The childhood asthma epidemic

Environmental Interventions for Asthma

Exposure and sensitization to environmental factors play a fundamental role in asthma development and is strongly associated with asthma morbidity. While hereditary factors are critical determinants of asthma, exposures to environmental factors are implicated in the phenotypic expression of asthma and have been strongly associated in the risk of its development. Significant interest has thus been geared toward potentially modifiable environmental exposures which may lead to the development of asthma. Allergen exposure, in particular indoor allergens, plays a significant role in the pathogenesis of asthma, and remediation is a primary component of asthma management. In the home, multifaceted and multitargeted environmental control strategies have been shown to reduce home exposures and improve asthma outcomes. In addition to the home environment, assessment of the school, daycare, and workplace environments of patients with asthma is necessary to ensure appropriate environmental control measures in conjunction with medical care. This article will discuss the role of the environment on asthma, review targeted environmental therapy, and examine environmental control measures to suppress environmental exposures in the home and school setting.

Effects of particulate matter (PM) on childhood asthma exacerbation and control in Xiamen, China

BACKGROUND

The short-term effects of particulate matter (PM) exposure on childhood asthma exacerbation and disease control rate is not thoroughly assessed in Chinese population yet. The previous toxic effects of PM exposure are either based on long-term survey or experimental data from cell lines or mouse models, which also needs to be validated by real-world evidences.

METHODS

We evaluated the short-term effects of PM exposure on asthma exacerbation in a Chinese population of 3106 pediatric outpatientsand disease control rate (DCR) in a population of 3344 children using case-crossover design. All the subjects enrolled are non-hospitalized outpatients. All data for this study were collected from the electronic health record (EHR) in the period between January 1, 2016 and June 30, 2018 in Xiamen, China.

RESULTS

We found that exposure to PM2.5 and PM10 within the past two weeks was significantly associated with elevated risk of exacerbation (OR = 1.049, p < 0.001 for PM2.5and OR = 1.027, p < 0.001 for PM10). In addition, exposure to PM10 was associated with decreased DCR (OR = 0.976 for PM10, p < 0.001).

CONCLUSIONS

Our results suggest that exposure to both PM10 and PM2.5 has significant short-term effects on childhood asthma exacerbation and DCR, which serves as useful epidemiological parameters for clinical management of asthma risk in the sensitive population.

Multi-Factor Analysis of Single-Center Asthma Control in Xiamen, China

We evaluated the effects of air pollutants, age, allergic history, family allergic history, treatment, treatment steps, and compliance on uncontrolled childhood asthma in Xiamen, China. The clinical data of children with asthma in the pediatric outpatient department of the First Affiliated Hospital of Xiamen University from January 2016 to June 2018 were analyzed retrospectively. According to the assessment of the patients' outcome including well-controlled, partly-controlled and uncontrolled, 7,211 cases of 3,268 patients were selected. Rank sum test and ordered multi-class logistic regression analysis were used. In the rank sum test, age, allergic history, family allergic history, season, treatment, treatment steps and compliance were found associated with uncontrolled rate (all P < 0.001). Logistic regression analysis showed that PM₁₀, NO₂, and SO₂ raised uncontrolled-asthma rate (aOR 1.311, aOR 1.281, aOR 1.252, respectively). Older children had lower uncontrolled rate (OR = 0.849, 95% CI: 0.758-0.950), children with higher treatment steps had higher uncontrolled rate (OR = 1.227, 95%CI: 1.040-1.448), and children with better treatment compliance have lower uncontrolled rate (OR = 0.374 95% CI: 0.331-0.424). The order of the uncontrolled rate of asthma from high to low was winter, spring, autumn, and summer. PM₁₀, NO₂, SO₂, age, season, treatment steps, and treatment compliance have significance for predicting the control rate of childhood asthma in Xiamen, China.

Pregnancy diet and offspring asthma risk over a 10-year period: the Lifeways Cross Generation Cohort Study, Ireland

OBJECTIVE

The association of maternal pregnancy diet with offspring asthma risk have been reported. However, literature on longitudinal patterns of asthma risk relative to intrauterine nutrient exposure is limited. We aimed to establish whether vegetable, oily fish and vitamin D intake during pregnancy are associated with childhood asthma risk over a 10-year period in the Irish Republic.

DESIGN

Mother-child pairs (n=897) from the Lifeways prospective birth cohort, with data on nutrient intake during pregnancy and asthma status, respectively, were eligible for inclusion in the analysis. Data on socioeconomic and morbidity indicators over 10 years of follow-up on mothers and the index child were collected through self-administered questionnaires. Asthma status as diagnosed by the general practitioner at any time point over 10 years was related to maternal vegetable, oily fish and vitamin D intake during pregnancy, while adjusting for gestational age, socioeconomic status, smoking at delivery, breast feeding, season of birth and supplement use. Data were modelled with a marginal model on correlated observations over time within individuals.

RESULTS

In the fully adjusted model, asthma was inversely associated with higher daily average intake of oily fish (OR 0.23 per serving/day, 95% CI 0.04 to 1.41) and of vegetables (OR 0.96 per serving/day, 95% CI 0.88 to 1.05), but the confidence limits overlapped 1. A higher daily vitamin D intake was associated with reduced odds of asthma (OR 0.93 per μg/day, 95% CI 0.89 to 0.98).

CONCLUSION

This analysis suggests higher daily average intake of vitamin D in pregnancy is associated with asthma risk in offspring over the first 10 years of life.

Modifiable exposures to air pollutants related to asthma phenotypes in the first year of life in children of the EDEN mother-child cohort study

Background

Studies have shown diverse strength of evidence for the associations between air pollutants and childhood asthma, but these associations have scarcely been documented in the early life. The purpose of this study was to evaluate the impacts of various air pollutants on the development of asthma phenotypes in the first year of life.

Methods

Adjusted odds ratios were estimated to assess the relationships between exposures to air pollutants and single and multi-dimensional asthma phenotypes in the first year of life in children of the EDEN mother-child cohort study (n = 1,765 mother-child pairs). The Generalized Estimating Equation (GEE) model was used to determine the associations between prenatal maternal smoking and in utero exposure to traffic-related air pollution and asthma phenotypes (data were collected when children were at birth, and at 4, 8 and 12 months of age). Adjusted Population Attributable Risk (aPAR) was estimated to measure the impacts of air pollutants on health outcomes.

Results

In the first year of life, both single and multi-dimensional asthma phenotypes were positively related to heavy parental smoking, traffic-related air pollution and dampness, but negatively associated with contact with cats and domestic wood heating. Adjusted odds ratios (aORs) for traffic-related air pollution were the highest [1.71 (95% Confidence Interval (CI): 1.08-2.72) for ever doctor-diagnosed asthma, 1.44 (95% CI: 1.05-1.99) for bronchiolitis with wheezing, 2.01 (95% CI: 1.23-3.30) for doctor-diagnosed asthma with a history of bronchiolitis]. The aPARs based on these aORs were 13.52%, 9.39%, and 17.78%, respectively. Results persisted for prenatal maternal smoking and in utero exposure to traffic-related air pollution, although statistically significant associations were observed only with the asthma phenotype of ever bronchiolitis.

Conclusions

After adjusting for potential confounders, traffic-related air pollution in utero life and in the first year of life, had a greater impact on the development of asthma phenotypes compared to other factors.

Fifty years of pediatric asthma in developed countries: how reliable are the basic data sources?

Given the difficulties in diagnosing, or even defining, asthma in children, claims of a pediatric asthma epidemic in Canada and other developed countries are accepted with surprisingly little critical examination. We reviewed a broad range of data sources to understand how the epidemic evolved during the last 50 years and also to assess the reliability of the conclusions drawn from that data. We obtained Canadian National and Provincial data from Statistics Canada National Population Health Survey, and the British Columbia Ministry of Health respiratory database. International data were obtained by extensive review of pediatric asthma epidemiological surveys published during the last 50 years. In many developed countries, there have been three separate epidemics involving different aspects of pediatric asthma during the last 50 years: a double peaked mortality epidemic (1960s and 1980s), a hospital admission epidemic (peaked around 1990) and a steadily growing epidemic of children who report asthmatic symptoms on questionnaires. Canadian pediatric rates for asthma mortality (1-2/million/year) and hospital admission (1-2/thousand/year) are low and have fallen for the last 20 years. Rates based on questionnaire studies are high (10-15/hundred) and rose steadily over the same period. Objective reductions in asthma deaths and hospital admission likely reflect improved education and treatment programmes. Current claims of an epidemic based largely on subjective self-reported symptoms require more careful analysis. The possibility that symptom misperception, disease fashions, and poor recall, may be part of the explanation for the current high levels of self-reported symptoms deserves more attention.

Asthma and risk of injury for Australian males aged 6-30 years: a population-based birth cohort study

BACKGROUND

A history of asthma could lead to a higher risk of injury according to a recent study, but both asthma status and injury events of participants were self-reported, so that the findings might be affected by recall bias and inaccuracy of diagnosis.

OBJECTIVE

To ascertain the association between asthma and risk of injury for Australian males using linked hospitalization records.

METHODS

A population-based birth cohort study of males born between 1980 and 1984 in Western Australia was conducted. Eligible subjects were identified from birth registry records and followed up from 6 years of age until death or 31 December 2009. Hospitalizations for asthma and injury of the cohort were extracted from the linked health databases. Multivariate Poisson regression models were fitted to estimate the relative risks of injury in relation to both previous and recent asthma admissions.

RESULTS

Australian males with asthma admission within the past 2 years or in previous years were found to experience an increased risk of injury. A recent asthma admission was associated with a higher risk of injury than a previous history of asthma admissions.

CONCLUSIONS

Physiological and mental side effects of asthma medication as well as the presence of asthmatic symptoms may contribute to the elevated injury risk. Further research of the underlying causes is needed to develop an injury prevention strategy for male patients with asthma.

On the causes of variability in amounts of airborne grass pollen in Melbourne, Australia

In Melbourne, Australia, airborne grass pollen is the predominant cause of hay fever (seasonal rhinitis) during late spring and early summer, with levels of airborne grass pollen also influencing hospital admissions for asthma. In order to improve predictions of conditions that are potentially hazardous to susceptible individuals, we have sought to better understand the causes of diurnal, intra-seasonal and inter-seasonal variability of atmospheric grass pollen concentrations (APC) by analysing grass pollen count data for Melbourne for 16 grass pollen seasons from 1991 to 2008 (except 1994 and 1995). Some of notable features identified in this analysis were that on days when either extreme (>100 pollen grains m(-3)) or high (50-100 pollen grains m(-3)) levels of grass pollen were recorded the winds were of continental origin. In contrast, on days with a low (<20 pollen grains m(-3)) concentration of grass pollen, winds were of maritime origin. On extreme and high grass pollen days, a peak in APC occurred on average around 1730 hours, probably due to a reduction in surface boundary layer turbulence. The sum of daily APC for each grass pollen season was highly correlated (r = 0.79) with spring rainfall in Melbourne for that year, with about 60% of a declining linear trend across the study period being attributable to a reduction of meat cattle and sheep (and hence grazing land) in rural areas around Melbourne. Finally, all of the ten extreme pollen events (3 days or more with APC > 100 pollen grains m(-3)) during the study period were characterised by an average downward vertical wind anomaly in the surface boundary layer over Melbourne. Together these findings form a basis for a fine resolution atmospheric general circulation model for grass pollen in Melbourne's air that can be used to predict daily (and hourly) APC. This information will be useful to those sectors of Melbourne's population that suffer from allergic problems.

Quantitative assessments of indoor air pollution and respiratory health in a population-based sample of French dwellings

BACKGROUND

Various volatile organic compounds (VOCs) have been related to respiratory health effects, but have generally been assessed individually without taking into account the fact that such pollutants are highly correlated to one other.

AIMS

We investigated the effects of exposure to various VOC, and considered their combined effect on adult asthma and rhinitis.

METHOD

A national cross-sectional representative survey conducted by the Indoor Air Quality Observatory objectively assessed 20 VOCs in 490 main dwellings in France. A standardized questionnaire determined the prevalence of asthma and rhinitis among 1012 inhabitants of the dwellings (≥ 15 years). Marginal models for binary outcome were used to relate VOCs exposure to asthma and rhinitis, controlling for potential confounders. A global score representing the number of VOCs in each dwelling with an elevated concentration (using the 3(rd) quartile value of the distribution as a threshold value) was then derived as a measure of the combined effect of VOCs. Specific scores were built using a similar approach, grouping VOCs by family.

RESULTS

Asthma (8.6%) was significantly associated with N-undecane and 1,2,4-trimethylbenzene and rhinitis (38.3%) with ethylbenzene, trichloroethylene, m/p- and o-xylene. The global VOC score was associated with a significant risk of asthma and rhinitis (odds ratio (OR) of 1.40 and 1.22, respectively, for 5 additional VOCs with high exposure level). Both specific scores for aromatic hydrocarbons and aliphatic hydrocarbons were associated with a significantly risk of asthma (OR=1.12; 95% confidence interval (CI): 1.01-1.24 and OR=1.41; 95% CI=1.03-1.93, respectively). The specific VOC score for halogenated hydrocarbons was associated with a significant risk of rhinitis (OR=1.28; 95% CI: 1.07-1.54).

CONCLUSION

We have shown that high concentrations of VOCs in homes were associated with an increasing prevalence of asthma and rhinitis in adults.

Is asthma associated with increased risk of injury?

BACKGROUND

Asthmatic patients are at higher risk of fracture and bruising due to the systemic side effects of corticosteroid medication. However, the link between asthma and injury leading to these adverse outcomes remains unclear.

OBJECTIVE

This study investigated asthma and cause- and type-specific injury at the population level.

METHODS

Using data from the 2001 and 2004 Australian National Health surveys (n = 52,768), the prevalence and risk of experiencing specific causes and types of injury in the past 4 weeks were assessed by logistic and Poisson regression analyses.

RESULTS

A history of asthma was associated with a higher prevalence of injury for both adults and children, as well as increased risk of incurring various causes and types of injury, after accounting for the effects of confounding factors.

CONCLUSIONS

The associations cannot be explained by the physiological systemic side effects of medication alone. Further research is needed to understand the underlying relationship so that an appropriate injury prevention strategy can be developed for asthma sufferers.

Inflammatory Disease Processes and Interactions with Nutrition

Inflammation is a stereotypical physiological response to infections and tissue injury; it initiates pathogen killing as well as tissue repair processes and helps to restore homeostasis at infected or damaged sites. Acute inflammatory reactions are usually self-limiting and resolve rapidly, due to the involvement of negative feedback mechanisms. Thus, regulated inflammatory responses are essential to remain healthy and maintain homeostasis. However, inflammatory responses that fail to regulate themselves can become chronic and contribute to the perpetuation and progression of disease. Characteristics typical of chronic inflammatory responses underlying the pathophysiology of several disorders include loss of barrier function, responsiveness to a normally benign stimulus, infiltration of inflammatory cells into compartments where they are not normally found in such high numbers, and overproduction of oxidants, cytokines, chemokines, eicosanoids and matrix metalloproteinases. The levels of these mediators amplify the inflammatory response, are destructive and contribute to the clinical symptoms. Various dietary components including long chain ω-3 fatty acids, antioxidant vitamins, plant flavonoids, prebiotics and probiotics have the potential to modulate predisposition to chronic inflammatory conditions and may have a role in their therapy. These components act through a variety of mechanisms including decreasing inflammatory mediator production through effects on cell signaling and gene expression (ω-3 fatty acids, vitamin E, plant flavonoids), reducing the production of damaging oxidants (vitamin E and other antioxidants), and promoting gut barrier function and anti-inflammatory responses (prebiotics and probiotics). However, in general really strong evidence of benefit to human health through anti-inflammatory actions is lacking for most of these dietary components. Thus, further studies addressing efficacy in humans linked to studies providing greater understanding of the mechanisms of action involved are required.

[Allergic respiratory diseases and outdoor air pollution]

INTRODUCTION

After having increased for some time, the prevalence of allergic diseases may have reached a plateau. During this increase, considerable concomitant changes in air pollution have occurred. Photo-oxidant air pollution, related to traffic, has become preponderant. The implication of air pollution in the epidemic of allergies is still debated.

BACKGROUND

Experimental studies have suggested that the effect of air pollutants, including particulates and ozone, on the worsening and even the induction of allergies is biologically plausible. In addition, epidemiological studies have shown a short term impact of the peaks of air pollution on exacerbations of asthma. On the other hand, the results of epidemiological studies dealing with the long-term effects of chronic exposure to air pollution on the prevalence of allergies are less consistent.

VIEWPOINTS

The implementation of new-born cohorts, the use of dispersion models to improve exposure assessment and the study of gene-environment correlations, should increase our knowledge of the role of traffic-related air pollutants in the development of allergies and identify subjects more sensitive to their effects.

CONCLUSIONS

Some traffic-related air pollutants may have played a more important role in the increase in the prevalence of allergies than was assumed from the first epidemiological studies.

Randomized, double-blind, placebo-controlled trial of probiotics for primary prevention: no clinical effects of Lactobacillus GG supplementation

BACKGROUND

The value of probiotics for primary prevention is controversial. Published trials vary considerably in study design and the applied probiotics, thereby limiting comparability of the results.

OBJECTIVE

The purpose of this trial was to study the preventive effect of the probiotic Lactobacillus GG on the development of atopic dermatitis.

METHODS

In a double-blind, placebo-controlled prospective trial, 105 pregnant women from families with > or = 1 member (mother, father, or child) with an atopic disease were randomly assigned to receive either the probiotic Lactobacillus GG (American Type Culture Collection 53103; 5 x 10(9) colony-forming units of Lactobacillus GG twice daily) or placebo. Ninety-four families (89.5%) completed the trial. The supplementation period started 4 to 6 weeks before expected delivery, followed by a postnatal period of 6 months. The primary end point was the occurrence of atopic dermatitis at the age of 2 years. Secondary outcomes were severity of atopic dermatitis, recurrent episodes of wheezing bronchitis, and allergic sensitization at the age of 2 years.

RESULTS

Atopic dermatitis was diagnosed in 14 (28%) of 50 in the Lactobacillus GG group and in 12 (27.3%) of 44 in the placebo group. The risk of atopic dermatitis in children on probiotics relative to placebo was 0.96 (confidence interval 0.38-2.33). Severity of atopic dermatitis was comparable between the 2 groups. Notably, children with recurrent (> or = 5) episodes of wheezing bronchitis were more frequent in the Lactobacillus GG group (26%; n = 13), as compared with the placebo group (9.1%; n = 4). No difference was observed between both groups in total immunoglobulin E concentrations or numbers of specific sensitization to inhalant allergens.

CONCLUSIONS

Supplementation with Lactobacillus GG during pregnancy and early infancy neither reduced the incidence of atopic dermatitis nor altered the severity of atopic dermatitis in affected children but was associated with an increased rate of recurrent episodes of wheezing bronchitis. Therefore, Lactobacillus GG cannot be generally recommended for primary prevention.

Sulphidoleukotriene release of cord blood basophils in response to allergen stimulation correlates with neither a family history of atopy nor a subsequent development of atopic eczema

OBJECTIVE

We tested a possible relationship between sulphidoleukotriene (SLT) release of cord blood (CB) basophils, a family history of atopy (HA) and subsequent development of atopic eczema. Population and methods A cohort of 86 neonates were involved (48.8% males; 46.5% with a positive HA(+)). CB samples were analysed for in vitro SLT release quantified by ELISA, and in a subgroup for basophilic activation (CD 63 expression) by flow cytometry in response to a positive control (anti-IgE-receptor antibody), an allergen-mix (TOP and PTOP), egg white (EW), egg yolk (EY), and the purified allergens beta-lactoglobulin (BLG) and alpha-lactalbumin (ALA).

RESULTS

Median concentrations of SLT were 124.2 (negative), 3871.5 (positive), 123.9 (TOP), 128.5 (PTOP), 113.1 (EW), 108.4 (EY), 125.2 (BLG) and 122.3 (ALA) pg/mL. Groups of HA(+) and HA(-) show no difference in all analysed allergens. An allergen-specific SLT release (defined as SLT>125 pg/mL above individual baseline and a stimulation index >2) was detected in 98% (positive control), 5% (TOP), 7% (BLG), 3% (ALA) and 2% (EW and EY), respectively. After a median observation period of 18 months, n=7 out of 70 children developed an atopic eczema, but we observed no association between CB SLT release (positive response to at least one tested allergen).

CONCLUSION

Allergen-specific SLT release is detectable in 15.5% of healthy neonates, irrespective of their family history of atopy. However, early allergen-specific SLT release is not predictive for the development of atopy.

Paediatric prescribing of asthma drugs in the UK: are we sticking to the guideline?

BACKGROUND

Asthma guidelines should lead to improved, more rational asthma medication prescribing. The aims of this study were to assess trends in paediatric asthma drug prescribing in the UK and to assess the potential impact of the publication of the British Thoracic Society (BTS) asthma guideline.

METHODS

The estimated community paediatric prescribing figures for asthma medications in the UK were studied using data from the NHS Information Centre for Health and Social Care for the years 2000-2006.

RESULTS

The numbers of prescriptions for bronchodilator syrups decreased by 60% from 2000 to 2006. However, this still represents 121,000 prescriptions for bronchodilator syrups in 2006 despite minimal recommendations for their use. The percentage of steroid inhalers prescribed as combination inhalers of a steroid and a long-acting beta agonist increased from 2.6% in 2000 to 20.6% in 2006.

CONCLUSIONS

Steroid-alone inhalers should be the mainstay for the vast majority of patients with asthma who require controller medications. The increase in the number of combination inhalers prescribed is not consistent with the guideline recommendations that combination inhalers should only be introduced in those patients with asthma not controlled on adequate doses of inhaled steroids. Further education of health professionals is required.

Do levels of airborne grass pollen influence asthma hospital admissions?

BACKGROUND

The effects of environmental factors and ambient concentrations of grass pollen on allergic asthma are yet to be established.

OBJECTIVE

We sought to estimate the independent effects of grass pollen concentrations in the air over Melbourne on asthma hospital admissions for the 1992-1993 pollen season.

METHODS

Daily grass pollen concentrations were monitored over a 24-h period at three stations in Melbourne. The outcome variable was defined as all-age asthma hospital admissions with ICD9-493 codes. The ambient air pollutants were average daily measures of ozone, nitrogen dioxide and sulphur dioxide, and the airborne particle index representing fine particulate pollution. Semi-parametric Poisson regression models were used to estimate these effects, adjusted for air temperature, humidity, wind speed, rainfall, day-of-the-week effects and seasonal variation.

RESULTS

Grass pollen was a strong independent non-linear predictor of asthma hospital admissions in a multi-pollutant model (P=0.01). Our data suggest that grass pollen had an increasing effect on asthma hospital admissions up to a threshold of 30 grains/m3, and that the effect remains stable thereafter.

CONCLUSION

Our findings suggest that grass pollen levels influence asthma hospital admissions. High grass pollen days, currently defined as more than 50 grains/m3, are days when most sensitive individuals will experience allergic symptoms. However, some asthmatic patients may be at a significant risk even when airborne grass pollen levels are below this level. Patients with pollen allergies and asthma would be advised to take additional preventive medication at lower ambient concentrations.