Relationship between bronchial hyperresponsiveness and development of asthma in wheezy infants

Severe bronchial hyperresponsiveness along with house dust mite allergy indicates persistence of asthma in young children

BACKGROUND

Significant risk factors for persistence of asthma later in life are family history of allergies, early allergic sensitization and bronchial hyperresponsiveness (BHR). The evolution of BHR in young children without allergic sensitization and with house dust mite allergy (HDM) was investigated.

METHODS

In this retrospective analysis, electronic charts of 4850 young children with asthma and wheezy bronchitis between 2005 and 2018 were reviewed in order to study all patients ≤6 years with BHR assessed by methacholine provocation tests (MCT) at least once (n = 1175). Patients with more than two follow-up measurements were divided in group 1 (no allergic sensitization; n = 110) and group 2 (HDM allergy; n = 88). Additionally, skin prick test, exhaled nitrite oxide (eNO), and asthma treatment were analyzed.

RESULTS

Forty-seven patients of group 1 aged median 4.3 years and 48 patients of group 2 aged median 4.7 years showed initially severe BHR <0.1 mg. At follow-up, patients with HDM were more likely to show persistence of severe BHR than non-sensitized patients (severe BHR group 1: n = 5 (10.6%) vs. group 2: n = 21 (43.8%), p < .001). In addition, 89.4% of group 1 had mild to moderate or no BHR, compared to only 56.2% of group 2. There was a significant difference in eN0 (median group 1: 9 ppb vs. group 2: 26 ppb, p < .001), at last follow-up. Age, sex, and asthma therapy had no effect on BHR.

CONCLUSION

In young children without sensitization BHR normalizes, whereas HDM allergy indicates a persistence of asthma beyond infancy.

Remodeling, inflammation and airway responsiveness in early childhood asthma

PURPOSE OF REVIEW

Remodeling and inflammation together with airway hyperresponsiveness are essential components of asthma but their role in development of the disease is still obscure.

RECENT FINDINGS

Recent data imply that remodeling can occur early in childhood, not necessarily subsequent to but rather, in parallel with inflammation. The assumption of thickening of the reticular basement membrane being a prerequirement for chronic asthma is questioned but development of airway responsiveness is a significant factor. Airway responsiveness is at least partially linked to bronchial inflammation but there are several other genes and pathways regulating airway responsiveness. Increased airway smooth muscle in early childhood is associated with later development of asthma and may be one link between inflammation and airway responsiveness. Novel findings on genetic variation in genes regulating lung growth and remodeling in early childhood shed light on the pathophysiological mechanisms leading to chronic asthma.

SUMMARY

Even young children with chronic asthma have detectable elements of airway remodeling, inflammation and increased airway responsiveness, which all contribute to impaired lung function.

Rhinovirus-associated wheeze during infancy and asthma development

Rhinovirus is commonly associated with bronchiolitis - only second to RSV during the first year life. The prevalence of HRV-bronchiolitis may be very high in predisposed infants. HRV diagnosis is almost exclusively based on PCR, which detects respiratory infections with or without symptoms. Two immunologic factors, interferon responses and atopy, have been associated with susceptibility to HRV-bronchiolitis in multiple studies. The current data supports the hypothesis that susceptibility to HRV-bronchiolitis is likely to be an early manifestation of biased immune responses, which are linked to both decreased viral defence and atopic airway inflammation. Prospective studies have consistently shown that early wheezing associated with HRV infection is closely associated with recurrent wheezing and the development of asthma in children. Collectively, these studies suggest that HRV infection in wheezing children could serve as a clinically useful marker for early identification of asthma prone children. The findings to date provide the rationale for future studies to incorporate rhinovirus illnesses into asthma risk indices.

Evaluation of airway reactivity and immune characteristics as risk factors for wheezing early in life

BACKGROUND

Childhood asthma is most often characterized by recurrent wheezing, airway hyperreactivity, and atopy; however, our understanding of these relationships from early in life remains unclear. Respiratory tract illnesses and atopic sensitization early in life might produce an interaction between innate and acquired immune responses, leading to airway inflammation and heightened airway reactivity.

OBJECTIVE

We hypothesized that premorbid airway reactivity and immunologic characteristics of infants without prior episodes of wheezing would be associated with subsequent wheezing during a 1-year follow-up.

METHODS

One hundred sixteen infants with chronic dermatitis were enrolled before episodes of wheezing. Airway reactivity, allergen-specific IgE levels, cytokine production by stimulated PBMCs, and percentages of dendritic cells were measured on entry, and airway reactivity was reassessed at the 1-year follow-up. Linear regression models were used to evaluate a predictor's effect on continuous outcomes.

RESULTS

Milk sensitization, egg sensitization, or both were associated with heightened airway reactivity before wheezing and after the onset of wheezing; however, these factors were not associated with an increased risk of wheezing. There was an interaction between initial airway reactivity and wheezing as a determinant of airway reactivity at follow-up. In addition, cytokine production by stimulated PBMCs was a risk factor for wheezing, whereas increased percentages of conventional dendritic cells were protective against wheezing.

CONCLUSION

Our data in a selected cohort of infants support a model with multiple risk factors for subsequent wheezing that are independent of initial airway reactivity; however, the causative factors that produce wheezing very early in life might contribute to heightened airway reactivity.

[Consensus conference on acute bronchiolitis (VI): prognosis of acute bronchiolitis. Review of scientific evidence]

We present a review of the evidence on prognosis of acute bronchiolitis, risk factors for severe forms, symptom or severity scores and risk of post-bronchiolitis asthma. Documented risk factors of long stay or PICU admission in hospitalized patients are: bronchopulmonary dysplasia and/or chronic lung disease, prematurity, congenital heart disease and age less than 3 months. Other less well documented risk factors are: tobacco exposure, history of neonatal mechanical ventilation, breastfeeding for less than 4 months, viral co-infection and other chronic diseases. There are several markers of severity: toxic appearance, tachypnea, hypoxia, atelectasis or infiltrate on chest radiograph, increased breathing effort, signs of dehydration, tachycardia and fever. Although we have some predictive models of severity, none has shown sufficient predictive validity to recommend its use in clinical practice. While there are different symptom or severity scores, none has proven to be valid or accurate enough to recommend their preferable application in clinical practice. There seems to be a consistent and strong association between admission due to bronchiolitis and recurrent episodes of wheezing in the first five years of life. However it is unclear whether this association continues in subsequent years, as there are discordant data on the association between bronchiolitis and asthma.

[Recurrent wheezing in three year-olds: facts and opportunities]

The 3 year-old group of children has an increased incidence and prevalence of recurrent wheezing episodes. There are different subgroups, who give different inflammatory responses to different triggering agents, and subgroups that differ in aetiopathology and immunopathology. Current diagnostic methods (exhaled nitric oxide in multiple breaths, nitric oxide in exhaled air condensate, induced sputum, broncho-alveolar lavage and endo-bronchial biopsy), enable the inflammatory pattern to be identified and to give the most effective and safe treatment. The various therapeutic options for treatment are reviewed, such as inhaled glucocorticoids when the inflammatory phenotype is eosinophilic, and leukotriene receptor antagonists, when the inflammatory phenotype is predominantly neutrophilic. In accordance with the current recommendations, for the diagnosis as well as for the therapy initiated in children of this age, they must be regularly reviewed, so that if the benefit is not clear, the treatment must be stopped and an alternative diagnosis and treatment considered. The start of treatment should be determined depending on the intensity and frequency of the symptoms, with the aim of decreasing morbidity and increasing the quality of life of the patient.

Childhood asthma and increased airway responsiveness: a relationship that begins in infancy

RATIONALE

Asthma is associated with increased airway responsiveness (AR), but the age when this relationship becomes established is not clear. The present study tested the hypothesis that the association between increased AR and asthma is established after 1 month of age.

OBJECTIVES

To relate AR in infancy to asthma in childhood.

METHODS

As part of a birth cohort study, AR was determined at 1 (early infancy), 6 (mid-infancy), and 12 months of age (late infancy). At 11 years of age (childhood), AR and the presence of asthma symptoms were determined.

MEASUREMENTS AND MAIN RESULTS

Of the 253 study subjects enrolled, AR was determined in 202 in early infancy, 174 in mid-infancy, 147 in late infancy, and 176 in childhood. Increased AR in late infancy, but not in early or mid-infancy, was associated with increased wheeze at 11 years of age (P = 0.016). Increased AR in infancy persisted into childhood in association with male gender, early respiratory illness, and maternal smoking and asthma. Among the 116 subjects assessed in late infancy and childhood, recent wheeze was present in 35% of children with increased AR at both ages, 13% with increased AR in childhood only, 12% for those with increased AR in late infancy only, and 0% for those who did not have increased AR at either age (P = 0.023); the proportions of children with diagnosed asthma in the corresponding groups were 27, 20, 12, and 0% (P = 0.038).

CONCLUSIONS

The association between increased infantile AR and childhood asthma emerges at the end of the first year of life.

Wheezing illness caused by respiratory syncytial virus and other agents

BACKGROUND

Respiratory syncytial virus (RSV) and other pathogenic agents cause lower respiratory infection with wheezing in infants (wheezing illness in infancy). Wheezing illness in infancy due to RSV can be life-threatening and can induce recurrent wheezing; but these events can also be produced by infection by other pathogenic agents. Thus, whether RSV induces more severe wheezing illness in infancy remains poorly understood.

METHODS

Infants with an initial wheezing illness were divided into an RSV-positive group and an RSV-negative group and the differences in disease severity, intensity of acute symptoms, and susceptibility to recurrent wheezing, between these two groups, were investigated.

RESULTS

The RSV-positive group accounted for 57.4% of the infants. The infants in the RSV-positive group were significantly younger than those in the RSV-negative group. Other background parameters, gender and family history, were not significantly different. There were no significant differences in indicators of severity (hospitalization periods, periods of persistent wheezing and requirement of oxygen supplementation) between the two groups.

CONCLUSION

Wheezing illness in infancy caused by RSV is more common in younger infants, but it is not more severe than that caused by other pathogenic agents.

Asthma management issues in infancy and childhood

The prevalence of asthma has been increasing worldwide over the past 2 decades, especially the prevalence of childhood asthma. Currently, the prevalence of childhood asthma is around 3-20% in different countries based on the report from the International Study of Asthma and Allergies in Children (ISAAC). Asthma in childhood is predominantly an extrinsic asthma. In general, countries in the coastal, temperate, and subtropical zones have the highest prevalence of mite- and cockroach-sensitive asthma. Countries in the sub-arctic or semi-arid areas have a lower prevalence of childhood asthma, mostly associated with sensitization to pet dander, moulds, and pollens. Many genes have been linked to asthma in different ethnic populations. A global consensus for the management of asthma in adults and children >5 years of age has been made possible in the Global Initiative for Asthma (GINA) guidelines, where a step-wise management program using inhaled medication with and without oral anti-inflammatory drugs is recommended. The management of asthma in children <5 years of age remains inconclusive. Recent studies suggest that inherited susceptibility associated with risk factors from the prenatal and postnatal environment is likely to promote allergic sensitization and development of asthma. Consequently, early prevention of prenatal sensitization in utero and environmental control of early life exposure to various allergens may decrease the incidence of childhood asthma. In the management of moderate persistent asthma in infants and young children <5 years of age, airway resistance tests (FEV(1) or PEF) are not of significance, but assessment of respiratory rate and skin pulse oximeter measurements of arterial oxygen saturation are helpful. Moreover, recent advances in pharmacogenetics and pharmacogenomics may provide better individualized care for early pharmacological prevention of childhood asthma via selective modulation of airway remodeling.

Adenosine Bronchial Provocation With Computerized Wheeze Detection in Young Infants With Prolonged Cough

BACKGROUND

Chronic cough in babies is often associated with bronchial hyperreactivity (BHR). The objective documentation of BHR in babies is difficult, and acoustic methods have been described (provocative concentration of a substance causing wheeze) for conducting bronchial provocation tests (BPTs). We conducted a study to evaluate automatic computerized wheeze detection (CWD) in determining BHR in young infants with prolonged cough, and its correlation with the subsequent development of wheezing.

METHODS

Infants aged < 24 months with prolonged cough (ie, > 2 months) underwent acoustic BPTs with the response determined by CWD and auscultation by a physician. Telephone interviews with parents were conducted after 1 month and yearly for the next 3 years.

RESULTS

A total of 28 infants who were 4 to 24 months old with prolonged cough were included in the study. Twenty of these infants (71.4%) had BHR as determined by a positive acoustic BPT result. In 11 of these 20 tests, the CWD occurred earlier, and in 9 tests it occurred at the same step as auscultation by a physician. Rhonchi or whistles often preceded wheezes. Seventeen of the 20 patients with BHR completed 3 years of follow-up. Of these, 14 had recurrent episodes of wheezing and shortness of breath, and 3 were well. Six of the eight adenosine-negative patients completed 3 years of follow-up and had no symptoms of BHR.

CONCLUSIONS

Acoustic BPT is a technically feasible test for the detection of BHR in young infants. CWD provides an earlier detection of wheeze than stethoscope auscultation. In our group of infants, a positive acoustic BPT result had high correlation with symptoms compatible with BHR over the next 3 years.

Attachment of mothers and children with recurrent asthmatic bronchitis

OBJECTIVE

This study on attachment in children with recurrent asthmatic bronchitis and their mothers addresses three issues. The first aim was to test whether children affected by recurrent asthmatic bronchitis more often display an insecure pattern of attachment in comparison with healthy children. The second aim was to verify whether the distribution of adult attachment representations in the mothers of children affected by recurrent asthmatic bronchitis is different from the one shown by the mothers of the healthy comparison group. The third aim was to investigate intergenerational transmission of attachment.

METHODS

Sixty Italian children, aged between 2 and 5 years, and their mothers participated in the study. The Adult Attachment Interview and the Attachment Q-Sort were used to assess, respectively, the security of mothers' attachment representations and of mother-child attachment.

RESULTS

Children affected by recurrent asthmatic bronchitis appeared to be less secure in comparison with healthy children. Their mothers showed a higher percentage of insecure attachment representations. Finally, the intergenerational transmission of attachment was not influenced by the preclinical condition of the children.

CONCLUSIONS

We propose a model of genetic and social transmission of insecure attachments in families struggling with asthma.

Recurrent wheezing in infants and young children and bronchial hyperresponsiveness: a perspective

Epidemiological studies report a 50% incidence of at least one wheezing episode in young children. If we can argue that 10% of children have asthma sometime during their pediatric years, it still leaves a significant percentage of children with an unexplained cause for their wheezing. Other recognized phenotypes of recurrent wheezing include young children exposed to excessive environmental tobacco smoke (ETS), while other infants wheeze recurrently following a significant episode of bronchiolitis. Bronchial hyperresponsiveness (BHR) is a universally recognized phenomenon of asthma, but its presence in young children with recurrent wheezing is not as well studied. Currently available studies demonstrates that BHR is also seen in young pediatric asthmatics, paralleling what is well recognized in adolescent or adult asthma. In those children with post-bronchiolitis wheezing, BHR appears to be present to a degree; while infants and young children exposed to ETS have increased BHR, as a group. If exaggerated BHR in recurrent wheezing children without asthma has the same inherent disadvantage as it does in asthmatic children, additional studies looking directly at this issue in a longitudinal fashion need to be designed. A hypothesis of BHR in non-asthmatic children is presented that could be studied prospectively.

The importance of maximal airway response to methacholine in the prediction of wheezing development in patients with cough-variant asthma

BACKGROUND

A significant proportion of patients diagnosed with cough-variant asthma eventually manifest classic asthma signs, such as wheezing and dyspnea. The aim of this study was to investigate whether the degree of airway hypersensitivity and/or the level of maximal airway response can predict the development of wheezing in subjects with cough-variant asthma.

METHODS

At study initiation, a high-dose methacholine inhalation test was performed to measure provocative concentration causing a 20% fall (PC20) in forced expiratory volume in 1 s (FEV1) and maximal airway response. Each person was evaluated regularly every 3 months for 4 years and also on the occasion of wheezing being perceived for the first time.

RESULTS

Of the 48 patients available in the follow-up period, 21 (Group 1) developed clinical wheezing, while 27 (Group 2) did not. There was no significant difference in PC20 levels between the two groups. The level of maximal airway response, however, was significantly higher in Group 1 than in Group 2. The score test for trend revealed a significant association between the future development of wheezing and the level of maximal airway response (P = 0.007), but not the level of methacholine PC20 (P = 0.423).

CONCLUSIONS

The level of maximal airway response, rather than the degree of airway hypersensitivity, may be an important risk factor for the future development of classic asthma in patients with cough-variant asthma.

Reduced lung function both before bronchiolitis and at 11 years

BACKGROUND AND AIMS

We have previously shown an association between reduced premorbid lung function (V'maxFRC) and bronchiolitis. We hypothesised that individuals with bronchiolitis will go on to have reduced lung function and increased respiratory symptoms in childhood.

METHODS

V'maxFRC was measured at 1 month of age; individuals with bronchiolitis were prospectively identified. Annual symptom questionnaires were completed from 3 to 6 years. At 11 years of age, children underwent an assessment including questionnaire, lung function, airway response to histamine (AR), and skin prick testing.

RESULTS

Eighteen individuals with bronchiolitis were ascertained from 253 cohort members. Children with bronchiolitis had increased viral induced wheeze at 3 (OR 5.8, 95% CI 1.4 to 25.2; n = 103) and 5 years (OR 5.3, 95% CI 1.1 to 25.5; n = 101). At 11 years of age, 194 children were assessed including 16 with past bronchiolitis. These 16 individuals had reduced mean z scores for % V'maxFRC compared with other children (-0.56 and 0.06 respectively) and mean z scores for % FEF(25-75) at 11 years (-0.53 and 0.06 respectively). At 11 years, FEV(1), FVC PEF, AR, atopy, wheeze, and diagnosed asthma were not different between groups.

CONCLUSIONS

Reduced lung function is present before and after bronchiolitis; the level of reduction is comparable. The mechanism for wheeze and reduced lung function after bronchiolitis appears to be related to premorbid lung function and not bronchiolitis per se.