The role of symptomatic colds in asthma exacerbations: Influence of outdoor allergens and air pollutants

Impact of Annual Exposure to Polycyclic Aromatic Hydrocarbons on Acute Exacerbation Frequency in Asthmatic Patients

Purpose

Exposure to polycyclic aromatic hydrocarbons (PAHs) associated with ambient air particulate matter (PM) poses significant health concerns. Increased acute exacerbation (AE) frequency in asthmatic patients has been associated with ambient PAHs, but which subgroup of patients are particularly susceptible to ambient PAHs is uncertain. We developed a new model to simulate grid-scale PM_2.5-PAH levels in order to evaluate whether the severity of asthma as measured by the Global Initiative of Asthma (GINA) levels of treatment is related to cumulative exposure of ambient PAHs.

Methods

Patients with asthma residing in the northern Taiwan were reviewed retrospectively from 2014 to 2017. PM_2.5 were sampled and analysed for PAHs twice a month over a 72-hour period, in addition to collecting the routinely monitored air pollutant data from an established air quality monitoring network. In combination with correlation analysis and principal component analysis, multivariate linear regression models were performed to simulate hourly grid-scale PM_2.5-PAH concentrations (ng/m³). A geographic information system mapping approach with ordinary kriging interpolation method was used to calculate the annual exposure of PAHs (ng/m).

Results

Among the 387 patients with asthma aged 18 to 93 (median 62), 97 subjects were treated as GINA step 5 (24%). Asthmatics in GINA 5 subgroup with high annual PAHs exposure were likely to have a higher annual frequency of any AE (1 (0–12), p<0.0001). Annual PAHs exposure was correlated with the annual frequency of any exacerbation (r=0.11, p=0.02). This was more significant in the GINA 5 subgroup (r=0.29, p=0.005) and in the GINA 5 subgroup with severe acute exacerbations (r=0.51, p=0.002). Annual PAHs exposure, severe acute exacerbation and GINA steps were independent variables that predict annual frequency of any exacerbation.

Conclusion

Asthmatic patients in the GINA 5 subgroup with acute exacerbations were more susceptible to the effect of environmental PAHs on their exacerbation frequency. Reducing environmental levels of PAHs will have the greatest impact on the more severe asthma patients.

Sulfur dioxide exposure enhances Th2 inflammatory responses via activating STAT6 pathway in asthmatic mice

Sulfur dioxide (SO₂) is one of potential risk factors for induction and/or exacerbation of asthma, but the underlying mechanisms are not well understood. In this study, we investigate the role of SO₂ in asthma using a classical asthmatic model with allergic airway inflammation by treating C57BL/6 mice with ovalbumin (OVA) and/or 10 mg/m³ SO₂. Our results showed that SO₂ exposure alone induced slight pathological changes but did not significantly increase inflammatory cell counts, pro-inflammatory cytokine expression, and mucus production in the airway of mice, whereas SO₂ exposure in OVA-induced asthmatic mice caused marked pulmonary pathological changes and significantly increased the counts of eosinophil-rich leukocytes compared with OVA alone asthmatic mice. The expression of MUC5AC, TNF-α, Th2 cytokines (IL-4, IL-5, and IL-13) and STAT6 was further up-regulated in OVA plus SO₂ treated mice compared with OVA alone treated mice. In addition, exposure to SO₂ alone markedly elevated STAT6 mRNA levels and hydrogen peroxide (H₂O₂) content in the lung. These findings suggest that SO₂ amplifies Th2 inflammatory responses in OVA-induced asthmatic mice by activating STAT6, which can further induce Th2 cytokine expression. Induction of STAT6 expression might be an important mechanism underlying the increased risk for asthma after environmental exposure.

Infections and Asthma

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Wheezing viral respiratory illnesses are the most common initial presentation of childhood asthma.

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Once asthma is established, viral infections, most notably rhinovirus (RV), are the most frequent trigger of severe asthma exacerbations. RV-C appears to be a particularly pathogenic virus in children with asthma.

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Evidence has recently emerged to suggest that bacterial pathogens in the lower airway may contribute to the expression of asthma. Ongoing studies are critical to our understanding of the role of the airway microbiome in asthma inception and exacerbation.

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Synergistic interactions between underlying allergy and virus infections play an important mechanistic role in asthma inception and exacerbation, and are an important therapeutic target.

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Novel therapies are needed to prevent and treat virus-induced wheezing and asthma exacerbations.

Seasonal risk factors for asthma exacerbations among inner-city children

BACKGROUND

Asthma exacerbations remain common, even in children and adolescents, despite optimal medical management. Identification of host risk factors for exacerbations is incomplete, particularly for seasonal episodes.

OBJECTIVE

We sought to define host risk factors for asthma exacerbations unique to their season of occurrence.

METHODS

This is a retrospective analysis of patients aged 6 to 20 years who comprised the control groups of the Asthma Control Evaluation study and the Inner City Anti-IgE Therapy for Asthma study. Univariate and multivariate models were constructed to determine whether patients' demographic and historical factors, allergic sensitization, fraction of exhaled nitric oxide values, spirometric measurements, asthma control, and treatment requirements were associated with seasonal exacerbations.

RESULTS

The analysis included 400 patients (54.5% male; 59.0% African American; median age, 13 years). Exacerbations occurred in 37.5% of participants over the periods of observation and were most common in the fall (28.8% of participants). In univariate analysis impaired pulmonary function was significantly associated with greater odds of exacerbations for all seasons, as was an exacerbation in the previous season for all seasons except spring. In multivariate analysis exacerbation in the previous season was the strongest predictor in fall and winter, whereas a higher requirement for inhaled corticosteroids was the strongest predictor in spring and summer. The multivariate models had the best predictive power for fall exacerbations (30.5% variance attributed).

CONCLUSIONS

Among a large cohort of inner-city children with asthma, patients' risk factors for exacerbation vary by season. Thus information on individual patients might be beneficial in strategies to prevent these seasonal events.

Contribution of lung macrophages to the inflammatory responses induced by exposure to air pollutants

Large population cohort studies have indicated an association between exposure to particulate matter and cardiopulmonary morbidity and mortality. The inhalation of toxic environmental particles and gases impacts the innate and adaptive defense systems of the lung. Lung macrophages play a critically important role in the recognition and processing of any inhaled foreign material such as pathogens or particulate matter. Alveolar macrophages and lung epithelial cells are the predominant cells that process and remove inhaled particulate matter from the lung. Cooperatively, they produce proinflammatory mediators when exposed to atmospheric particles. These mediators produce integrated local (lung, controlled predominantly by epithelial cells) and systemic (bone marrow and vascular system, controlled predominantly by macrophages) inflammatory responses. The systemic response results in an increase in the release of leukocytes from the bone marrow and an increased production of acute phase proteins from the liver, with both factors impacting blood vessels and leading to destabilization of existing atherosclerotic plaques. This review focuses on lung macrophages and their role in orchestrating the inflammatory responses induced by exposure to air pollutants.

Chronic exposure to sulfur dioxide enhances airway hyperresponsiveness only in ovalbumin-sensitized rats

Sulfur dioxide (SO(2)) is a common air pollutant that triggers asthmatic symptoms, but its toxicological mechanisms are not fully understood. Specifically, it is unclear how airborne SO(2) affects airway hyperresponsiveness (AHR) - a hallmark feature of asthma. To this end, we investigated the effects of chronic exposure to SO(2) on AHR, airway inflammation, tissue remodeling, cell stiffness (G') and contractility of the airway smooth muscle cell (ASMC). Newborn Sprague-Dawley (SD) rats sensitized to ovalbumin (OVA) was used as the model to mimic asthmatic symptoms. The experimental results show that exposure to SO(2): (1) significantly increased Penh (an indicator of AHR) in the OVA-sensitized rats (p<0.01) but not in the normal rats (p>0.05), which correlated with the increase of airway smooth muscle mass; (2) increased IL-4 production in BALF of both the normal (p<0.05) and OVA-sensitized rats (p<0.001), but decreased IFN-γ in BALF of only the normal rats, and in serum only increased IL-4 production of the OVA-sensitized rats (p<0.001); (3) increased ASMC stiffness (G') and contractility only in the OVA-sensitized rats (p<0.001, p<0.05, respectively). Taken together, these results demonstrate that SO(2) may be a universal airway inflammatory factor, but more importantly, specific to exacerbating AHR in asthmatics only. These findings uncover a potential mechanism of SO(2)-induced health effects and may provide a basis for therapeutic targets.

Allergens and bacteria interaction in the induction of basophil activation: is this the lost ring between allergy and infections in pediatric patients?

PURPOSE OF REVIEW

The aim of this review is to describe the relationships between allergy and infectious diseases, with specific attention on bacterial infection. According to the most recent literature, bacteria could be considered also as one of the major causes of asthma exacerbations that we need to further explore.

RECENT FINDINGS

The availability of novel methods to detect large panels of pathogens, including viruses and bacteria specific for the upper respiratory tract, together with the capacity of evaluating how basophils are activated, has changed the point of view of the mechanisms related to asthma exacerbations. The recent finding that basophils are activated in the presence of suboptimal doses of allergens and bacteria has been recently described and may explain the clinical behavior of allergy exacerbation. Indeed the activation of basophils induces the secretion of mediators, which, at bronchial level, may cause bronchospasm that leads to an asthma exacerbation in patients with infection. The contrary is also true.

SUMMARY

Although the explanations for these facts are numerous, at present, bacteria seem to play a relevant role in the worsening of asthma in infected patients.

Infection, eosinophilia and childhood asthma

There is a growing list of viruses and bacteria associated with wheezing illness and asthma. It is well known that a few of these pathogens are strongly associated with wheezing illness and asthma exacerbations. What is not known is if early childhood infections with these pathogens cause asthma, and, if so, exactly what are the pathophysiologic mechanisms behind its development. The current consensus is respiratory infection works together with allergy to produce the immune and physiologic conditions necessary for asthma diasthesis. One link between respiratory infection and asthma may be the eosinophil, a cell that plays prominently in asthma and allergy, but can also be found in the body in response to infection. In turn, the eosinophil and its associated products may be novel therapeutic targets, or at the very least used to elucidate the complex pathophysiologic pathways of asthma and other respiratory illnesses. Together or separately, they can also be used for diagnosis, treatment and monitoring. The optimal care of a patient must take into consideration not only symptoms, but also the underlying disease mechanisms.

Association between tree pollen counts and asthma ED visits in a high-density urban center

BACKGROUND

Asthma exacerbation patterns are cyclic in nature and often correlate with air particle concentrations.

OBJECTIVE

To examine the relationship between asthma-related emergency department (ED) visits and outdoor air quality for pediatric and adult patients in a high asthma prevalence area, the New York City borough of the Bronx.

METHODS

Numbers of daily asthma-related adult and pediatric ED visits during one complete year (1999) were obtained from the seven major Bronx hospitals. Daily values of nitrogen oxides (NO(x)), ozone (O(3)), sulfur dioxide (SO(2)), and pollen counts were acquired.

RESULTS

Asthma-related ED visit numbers were highest in December-January and lowest in July. There were three distinct peaks of increased asthma ED visits: winter (December-January), spring (late April-May), and fall (October). The spring peak was the most striking and coincided with high tree pollen counts (tree pollen: r = 0.90, p = .03). We observed a positive correlation between asthma ED visits in the winter and SO(2) and NO(x) levels. Winter peaks of SO(2) and NO(x) in early December appeared to precede the winter asthma peak.

CONCLUSIONS

The spring asthma peak is closely associated with increased tree pollen counts, and the asthma increase at this time is likely due to allergic reactions to pollen. No significant associations could be established with the fall peak. The winter peak correlates with elevated SO(2) and NO(x) levels.

Respiratory viruses, eosinophilia and their roles in childhood asthma

With the advent of highly sensitive and specific screening of respiratory specimens for viruses, new viruses are discovered, adding to the growing list of those associated with wheezing illness and asthma exacerbations. It is not known whether early childhood infections with these viruses cause asthma, and, if so, what exactly are the pathophysiologic mechanisms behind its development. The current consensus is that respiratory viral infection works together with allergy to produce the immune and physiologic conditions necessary for asthma diasthesis. One link between viruses and asthma may be the eosinophil, a cell that plays a prominent role in asthma and allergy, but can also be found in the body in response to viral infection. In turn, the eosinophil and its associated products may be novel therapeutic targets, or at the very least, used to elucidate the complex pathophysiologic pathways of asthma and other respiratory illnesses. Together or separately, they can be used for diagnosis, treatment and monitoring. Not only symptoms, but also the underlying disease mechanisms must be taken into consideration for the optimal care of a patient.

The ABCs of rhinoviruses, wheezing, and asthma

Human rhinoviruses (HRVs) were discovered as common cold pathogens over 50 years ago. Recent advances in molecular viral diagnostics have led to an appreciation of their role in more-significant respiratory illnesses, including bronchiolitis in infancy, childhood pneumonia, and acute exacerbations of chronic respiratory diseases such as asthma, chronic obstructive lung disease, and cystic fibrosis. Until a few years ago, only two groups of HRVs (A and B) had been recognized. However, full and partial sequencing of HRVs led to the discovery of a third species of HRV (HRV-C) that has distinct structural and biologic features. Risk factors and pathogenic mechanisms for more-severe HRV infections are being defined, and yet fundamental questions persist about mechanisms relating this common pathogen to allergic diseases and asthma. The close relationship between HRV infections and asthma suggests that antiviral treatments could have a major impact on the morbidity associated with this chronic respiratory disease.

Role of infection in the development and exacerbation of asthma

Respiratory infections are associated with wheezing illnesses in all ages and may also impact the development and severity of asthma. Respiratory tract infections caused by viruses, Chlamydophila or Mycoplasma have been hypothesized to have significant roles in the pathogenesis of asthma. Progress is being made toward establishing the mechanisms by which these agents can cause acute wheezing and impact the pathophysiology of asthma. Host factors probably contribute to the risk of asthma inception and exacerbation, and these contributions may also vary with respect to early- versus adult-onset disease. This review discusses these various associations as they pertain to the development and exacerbation of asthma.

Viral respiratory infection and the link to asthma

Viral respiratory infections are closely associated with wheezing illnesses and exacerbations of asthma throughout childhood, and yet there are a number of remaining questions pertaining to the specific nature of this relationship. Infection with an expanding list of respiratory viruses is an important cause of acute wheezing in infancy, and viruses are detected in most exacerbations of asthma throughout childhood. Furthermore, infants who develop severe viral respiratory infections are more likely to have asthma later in childhood. There has been progress in understanding the pathogenesis of viral respiratory illnesses, and this has led to new insights into how these processes might differ in asthma. Several host factors, including respiratory allergy and virus-induced interferon responses, modify the risk of virus-induced wheezing. In the absence of effective antiviral therapies, treatment of virus-induced wheezing and exacerbations of asthma can be challenging, and studies evaluating current treatment strategies are reviewed. Understanding the host-pathogen interactions that determine the severity of respiratory illnesses and long-term sequelae is likely to be of great help in identifying at-risk individuals, and in designing new and more effective treatments.

Use of diagnostic algorithms and new technologies to study the incidence and prevalence of viral upper respiratory tract infections and their complications in high risk populations

PURPOSE OF REVIEW

Most studies on the natural history of viral upper respiratory tract infections and their complications rely for ascertainment on self-assessed cold/flu illness or the identification of presumed complications. The criteria for cold/flu definition, however, are variable within and between individuals and illness is not prerequisite for a viral upper respiratory tract infection. These factors bias estimates of the incidence and prevalence of viral upper respiratory tract infections and their complications. Here we review new methodologies that can be adapted for use in future studies to refine those estimates.

RECENT FINDINGS

We present a theoretical basis for standardized assignment of cold/flu episodes using a minimal algorithm template that operates on a structured set of symptoms/signs. We emphasize the greater accuracy of information derived from longitudinal studies that incorporate identification algorithms and assay of nasal secretions for causal virus by polymerase chain reaction and for proinflammatory chemicals to confirm nasal inflammation.

SUMMARY

The methodologies and sampling strategies that we describe hold promise for better characterizing the incidence of complications for symptomatic and asymptomatic expressions of a viral upper respiratory tract infection caused by specific viruses. These data can then be used to estimate the efficacy and efficiency in a specified target population of prophylactic or intercurrent treatments to prevent the complications.

The asthma trigger inventory: validation of a questionnaire for perceived triggers of asthma

BACKGROUND

Asthma patients' perceptions of triggers have been explored in a largely unstructured fashion in the past. We therefore developed and validated a questionnaire of commonly perceived asthma triggers.

METHODS

Two hundred forty-seven primary care patients with asthma filled in an asthma trigger survey together with questionnaires on demographics, asthma-relevant information, perceived control of asthma, and general health status. Factor structure of the item pool and psychometric properties of trigger subscales were evaluated. We also investigated the relationship between allergen or psychological trigger reports and allergy skin test response or respiratory impedance during emotional film viewing, respectively.

RESULTS

Principal component analysis yielded six factors that were thematically associated with psychology, animal allergens, pollen allergens, physical activity, infection, and air pollution/irritants. Subscales showed good internal consistencies and low to moderately positive intercorrelations. Psychological triggers were consistently associated with less favorable health status, a reduced perception of asthma control, and greater medical treatment utilization. Animal allergen scores correlated positively with skin test responses to animal allergens. Respiratory impedance increases during emotional film clips were positively correlated with the psychological trigger subscale.

CONCLUSION

The questionnaire is a reliable measure of commonly perceived asthma triggers. Aspects of patients' trigger reports reflect actual reactivity to specific trigger factors.

Air pollution-associated changes in lung function among asthmatic children in Detroit

In a longitudinal cohort study of primary-school-age children with asthma in Detroit, Michigan, we examined relationships between lung function and ambient levels of particulate matter < or = 10 microm and < or = 2.5 microm in diameter (PM10 and PM2.5) and ozone at varying lag intervals using generalized estimating equations. Models considered effect modification by maintenance corticosteroid (CS) use and by the presence of an upper respiratory infection (URI) as recorded in a daily diary among 86 children who participated in six 2-week seasonal assessments from winter 2001 through spring 2002. Participants were predominantly African American from families with low income, and > 75% were categorized as having persistent asthma. In both single-pollutant and two-pollutant models, many regressions demonstrated associations between higher exposure to ambient pollutants and poorer lung function (increased diurnal variability and decreased lowest daily values for forced expiratory volume in 1 sec) among children using CSs but not among those not using CSs, and among children reporting URI symptoms but not among those who did not report URIs. Our findings suggest that levels of air pollutants in Detroit, which are above the current National Ambient Air Quality Standards, adversely affect lung function of susceptible asthmatic children.

The Totton-Ken Seibu earthquake and exacerbation of asthma in adults

The aim of the study was to characterize patients at risk for exacerbations of their asthma as a result of the Tottori-Ken Seibu earthquake and to identify factors that predict exacerbation of asthma after an earthquake. A retrospective cohort study-analysis was conducted of 156 asthmatic patients, aged 18 to 89 years, who were out-patients of Tottori University Hospital and who had completely recorded their asthmatic symptoms and measured their peak expiratory flow (PEF) rates for more than one year prior to the earthquake. Seventeen (11%) patients who experienced the earthquake were identified as having an exacerbation within one month after the earthquake. Diurnal variability of PEF during the month after the earthquake was compared to values during a matched month one year previously. When factors associated with exacerbation were identified by a review of the medical case notes and the contribution of these factors to the exacerbation was determined using multivariate analysis, airflow limitation was shown to be independently associated with exacerbation after the earthquake. Acute asthma attacks are more likely to occur within the first week after the earthquake event without diurnal PEF variability. Asthma is likely to worsen after an earthquake.

The effects of outdoor air pollution and tobacco smoke on asthma

Outdoor air pollution and environmental tobacco smoke adversely affect health in persons with asthma. Increased levels of ozone, particulate matter, and environmental tobacco smoke have been associated with increased asthma symptoms and health care use and with reduced lung function. These air contaminants have proinflammatory actions that can magnify existing lower airway inflammation in patients with asthma. Exposure to air contaminants can increase the risk of developing asthma in susceptible persons. Outdoor air pollution and environmental tobacco smoke may affect allergen-induced inflammation by initiating TH(2) responses to antigens or by exacerbating such inflammation in persons already sensitized.

Viral respiratory infection and the link to asthma

BACKGROUND

Acute wheezing secondary to viral infection is common in children. Whereas many children suffer primarily mild to moderate symptoms, others develop severe coughing and wheezing.

METHODS

Review of recent medical literature regarding the correlation between viral illness and increased susceptibility to develop severe respiratory illnesses and subsequent asthma.

DISCUSSION

In infants factors that predispose to severe disease and lower respiratory airway effects include small lung size, passive smoke exposure, virus-induced immune responses, severe disease and infection at a young age. Acute asthma symptoms have been correlated with a variety of viral pathogens, most commonly respiratory syncytial virus bronchiolitis in infancy and rhinovirus in older children. Epidemiologic and biologic factors that influence development of asthma include repeated exposure to infectious disease during early childhood, early exposure to pets, a farming lifestyle, alterations in bacterial flora of the intestine and increased use of antibiotics. Thus the likelihood of asthma is related to the specific pathogen, severity of infection, cumulative number of infections and stage of immunologic development. Progress is also being made in understanding how viruses can adversely affect lung or immune development. In asthmatic children viral infections initiate bronchospasm and airway obstruction. It is hoped that research on virus-induced airway alterations and the host factors that lead to severe clinical illnesses can help clinicians to identify children whose wheezing is an early sign of asthma.

Treating exacerbations of asthma in children: the role of systemic corticosteroids

OBJECTIVE

To review the use of systemic corticosteroids to treat recurrent, acute asthma episodes in children, with a focus on the role of oral corticosteroids.

METHODS

A comprehensive review of the literature was performed using the Medline database (January 1966-October 2002) and the Embase database (January 1980-August 2002).

RESULTS

The significant findings of 17 selected, controlled clinical trials of oral corticosteroids (OCSs) for acute exacerbations of asthma in children, compared with placebo or with other formulations of corticosteroids, can be summarized as follows: 1) OCSs are effective for the outpatient treatment of acute asthma, 2) pulmonary function tests may not be the best means of assessing the efficacy of OCSs for acute asthma, 3) early administration of OCSs for acute asthma reduces hospitalizations, 4) the critical factor for a positive outcome is early administration of the corticosteroid, and 5) OCSs are preferred for the outpatient treatment of acute asthma.

CONCLUSIONS

Early treatment of acute asthma symptoms with OCSs in children with a pattern of recurrent acute asthma may decrease the severity of acute asthma episodes and reduce the likelihood of subsequent relapses. Attention should be given to identifying these children and standardizing a treatment approach based on accepted, consistent definitions of what constitutes an asthma exacerbation and recurrence. A suggested protocol is described.

Infectious triggers of pediatric asthma

Respiratory infections can cause wheezing illnesses in children of all ages and also can influence the causation and disease activity of asthma. For years it has been recognized that respiratory syncytial virus infections often produce the first episode of wheezing in children who go on to develop chronic asthma. More recently, it has been proposed that repeated infections with other common childhood viral pathogens might help the immune system develop in such a way as to prevent the onset of allergic diseases and possibly asthma. In addition to the effects of viral infections, infections with certain intracellular pathogens, such as chlamydia and mycoplasma, may cause acute and chronic wheezing in some individuals, whereas common cold and acute sinus infections can trigger acute symptoms of asthma. In this article, the epidemiologic, mechanistic, and treatment implications of the association between respiratory infections and asthma are discussed.