTING

A prospective cross-sectional study performed on healthy children selected according to strict criteria of American Thoracic Society and European Respiratory Society recommendations.

MEASUREMENTS

Triplicate measures were obtained of resistance and reactance at 5, 10, 15, 20, 25, and 35 Hz as well as Fres through the impulse oscillometer (MasterScreen IOS; Jaeger/Toennies; Höchberg, Germany). Two hundred twenty-two white children--normally distributed within the 3- to 10-year age range and 100 to 150 cm in height--were recruited in Montreal, Canada. We used regression analysis to generate multiple predictive equations separately per gender and frequency on age, height, and body weight.

RESULTS

Stepwise multiple regression in both natural and logarithmic forms for height, weight, age, and gender showed that standing height was the only significant predictor for all variables. Minimal variability was noted in each subject among the triplicate measurements (p = 0.68 to 0.96). Coherence was > 0.9 at all oscillating frequencies except 5 Hz (< 0.72), with tendencies to lower values in young children.

CONCLUSIONS

Resistance and Fres decrease by height, but also by age; and reactance increases. As opposed to our past experience with spirometry in compatible age groups, the Rfo technique was well accepted by preschool children.

Towards improving the accuracy of diagnosing asthma in early childhood

OBJECTIVES

Early and correct diagnosis of asthma in wheezing children is essential for early treatment and prevention of under- or over-treatment. The aim was to study whether combining frequency and age of onset of wheezing illness with respiratory and atopic morbidity at age 0-6 years and sociodemographic parameters for asthma might be helpful for the general practitioner to diagnose asthma early and accurately.

METHODS

Birth cohort, mean follow-up 20 years (SD 4.8) in general practice. The outcome, adolescent asthma, was analysed in relation to wheezing and non-wheezing respiratory and personal and familial atopic morbidity. All diagnoses were from the Continuous Morbidity Registration of the Department of General Practice of the University of Nijmegen, the Netherlands.

RESULTS

1586 (64%) of the children could be followed. Adolescent asthma occurred in 6.4%. There were indications for under- and over-diagnosis of asthma at age 0-6 years. Non-recurrent wheezing (only one episode) and recurrent wheezing (>or =2 episodes) in the first three years of life, and recurrent wheezing at age 4-6 increased the risk with odds ratios (95% confidence interval) of 3.3 (1.9-5.6), 4.7 (2.8-8.2) and 15.4 (7.1-33.7), respectively. The risk additionally increased independently with a family history for asthma, (2.0 [1.1-3.6]), atopic dermatitis (1.7 [1.1-2.7]) and sinusitis (2.9 [1.3-6.4]) and decreased for > or =2nd born children (0.38 [0.19-0.47]) and those with a low social-economic status (0.61 [0.39-0.94]).

CONCLUSION

Easily available history and clinical data may facilitate the early diagnosis of asthma in children with wheezing illness.

Exercise-induced respiratory symptoms are poor predictors of bronchoconstriction

Exercise-induced asthma (EIA) is a possible cause of poor physical performance in children. No data are available on the value of respiratory symptoms to discriminate children with bad physical fitness from children with EIA. We evaluated respiratory symptoms in school-age children during and after exercise in relation to EIA. The population of 149 primary schools (849 classes with 15,241 children) was enrolled in the study. EIB was assessed using the 6-min free-running-test (6MFRT) in 15,241 children. At the end or at premature arrest of the 6MFRT, signs reported by the children and clinical symptoms observed by supervising physicians were recorded. Peak flow measurements were obtained before and 5 and 10 min after the 6MFRT, a decrease of 15% or more being defined as significant. The 6MFRT was positive in 7.4% of primary schoolchildren. Girls were more likely to have a positive test than boys (8.5% vs. 6.4%, P < 0.001), and children living in urban areas more than those living in rural areas (8.9% vs. 7.0%, P < 0.01). Premature arrest was seen in 3.5% (i.e., n = 353) of the children. The main reasons for premature arrest were dyspnea and chest pain. Among them, only 21% had a positive 6MFRT, while 89% with a positive 6MFRT could terminate the test. Premature arrest, breathlessness, chest tightness, wheezing, and cough had a positive predictive value to detect a EIA of 21.9%, 20.8%, 36.4%, 41.2%, and 28.3%, respectively, and a sensitivity of 10.8%, 29.5%, 14.9%, 4.8%, and 13.0%, respectively. In conclusion, EIA was detected in 7.4% of schoolchildren. A slightly higher incidence was observed in girls and children from an urban area. Neither premature arrest nor clinical signs and symptoms were good predictors of EIA in primary schoolchildren.

The burden of asthma in children: an Australian perspective

The burden of asthma among children is high in Australia compared with many other countries. Recent data show that 14-16% of children report a diagnosis of asthma that remains a problem. Boys, children under the age of 5 years and urban indigenous children experience a greater burden of asthma than other children. More than one-third of children with asthma have sleep disturbance due to the illness and 60% have missed school and/or experienced other restrictions in their activities due to the disease. Despite this, there is continuing evidence of under-utilisation of effective treatment for the disease. Asthma is a major cause of healthcare utilisation among children. Since the early 1990s, there has been a decline in both hospitalisation rates and general practitioner consultation rates for asthma among children. It remains to be seen whether this favourable trend will continue and extend into the adult age range.

Rationale for the Dutch hypothesis. Allergy and airway hyperresponsiveness as genetic factors and their interaction with environment in the development of asthma and COPD

The Dutch hypothesis, formulated in the 1960s, holds that the various forms of airway obstruction are different expressions of a single disease entity. It suggests that genetic factors (eg, airway hyperresponsiveness [AHR] and atopy), endogenous factors (eg, sex and age), and exogenous factors (eg, allergens, infections, and smoking) all play a role in the pathogenesis of chronic nonspecific lung disease. This review finds evidence that AHR and smoking are common risk factors for asthma and COPD. To prove the Dutch hypothesis definitively, however, genetic studies, preferably longitudinal, must be performed. Such studies must include subjects who have airway obstruction that does not necessarily meet the current strict definitions of asthma or COPD (ie, the extremes of these conditions) that are used in clinical studies.

Bronchial hyperresponsiveness in children with atopic rhinitis: a 7-year follow-up

BACKGROUND

A high prevalence of bronchial hyperresponsiveness (BHR) was found in atopic subjects with rhinitis. Those subjects may be at higher risk for developing bronchial asthma. We evaluated, in a 7-year follow-up, BHR and atopy in a homogeneous population of nonasthmatic children with allergic rhinitis (AR), and their role in asthma development.

METHODS

Twenty-eight children (6-15 years) with AR were studied. At enrollment (T(0)), skin tests, total serum IgE assay, peak expiratory flow (PEF) monitoring and methacholine (Mch) bronchial challenge were performed. BHR was computed as the Mch dose causing a 20% forced expiratory volume (FEV)(1) fall (PD(20)FEV(1)) and as dose-response slope (D(RS)). Subjects were reassessed after 7 years (T(1)) using the same criteria.

RESULTS

At T(0), 13 children (46%), showing a PD(20)FEV(1) <1526 microg of Mch, had BHR (Mch+), although PEF variability (PEFv) was within normal limits. None of the children with negative methacholine test developed bronchial asthma after 7 years. Of the 13 Mch+, only two reported asthma symptoms after 7 years. No significant change was seen in the other parameters of atopy considered.

CONCLUSION

Children with allergic rhinitis present a high prevalence of BHR. Nevertheless, their PEFv is normal and the rate of asthma development low.

Lung hyperpermeability and asthma prevalence in schoolchildren: unexpected associations with the attendance at indoor chlorinated swimming pools

AIMS

To study whether exposure to nitrogen trichloride in indoor chlorinated pools may affect the respiratory epithelium of children and increase the risk of some lung diseases such as asthma.

METHODS

In 226 healthy children, serum surfactant associated proteins A and B (SP-A and SP-B), 16 kDa Clara cell protein (CC16), and IgE were measured. Lung specific proteins were measured in the serum of 16 children and 13 adults before and after exposure to NCl(3) in an indoor chlorinated pool. Relations between pool attendance and asthma prevalence were studied in 1881 children. Asthma was screened with the exercise induced bronchoconstriction test (EIB).

RESULTS

Pool attendance was the most consistent predictor of lung epithelium permeability. A positive dose-effect relation was found with cumulated pool attendance and serum SP-A and SP-B. Serum IgE was unrelated to pool attendance, but correlated positively with lung hyperpermeability as assessed by serum SP-B. Changes in serum levels of lung proteins were reproduced in children and adults attending an indoor pool. Serum SP-A and SP-B were already significantly increased after one hour on the pool side without swimming. Positive EIB and total asthma prevalence were significantly correlated with cumulated pool attendance indices.

CONCLUSIONS

Regular attendance at chlorinated pools by young children is associated with an exposure dependent increase in lung epithelium permeability and increase in the risk of developing asthma, especially in association with other risk factors. We therefore postulate that the increasing exposure of children to chlorination products in indoor pools might be an important cause of the rising incidence of childhood asthma and allergic diseases in industrialised countries. Further epidemiological studies should be undertaken to test this hypothesis.

Hypertonic saline challenge tests in the diagnosis of bronchial hyperresponsiveness and asthma in children

The hypertonic saline challenge test is the recommended method to assess bronchial hyperresponsiveness in the International Study of Asthma and Allergies in Childhood (ISAAC). The sensitivity of this procedure to assess asthma symptoms, however, has been reported to vary among study centers. The purpose of our study was to evaluate the value of this provocation test in an epidemiological survey in children, and to relate the degree of bronchial hyperresponsiveness to the severity of asthma symptoms. All 11-13-year-old children from 16 randomly selected schools in Linköping, Sweden received a questionnaire regarding respiratory symptoms and allergic disease. Skin prick tests with eight inhalant allergens were performed. In addition, all children with wheeze over the past 12 months (current wheeze) and a random sample of children without current wheeze were invited to perform hypertonic saline provocation tests. A complete data set was available for 170 children, including 50 with and 120 without current wheeze. Bronchial hyperresponsiveness (BHR) was defined as at least 15% decline in FEV1. The degree of BHR was represented by the response/dose ratio, i.e. the fall in FEV1 divided by total dose of inhaled saline. The severity of asthma symptoms was classified by the number of wheezing episodes over the past 12 months. 'Asthma ever' was defined by a combination of symptoms in the questionnaires. Children with 'asthma ever' and current wheeze were considered as having current asthma. Current atopic asthma was defined as current asthma with at least one positive skin prick test. The sensitivity of the procedure to detect 'asthma ever', current asthma and current atopic asthma was 62, 61 and 83%, and the specificity 83, 81 and 60%, respectively. The positive challenge rate was 52, 34, 13 and 7% among current wheezers, previous wheezers, non-wheezers with a history of allergy and healthy children. The degree of bronchial hyperresponsiveness increased with the number of wheezing episodes. Thus, the median and range of the response/dose ratio were 4.8%/ml (2.1-14.8), 2.6%/ml (0.7-8.6) and 1.3%/ml (0.8-2.7), respectively, for children with >/= 4 episodes, 1-3 episodes and no wheezing episodes over the past 12 months (p<0.001). In conclusion, hypertonic saline provocation test is useful as a tool to detect asthma in epidemiological studies in children. The degree of bronchial hyperresponsiveness, as represented by the response/dose ratio, reflects the severity of asthma symptoms.

Outcome in adulthood of asymptomatic airway hyperresponsiveness in childhood: a longitudinal population study

The clinical outcome of asymptomatic airway hyperresponsiveness (AHR) first detected in childhood is sparsely reported, with conflicting results. We used a birth cohort of 1,037 children followed to age 26 years to assess the clinical outcome of asymptomatic AHR to methacholine first documented in study members at age 9 years. Of 547 study members who denied wheezing symptoms ever at age 9 years, 41 (7.5%) showed AHR. Forty showed methacholine responsiveness, with a provocation concentration of methacholine that elicited a 20% drop in forced expired volume in 1 sec (PC(20)) < or = 8 mg/mL, and one had baseline airway obstruction with a bronchodilator response exceeding 10%. Of these 41 study members, 18 (44%), 11 (27%), and 4 (10%) maintained AHR in 1, 2, and 3 later assessments, respectively, while 23 (56%) manifested AHR only at age 9. Compared with asymptomatic study members without AHR, those with asymptomatic AHR at age 9 years were more likely to report asthma and wheeze at any subsequent assessment, were more likely to have high IgE levels and eosinophils at ages 11 and 21, and more often demonstrated positive responses to skin allergen testing at ages 13 and 21 years. Persistent AHR at later assessments increased these likelihoods further.In conclusion, asymptomatic children with AHR are more likely to develop asthma and atopy later in life compared with asymptomatic children without AHR. Persistent AHR, even though initially asymptomatic, was associated with an even greater increased risk of development of asthma. We suggest that rather than considering AHR as a marker of asthma, it should be regarded as a parallel pathological process that may lead to subsequent symptoms and clinical evidence of asthma.

Puberty and prognosis of asthma and bronchial hyper-reactivity

It is a commonly held view that pediatric asthma frequently abates during puberty. However, little data are available that associate the stage of puberty with the prognosis of asthma and bronchial hyper-reactivity (BHR). In this study, 155 children with active asthma at 10 years of age (60 girls [38.70%], 95 boys [61.3%]) were followed-up until they reached 14 years of age. The stage of puberty was assessed by parental questionnaire; in addition, serum 3-alpha-androstanediolglucuronide, as an endocrinological marker for peripheral androgen status, was measured in 107 subjects. Persistence of asthma was determined via questionnaire, lung function testing, and bronchial provocation (hyperventilation of cold, dry air). At 14 years of age, 73.3% of girls were reported to have had menarche and 40.8% of boys a voice change, and only 35.5% of the subjects had experienced acute asthma symptoms during the last 12 months, with an almost unchanged gender ratio (19 girls [34.5%], 36 boys [65.5%]) vs. that recorded at 10 years of age. The level of androstanediolglucuronide was higher in the children who reported puberty (mean+/-SD): 3.03+/-2.13 nmol/l vs. 1.89+/-1.26 nmol/l, p = 0.003. No statistically significant relationship was found between the reported signs of late puberty and loss of asthma or BHR. Likewise, no significant association was found between asthma persistence and the level of androstanediolglucuronide (2.39+/-1.75 nmol/l vs. 2.44+/-1.82 nmol/l, p = 0.84), or BHR and the level of androstanediolglucuronide (3.02+/-1.97 nmol/l vs. 2.28+/-1.67 nmol/l, p = 0.13), at 14 years of age, in girls or boys. At 14 years of age, no change in the gender ratio of children with active asthma had occurred. These results may indicate that the change in gender predominance of asthma through the second decade of life is not caused by increased loss of established asthma in boys between 10 and 14 years of age.

Bronchial hyperresponsiveness to 4.5% hypertonic saline indicates a past history of asthma-like symptoms in children

SUMMARY. To evaluate the importance of a past history of asthma-like symptoms over a period of 2 years and current bronchial hyperreactivity (BHR), 538 randomly selected schoolchildren, initially aged 7-8 years, were examined. At yearly intervals, three standardized questionnaires, including items from the ISAAC panel, were answered by parents. Following the last questionnaire, BHR to 4.5% hypertonic saline (HS) was recorded. In survey 1, lifetime prevalence of asthma was 4.9%. During the 12-month period, prevalence of wheeze and dyspnea ranged between 9.3 and 5.2% (Survey 1) and 5.9% and 4.4% (Survey 2). Among children with wheeze or dyspnea in Survey 3, BHR (defined as a fall of baseline FEV(1) > or = 15%) was significantly more frequent (50.0% and 60.7%, respectively) than among children without these symptoms (12.8%, P < 0.001, and 12.8%, P < 0.001, respectively). The negative predictive value of BHR to have neither wheeze nor dyspnea was about 88% and did not vary throughout the study (Survey 1, 87%; Survey 2, 88%; Survey 3, 88%). The relative risk of showing BHR was significantly increased in children with wheeze (survey 2, odds ratio (OR) 3.0 (95% confidence interval (CI) 1.0-8.7)) or dyspnea (Survey 1: OR 5.9 (95% CI 1.9-18.5), Survey 3: 5.2 (1.7-16.2), but not in children with dry cough or nocturnal cough (data not shown). Wheeze and dyspnea occurred repeatedly in the same individuals with BHR in a high percentage of children (83.3% and 76.5%, respectively). In conclusion, there is a strong association between recent and previous dyspnea and current BHR, and it indicates intraindividual persistence of symptom history.

Effects of specific immunotherapy in allergic rhinitic individuals with bronchial hyperresponsiveness

Allergic rhinitis can be associated with bronchial hyperresponsiveness (BHR), and carries an increased risk for the development of asthma. The aim of this study was to evaluate the ability of specific immunotherapy (SIT) to reduce the progression of allergic rhinitis to asthma and prevent the associated increase in BHR. Forty-four subjects monosensitized to Dermatophagoides pteronyssinus, with perennial rhinitis and BHR to methacholine, were randomly assigned to receive SIT or placebo in a double-blind study conducted over a period of 2 yr. After 1 yr of treatment, a 2.88-fold increase in the provocative dose of methacholine producing a 20% decrease in FEV(1) (PD(20)FEV(1)) was recorded in the SIT-treated group (95% confidence interval [CI]: 3.98- to 2.09-fold; p < 0.001), with a further increase to fourfold at the end of Year 2 (95% CI: 2.9- to 5.7-fold; p < 0.001). At the end of the study, the methacholine PD(20)FEV(1) was within the normal range in 50% of treated subjects (p < 0.0001), and was significantly higher in this group than in the group receiving placebo (p < 0.0001). In contrast, no changes in methacholine PD(20)FEV(1) were found in the placebo group throughout the study. Although 9% of subjects given placebo developed asthma, none of those treated with SIT did. This study suggests that SIT, when administered to carefully selected, monosensitized patients with perennial allergic rhinitis, reduces airway responsiveness in subjects with rhinitis, and may be an appropriate prophylactic treatment for rhinitic patients with hyperreactive airways.

Problems and possibilities in understanding the natural history of asthma

In early life, asthma symptoms can occur intermittently or may not be severe enough to limit normal activities, which makes it difficult for the clinician to make reliable predictions and administer therapy with some precision. In the case of pediatric asthma, the identification of children who will experience the development of a clinically important illness that will impair their quality of life can be a complex process. The usual methods for describing this information include the prognostic statistics of sensitivity, specificity, likelihood ratio, and positive predictive value. The sensitivity, specificity, and likelihood ratio of various early markers of asthma have been calculated from several cohort studies.

Airway hyperresponsiveness and symptoms of asthma in a six-year follow-up study of childhood asthma

BACKGROUND AND AIM

In an inception cohort study of 457 asthmatic children diagnosed at the age of 3 to 4 years, airway hyperresponsiveness (AHR) was assessed 6 years after first diagnosis in a subgroup of 84 children. Our objective was to associate the level of AHR with the symptomatic asthma status at follow-up.

METHODS

Information on respiratory symptoms and medication use for the previous 6 years was obtained. Children with reported wheezing episodes during the previous year (n = 169) or for > or = 2 years at any time during the follow-up period (n = 85) were eligible for the challenge test.

RESULTS

Among the 254 eligible children, 166 were randomly selected. The parents of 88 of them consented to have their child participate. At the time of assessment of AHR, 19 children (22%) were asymptomatic and 24 others (29%) had symptoms but did not use any medication. Forty-one children (49%) were symptomatic and required medication, including antiinflammatory preparations in 26 instances (31%). All but two children had significant AHR. There was no significant association between the level of AHR and graded symptomatic and medication score. Twenty-four of the 70 children (34%) with greatly enhanced AHR used no medication.

CONCLUSIONS

This study shows that (1) almost all children first diagnosed with asthma 6 years ago and with persisting but not necessarily current symptoms of asthma have increased AHR, which satisfies a proposed epidemiologic definition of asthma; (2) AHR was present in 95% of the 20 currently asymptomatic children; and (3) one third of children with greatly enhanced AHR did not use any treatment.

Use of pocket-sized turbine spirometer in monitoring exercise-induced bronchospasm and bronchodilator responses in children

For field studies of asthma, portable hand-held pulmonary function testing devices are required. Other than for peak flow measurements, little has been done to validate their use in children. Fifty children aged 5-15 years having asthma symptoms were examined using an exercise challenge (8 min free running outdoors) and a bronchodilation test (salbutamol inhalation at a dose of 0.15 mg/kg). Pulmonary function was measured with a turbine spirometer, with a Wright peak flow meter (WPEF) and with a flow-volume spirometer (FVS). A fall of 15% or more in peak expiratory flow associated with wheezing or cough was considered diagnostic for bronchial hyper-responsiveness to exercise (BHRE). A rise of 15% or more from baseline in peak expiratory flow after salbutamol inhalation was considered as a positive bronchodilator response (BDR). BHRE was present in 16 children (32%). Using the limit of a 15% or greater fall in FEV1, turbine spirometry identified 12 as BHRE-positive and no additional cases, giving a sensitivity of 75% and a specificity of 100%. The turbine spirometer showed lower FEV1 values than the FVS, the difference increasing with airway obstruction. BDR was positive in eight children (16%). Using the limit of a 10% or greater rise in FEV1, turbine spirometry was positive in six cases. FEV1 measured by turbine spirometry could not be used interchangeably with conventional FVS. However, the turbine spirometer offers the possibility to measure FEV1 repeatedly in field conditions, such as during exercise challenges outdoors.

Interrupter technique for evaluation of exercise-induced bronchospasm in children

The free running test is a useful method for evaluation of exercise-induced bronchospasm in children. In young children this test simulates real-life circumstances and can be done more easily than histamine or methacholine challenges. The interrupter technique is a noninvasive method for measuring airflow resistance during tidal breathing. This approach requires minimal cooperation, and is therefore promising for use in young children. Fifty children aged 5-15 years with asthma symptoms were tested by exercise challenge consisting of free outdoor running for 8 min at 85% of maximal predicted heart rate for age. Pulmonary function was measured by using the interrupter technique (IR), with a Wright's peak flow meter (WPEF), and by flow-volume spirometry (FVS). The measurements were done before and 10 min after exercise. In addition, WPEF was measured at 5, 15, and 20 min after exercise. A fall of 15% or more in WPEF associated with wheezing or cough symptoms was considered a positive test. The exercise challenge was positive in 16 (32%) of the 50 children. Measurements at 10 min by WPEF identified 9 positive cases. At the same time point the IR identified 10 positive cases; a rise in resistance of 15% or more was considered positive, giving it 80% sensitivity and 93% specificity. The repeatability coefficient (CoR) for the interrupter technique was 0.06 kPa x L(-1) x s (13%) before and 0.07 kPa x L(-1) x s (14%) after exercise. The IR provides a useful alternative for estimation of airway obstruction in children following exercise challenge. The results were comparable with the current reference methods of forced expiratory volume in 1 s and peak flow measurements.

The relationship of skin test positivity, high serum total IgE levels, and peripheral blood eosinophilia to symptomatic and asymptomatic airway hyperresponsiveness

The relationships of skin test positivity, high serum total IgE levels (> 100 kU/L), and peripheral blood eosinophilia (>/= 275 cells/microliter) to symptomatic (either chronic cough, chronic phlegm, bronchitis episodes, dyspnea, wheeze, or asthma) and asymptomatic bronchial hyperresponsiveness (BHR) were studied cross-sectionally in 620 adult subjects who participated in the Vlagtwedde-Vlaardingen Study of 1989 and 1990. Eosinophilia (OR = 2.06, 95% CI = 1.28 to 3.31) and skin test positivity (OR = 1.66, 95% CI = 1.02 to 2.71) were both significantly associated with BHR independent of age, sex, smoking, and urban area of residence. High serum total IgE levels were not associated with BHR (OR = 1.29, 95% CI = 0.81 to 2.03). Separate analyses for symptomatic and asymptomatic subjects showed that the higher risk of BHR with skin test positivity applied only to symptomatic subjects (OR = 5.78, 95% CI = 1.63 to 20.51), independent of eosinophilia and high serum total IgE levels. The higher risk of BHR with eosinophilia was not different between symptomatic and asymptomatic subjects, and independent of skin test positivity and high serum total IgE levels. The results of this study show that, in the general adult population, eosinophilia is associated with BHR both in symptomatic and asymptomatic persons, whereas skin test positivity is associated with BHR only in symptomatic subjects.

Reducing antibiotics for respiratory tract symptoms in primary care: consolidating 'why' and considering 'how'

We summarize recently published evidence showing that antibiotic treatment offers little or no benefit to most patients presenting with sore throats, acute otitis media, maxillary sinusitis, and acute bronchitis. Despite this research, the prescription of antibiotics for respiratory tract conditions is rising in Britain. This wastes money, encourages people to consult for self-limiting conditions, and causes bacteria to become resistant to antimicrobials. Ways of changing present practice are underresearched. Enhanced consulting skills, guidelines and monitoring strategies, patient education, and anti-inflammatory drugs for recurrent and chronic sufferers all hold promise.

Effect of dampness at home in childhood on bronchial hyperreactivity in adolescence

BACKGROUND

Relatively little is known about risk factors for the persistence of asthma and respiratory symptoms from childhood into adolescence, and few studies have included objective measurements to assess outcomes and exposure.

METHODS

From a large cross sectional study of all 4th grade school children in Munich (mean age 10.2 years), 234 children (5%) with active asthma were identified. Of these, 155 (66%) were reinvestigated with lung function measurements and bronchial provocation three years later (mean age 13.5 years).

RESULTS

At follow up 35.5% still had active asthma. Risk factors for persisting asthma symptoms in adolescence were more severe asthma (OR 4.94; CI 1.65 to 14.76; p = 0.004) or allergic triggers (OR 3.54; CI 1.41 to 8.92; p = 0.007) in childhood. Dampness was associated with increased night time wheeze and shortness of breath but not with persisting asthma. Risk factors for bronchial hyperreactivity in adolescence were bronchial hyperreactivity in childhood (p = 0.004), symptoms triggered by allergen exposure (OR 5.47; CI 1.91 to 25.20; p = 0.029), and damp housing conditions (OR 16.14; CI 3.53 to 73.73; p < 0.001). In a subgroup in whom house dust mite antigen levels in the bed were measured (70% of the sample), higher mite antigen levels were associated with bronchial hyperreactivity (OR per quartile of mite antigen 2.30; CI 1.03 to 5.12; p = 0.042). Mite antigen levels were also significantly correlated with dampness (p = 0.05). However, the effect of dampness on bronchial hyperreactivity remained significant when adjusting for mite allergen levels (OR 5.77; CI 1.17 to 28.44; p = 0.031).

CONCLUSION

Dampness at home is a significant risk factor for the persistence of bronchial hyperreactivity and respiratory symptoms in children with asthma. This risk is only partly explained by exposure to house dust mite antigen.

Why do only some of the young adults with bronchial hyperreactivity wheeze?

The significance of nonspecific bronchial hyperreactivity (BHR) is a controversial issue in asthma. The natural history of BHR has not been investigated adequately although its importance as a cross-sectional risk factor for asthma is widely accepted. This paper investigates the risk factors for wheeze among people with BHR. Subjects were young adults who had participated in the second phase of the European Community Respiratory Health Survey in Melbourne, Australia. We compared the participants with wheeze and BHR (n=186) to those with asymptomatic BHR (n=66). Information was collected on sociodemographic factors, family history of asthma, and relevant environmental factors using an interviewer-administered questionnaire. Atopy to a range of aeroallergens was examined by skin prick tests. Risk factors were examined by adjusting the odds ratios (OR) by a logistic regression to control for confounding effects. Parental asthma (OR=4.2), keeping pets during childhood (OR=3.3), allergy to house dust mite (OR=2.7), allergic rhinitis (OR=2.6), and having ever smoked (OR=2.4) were associated with an increased risk of wheeze, independent of the other factors examined. When allergic rhinitis was not included as an explanatory variable, being atopic to any of the allergens assessed was found to increase the risk of current wheeze (OR=4.8). Allergic rhinitis may represent an intermediate stage in the natural history of BHR. Avoidance of pets during childhood, not smoking, and taking steps to minimize dust exposure are likely to prevent the progression from asymptomatic BHR to asthma.

Prevalence of bronchial hyper-responsiveness in the southern, central and northern parts of Sweden

Studies have suggested that there is a higher prevalence of asthma in northern Sweden than in southern Sweden. Bronchial hyper-responsiveness (BHR) has been shown to be associated with asthma. The aim of this study was to explore the prevalence of bronchical hyper-responsiveness in different parts of Sweden. As part of the European Community Respiratory Health Survey (ECRHS), interviews, skin prick tests, lung function tests and methacholine provocation tests of the airways were performed in 1448 randomly selected subjects in southern, central and northern Sweden. The Mefar dosimeter was used according to the ECRHS protocol. The responsiveness was calculated both as the PD20 and as the dose response slope (DRS). BHR was defined as a PD20 of < or = 1.6 mg. Atopy was defined as at least one skin prick test of > or = 3 mm. The prevalence of BHR was 12.7%, 10.6% in men and 15.0% in women. No difference in prevalence was found between the three different regions of Sweden. The prevalence of BHR was higher in women than in men and higher in smokers than in non-smokers. Using multiple logistic regression, with BHR as the dependent variable, atopy, being female, having a low FEV1 (% predicted) and smoking (both own and passive) increased the odds of having BHR, while age and the region of Sweden did not influence BHR. Defining BHR as a PD20 of < or = 1.0 mg or a PD20 of < or = 2.0 mg did not change this. Multiple regression using log DRS as the dependent variable produced the same result. Both BHR and increasing DRS were associated with self-reported wheezing, attacks of shortness of breath during the daytime at rest or after strenuous activity, being awakened by a feeling of tightness in the chest or an attack of shortness of breath. In subjects without self-reported asthma, BHR was associated with self-reported wheezing and attacks of shortness of breath after strenuous activity. In conclusion, we found that the prevalence of BHR in the three investigated areas was 12.7%. We found a trend towards a higher prevalence of BHR in the most northerly of the study areas, but the difference between the areas was not statistically significant. BHR and DRS were associated with atopy, smoking, female sex and FEV1 (% predicted). The reporting of symptoms from the airways was associated with the degree of bronchical responsiveness.

The spectrum of irritant-induced asthma: sudden and not-so-sudden onset and the role of allergy

A retrospective investigation of 86 asthmatic subjects defined clinical features of irritant-induced asthma and assessed the contributory role of an allergic predisposition. Three categories of asthma were evaluated: (1) occupational asthma due to a sensitizer (11 subjects, 13%); (2) irritant-induced asthma (54 persons, 63%); and (3) not occupational/environmental exposure-related asthma (21 subjects, 24%). Two distinct clinical presentations of irritant-induced asthma emerged: the first was sudden onset (29 subjects) and the second was not so sudden in onset (25 subjects). Sudden-onset, irritant-induced asthma was analogous to the reactive airways dysfunction syndrome. Clinical manifestations began immediately or within a few hours (always within 24 h) following an accidental, brief, and massive exposure. In contrast, for the not-so-sudden-onset asthma subjects, the causative irritant exposure was not brief, usually not massive, continued for > 24 h, and the initiation of asthma took longer to evolve. Eighty-eight percent of individuals with not-so-sudden irritant-induced asthma displayed an atopy/allergy status (p < 0.01). Some of the atopy/allergy subjects with presumed new-onset asthma were found to have suffered preexisting asthma that had been clinically quiescent for at least 1 year before the triggering exposure (16 persons). We conclude that preexisting allergic/atopy and/or preexisting asthma were significant contributors to the pathogenesis of not-so-sudden, irritant-induced asthma and emphasizes a critical interaction between environmental and host factors in the pathogenesis of asthma.

Cold air challenge at age 6 and subsequent incidence of asthma. A longitudinal study

The aim of this study was to assess the relation between bronchial hyperresponsiveness to dry, cold air at age 6 and the subsequent incidence of asthma. The cumulative incidence of newly diagnosed asthma between ages 6 and 11 among 360 children included in this study was 12.0%. Survival analysis showed that hyperresponsiveness to cold air at age 6 was associated with an increased risk of developing subsequent asthma (hazard ratio = 2.6, 95% CI = 1.2-5.4; p = 0.01). However, after adjusting for potential confounders, only mild wheezing at age 6 (adjusted hazard ratio 7.5, 95% CI = 3.6-15.9; p < 0.001) and skin test reactivity to allergens at age 6 (adjusted hazard ratio 3.6, 95% CI = 1.5-8.5; p < 0.01), but not hyperresponsiveness to cold air (adjusted hazard ratio = 0.9, 95% CI = 0.4-2.2; p = 0.8), remained significant predictors of subsequent development of asthma. These findings were substantially confirmed after stratifying for wheezing illnesses before age 3. We conclude that hyperresponsiveness to cold air at age 6 was associated with subsequent development of a diagnosis of asthma but this effect was not independent of atopy and mild wheezing at age 6.

Asymptomatic airway hyperresponsiveness: a three-year follow-up

The physiopathology and significance of asymptomatic airway hyperresponsiveness (AHR) are still to be defined. Over a 3-yr period, we compared clinical, immunologic, and physiologic features of 30 subjects who had asymptomatic AHR with those of 30 symptomatic asthmatic subjects and 30 normoresponder subjects (age: 31.9 +/- 1.4 yr [mean +/- SEM]; n = 90). Each subject completed a respiratory questionnaire and underwent spirometry, measurement of bronchodilator response and peak expiratory flows, an allergy skin-prick test, blood eosinophil count, assay for total serum IgE level, and methacholine challenge. These tests were repeated annually, at the same period of the year, for 3 yr. Subjects with asymptomatic AHR had greater bronchodilator responses (p = 0.001), variability of peak expiratory flow rate (PEFR) (p = 0.02), and prevalence of atopy (p = 0.02) than did the normoreactive subjects. Compared with asthmatic subjects, subjects with asymptomatic AHR had a lower blood eosinophil count (p = 0.004), higher mean FEV1 (p = 0.006), and weaker bronchodilator response (p = 0.02), but an even greater perception of bronchoconstriction (p < 0.001). After 3 yr, the concentration of methacholine provoking a 20% decrease in FEV1 (PC20) had decreased significantly in the asymptomatic AHR subjects (p < 0.0001) as compared with the other two groups, and of the 28 subjects studied at this time, four (14.3%) had developed asthma symptoms. These last four subjects were atopic and exposed to animals when they developed asthma, had a familial history of asthma, and had an increased baseline AHR as compared with the subjects who did not develop symptoms. In conclusion, this study shows that over a 3-yr period, subjects with asymptomatic AHR had a greater increase in airway responsiveness and frequency of development of asthma symptoms than did normoresponsive subjects. Allergen exposure in sensitized subjects at the time of the study, and genetic predisposition, seemed the main risk factors for the development of symptomatic asthma in this population.

New insights into risk factors of asthma

The prevalences of bronchial asthma in the Asia-Pacific region range from 0 to 24% and appear to be increasing in some countries. The increased prevalence of asthma may be related to the urbanization of these countries or areas. Risk factors relating to the development of asthma are multiple and complex. These include: Predisposing or genetic factors: (atopy and bronchial hyperresponsiveness; BHR) that increase an individuals susceptibility. Longitudinal studies in children have shown that BHR precedes asthma in some individuals. A gene governing BHR is located near a major locus that regulates serum IgE levels on chromosome 5 q. An additional gene that determines the specificity of the immune response located in the human leukocyte antigen complex (HLA) may govern the specificity of the immune response to common aeroallengens in some individuals. Causal Factors: inhaled allergens are the most important causal factors of asthma, which include indoor allergens (domestic mites, animal, cockroach and fungus allergens), domestic mites being the most common potential allergen, and outdoor allergens (pollens from trees, grasses and weeds). Owing to the geographic location and different sensitivity to allergen between races, allergens vary from area to area. Certain drugs, food and food additives are also the cause of asthma attack. Contributing factors: smoking is an important trigger and a serious problem in most Asian-Pacific countries. Air pollution in particular sulfur dioxide (SO2), nitrogen dioxide (NO2) and respirating particles are common contributing factors. Very low concentration of SO2 (0.5 ppm) can cause bronhospasm in asthmatics. A combination of low concentration of SO2 and NO2 often encountered in heavy traffic further enhances the airway responsiveness to inhaled allergen. In addition, respiratory virus infection is closely associated to the development of asthma in childhood.

Prognostic factors for the outcome of childhood asthma in adolescence

By the second decade of life asthma symptoms often abate and it may seem that patients with mild asthma have "outgrown" the disease. Unfortunately this is likely to be the exception rather than the rule. Although the severity of asthma symptoms fluctuates with time, the inherited tendency towards respiratory symptoms never disappears and many teenagers who seem to be free of symptoms do, in fact, have persistent asthma. During symptom-free periods subclinical, but nevertheless significant, airways obstruction and/or bronchial hyperresponsiveness may be present. It is not unusual for adults who have been asymptomatic for a number of years to redevelope asthma symptoms. Indeed, much of the so-called adult onset asthma has its roots in childhood. Levison concluded that, in these subjects, it is often not the asthma that is outgrown but the paediatrician. The more severe asthma is in childhood the more likely it is that the disease will persist in adulthood. A complete list of the characteristics of the disease in childhood, and the potential risk factors associated with an unfavourable prognosis, such as pulmonary function and bronchial responsiveness and markers of airway inflammation, is therefore needed. As properly matched and controlled prospective long term studies have not been published it has not been possible to evaluate the effects on prognosis of any single class of antiasthma agent. Such studies are needed to find out if it is possible to alter the natural history of the disease. In theory modern asthma treatments, because they are able to improve symptoms and underlying disease phenomena, are also beneficial in the long term prognosis of childhood asthma. The majority of patients with persistent asthma included in the currently available studies were not receiving adequate treatment. Since compliance with therapeutic regimens in asthma, especially in adolescence, is low, a monitoring system is needed to guarantee adequate follow up and treatment during and beyond puberty.

Towards a better understanding of childhood asthma

OBJECTIVE

To explore the ways asthma may be defined in childhood and consider the current evidence to support these possible definitions.

METHODOLOGY

The relationship of symptoms, atopy, bronchial hyperresponsiveness (BHR) and airway inflammation in defining childhood asthma is reviewed.

RESULTS

While none of the four proposed methods of defining asthma can stand alone as the 'gold standard', in childhood asthma, all four, namely clinical symptoms, atopy, BHR and airway inflammation, are intimately related. The degree of atopy and BHR, and the presence of airway inflammation, should be viewed as significant risk factors for persistent wheezing in childhood.

CONCLUSION

At present the clinical diagnosis of asthma in childhood remains largely based on symptoms but it is likely that, with further research, the group of children who are now labelled as having asthma will be subdivided into different subgroups with implications for both treatment and outcome.