Prognosis of asthma from childhood to adulthood

The outcome of childhood asthma was studied in 101 adults who came from a group of 119 asthmatic children (85%) 6 to 14 yr of age who had originally been investigated between 1966 and 1969. Changes in respiratory symptoms, spirometry, and airway responsiveness to histamine in childhood and adult life were analyzed. It was found that 43 of the 101 adults (43%) had current symptoms; 29 of the 43 (67%) were receiving maintenance therapy. In the first study, 83 of the 101 children (82%) showed a response on inhalation of histamine (PC10-histamine less than or equal to 16 mg/ml). The number of subjects in the second study who still had a PC10-histamine less than or equal to 16 mg/ml fell to 29, suggesting that airway responsiveness decreases from childhood to adulthood. During the second survey (in adults), 25 of the 43 (59%) subjects with current symptoms and four of the 58 (7%) without respiratory symptoms responded to histamine. Adults with current symptoms had a significantly lower %FEV1 in both childhood and adulthood than did adults without current symptoms; %FEV1 was not different in females and males or in smokers and nonsmokers in either the first or the second survey. The outcome of childhood asthma is primarily predicted by the initial degree of bronchial obstruction (p = 0.041) and airway responsiveness to histamine (p = 0.050), and does not appear to be related to sex, smoking habits, or age of onset of respiratory symptoms.     

The relationship between airway responsiveness to histamine and pulmonary function level in a random population sample

The association of nonspecific bronchial responsiveness (BR) with pulmonary function level has been studied in a random population sample of 2,156 male and female subjects 15 to 64 yr of age participating in the Vlagtwedde-Vlaardingen field survey on chronic obstructive pulmonary disease (COPD) being conducted in the Netherlands. About 25% of the subjects responded with a decrease in baseline FEV1 of 10% or more after challenge with histamine in a concentration of 16 mg/ml or less inhaled over 30 s (PC10). In a stratified analysis, pulmonary function level appeared to be associated with BR in a dose-response relationship. The mean %FEV1 was consistently lower in the more responsive subjects. This relationship was confirmed in linear regression analyses, adjusting for age, sex, area of residence, and smoking habits. Exclusion of subjects with %FEV1 less than 80% diminished but did not change the association between FEV1 and BR. The magnitude of the effect of responsiveness on level of pulmonary function was considerable and statistically significant. In the subjects older than 21 yr of age, male responders (PC10 at less than or equal to 16 mg/ml) on average had an adjusted FEV1 of 32.5 centiliters less than nonresponders, and female responders had an adjusted FEV1 of 30.5 centiliters less (p less than 0.001). BR appeared to be an independent predictor of pulmonary function level after adjustment for age, sex, area of residence, respiratory symptom prevalence, and cigarette smoking. The effect of cigarette smoking on pulmonary function level in this population sample was significant only in men older than 21 yr of age.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cough threshold to inhaled tartaric acid and bronchial responsiveness to methacholine in patients with asthma and sino-bronchial syndrome.

To evaluate the effect of chronic airway inflammation on cough sensitivity and bronchial responsiveness, we measured the cough threshold to tartaric acid and bronchial responsiveness to methacholine (PC20-FEV1) in 13 asthmatic, 13 bronchitic (sino-bronchial syndrome) and 49 healthy non-atopic subjects. All subjects were non-smokers. The geometric mean value of the cough threshold was 9.55, 5.62 and 12.3% in asthmatic, bronchitic and normal subjects, respectively. The value in bronchitic subjects was significantly (p less than 0.02) lower than that in normal subjects. The geometric mean value of PC20-FEV1 in asthmatic subjects (0.63 mg/ml) was significantly lower than those in bronchitic (8.7 mg/ml) (p less than 0.01) and normal subjects (21.4 mg/ml) (p less than 0.01). There was no correlation between cough threshold and PC20-FEV1 values [correlation coefficient (r) = 0.06, p greater than 0.1]. These results indicate that cough sensitivity is potentiated by chronic airway inflammation in bronchitis but not in asthma and suggest that cough sensitivity and bronchial responsiveness may be independently potentiated by different mechanisms resulting from chronic airway inflammation.     

Airway responsiveness in early infancy predicts asthma, lung function, and respiratory symptoms by school age

Asthma is the most common chronic childhood disease in developed nations. Little is known about the relationship between airway responsiveness in infancy and the development of asthma later in life. The relationship of airway responsiveness at 1 mo with asthma, atopy, lower respiratory symptoms, and lung function at 6 yr of age was investigated prospectively in 95 white children from a randomly ascertained birth cohort. Baseline spirometry, airway responsiveness to histamine, and skin reactivity to common allergens were assessed at the age of 1 mo and 6 yr. Total serum immunoglobulin E (IgE) was measured from cord blood and at 6 yr. Blood eosinophil counts were measured at 6 yr only. Family, symptom, and exposure histories at both time points were derived from questionnaire data. Independently of the other factors assessed, increased airway responsiveness at 1 mo was significantly associated with the following parameters measured at six yr: decreased FEV(1) (p < 0.001); decreased FVC (p < 0.001); physician-diagnosed asthma (p < 0.001); and lower respiratory tract symptoms (p < 0.05). None of the other physiologic factors measured in infancy showed such consistent associations with important clinical and physiologic outcomes at age 6. These data suggest that airway responsiveness in early life defines a functional state that is associated with abnormal airway function, lower respiratory symptoms, and the emergence of asthma by 6 yr of age.     

Histamine induced airway response in pre-school children assessed by a non-invasive EMG technique

The aim of the study was to investigate the association between surface electromyographic (EMG) activity of the diaphragm and intercostal muscles, and clinical symptoms (wheeze, cough, increased respiratory rate and prolonged expiration) during bronchial challenge testing and after administration of salbutamol in asthmatic pre-school children. A histamine challenge test was performed in 20 asthmatic pre-school children. The histamine dose at the appearance of 1 or more clinical symptoms was defined as the maximum histamine provocation dose (PDcs). The clinical symptoms were recorded with a microphone over the trachea. The logarithm of the EMG-Activity-Ratio (log EMGAR; mean peak activity ratio to baseline of respiratory muscles during tidal breathing) was used as EMG parameter. In both the diaphragmatic and the intercostal log EMGAR values a linear increase was observed in the four histamine dose-steps prior to PDcs. At PDcs the mean log EMGAR of the diaphragm (di) and intercostal muscles (int) was significantly increased as compared to the baseline values. After administration of salbutamol the log EMGARdi and log EMGARint returned to baseline values and the clinical symptoms normalized in all children. At PDcs, no significant differences in the log EMGAR values could be detected at the appearance of the distinctive clinical symptoms, which suggests that wheezing is not the only indicator for the detection of airway responsiveness in young children. We found a linear association between histamine dose and the increase in surface diaphragmatic and intercostal respiratory EMG activity during a bronchial challenge test in pre-school asthmatic children, which returned to baseline values after inhalation of salbutamol. These findings support the idea that EMG measurements of the diaphragm and intercostal muscles may offer an opportunity to estimate airway response in young children in an alternative way.     

Effect of whooping cough in infancy on subsequent lung function and bronchial reactivity

Thirty-six children younger than 1 yr of age hospitalized for whooping cough approximately 9 yr previously (cases) were compared with 36 control children of the same age and sex. Subjects were sampled from participants in an earlier large field study of the long-term sequelae of whooping cough. Respiratory symptoms were more common in cases, although the differences were not statistically significant. Cases were significantly more likely either to be atopic or to have a family history of wheezing illness. There were no significant differences between cases and control subjects in lung function indices derived from maximal expiratory flow volume loops or from single-breath nitrogen washout tests or in bronchial reactivity as judged by the histamine challenge PC20. The evidence from both the present and the earlier study indicates that whooping cough is unlikely to be a causal factor in later respiratory illnesses and symptoms and that no deficit in lung function can be detected in later childhood. The disease may, however, occur more frequently or be more easily recognized in children with environmental or constitutional factors that predispose to respiratory morbidity.     

Airway responsiveness to inhaled histamine in chronic obstructive airways disease. Chronic bronchitis vs emphysema

Airway responsiveness to inhaled histamine was examined in two groups of carefully selected patients with nonasthmatic chronic obstructive airways disease (COAD). Twelve patients with chronic bronchitis and airflow obstruction but little emphysema and 13 with predominantly emphysema and airflow obstruction but little bronchitis were selected based on history, chest roentgenogram, and diffusing capacity for carbon monoxide (Dsb). Emphysema patients had less cough, less sputum, less chronic bronchitis, lower Dsb, and more radiographic evidence of vascular deficiency. There was no difference in anthropometric features, smoking history, atopic skin sensitivity, hemoglobin, blood eosinophilia, PaO2, PaCO2, ECG, lung volumes, or expiratory flow rates. The two groups had similar airway responsiveness to inhaled histamine; the geometric mean provocation concentrations producing a 20 percent FEV1 fall (PC20) was 0.56 mg/ml for the bronchitis patients and 0.28 mg/ml for the emphysema patients (p greater than 0.20). Regression of log histamine PC20 vs percent predicted FEV1 showed a high correlation in both groups (r = 0.73, p less than 0.01 in bronchitis and r = 0.79, p less than 0.001 in emphysema). The regression lines were almost identical. These data suggest that in COAD bronchial responsiveness to inhaled histamine is mainly due to the altered airway geometry, and that there is no difference in histamine responsiveness between patients with emphysematous COAD and nonemphysematous COAD with chronic bronchitis.     

Airway cough sensitivity to inhaled capsaicin and bronchial responsiveness to methacholine in asthmatic and bronchitic subjects

The objective of this study was to evaluate the effect of chronic airway inflammation on airway cough sensitivity and non-specific bronchial responsiveness, and the relationship between them. The capsaicin cough threshold, defined as the lowest concentration of capsaicin causing five or more coughs, and non-specific bronchial responsiveness, defined as the methacholine concentration causing a 20% fall in forced expiratory volume in 1 s (FEV1) (PC20-FEV1), were measured in 18 asthmatic, 13 bronchitic (sinobronchial syndrome) and 28 healthy non-atopic subjects. All subjects were non-smoking men. The geometric mean values (mumol) of the cough threshold were 18.9 (GSEM 1.29), 8.69 (GSEM 1.29) and 27.6 (GSEM 1.31) in asthmatic, bronchitic and normal subjects, respectively. The value in bronchitic subjects was significantly lower (P < 0.02) than that in normal subjects. The geometric mean value of PC20-FEV1 in asthmatic subjects (0.48 mg/ml (GSEM 1.38)) was significantly lower than that in bronchitic subjects (18.5 mg/ml (GSEM 1.75)) (P < 0.001). There was no correlation between cough threshold and PC20-FEV1 values (correlation coefficient (r) = 0.155). These results indicate that cough sensitivity is potentiated by chronic airway inflammation in bronchitis but not in asthma, and suggest that cough sensitivity and bronchial responsiveness may be independently potentiated by different mechanisms resulting from chronic airway inflammation.     

Prostaglandin D2 potentiates airway responsiveness to histamine and methacholine

In the bronchi of asthmatic subjects many bronchoconstrictor mediators and neurotransmitters might be released together, and therefore, potential interactions might occur that could be important in airway hyperreactivity. We have studied the effect of inhaled methacholine, bradykinin, and prostaglandin D2 (PGD2) on bronchial reactivity to inhaled histamine in 6 mild asthmatic subjects, 22 to 36 yr of age. All of the test spasmogens were given at equivalent bronchoconstricting concentrations. Simultaneous dosing with PGD2 caused a significant increase in reactivity to histamine, mean dose of histamine causing a 35% fall in specific airway conductance being 0.72 mumol before, and 0.32 mumol with, PGD2; (p less than 0.01). This was not seen with histamine itself, methacholine, or bradykinin. Prostaglandin D2 caused a similar increase in bronchial reactivity to inhaled methacholine, suggesting a postreceptor potentiation of airway smooth muscle contractility. This positive interaction between inflammatory mediators known to be released in asthma has important implications for understanding bronchial hyperreactivity.     

Spontaneous changes in bronchial responsiveness in children and adolescents: an 18-month follow-up

The purpose of this study was to investigate spontaneous changes in bronchial responsiveness to inhaled histamine over a period of 18 months. The first measurements in 495 subjects, 7 to 16 years of age, were made in 1986. Bronchial hyperresponsiveness (BHR), i.e., PC-20 FEV1 less than or equal to 8.0 mg/mL, was found in 79 (16%) individuals, of whom 28 (35%) had symptoms of asthma. Twenty asthmatic and 42 non-asthmatic subjects who had BHR (78%) were re-examined 18 months later. The asthmatics had a modest change in BHR, while in the non-asthmatics bronchial response to inhaled histamine and exercise was significantly decreased. In twenty-two subjects (36%) bronchial response was within the normal range; of these 18 were non-asthmatic. Six asthmatics (30%) and two non-asthmatics (5%) had an increased BHR at follow-up. Two subjects (5%) developed symptoms of asthma by the time of follow-up, with an unchanged degree of BHR. Sex, age, atopic symptoms, and viral respiratory infections at the first examination were unrelated to changes in bronchial responsiveness. However, changes of BHR in the non-asthmatic subjects were significantly correlated to changes in bronchial response to exercise. Although spontaneous changes in bronchial responsiveness occur in asthmatic, as well as non-asthmatic subjects, asthmatics persistently have hyperresponsive airways. Development of asthma was found to occur among subjects with persistent BHR.     

Epidemiology of respiratory symptoms,lung function and important determinants: Report from the obstructive lung disease in northern Sweden project

Setting: Cross-sectional epidemiological study based on a representative sample of the general population in northern Sweden.Objectives: To assess the prevalence of respiratory symptoms, the role of respiratory symptoms as indicators of impairment of lung function, and to define risk factors for respiratory symptoms and lung function impairment.Design: The 1340 subjects of 6610 who reported respiratory symptoms suggestive of asthma or chronic bronchitis in a postal questionnaire study were invited to a structured interview and lung function tests. A control group of 315 subjects was also invited. Risk factors were assessed from the postal questionnaire.Results: 400 subjects in the symptomatic group had attacks of breathlessness and wheezing, while none in the control group had them, corresponding to 7% of the original study population. Chronic productive cough was present in 537 subjects, of whom 13 were from the control group, suggesting that 12% of the original study population had this symptom. Persistent wheeze was the symptom that predicted the greatest proportion of cases of impaired lung function. Attacks of breathlessness, wheezing, long-standing cough and sputum production were all related to age, smoking and a family history of asthma. Both chronic productive cough and impaired lung function correlated strongly with smoking and age, and their prevalences differed in different socio-economic groups.Conclusion: Impaired lung function can be predicted from respiratory symptoms. Data collected in postal questionnaires suffice for the identification of risk factors. Combinations of symptoms gave greater odds ratios than individual symptoms.     

Sputum eosinophilia and bronchial responsiveness in patients with chronic non-productive cough responsive to anti-asthma therapy

OBJECTIVE: We aimed to examine airway inflammation and bronchial responsiveness in patients with chronic non-productive cough responsive to anti-asthma therapy. METHODOLOGY: Bronchial responsiveness to methacholine as well as the number of inflammatory cells and concentration of eosinophil cationic protein (ECP) in induced sputum were measured in 42 patients with chronic non-productive cough of unknown origin. Their response to bronchodilator, antiallergic and inhaled or oral glucocorticoid therapy was subsequently assessed. RESULTS: Complete remission of coughing was attained with anti-asthma therapies in 34 patients (responder group), while eight patients did not respond (non-responder group). Twenty patients in the responder group and three in the non-responder group showed bronchial hyperresponsiveness (BHR). The number of eosinophils and ECP levels in the sputum from responders with BHR were significantly increased when compared with those from non-responders and healthy subjects. These sputum measures were also significantly increased in responders without BHR when compared with healthy subjects. However, there were no significant differences in these inflammatory markers between the responders with and without BHR. The neutrophil numbers in the sputum from non-responders and responders both with and without BHR were also significantly higher than in control subjects, but there were no significant differences. CONCLUSIONS: These findings suggest that patients with chronic non-productive cough responsive to anti-asthma therapy characteristically have eosinophilic airway inflammation, which may play an important role in the development of chronic cough. Furthermore, the evaluation of not only bronchial responsiveness but also airway inflammation by examination of induced sputum may be useful for diagnosis and deciding on therapeutic strategies.     

Occupation, chronic bronchitis, and lung function in young adults. An international study

We studied the relationship between occupational exposures, chronic bronchitis, and lung function in a general population survey in 14 industrialized countries, including 13,253 men and women aged 20 to 44 yr. We studied associations between occupational group, occupational exposures, bronchitis symptoms (cough and phlegm production for at least 3 mo each year), FEV(1), and nonspecific bronchial responsiveness (NSBR) separately in lifetime nonsmokers, cigarette smokers, and ex-smokers. Occupational exposure to vapors, gas, dust, or fumes, estimated with a job exposure matrix (JEM), was associated with chronic bronchitis among current smokers only (prevalence ratio (PR): 1.2 to 1.7). The interaction of occupational exposure with smoking, however, was not statistically significant (p > 0.1). Self-reported exposure was related to chronic bronchitis in all smoking groups. An increased risk for chronic bronchitis was found in agricultural, textile, paper, wood, chemical, and food processing workers, being more pronounced in smokers. Lung function and NSBR were not clearly related to occupational exposures. Findings were similar for asthmatic and nonasthmatic subjects. In conclusion, occupational exposures contributed to the occurrence of chronic (industrial) bronchitis in young adults. Fixed airflow limitation was not evident, probably due to the relatively young age of this population.     

The relationship of nonspecific bronchial responsiveness to the occurrence of respiratory symptoms and decreased levels of pulmonary function. The Normative Aging Study

Nonspecific bronchial responsiveness was assessed by an abbreviated methacholine challenge test in 458 male participants of the Normative Aging Study, who also completed a respiratory questionnaire and spirometry. A positive response to the methacholine challenge test was defined as a greater than or equal to 20% decline in FEV1 during the test. Cigarette smoking was significantly associated with a positive methacholine response (p less than 0.001). Logistic regression analyses indicated that there was a significant association between a positive response to methacholine and both any wheeze (p = 0.002) and persistent wheeze (p less than 0.001) after taking into account smoking status and age; an association between responsiveness and chronic cough was of borderline significance (p = 0.06). Multiple linear regression analyses indicated that positive methacholine responsiveness was independently associated with lower levels of FEV1 (p less than 0.001) and FEF25-75 (p less than 0.001). Using the log of the dose-response slope rather than a dichotomous variable to characterize responder status yielded very similar results in the linear and logistic models. The findings of this cross-sectional study suggest that increased level of nonspecific responsiveness is significantly associated with wheeze and cough symptoms and decreased levels of pulmonary function in adult men. Longitudinal follow-up of these men should shed light on the importance of nonspecific responsiveness as a risk factor for the subsequent development of chronic obstructive pulmonary disease.     

Roles of hyperresponsiveness and airway inflammation in bronchial asthma

Bronchial hyperresponsiveness is one important feature of bronchial asthma, and evidence has been accumulated that airway inflammation contributes to the specific airway response in asthmatic patients. Increase in airway responsiveness following viral infection, exposure to allergen, ozone or chemical sensitizers supports the evidence for a link between hyperresponsiveness and airway inflammation. However, as only some respiratory tract infections induce an increase in hyperresponsiveness, and patients with chronic bronchitis and cystic fibrosis have less airway hyperresponsiveness than asthmatics, airway inflammation is considered to be only one of many factors contributing to the hyperresponsiveness of asthmatic airways.     

A trial of inhaled budesonide on airway responsiveness in smokers with chronic bronchitis

The aim of the present randomized, double-blind study was to evaluate the effect of inhaled budesonide on daily symptoms, ventilatory capacity, and airway responsiveness in smokers with chronic bronchitis. Twenty-five subjects with a provocative concentration producing a 20% fall in forced expiratory volume in one second PC20(FEV1) less than 2.0 mg.ml-1, by bronchial histamine challenge, were included. Eighteen subjects accomplished the entire 12 week study, eight receiving inhaled budesonide 400 micrograms b.i.d. and ten receiving placebo. Cough decreased significantly in the actively treated group during the treatment period, but no change could be demonstrated in expectoration, dyspnoea, or sleep disturbances. No changes in any of these symptoms were found in the placebo group, and no differences in symptoms scores were found between the groups. No significant differences in ventilatory capacity or bronchial responsiveness could be demonstrated. In conclusion, a moderately high dose of inhaled steroid in eight subjects with chronic bronchitis did not improve the symptom scores, ventilatory capacity, or airway responsiveness to any clinically relevant degree.     

Increases in airway responsiveness following acute exposure to respiratory irritants. Reactive airway dysfunction syndrome or occupational asthma?

We describe a persistent increase in nonspecific bronchial responsiveness following acute exposure to strong respiratory irritants in four subjects with no past history of asthma or atopy and in a subject with mild asthma. They were exposed either to a bleaching agent, sulfuric acid, hydrochloric acid, perchloroethylene, or toluene diisocyanate fumes. In all cases the inhalation of high concentrations of irritant fumes was brief (less than one hour) and induced acute symptoms of cough and dyspnea. The asthmatic subject developed a severe bronchospasm which required mechanical ventilation. In all subjects the exposure led to prolonged (more than one year) symptoms of variable airflow obstruction induced on contact with common respiratory irritants. In the previously normal subjects, a mild hyperresponsiveness to methacholine could be observed. The asthmatic subject became dependent on steroids. No change in the forced expiratory volume in one second was observed when the subject exposed to sulfuric acid was rechallenged in the laboratory, but her nonspecific bronchial responsiveness was then back to normal at this time. When those exposed to perchloroethylene or toluene diisocyanate fumes were reexposed to these agents, a late asthmatic response occurred, suggesting that the subjects developed occupational asthma after an intense short-term exposure to perchloroethylene or toluene diisocyanate. We conclude that airway hyperresponsiveness can develop or increase after the inhalation of high concentrations of irritants and that these changes may be prolonged. Occupational asthma following intense short-term exposure to sensitizing agents should be differentiated from airway hyperresponsiveness which results from a nonsensitizing mechanism, as in the reactive airway dysfunction syndrome.     

Respiratory symptoms and lung function in habitual heavy smokers of marijuana alone, smokers of marijuana and tobacco, smokers of tobacco alone, and nonsmokers

To evaluate the possible pulmonary effects of habitual marijuana smoking with and without tobacco, we administered a detailed respiratory and drug use questionnaire and/or lung function tests to young, habitual, heavy smokers of marijuana alone (n = 144) or with tobacco (n = 135) and control subjects of similar age who smoked tobacco alone (n = 70) or were nonsmokers (n = 97). Mean amounts of marijuana and/or tobacco smoked were 49 to 57 joint-years marijuana (average daily number of joints times number of years smoked) and 16 to 22 pack-years of tobacco. Among the smokers of marijuana and/or tobacco, prevalence of chronic cough (18 to 24%), sputum production (20 to 26%), wheeze (25 to 37%) and greater than 1 prolonged acute bronchitic episode during the previous 3 yr (10 to 14%) was significantly higher than in the nonsmokers (p less than 0.05, chi square). No difference in prevalence of chronic cough, sputum production, or wheeze was noted between the marijuana and tobacco smokers, nor were there additive effects of marijuana and tobacco on symptom prevalence. We noted significant worsening effects of marijuana but not to tobacco on specific airway conductance and airway resistance (tests of mainly large airways function) in men and of tobacco but not of marijuana on carbon monoxide diffusing capacity and on closing volume, closing capacity, and the slope of Phase III of the single-breath nitrogen washout curve (tests reflecting mainly small airways function) (p less than 0.03, two-way ANCOVA). No adverse interactive effects of marijuana and tobacco on lung function were found.     

Airways responsiveness in a population sample of adults and children

Nonspecific bronchial responsiveness was assessed with eucapneic hyperpnea to subfreezing air in a population-based sample of 134 adults and 213 children in East Boston, Massachusetts. Increased responsiveness was considered to be present if the decrease in forced expiratory volume in one second with cold air divided by the initial vital capacity was greater than 9%. Men and women had similar bronchial responsiveness, but children and young adults (24 yr of age and younger) were significantly more likely to be responders than were older subjects (p less than 0.001). Children with a doctor's diagnosis of asthma at any time in the past were twice as likely (42.9%) to be responders as were nonasthmatic children (19%) (p = 0.004). Ninety-two percent (11/12) of currently active asthmatics were responders. However, a large percentage of asymptomatic children had increased levels of bronchial responsiveness (18.9%). This cross-sectional study demonstrates the feasibility of measurement of nonspecific bronchial responsiveness in epidemiologic studies, and its relationship to age and wheeze symptoms in children.     

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.