Relationship between socioeconomic status and asthma: a longitudinal cohort study

BACKGROUND

There is conflicting information about the relationship between asthma and socioeconomic status, with different studies reporting no, positive, or inverse associations. Most of these studies have been cross sectional in design and have relied on subjective markers of asthma such as symptoms of wheeze. Many have been unable to control adequately for potential confounding factors.

METHODS

We report a prospective cohort study of approximately 1000 individuals born in Dunedin, New Zealand in 1972-3. This sample has been assessed regularly throughout childhood and into adulthood, with detailed information collected on asthma symptoms, lung function, airway responsiveness, and atopy. The prevalence of these in relation to measures of socioeconomic status were analysed with and without controls for potential confounding influences including parental history of asthma, smoking, breast feeding, and birth order using cross sectional time series models.

RESULTS

No consistent association was found between childhood or adult socioeconomic status and asthma prevalence, lung function, or airway responsiveness at any age. Having asthma made no difference to educational attainment or socioeconomic status by age 26. There were trends to increased atopy in children from higher socioeconomic status families consistent with previous reports.

CONCLUSIONS

Socioeconomic status in childhood had no significant impact on the prevalence of asthma in this New Zealand born cohort. Generalisation of these results to other societies should be done with caution, but our results suggest that the previously reported associations may be due to confounding.

Bronchodilator tolerance: the impact of increasing bronchoconstriction

Chronic exposure to beta-agonists causes tolerance to their bronchodilator effects, which is best demonstrated during acute bronchoconstriction. The aim of the present study was to assess whether tolerance becomes more evident with increasing bronchoconstriction, as might occur in acute asthma. In a randomised, double-blind, placebo-controlled, crossover study comprising 15 patients, the treatments were salbutamol 400 microg q.i.d. or placebo given via Diskhaler for 28 days with a 2-week washout between treatments. Patients attended on days 14, 21 and 28. Bronchoconstriction was induced on two of these three occasions to achieve a reduction in the forced expiratory volume in one second (FEV1) of 0 (no methacholine), 15 and 30% (using methacholine) in a randomised order. Immediately after this, salbutamol 100 microg, 100 microg and 200 microg was inhaled at 0, 5, and 10 min. FEV1 was measured over 40 min. Dose/response curves were plotted and values for the area under the curve (AUC)0-40 FEV1 were compared between treatments and by degree of bronchoconstriction. Regular salbutamol resulted in attenuation of the acute response to beta-agonist, which was increasingly evident with greater bronchoconstriction. With a reduction in FEV1 of 0, 15 and 30%, the AUC0-40 FEV1 with salbutamol were 11.2, -14.6 and -35.7% respectively, compared to placebo. There was a linear relationship between the magnitude of bronchoconstriction and the between-treatment differences in AUC0-40 FEV1. Increasing bronchoconstriction conferred greater susceptibility to the effects of bronchodilator tolerance.

Exhaled NO and assessment of anti-inflammatory effects of inhaled steroid: dose-response relationship

Exhaled nitric oxide (eNO) is an easily measured marker of airway inflammation. This study was undertaken to evaluate the usefulness of serial eNO in investigating the dose-response relationship for inhaled beclomethasone (BDP), and to compare eNO with other markers of airway inflammation. Following withdrawal of inhaled corticosteroid (ICS) therapy, 65 patients entered a double-blind, parallel-group, placebo-controlled trial of 50, 100, 200 or 500 microg x BDP x day(-1) for eight weeks. eNO and spirometry were performed weekly and a hypertonic saline challenge with sputum induction was performed at the beginning and end of treatment. The relationship between the dose of ICS and changes in eNO and forced expiratory volume in one second (FEV1) was linear at 1 week and at the end of treatment. A linear dose-response relationship was also seen for sputum eosinophils. Changes in eNO correlated significantly with changes in sputum eosinophils. Changes in the provocative dose of saline causing a 15% fall in FEV1 saline did not differ across the treatment groups nor did they correlate with changes in other measurements. Exhaled nitric oxide may be used to assess the dose-response relationship for the anti-inflammatory effects of inhaled beclomethasone. The relationship found in this study was linear over the dose range 0-500 microg x day(-1) soon after commencing therapy and continued over time.

House dust mite allergen levels in university student accommodation in Dunedin

AIM

To quantify the levels of Dermatophagoides pteronyssinus (Der p1) in different university student accommodation in Dunedin, and to assess relationships with housing characteristics and housekeeping practices.

METHODS

Dwellings (n=178) were randomly selected from a database of first year university students in Dunedin. Dust samples were collected from both bed and the bedroom floor by standardised procedures. Der p1 levels were quantified by monoclonal antibody ELISA techniques. Details of housing characteristics, occupancy and housekeeping practices were obtained by questionnaire.

RESULTS

Geometric mean (95% confidence intervals) Der p1 allergen levels from bedroom floors were: family homes (n=61) 5.58 (3.73-8.36) microg/g; student flats (n=43) 3.89 (2.49-6.07) microg/g; halls of residence (n=74) 0.26 (0.16-0.43) microg/g. Der p1 allergen levels from beds were: family homes 15.85 (9.78-26.57) microg/g; student flats 10.5 (6.41-17.19) microg/g; halls of residence 3.25 (2.33-4.54) microg/g. In all accommodation lower levels of Der p1 were found on the floor compared to the bed (p<0.005). Halls of residence had significantly lower Der p1 levels in both bed and floor (p<0.0005). Higher levels of Der p1 were associated with longer duration of occupancy, a history of condensation or mold in the accommodation, failure to use a hot wash for sheets, mattress age greater than one year and infrequent vacuuming of the bedroom floor.

CONCLUSIONS

Wide variations in Der p1 levels were observed between different forms of student accommodation. Higher levels of Der p1 are found in family homes than in student flats or halls of residence.

The predictive value of exhaled nitric oxide measurements in assessing changes in asthma control

Exhaled nitric oxide (eNO) levels are increased in untreated or unstable asthma and measurements can be made easily. Our aim was to assess the usefulness of eNO for diagnosing and predicting loss of control (LOC) in asthma following steroid withdrawal. Comparisons were made against sputum eosinophils and airway hyperresponsiveness (AHR) to hypertonic saline (4.5%). Seventy-eight patients with mild/moderate asthma had their inhaled steroid therapy withdrawn until LOC occurred or for a maximum of 6 wk. Sixty (77.9%) developed LOC. There were highly significant correlations between the changes in eNO and symptoms (p < 0.0001), FEV(1) (p < 0.002), sputum eosinophils (p < 0.0002), and saline PD(15) (p < 0.0002), and there were significant differences between LOC and no LOC groups. Both single measurements and changes of eNO (10 ppb, 15 ppb, or an increase of > 60% over baseline) had positive predictive values that ranged from 80 to 90% for predicting and diagnosing LOC. These values were similar to those obtained using sputum eosinophils and saline PD(15) measurements. We conclude that eNO measurements are as useful as induced sputum analysis and AHR in assessing airway inflammation, with the advantage that they are easy to perform.

Reversing acute bronchoconstriction in asthma: the effect of bronchodilator tolerance after treatment with formoterol

Continuous treatment with a short-acting beta2-agonist can lead to reduced bronchodilator responsiveness during acute bronchoconstriction. This study evaluated bronchodilator tolerance to salbutamol following regular treatment with a long-acting beta2-agonist, formoterol. The modifying effect of intravenous corticosteroid was also studied. Ten asthmatic subjects (using inhaled steroids) participated in a randomised, double-blind, placebo-controlled, cross-over study. Formoterol 12 microg b.i.d. or matching placebo was given for 10-14 days with >2 weeks washout. Following each treatment, patients underwent a methacholine challenge to induce a fall in forced expired volume in one second (FEV1) of at least 20%, then salbutamol 100 microg, 100 microg, and 200 microg was inhaled via a spacer at 5 min intervals, with a further 400 microg at 45 min. After a third single-blind formoterol treatment period, hydrocortisone 200 mg was given intravenously prior to salbutamol. Dose-response curves for change in FEV1 with salbutamol were compared using analysis of covariance to take account of methacholine-induced changes in spirometry. Regular formoterol resulted in a significantly lower FEV1 after salbutamol at each time point compared to placebo (p<0.01). The area under the curves (AUCs) for 15 (AUC0-15) and 45 (AUC0-45) min were 28.8% and 29.5% lower following formoterol treatment (p<0.001). Pretreatment with hydrocortisone had no significant modifying effect within 2 h of administration. It is concluded that significant tolerance to the bronchodilator effects of inhaled salbutamol occurs 36 h after stopping the regular administration of formoterol. This bronchodilator tolerance is evident in circumstances of acute bronchconstriction.

The influence of polymorphism at position 16 of the beta2-adrenoceptor on the development of tolerance to beta-agonist

Polymorphism at position 16 of the beta2-adrenoceptor alters receptor down-regulation in vitro. Our aim was to compare the development of tolerance to beta-agonist in homozygous Gly-16 patients with patients harboring the "wild" genotype (homozygous Arg-16) during regular treatment with salmeterol. In a prospective, randomized, double-blind, placebo-controlled, cross-over study, 20 subjects with mild to moderate asthma (10 Gly-16, 10 Arg-16) received 2 weeks of treatment with inhaled salmeterol 100 microg b.i.d. Thereafter, dose responses to inhaled salbutamol were constructed for forced expiratory volume in 1 sec (FEV1), heart rate, QTc interval, serum potassium and glucose, and finger tremor. The protective effect of salbutamol against adenosine monophosphate (AMP) challenge was also measured. Salmeterol resulted in a significant reduction in the area under curve (AUC) for FEV1 (p = 0.01), heart rate (p = 0.01), QTc interval (p = 0.01), and tremor (p = 0.05), and in the maximum responses for FEV1 (p = 0.05), heart rate (p = 0.02), and glucose (p = 0.02). The protective effect of salbutamol against AMP was reduced by 3.61 doubling doses (p < 0.001). However, differences between Gly-16 and Arg-16 patients were small and nonsignificant. Thus, although tolerance is influenced in vitro by polymorphism of the beta2-adrenoceptor, the magnitude of between-genotype differences in vivo is unlikely to be significant.

Bronchodilator tolerance and rebound bronchoconstriction during regular inhaled beta-agonist treatment

There is uncertainty about the development of airway tolerance to beta-agonists and the phenomenon of rebound bronchoconstriction on beta-agonist withdrawal. We have recently completed a study of the regular terbutaline and budesonide treatment in asthma. We report our observations on the effect of starting and stopping terbutaline treatment on morning and evening peak flows. The study was a randomized four-way, double-dummy, cross-over comparison of regular inhaled terbutaline (500-1000 microg four times daily), budesonide, combined treatment and matching placebo. Each treatment was given for 6 weeks following a 4 week single-blind placebo washout. Ipratropium was used for symptom relief. No other asthma medication was permitted during either the treatment or wash-out periods. Evaluable data were obtained from 52 subjects for both placebo and terbutaline treatment. Changes in mean morning and evening peak flows during terbutaline treatment were compared to the baseline peak flows during the last 2 weeks of the preceding washout. The peak flow changes on stopping terbutaline were also analysed. Mean morning peak flow was not significantly different during terbutaline treatment when compared to either baseline or placebo treatment. Evening peak flows were significantly higher during terbutaline treatment [mean increase 23.1 l min(-1) (95% CI = 18.8, 27.4)]. Analysis of the peak flow changes on a day-by-day basis revealed an initial increase in morning peak flows for the first 2 days of treatment of 19.2 and 13.41 min(-1) [increases of 25.0 and 17.31 min(-1) in comparison with the corresponding values during placebo (P<0.01)] followed by a return to baseline. The increase in evening peak flows was also greater for the first 2 days of treatment than for the remainder of the treatment period (P<0.01). On ceasing terbutaline treatment there was a fall in mean morning peak flow below the baseline on the following morning of 21.6 l min(-1) (P<0.05 compared to placebo). The temporary increase in morning peak flows and greater than expected rise in evening peak flows for the first 2 days of treatment suggest the development of tolerance to the bronchodilator effect of terbutaline. Similarly, the fall in morning peak flows on treatment withdrawal suggests rebound bronchoconstriction. These effects are likely to be mediated by downregulation of the beta-receptor during treatment. The clinical significance of these changes is uncertain in view of the stability of overall asthma control during terbutaline treatment, but sudden withdrawal of beta-agonist treatment could conceivably lead to a deterioration in asthma control.

Relationship between fetal growth and the development of asthma and atopy in childhood

BACKGROUND

A study was undertaken to investigate the relationship between birth anthropometric measures and the subsequent development of asthma, airway hyperresponsiveness, and atopy in later childhood.

METHODS

A longitudinal study was performed on 734 subjects (71%) from a cohort of children born in Dunedin, New Zealand in 1972-73. The birth anthropometric measures were available from hospital records and the main outcome measures of reported asthma, skin prick tests, and methacholine hyperresponsiveness were measured at the age of 13 years, while the serum total IgE was measured at 11 years.

RESULTS

After adjustment for other factors, infants with a larger head circumference at birth tended to have higher serum total IgE at 11 years of age (p = 0.02) but IgE was not associated significantly with birth length or birth weight. The adjusted odds ratio for raised serum IgE (>150 IU/ml) in infants with a head circumference of 37 cm or more was 3.4 (95% CI 1.4 to 7.9). In contrast, recent asthma symptoms were positively associated with birth length (p = 0. 04) but not with head circumference. The adjusted odds ratio for asthma in the previous two years in infants with a birth length of 56 cm or more was 6.4 (95% CI 2.0 to 19.8). Infants with a birth weight of less than 3.0 kg had an odds ratio for reported asthma of 0.2 (95% CI 0.0-0.6). There were no significant associations of any of the birth parameters with skin prick positivity, reported hay fever, or eczema.

CONCLUSIONS

These results suggest that increased fetal growth is related to an increased risk of asthma and atopy in childhood. The precision of the findings is limited by the small numbers in the extreme categories of each birth parameter, but the results are consistent with intrauterine programming of the developing respiratory and immune systems.

Tolerance to beta-agonists during acute bronchoconstriction

Previous reports suggest that regular use of beta-agonists does not lead to tolerance to their bronchodilator effects. However, most studies have been conducted in stable asthma. This study investigates whether bronchodilator tolerance can be demonstrated during acute bronchoconstriction. Thirty-four asthmatic subjects were treated with 6 weeks inhaled terbutaline (1 mg q.i.d.), budesonide (400 microg, b.i.d.), both drugs or placebo in a randomized, double-blind, cross-over study. After each treatment methacholine was administered to induce a 20% fall in the forced expiratory volume in one second (FEV1). The response to inhaled salbutamol 100, 100, 200 microg at 5 min intervals) was then measured. Dose-response curves were compared using an analysis of covariance. Pre-methacholine FEV1, the highest pre-methacholine FEV1, the fall in FEV1 induced by methacholine and the logarithm of the provocative dose of methacholine required to induce the 20% fall in FEV1 (PD20) were used as covariates. There was a significantly reduced response to salbutamol after 6 weeks terbutaline treatment: the mean (95% confidence intervals (CI)) area under the dose-response curve was reduced by 36% (24, 47) compared to placebo (p<0.0001). The reduction in bronchodilator response was not affected by concomitant treatment with budesonide. Significant tolerance to the bronchodilator effect of inhaled beta-agonists may be demonstrated when tested during acute bronchoconstriction. Continuous treatment with inhaled beta-agonists may lead to a reduced response to emergency beta-agonist treatment during asthma exacerbations.

Randomised trial of an inhaled beta2 agonist, inhaled corticosteroid and their combination in the treatment of asthma

BACKGROUND

Although many asthmatic patients are treated with a combination of beta2 agonist and corticosteroid inhalers, the clinical effects of combining the drugs are unknown. Studies on the early asthmatic response to allergen suggest that beta2 agonists may reduce the benefit of inhaled corticosteroids. A study of the effects of combining the drugs on asthma control was undertaken.

METHODS

Sixty one subjects with mild to moderate asthma were randomised to a double blind crossover comparison of inhaled budesonide (200-400 microg twice daily), terbutaline (500-1000 microg four times daily), combined treatment, and placebo. Each treatment was given for six weeks following a four week washout period. Ipratropium was used for symptom relief. Treatments were ranked from worst (1) to best (4) based on need for oral steroid, mean morning peak flow, nocturnal awakening, ipratropium use, and asthma symptoms. Lung function and bronchial hyperresponsiveness were measured before and after each treatment.

RESULTS

Evaluable data for all four treatments were obtained from 47 subjects. The mean rank of each treatment was: placebo = 2.05; terbutaline = 2.13; budesonide = 2.48; combined treatment = 3.34. Combined treatment was ranked significantly better than any other treatment (p<0.01). Mean (95% CI) morning and evening peak flows were 14 (5 to 23) and 24 (15 to 34) l/min higher, respectively, during combined treatment than during budesonide, and 27 (17 to 37) and 15 (7 to 23) l/min higher than during terbutaline. Asthma symptoms tended to be least frequent during combined treatment but were not significantly different from budesonide alone. There was no significant difference between combined treatment and budesonide alone for lung function and bronchial hyperresponsiveness.

CONCLUSIONS

In this group of mild to moderate asthmatic subjects the combination of beta2 agonist and corticosteroid gave better asthma control than either treatment alone. There was no evidence that regular beta2 agonist treatment impaired the beneficial effect of inhaled corticosteroid.

Asthma control during long-term treatment with regular inhaled salbutamol and salmeterol

BACKGROUND

The adverse effects of long term treatment of asthma with the short acting beta agonist fenoterol have been established in both epidemiological and clinical studies. A study was undertaken to investigate the efficacy and safety of long term treatment with salbutamol and salmeterol in patients with mild to moderate bronchial asthma.

METHODS

In a two centre double dummy crossover study 165 patients were randomly assigned to receive salbutamol 400 micrograms q.i.d., salmeterol 50 micrograms b.i.d., or placebo via a Diskhaler. All patients used salbutamol as required for symptom relief. The study comprised a four week run in and three treatment periods of 24 weeks, each of which was followed by a four week washout. Asthma control was assessed by measuring mean morning and evening peak expiratory flow rate (PEFR), a composite daily asthma score, and minor and major exacerbation rates. Washout assessments included methacholine challenge and bronchodilator dose response tests. Analysis was by intention to treat.

RESULTS

Data from 157 patients were analysed. Relative to placebo, the mean morning PEFR increased by 30 l/min (95% CI 26 to 35) for salmeterol but did not change for salbutamol. Evening PEFR increased by 25 l/min (95% CI 21 to 30) and 21 l/min (95% CI 17 to 26), respectively (p < 0.001). Salmeterol improved the asthma score compared to placebo (p < 0.001), but there was no overall difference with salbutamol. Only daytime symptoms were improved with salbutamol. The minor exacerbation rates were 0.29, 0.88, and 0.97 exacerbations/patient/year for salmeterol, salbutamol and placebo, respectively (p < 0.0001 for salmeterol). The corresponding major exacerbation rates were 0.22, 0.51 and 0.40, respectively (p < 0.03 for salmeterol). For salbutamol the asthma score deteriorated over time (p < 0.01), and the time spent in major exacerbation was significantly longer compared with placebo (12.3 days (95% CI 4.2 to 20.4) versus 8.4 days (95% CI 5.2 to 11.6), p = 0.02). There was no evidence of rebound deterioration in asthma control, lung function, or bronchial hyper-responsiveness following cessation of either active treatment, and no evidence of tolerance to salbutamol or salmeterol.

CONCLUSIONS

Regular treatment with salmeterol is effective in controlling asthma symptoms and reduces minor more than major exacerbation rates. Salbutamol was associated with improved daytime symptoms but subtle deterioration in asthma control occurred over time. Salbutamol should therefore be used only as required.

The efficacy of inhaled corticosteroids in the management of non asthmatic chronic airflow obstruction

AIMS

The aims of this investigation were to evaluate the efficacy of regular inhaled beclomethasone in the control of symptoms and lung function with non-asthmatic smoking related obstructive pulmonary disease and to evaluate the relationship between clinical responses to a short course of oral prednisone and longer term outcomes using inhaled steroid.

METHODS

The study was a randomised, double blind, placebo controlled, crossover investigation in 18 patients. The active treatment was inhaled beclomethasone 1000 micrograms given twice daily for three months by metered dose inhaler. At the end of each treatment period, patients received oral prednisone 30 mg/day for ten days. The two treatment phases were separated by a one month washout interval. Peak flow rates, symptom scores and "rescue" bronchodilator use were recorded twice daily. Lung function (FEV1, FVC and lung volumes) and bronchial hyperresponsiveness (PC20 methacholine) were measured at monthly visits. The number of exacerbations requiring intervention therapy were also recorded.

RESULTS

There were no consistent benefits attributable to beclomethasone. Lung function was not significantly better as a result of active treatment. Sputum production improved but other symptom scores were similar during active and placebo therapy. Three patients exhibited an increase in FEV1 of 15% or more during active treatment but did not do so when oral prednisone was administered immediately after the period of placebo treatment. A further three patients showed an improvement in FEV1 of 15% or more with oral prednisone but failed to improve during treatment with inhaled beclomethasone. The predictive value of the "trial of steroid" was 0% and 81.3% for positive and negative outcomes respectively.

CONCLUSIONS

Our results indicate that in non-asthmatic chronic obstructive pulmonary disease inhaled corticosteroid fails to achieve significant improvements in either lung function or symptoms. The response to a "trial of steroid" using oral prednisone is not clinically helpful in selecting the small number of patients who may subsequently benefit from this form of therapy.

Comparison of reported prevalences of recent asthma in longitudinal and cross-sectional studies

A potential source of bias in prevalence rates reported for symptoms and diagnoses of asthma in longitudinal studies could arise if repeated questioning of subjects or previous experience of lung function and airway responsiveness tests increased awareness of respiratory symptoms. We wished to determine the extent of any such bias by comparing reported prevalence rates from a longitudinal and cross-sectional study within similar populations. The prevalences of wheezing in the last year, waking with chest tightness, waking with shortness of breath, waking with coughing, having an attack of asthma in the last year, and current use of medications for asthma were determined using identical questions in two populations. Self-completed questionnaire responses of 946 subjects, 21 yrs of age, participating in the seventh respiratory assessment in the longitudinal Dunedin Multidisciplinary Health and Development Research Study were compared with responses provided by 991 subjects, aged 20-22 yrs, completing a postal questionnaire on one occasion only for the New Zealand section of the European Community Respiratory Health Study. The prevalence rates were not significantly different between the two populations, for all of the reported symptoms and for medication use. Differences in responses between genders were similar in each study, with all responses being more common in females. We conclude that repeated questioning regarding respiratory symptoms and repeated lung function and bronchial challenge testing in a longitudinal study of asthma did not bias prevalence rates compared with those obtained in a similar population of the same age studied on only one occasion.

Parental and neonatal risk factors for atopy, airway hyper-responsiveness, and asthma

BACKGROUND

Previous studies have not resolved the importance of several potential risk factors for the development of childhood atopy, airway hyperresponsiveness, and wheezing, which would allow the rational selection of interventions to reduce morbidity from asthma. Risk factors for these disorders were examined in a birth cohort of 1037 New Zealand children.

METHODS

Responses to questions on respiratory symptoms and measurements of lung function and airway responsiveness were obtained every two to three years throughout childhood and adolescence, with over 85% cohort retention at age 18 years. Atopy was determined by skin prick tests at age 13 years. Relations between parental and neonatal factors, the development of atopy, and features of asthma were determined by comparison of proportions and logistic regression.

RESULTS

Male sex was a significant independent predictor for atopy, airway hyper-responsiveness, hay fever, and asthma. A positive family history, especially maternal, of asthma strongly predicted childhood atopy, airway hyperresponsiveness, asthma, and hay fever. Maternal smoking in the last trimester was correlated with the onset of childhood asthma by the age of 1 year. Birth in the winter season increased the risk of sensitisation to cats. Among those with a parental history of asthma or hay fever, birth in autumn and winter also increased the risk of sensitisation to house dust mites. The number of siblings, position in the family, socioeconomic status, and birth weight were not consistently predictive of any characteristic of asthma.

CONCLUSIONS

Male sex, parental atopy, and maternal smoking during pregnancy are risk factors for asthma in young children. Children born in winter exhibit a greater prevalence of sensitisation to cats and house dust mites. These data suggest possible areas for intervention in children at risk because of parental atopy.

Relation of the course of bronchial responsiveness from age 9 to age 15 to allergy

Bronchial responsiveness to methacholine was measured in a birth cohort of New Zealand children at ages 9, 11, 13, and 15. Overall bronchial hyperresponsiveness (BHR) decreased with age. While the response at age 9 was significantly related to responsiveness, symptom severity, and low lung function at age 15, these relationships were much closer when bronchial response levels after age 9 were taken into account. Also, among children who were unresponsive to methacholine at age 15, those with previous BHR had more frequent wheeze and lower lung function than those whose previous tests were all unresponsive. Both the overall tendency to BHR and the tendency to retain BHR were closely related to high serum IgE levels (determined at age 11) and to positive allergy skin tests (determined at age 13). These evidences of allergy, closely related to the severity and course of methacholine response, appeared to be important determinants of the frequency of wheeze and the degree of impairment of lung function at the end of follow-up. In view of the variability in BHR, a single estimate of bronchial responsiveness taken at an arbitrary point in time may not be an accurate index of the overall tendency to BHR.

Relations of bronchial responsiveness to allergy skin test reactivity, lung function, respiratory symptoms, and diagnoses in thirteen-year-old New Zealand children

BACKGROUND

Many factors have been found to relate univariately to bronchial responsiveness (BR), but their independent relationships are often unclear because many are interrelated.

OBJECTIVE

The purpose of this study was to present a multivariate analysis of the closeness of the association of various factors that are related univariately to BR, including allergy skin tests.

METHODS

The results of methacholine challenge were transformed into a continuous variable (BRindex), which has a nearly Gaussian distribution. With stepwise multiple regression, the closeness of the association of the independent variables with BRindex was evaluated.

RESULTS

Of the 11 skin tests applied, four showed independent relationships to BRindex (mite, cat, dog, and Aspergillus species). The sizes of these skin test reactions were correlated with BRindex, and their sum appeared to maximize the overall correlation of allergy skin tests with BRindex (r = 0.516). The lowness of the ratio of forced expiratory volume in 1 second to vital capacity and of percent predicted forced expiratory volume in 1 second added significantly to the skin tests in correlating with BRindex, (multiple r = 0.621). Adding diagnoses and symptoms increased the multiple r to 0.685.

CONCLUSIONS

The size of the reactions to the four skin tests noted above showed much closer correlations with BR than total serum IgE had shown at age 11, and the relationship was present in asthmatic and nonasthmatic subjects.

Sheepskins and bedding in childhood, and the risk of development of bronchial asthma

BACKGROUND

Sheepskin bedding might increase house dust mite exposure and so explain some of the increasing prevalence of severity of childhood asthma.

METHODS

Relationships between use of different types of bedding, and diagnoses of asthma, symptoms of wheezing, skin prick test evidence of house dust mite sensitivity, and airway responsiveness to methacholine, were examined retrospectively in a birth cohort of children followed longitudinally to age 15 years.

RESULTS

In the whole cohort, no associations were identified to suggest a causal relationship between use of any type of bedding and development of features of asthma. Although not an a priori hypothesis, we noted that among children with a family history of atopic disease, those who were house dust mite sensitive were more likely to have used an innerspring mattress (29.6% vs 10.2% who had not used an innerspring mattress, p = 0.005).

CONCLUSION

In this subgroup, increased airway responsiveness and mite sensitivity were significantly associated with use of innerspring mattresses, although whether this is a causal or secondary association is not certain. Use of a sheepskin in the bed in early childhood was not an additional risk factor for the development of asthma.

Indomethacin potentiates exercise-induced reduction in renal hemodynamics in athletes

Nonsteroidal anti-inflammatory drugs (NSAID) are frequently used in sports medicine but few studies have documented their potential importance in modifying exercise-induced changes in renal function. The effects of indomethacin (50 mg orally every 8 h for 36 h) on renal blood flow (RBF) and glomerular filtration rate (GFR) were investigated in eight fit healthy males (age 21-42) before and after 30-min treadmill exercise at 80% VO2max and during 120-min recovery. Each volunteer served as their own control. There were no differences between control and indomethacin for the resting values of RBF, GFR, or renal vascular resistance (RVR). Using analysis of variance for repeated measures, indomethacin produced a significant reduction in RBF compared with control (P = 0.009) that was associated with a significant elevation in RVR (P = 0.027). Changes in GFR mirrored the changes in RBF but differences failed to reach statistical significance. These results suggest that with sustained exercise indomethacin can compromise renal function and potentiate the risk of developing acute renal failure. Indomethacin and other NSAID are widely used in the sports arena, and athletes should be warned of the potential danger of their use when renal function may be compromised.

Atopy in childhood. III. Relationship with pulmonary function and airway responsiveness

The relationship between atopy and pulmonary function in children, and how these relate directly or indirectly to airway hyperresponsiveness, is uncertain. We have examined these relationships in a sample of 13-year-old children. A questionnaire on respiratory symptoms, skin-prick tests to 11 common allergens, spirometry and an abbreviated methacholine challenge test were completed by 662 members (341 boys) of a birth cohort of New Zealand children followed longitudinally to age 13. There was a significant relationship between the presence and degree of atopy, and baseline pulmonary function. Low FEV1/VC ratios were associated with a greater likelihood of airway responsiveness, not only in subjects with diagnosed asthma, but also in the full cohort and in the sub-group of 426 children who denied asthma or current wheeze. The relationships between baseline FEV1/VC and airway responsiveness were stronger in atopic than in non-atopic children, with the strongest relationships in children sensitive to house dust mite and/or cat dander. In the presence of atopy, progressively lower levels of lung function were strongly associated with a higher prevalence of airway responsiveness (P<0.001). In non-atopic subjects, only those with the most impaired lung function (FEV1/VC < 75%) showed any substantive prevalence of airway responsiveness. The relationship between the degree of atopy and the FEV1/VC ratio, although significant in univariate analysis, became completely non-significant after accounting for airway responsiveness. In 13-year-old children, atopy, especially to house dust mite and cat dander, was correlated with pulmonary function expressed as FEV1/VC ratio. Airway responsiveness likewise correlated with impaired baseline lung function. The apparent relationship of lung function to atopy occurred primarily as a result of the relationship between atopy and airway responsiveness. Atopy and impaired lung function were additive factors predicting airway responsiveness.

Atopy in childhood. II. Relationship to airway responsiveness, hay fever and asthma

While airway hyperresponsiveness is usually associated with a diagnosis of asthma or symptoms of wheezing, some individuals with rhinitis show airway hyperresponsiveness as do some with no symptoms whatsoever. We have studied the correlations between symptoms, airway hyperresponsiveness and atopy as determined by skin-prick tests in a cohort of New Zealand children. A total of 662 members of a birth cohort were studied at age 13 years using a respiratory questionnaire, skin-prick tests to 11 common allergens, and an abbreviated validated methacholine challenge test to determine airway responsiveness. Airway hyperresponsiveness (methacholine PC20 FEV1 < or = 8 mg/ml) was strongly correlated with reported asthma and current wheezing (P<0.0001) and also with atopy, especially to house dust mite and cat (P<0.0001). As weal size for both house dust mite and cat increased, so did the proportion of children with airway hyperresponsiveness. All children with diagnosed asthma and airway hyperresponsiveness were atopic. Skin-test reactions to house dust mite and cat were strongly correlated with any degree of measurable airway responsiveness (PC20 FEV1 < or = 25 mg/ml) in children with rhinitis (P<0.00001), and remained significantly correlated even in children without current asthma, without asthma ever and without rhinitis (P<0.001). Atopy is a major determinant of airway hyperresponsiveness in children, not only in those with reported histories of asthma and wheezing, but also in the absence of any history suggesting asthma and rhinitis.

Atopy in childhood. I. Gender and allergen related risks for development of hay fever and asthma

Reasons for the gender differences in prevalence rates for asthma remain unclear. We have examined the relationships between allergen skin-test reactions and diagnoses of hay fever and asthma in New Zealand boys and girls examined at the age of 13 years. Information on current and past wheezing, diagnosed asthma, and hay fever was obtained for 662 subjects (341 boys) of a birth cohort followed longitudinally to the age of 13 years, using a physician-administered questionnaire. Atopic status was determined by skin-prick tests to 11 common allergens. The proportion of 13-year-old boys with current asthma was 1.6 times higher and of ever-diagnosed asthma 1.4 times higher than in girls, but the prevalence of recurrent wheeze (> or = three episodes per year) not diagnosed as asthma, or of hay fever, was not significantly different between the sexes. The prevalence of diagnosed asthma increased with increasing numbers of positive skin tests, but hay fever without asthma was little affected above one positive skin-test. Boys had a greater prevalence of any positive skin-test (50.1% vs 37.1%), two or more positive tests (29.3% vs 21.8%), and responses to house dust mite (34.0% vs 23.1%) and cat (14.7% vs 11.2%). Gender differences for asthma became insignificant when adjusted for skin-test responsiveness to house dust mite and/or cat. The proportion of children with diagnosed asthma increased with increasing size of weals to house dust mite and cat dander. Gender differences in allergen sensitivities partly explain the gender differences in diagnosed asthma in children. In both sexes, risk of asthma was primarily associated with sensitization to indoor allergens (house dust mite and cat), and was related to the magnitude of the skin-test response, while the risk of hay fever was primarily associated with grass pollen sensitivity.

Methotrexate in the management of severe steroid dependent asthma

AIMS

This study was designed to assess the efficacy of low dose methotrexate, 15 mg weekly, as a steroid-sparing agent in asthmatic patients requiring long-term oral prednisone treatment.

METHODS

The study was a randomised, double blind, placebo controlled, cross over study of 48 weeks duration. Eleven patients with severe steroid-dependent asthma were included. A successful outcome was defined as a reduction in mean prednisone requirements of 7 mg daily compared to baseline requirements, during active treatment.

RESULTS

Two patients were required to be withdrawn owing to methotrexate-related adverse effects. The mean prednisone dose for patients who completed the study was 14.4 mg per day (95% CI; 13.6, 15.1) during active treatment, and 12.9 mg per day (95% CI: 12.2, 13.6) during placebo treatment (NS). Only one patient reduced his individual dose requirements by more than 7 mg per day, whereas in three patients prednisone requirements actually increased during active treatment. There were no significant differences in symptom scores, pulmonary function data, and exacerbations between active and placebo treatments.

CONCLUSION

No significant steroid-sparing effect was obtained using low dose methotrexate in this study. This negative outcome may be attributable to the small population of patients studied, low baseline FEV1, and the omission of a steroid minimisation run-in period. Our results highlight the importance of careful patient selection and a painstaking approach in the management of patients with steroid-dependent asthma.

Regular inhaled beta agonist in asthma: effects on exacerbations and lung function

BACKGROUND

A comparison of the effects of regular upsilon as needed inhaled beta agonist treatment on the control of asthma in the last 16 weeks of each of two 24 week treatment periods has been reported. This paper presents additional information on exacerbations of asthma and trends in lung function, airways hyperresponsiveness to methacholine, and bronchodilator responsiveness during the entire 24 week periods of regular or as needed beta agonist treatment.

METHODS

Subjects undertook a year long randomised, double blind crossover study of regular upsilon as needed inhaled beta agonist treatment. Fenoterol (400 micrograms) or matching placebo was inhaled as a dry powder four times daily for 24 weeks, then subjects crossed over to the alternative regimen. Treatment with inhaled corticosteroids was used by 50 of the 64 subjects in constant doses throughout the study. Symptoms, peak expiratory flow rates, and drug use were recorded daily, spirometry was performed every four weeks, and methacholine and bronchodilator responsiveness were measured every eight weeks.

RESULTS

Exacerbations of asthma symptoms occurred earlier and more often during regular treatment with fenoterol and four of five severe exacerbations requiring admission to hospital occurred during the period of regular treatment. Prebronchodilator forced expiratory volume in one second (FEV1) was on average 0.15 litres lower (95% confidence interval (95% CI) 0.11-0.19) and vital capacity (VC) 0.12 litres lower (95% CI 0.08-0.16) than during the placebo period. Morning peak flow rates were significantly lower and evening peak flow rates significantly higher, with an increase in diurnal variation from 9.8% (95% CI 6.9-12.8) to 17.5% (95% CI 13.8-21.3) during regular treatment. Geometric mean concentration of methacholine causing a 20% fall in FEV1 from the value after saline (PC20) decreased significantly from 1.63 to 1.15 mg/ml, indicating increased bronchial hyperresponsiveness during regular treatment. Response to bronchodilator, as measured by the % increase in postbronchodilator FEV1 related to prebronchodilator FEV1, was maintained with no evidence for tachyphylaxis.

CONCLUSION

Chronic use of inhaled fenoterol resulted in more exacerbations, a significant decline in baseline lung function, and an increase in airway responsiveness to methacholine in asthmatic subjects, but did not alter bronchodilator responsiveness. These findings support the previous report that regular inhaled beta agonist treatment is deleterious in the long term control of asthma.

Increased inhaled bronchodilator vs increased inhaled corticosteroid in the control of moderate asthma

Undertreatment of chronic asthma may reflect uncertainty as to how it may be best controlled. We compared the effects of increased inhaled corticosteroid vs regular inhaled bronchodilator in 32 adult asthmatics. During three 16-week treatment periods, comprising baseline inhaled corticosteroid (mean 505 micrograms daily) and on-demand beta-agonist, baseline inhaled corticosteroid and increased (regularly scheduled four times daily) beta-agonist, and increased inhaled corticosteroid (mean 1478 micrograms daily) and on-demand beta-agonist, subjects recorded symptoms, morning and evening peak flow, and additional medication. Of 25 subjects whose control differed significantly between treatments with baseline vs increased corticosteroid, 22 (88 percent) favored the increased dosage (p < 0.001). Of 28 subjects whose control differed between treatments with regular beta-agonist vs increased corticosteroid, 24 (86 percent) were better controlled with increased inhaled corticosteroid and were worse with regular beta-agonist (p < 0.001). Only one quarter the number of exacerbations were experienced during treatment with increased inhaled corticosteroid. Upper airway adverse effects were minor and easily controlled. Hence, asthma with persistent symptoms was better controlled by increased inhaled corticosteroid therapy than by increased use of inhaled beta-agonist.

Interaction between corticosteroid and beta-agonist drugs. Biochemical and cardiovascular effects in normal subjects

The aim of this study was to investigate whether the administration of prednisone potentiates any of the acute biochemical and cardiovascular effects of high-dose inhaled beta-agonist drugs. These agents are known to cause dose-related changes in plasma potassium and glucose, as well as ECG changes in heart rate, corrected QT interval (QTc), T wave, and U wave. On theoretical grounds, the concomitant use of systemic corticosteroids might enhance these actions. Twenty-four healthy subjects were randomized to receive one of three treatments: salbutamol 5 mg or fenoterol 5 mg or normal saline solution. Each drug was administered twice, 30 min apart by nebulizer, and the procedure was repeated after each subject had received prednisone 30 mg daily for one week. Plasma potassium and glucose levels were measured, and ECGs were obtained after each treatment, together with 12-h Holter monitoring for arrhythmias. Changes in plasma potassium and glucose following nebulized beta-agonist were significantly greater after treatment with prednisone. Baseline potassium level fell from 3.75 mmol/L (95 percent CI 3.61, 3.89) to 3.50 mmol/L (95 percent CI 3.36, 3.64), and thereafter all values were significantly lower at each time point (p = 0.003). The lowest mean plasma potassium was obtained 90 min after fenoterol administration with prednisone pretreatment: 2.78 mmol/L (95 percent CI 2.44, 3.13). Increases in heart rate and QTc interval following both beta-agonist drugs were significant, but T-wave amplitude reductions did not reach significance. Prednisone treatment did not significantly alter the cardiovascular responses. Supraventricular and ventricular ectopic activity was related to beta-agonist use, but no potentiating effect was noted following steroid treatment. We conclude that the acute biochemical effects of beta-agonist administration are augmented by prior treatment with prednisone, but this is not the case for ECG effects. However, the degree of hypokalemia noted as a result of this drug interaction may be of clinical significance in the hypoxic conditions of acute airways obstruction.

Relationships of bronchial responsiveness assessed by methacholine to serum IgE, lung function, symptoms, and diagnoses in 11-year-old New Zealand children

The relationship of bronchial responsiveness (BR), assessed by methacholine challenge, to serum IgE, baseline ventilatory function, and symptoms or diagnoses suggesting an atopic disorder were examined in 522 11-year-old New Zealand children. BR was assessed by the presence or absence of a PC20 25 mg/ml or less and by calculating a continuous index of the decline of the FEV1 during the methacholine test. The latter facilitated multivariate analyses and revealed significant relationships to predictor variables even in those considered "nonresponsive" by PC20 criteria. There was a close relationship of BR to the baseline FEV1/vital capacity ratio, seen even in patients with known asthma, but this relationship was seen only in subjects with at least moderate levels of serum IgE. There was a less close relation of BR to percent predicted FEV1, but this persisted even after accounting for the FEV1/vital capacity ratio and was present regardless of the level of serum IgE. Reported asthma was associated with increased BR independent of all other factors, but other diagnoses and symptoms contributed relatively little to the prediction of BR once the serum IgE and lung function were taken into account. The overall results are compatible with the concept that IgE is a critical factor in the development of bronchial responsiveness in childhood.

The effects of airway hyperresponsiveness, wheezing, and atopy on longitudinal pulmonary function in children: a 6-year follow-up study

We examined growth of spirometric lung function in 696 children of European ancestry who were followed from ages 9 to 15 years and stratified according to their degree of responsiveness to methacholine inhalation challenge, atopic status, and respiratory symptoms. Subjects were participants in the longitudinal Multidisciplinary Health and Development Study in Dunedin, New Zealand. Forced expired volume in 1 second (FEV1), and vital capacity (VC) were measured at 9, 11, 13, and 15 years of age, concurrently with assessment of airway responsiveness determined by the concentration of methacholine causing a 20% fall in FEV1 (PC20 FEV1). Atopic status was assessed at age 13 by skin-prick testing to 11 allergens. In children demonstrating airway hyperresponsiveness, FEV1 increased with age at a slower rate, and the FEV1/VC ratio had a faster rate of decline through childhood, compared to non-responsive children. Subjects with positive skin tests to house dust mite and cat dander also had lower mean FEV1/VC ratios than the control group. Any reported wheezing was associated with slower growth of FEV1 and VC in males. We conclude that in New Zealand children with airway responsiveness and/or atopy to house dust mite or cat growth of spirometric lung function is impaired.

Longitudinal effects of passive smoking on pulmonary function in New Zealand children

In this study we examined the longitudinal effects of smoke exposure on lung function in a cohort of New Zealand children observed from 9 to 15 yr of age. Possible exposures included in utero exposure from mothers smoking during pregnancy, passive smoke from parents, and active smoking by the children. Lung function measures of forced expiratory volume in one second (FEV1) and vital capacity (VC) were measured biennially and ratios (FEV1/VC) were computed. The data were analyzed using longitudinal methodology, and all subjects with at least one pulmonary function test and responses to the questions concerning smoke exposures were included (n = 634). Subjects reporting wheeze or asthma were examined as a separate subgroup. In the whole cohort, no significant detrimental effects were detected for absolute FEV1 or VC in either sex, related to active or passive smoke exposures. Parental smoking was, however, associated with persistent but mild and nonprogressive impairment of the FEV1/VC ratio in males, an effect that was present at the time lung function measurements were first made. This effect was not seen in females. In children with reported wheeze or asthma, parental smoking had progressive, more serious, and clinically significant effects on the FEV1/VC ratio among adolescents of both sexes, causing a mean reduction in FEV1/VC ratios by age 15 of 3.9% in males and 2.3% in females, in contrast to the observed increase in FEV1/VC ratios with age seen in nonexposed wheezing children. We conclude that passive smoking is a major contributing factor to the development and persistence of airflow limitation in wheezing children.

Relation between airway responsiveness and serum IgE in children with asthma and in apparently normal children

BACKGROUND

Although asthma diagnosed by a physician is known to be related to serum IgE levels, it is not known whether there is a relation between the level of IgE and airway hyperresponsiveness to a methacholine challenge. The characteristics of asymptomatic persons that predispose them to airway hyperresponsiveness are also unknown.

METHODS

We studied the relation between the serum total IgE level and airway hyperresponsiveness in the presence or absence of asthma and other atopic diseases in a birth cohort of children. Data from a questionnaire regarding respiratory symptoms, plus measurements of the serum total IgE level and airway responsiveness to inhaled methacholine, were obtained for 562 11-year-olds in New Zealand.

RESULTS

The boys had a higher prevalence than the girls of current diagnosed asthma (13 percent vs. 6 percent), current symptoms of wheezing (22 percent vs. 15 percent), and airflow obstruction at base line (6 percent vs. 1 percent) and had a wider distribution of IgE levels, although mean IgE levels (120.8 IU per milliliter in the boys and 98.1 IU per milliliter in the girls) did not differ significantly between the sexes. The prevalence of diagnosed asthma was strongly related to the serum IgE level (P for trend less than 0.0001). No asthma was reported in children with IgE levels less than 32 IU per milliliter, whereas 36 percent of those with IgE levels greater than or equal to 1000 IU per milliliter were reported to have asthma. This relation with the serum IgE level was not explained by a concomitant diagnosis of allergic rhinitis or eczema. Airway hyperresponsiveness to a methacholine challenge also correlated very highly (P less than 0.0001) with the serum IgE level. This relation remained significant even after the exclusion of children with diagnosed asthma (P less than 0.0001) and of all children with a history of wheezing, allergic rhinitis, or eczema (P less than 0.0001).

CONCLUSIONS

Even in children who have been asymptomatic throughout their lives and have no history of atopic disease, airway hyperresponsiveness appears to be closely linked to an allergic diathesis, as reflected by the serum total IgE level.

Regular inhaled beta-agonist treatment in bronchial asthma

89 subjects with stable asthma took part in a double-blind, placebo-controlled, randomized, crossover study of the effects of regular versus on-demand inhaled bronchodilator therapy. The subjects inhaled fenoterol or placebo by a dry powder delivery system for 24 weeks. Control of asthma was judged by daily morning and evening peak expiratory flow rates, symptom diaries, use of additional inhaled bronchodilator, and requirement for short courses of prednisone. Of 64 subjects who completed the trial, 57 showed a clear difference in degree of control of asthma between the fenoterol and placebo periods: in 17 (30% [95% confidence interval 18.4-43.4%]) asthma was better controlled during regular inhaled bronchodilator treatment, whereas in 40 (70% [56.6-81.6%]) control was better during placebo treatment with bronchodilator for symptom relief only. Mean airway responsiveness to methacholine increased slightly during the fenoterol period. The adverse effect of regular bronchodilator inhalation occurred not only among subjects who used a bronchodilator as sole treatment (2 were better and 10 were worse during regular bronchodilator treatment) but also among those who took inhaled corticosteroids (14 were better and 29 were worse). Thus, regular inhalation of a beta-sympathomimetic agent was associated with deterioration of asthma control in the majority of subjects. The trends to use of regular, higher doses or longer-acting inhaled beta-sympathomimetic treatment may be an important causal factor in the worldwide increase in morbidity from asthma.

The relative risks of sensitivity to grass pollen, house dust mite and cat dander in the development of childhood asthma

The associations between skin sensitivity to various common allergens and the development of childhood asthma were ascertained in a longitudinal study of a birth cohort of New Zealand children up to the age of 13 years. Of 714 children skin-tested, 45.8% were sensitive to at least one of 11 allergens, the most common responses being to rye grass pollen (32.5%), house dust mite (30.1%) and cat dander (13.3%). Allergen-specific relative risk analysis, controlled for the effect of sensitivity to other allergens, demonstrated that sensitivity to house dust mite and to cat dander were highly significant independent risk factors associated with the development of asthma (whether defined as recurrent typical respiratory symptoms, increased airway responsiveness, or the concurrent presence of both), whereas grass sensitivity was not a significant independent risk factor for asthma.

Childhood asthma in New Zealand

To determine the prevalence and severity of childhood asthma in New Zealand we studied 815 children from a birth cohort by questionnaire, clinical examination and pulmonary physiological measurements at age 9 years. More than 19% of the sample had experienced wheezing in the previous year, and 11% had wheezed in the month before assessment. In all, 220 of 815 children (27.1%) had had wheezing episodes by age 9; in 34 (4.2%) episodes had been of sufficient frequency to warrant regular anti-asthma treatment. Only 32% of all wheezing children were reported by their parents to suffer from asthma, and, in groups matched for frequency of symptoms, treatment given for wheezing was influenced strongly by whether or not the label of 'asthma' had been given. The detailed history provided most information useful in diagnosing asthma; clinical examination, peak flow records, spirometry and bronchial provocation testing provided only limited additional information. A wide spectrum of frequency and severity of recurrent wheezing disorders was evident in New Zealand children. Throughout all degrees of severity, prevalence rates appeared higher than those reported in studies from the United Kingdom.

Some family social background, developmental, and behavioural characteristics of nine year old children with asthma

Children with moderate and severe, mild, and trivial asthma were compared with a group of children who did not have asthma on a range of measures including family social background (socioeconomic status, family adversity, family environment), intelligence, reading, spelling, and behaviour. None of the background measures significantly differentiated among the groups. The group of children with moderate and severe asthma was found to have a significantly lower mean score for verbal intelligence, full scale intelligence, and spelling than those with mild asthma, but did not differ significantly from the remainder of the sample. Children with mild asthma were found to have slightly higher reading scores.

Prevalence of bronchial reactivity to inhaled methacholine in New Zealand children

The prevalence of bronchial hyperreactivity to inhaled methacholine and of a clinical history of symptoms of asthma was determined in a birth cohort of 9 year old New Zealand children. A history of current or previous recurrent wheezing was obtained in 220 of 815 children. Of 800 who had spirometric tests, 27 (3.4%) had resting airflow obstruction (FEV1/FVC less than 75%). Methacholine challenge was undertaken without problem in 766 children, the abbreviated protocol being based on five breaths and four concentrations. A fall in FEV1 of more than 20% was observed in 176 children (23% of challenges, 22% of the full cohort) after inhalation of methacholine in concentrations of up to 25 mg/ml. The prevalence of bronchial reactivity in children with symptoms was related to the frequency of wheezing episodes in the last year, and the degree of reactivity to the interval since the last episode. Sixty four children (8.0%) with no history of wheeze or recurrent dry cough were, however, also responsive to methacholine 25 mg/ml or less, while 35% of children with current or previous wheezing did not respond to any dose of methacholine. Bronchial challenge by methacholine inhalation was not sufficiently sensitive or specific to be useful as a major criterion for the diagnosis of asthma in epidemiological studies. The occurrence of airway reactivity in children without symptoms of asthma, however, raises the possibility that adult onset asthma and the development of airways obstruction in some subjects with chronic bronchitis could have origins in childhood.

Exercise-induced asthma: comparison of cromoglycate powder and aerosol four hours before exercise

To establish whether sodium cromoglycate delivered by pressurised aerosol was more effective than sodium cromoglycate powder in preventing exercise-induced asthma four hours after drug administration, eight subjects known to be protected by sodium cromoglycate taken immediately pre-exercise, underwent delayed exercise challenge following double-blind premedication with sodium cromoglycate powder, sodium cromoglycate aerosol and placebo. The maximum fall in FEV1 induced by exercise four hours after inhaling sodium cromoglycate was modified slightly by sodium cromoglycate powder and by a smaller amount, sodium cromoglycate aerosol, compared with the unpremedicated run, but the calculated protection provided by sodium cromoglycate was not significantly different from that given by placebo. It was concluded that asthmatics should not expect significant suppression of exercise-induced bronchoconstriction four hours after the last dose of either cromoglycate powder or aerosol.