Early childhood infectious diseases and the development of asthma up to school age: a birth cohort study

Asthma and atopy are associated with DEFB1 polymorphisms in Chinese children

Human beta-defensin (HBD)-1 is constitutively expressed in the airway, and hBD-1 plays crucial roles in innate immunity against respiratory pathogens. Asthma was associated with DEFB1 polymorphisms in Caucasians. This study investigates whether three single nucleotide polymorphisms (SNPs) in 5'-untranslated region of DEFB1 are associated with asthma phenotypes in Chinese children. Subjects aged 5-18 years were recruited from general pediatric clinics. Plasma IgE concentrations were measured by immunoassays. DEFB1 SNPs were characterized by restriction fragment length polymorphism. In all, 305 asthmatics and 156 controls were recruited. For asthma diagnosis, atopy and plasma total IgE, higher percentages of subjects with these outcomes had the minor alleles -20A and -52G (P = 0.041-0.0002). For log-transformed total IgE, the covariate was positive and significant for G-20A under recessive model (P = 0.001) and for G-52A under both recessive and codominant models (P = 0.008 and 0.035). The recessive model covariate was also positive and significant (P = 0.020) for C-44G on peripheral blood eosinophil count. The GCA haplotype of DEFB1 was significantly associated with asthma (odds ratio (95% confidence interval): 1.64 (1.05-2.57); P = 0.029). These results suggest that DEFB1 is a candidate gene for asthma and atopy in children.

Epidemiology

The common cold is the result of an upper respiratory tract infection causing an acute syndrome characterised by a combination of non-specific symptoms, including sore throat, cough, fever, rhinorrhoea, malaise, headache, and myalgia. Respiratory viruses, alone or in combination, are the most common cause. The course f illness can be complicated by bacterial agents, causing pharyngitis or sinusitis, but the are a rare cause of cold and flu-like illnesses (CFLIs). Our understanding of CFLI epidemiology has been enhanced by molecular detection methods, particularly polymerase chain reaction (PCR) testing. PCR has not only improved detection of previously known viruses, but within the last decade has resulted in the detection of many divergent novel respiratory virus species. Human rhinovirus (HRV) infections cause nearly all CFLIs and they can be responsible for asthma and chronic obstructive pulmonary disease exacerbations. HRVs are co-detected with other respiratory viruses in statistically significant patterns, with HRVs occurring in the lowest proportion of co-detections, compared to most other respiratory viruses. Some recently identified rhinoviruses may populate an entirely new putative HRV species; HRV C. Further work is required to confirm a causal role for these newly identified viruses in CFLIs. The burden of illness associated with CFLIs is poorly documented, but where data are available, the impact of CFLIs is considerable. Individual infections, although they do not commonly result in more severe respiratory tract illness, are associated with substantial direct and indirect resource use. The product of frequency and burden for CFLIs is likely to be greater in magnitude than for any other respiratory syndrome, but further work is required to document this. Our understanding of the viral causes of CLFIs, although incomplete, has improved in recent years. Documenting burden is also an important step in progress towards improved control and management of these illnesses.

Dental caries and allergic disorders in Japanese children: the Ryukyus Child Health Study

BACKGROUND

Dental caries is an infectious disease and is highly prevalent among children. In the etiology of allergic diseases, the hygiene hypothesis contends that infections might confer protection against the development of allergic diseases. The aim of this cross-sectional study was to investigate the association between dental caries and the prevalence of allergic disorders.

METHODS

Study subjects were 21,792 children 6 to 15 years of age in Okinawa, Japan. Outcomes were based on diagnostic criteria from the International Study of Asthma and Allergies in Childhood. Data on dental caries were obtained from school records. Children were classified as having dental caries if one or more teeth had decayed and/or had been filled. Adjustment was made for sex, age, region of residence, number of siblings, smoking in the household, paternal and maternal history of asthma, atopic eczema, or allergic rhinitis, and paternal and maternal educational level.

RESULTS

The prevalence of wheeze, asthma, atopic eczema, and allergic rhinoconjunctivitis in the previous 12 months was 10.8%, 7.6%, 6.8%, and 7.6%, respectively. In an overall analysis, no measurable relationship was found between dental caries and the prevalence of wheeze, asthma, atopic eczema, or allergic rhinoconjunctivitis. However, dental caries was significantly inversely associated with the prevalence of allergic rhinoconjunctivitis only among children with a positive parental allergic history: The adjusted odds ratio was 0.84 (95% confidence interval: 0.72, 0.99).

CONCLUSIONS

The present findings do not support the hypothesis that dental caries was protective against allergic diseases. However, a parental allergic history may affect the association between dental caries and allergic rhinoconjunctivitis.

The Asian side of asthma and allergy

PURPOSE OF REVIEW

There is wide variation in the global epidemiology of allergic diseases, and the prevalence rates of asthma and allergy differ significantly among different Asian populations. The diversity of environment and ethnic background in Asia provide excellent opportunities for research into the environmental and genetic determinants of asthma and allergies. This review summarizes important lessons learnt from research findings from Asia on asthma and allergy.

RECENT FINDINGS

Recent epidemiologic studies revealed wide variation and increasing prevalence of asthma and allergy in many Asian countries. Comparative studies of population of the same ethnic background living in different environments revealed important environmental risk factors for asthma. Ambient air pollution plays an important role in the morbidity of patients with asthma but does not seem to affect the prevalence of asthma. There were many genetic association studies for allergic diseases from Asia. These studies identified novel gene targets, such as CD40, DCNP1 and PTGS2, for asthma and allergen sensitization whereas many others replicated the genetic associations on known candidate genes for asthma and atopic dermatitis.

SUMMARY

Epidemiologic and genetic researches in Asia advance our knowledge on the disease prevalence, healthcare burden and pathogenesis of asthma and allergy.

Strategies for atopy prevention

Allergic diseases, particularly in childhood, have become one of the epidemics of the 21st century. Whereas previous strategies for allergy prevention focused on the avoidance of risk factors, more recent approaches are addressing attempts to provide protective factors to infants and young children to achieve immune modulation and tolerance to harmless nutritional or environmental allergens. This change of paradigm for allergy prevention might lead to more effective interventions, which hopefully contribute to reversing the epidemiologic trend of the last decades. In many industrialized countries, the increased prevalence of atopy and asthma has become a serious public health issue. If preventive intervention could be effective at all, it would have to be applied early in life, most probably in early infancy. Unfortunately, our understanding of the natural history of the process of atopic sensitization, atopic dermatitis, and allergic airway disease is still very limited. On the other hand, the evaluation of risk factors and determinants is a necessary prerequisite for any effective intervention.

Day-care attendance, position in sibship, and early childhood wheezing: a population-based birth cohort study

BACKGROUND

There are conflicting data on the effect of day-care attendance and position in sibship on the development of wheezing.

OBJECTIVE

To investigate the relationship between day-care attendance and position in sibship with early childhood wheeze.

METHODS

Prospective population-based birth cohort. At age 5 years, we collected information on parentally reported symptoms (n = 922); lung function was ascertained using plethysmography (n = 745) and allergic sensitization by skin testing (n = 815). Participants were assigned into categories according to the age of entry to day-care (0-6, 6-12, >12 mo) and number of older siblings (0, 1, 2, >2).

RESULTS

Current wheeze was reported by 203 participants (22%); 224 (28%) were sensitized. In the multivariate model, sensitization (odds ratio, 2.47; 95% CI, 1.66-3.67), male sex (1.49, 1.01-2.20), maternal asthma (1.72, 1.10-2.68), and maternal smoking during pregnancy (2.15, 1.26-3.66) significantly increased the risk of wheezing. Entering day-care between 6 and 12 or after 12 months of age was significantly and inversely associated with current wheeze (0.25, 0.11-0.60; and 0.65, 0.44-0.98, respectively). Entry into nursery between 6 and 12 months reduced the risk of persistent wheezing (P = .04). We found no association between day-care attendance and lung function. Entering nursery in the first 6 months of life was associated with increased risk of atopy (2.47, 1.23-4.95). Having older siblings was associated only with rhinoconjunctivitis (0.72, 0.54-0.97).

CONCLUSION

Day-care attendance was associated with a reduced risk of current wheezing in 5-year-old children. The protective effect appeared strongest for children who entered day-care between the ages of 6 and 12 months.

Potential health effects from non-specific stimulation of the immune function in early age: the example of BCG vaccination

There is increasing, but still inconsistent evidence that vaccinations and childhood infections may play a role in the normal maturation of the immune system, and in the development and balance of immune regulatory pathways, both of which might impact health later in life. This review covers the epidemiological evidence regarding the role of Bacillus Calmette-Guérin (BCG) vaccination on the following inflammatory or autoimmune diseases: asthma and allergic diseases, Crohn's disease (CD), insulin-dependent diabetes mellitus (IDDM), and specific cancers. The literature is more comprehensive for asthma and allergic diseases, with 16 studies reporting the absence of an association while seven rather suggest a protective effect of BCG. We found insufficient evidence on CD to conclude at this point. Overall, the evidence for IDDM based on four studies leans towards no association, although some effects were observed in population subsets. Five epidemiological investigations provide evidence on a possible link with cancer incidence or mortality at various sites, with indications of both increased and decreased risks. Given the potential public health implications, it is imperative to acquire a better understanding of how BCG vaccination could influence the development of such chronic health conditions in the population.

Antibiotics and allergic disorders in childhood

AIM

This paper explores the possible association between antibiotics prescribed in infancy and allergic disorders, mainly eczema and asthma, in childhood.

BACKGROUND

No-one fully understands why childhood asthma and eczema have become so common. Some authorities suggest that there may be an association between eczema and asthma and antibiotics prescribed in childhood; however, others disagree. METHOD/EVALUATION: The available literature was reviewed to examine the links between prescribed antibiotics and childhood eczema and asthma. FINDINGS/KEY ISSUE: Some, but not all, research indicates that antibiotic administration in pregnancy, childbirth or infancy may be linked to childhood asthma and eczema, but much uncertainty remains. None of the papers identified stated the doses of antibiotics prescribed. In addition, we were unable to locate studies reporting the interactions between antibiotics and the developing immune system.

CONCLUSION

Health care professionals should be selective when prescribing antibiotics. Further prospective work is needed to guide the prescribing of antibiotics in childbirth and infancy.

Diversity and seasonal dynamics of bacterial community in indoor environment

Background

We spend most of our lives in indoor environments and are exposed to microbes present in these environments. Hence, knowledge about this exposure is important for understanding how it impacts on human health. However, the bacterial flora in indoor environments has been only fragmentarily explored and mostly using culture methods. The application of molecular methods previously utilised in other environments has resulted in a substantial increase in our awareness of microbial diversity.

Results

The composition and dynamics of indoor dust bacterial flora were investigated in two buildings over a period of one year. Four samples were taken in each building, corresponding to the four seasons, and 16S rDNA libraries were constructed. A total of 893 clones were analysed and 283 distinct operational taxonomic units (OTUs) detected among them using 97% sequence similarity as the criterion. All libraries were dominated by Gram-positive sequences, with the most abundant phylum being Firmicutes. Four OTUs having high similarity to Corynebacterium-, Propionibacterium-, Streptococcus- and Staphylococcus- sequences were present in all samples. The most abundant of the Gram-negative OTUs were members of the family Sphingomonadaceae, followed by Oxalobacteraceae, Comamonadaceae, Neisseriaceae and Rhizobiaceae.

The relative abundance of alpha- and betaproteobacteria increased slightly towards summer at the expense of firmicutes. The proportion of firmicutes and gammaproteobacteria of the total diversity was highest in winter and that of actinobacteria, alpha- and betaproteobacteria in spring or summer, whereas the diversity of bacteroidetes peaked in fall. A statistical comparison of the libraries revealed that the bacterial flora of the two buildings differed during all seasons except spring, but differences between seasons within one building were not that clear, indicating that differences between the buildings were greater than the differences between seasons.

Conclusion

This work demonstrated that the bacterial flora of indoor dust is complex and dominated by Gram-positive species. The dominant phylotypes most probably originated from users of the building. Seasonal variation was observed as proportional changes of the phyla and at the species level. The microflora of the two buildings investigated differed statistically and differences between the buildings were more pronounced than differences between seasons.

Neonatal antibiotic treatment is a risk factor for early wheezing

OBJECTIVE

The use of antibiotics in infancy and subsequent changes in the intestinal bacterial flora have been discussed as risk factors for the development of asthma. However, it has been difficult to exclude the possibility that antibiotics have been given in early episodes of wheezing. As a result, there has been a risk of reverse causation. To minimize the risk of reverse causation, we have focused on the effect of antibiotics that are already administered on the neonatal ward.

METHODS

In a cohort study of infants born in western Sweden in 2003, we studied the development of wheezing. The families of the infants were randomly selected and sent a questionnaire at child ages 6 and 12 months. The response rate was 68.5% to the 6-month questionnaire and 68.9% to the 12-month questionnaire.

RESULTS

At 12 months, 20.2% of infants had had 1 or more episodes of wheezing, and 5.3% had had 3 or more episodes. Inhaled corticosteroids had been taken by 4.1% of the infants. Independent risk factors for wheezing disorder treated with inhaled corticosteroids were neonatal antibiotic treatment, male gender, gestational age of <37 weeks, having a mother with asthma, having a sibling with asthma or eczema, and breastfeeding for <5 months.

CONCLUSIONS

Treatment with antibiotics in the neonatal period was an independent risk factor for wheezing that was treated with inhaled corticosteroids at 12 months of age. These results indirectly support the hypothesis that an alteration in the intestinal flora can increase the risk of subsequent wheezing.

Predictors of the persistence of childhood asthma

BACKGROUND

The factors relevant to the prognosis of childhood asthma differ from one population to another.

OBJECTIVES

To characterize the course of childhood asthma in the catchment area of our hospital, and to identify prognostic factors for this population.

METHODS

All children given a diagnosis of asthma in the paediatric pulmonology service of a tertiary hospital were followed up for 5 years.

RESULTS

Satisfactory control of asthma was achieved in 69 % of cases. The factors identified as associated with poor control were allergy to cats and pollen, a large number of crises in the year prior to diagnosis, and younger age at onset.

CONCLUSIONS

In our region, childhood asthma has a relatively favourable prognosis. The subsequent course of the disease appears to be determined in childhood. The persistence of symptoms appears to depend to a significant extent on the degree of atopy.

Prevalence and associated factors of allergic rhinitis and atopic dermatitis in children

Allergic disorders are the chronic diseases of greatest pediatric morbidity, affecting over 25 % of the pediatric population. Indeed, this situation has been referred to as an "allergic epidemic". In comparison with asthma, atopic dermatitis and allergic rhinitis have been less extensively investigated, although this does not mean that they should be regarded as minor disorders but rather as alterations that affect the quality of life of the patients and their families, which generate considerable direct and indirect costs. Despite an important research effort, the reason for this allergic epidemic is not well known. These are multifactor disorders without a single causal agent, in which the most important component is the genetic predisposition of the patient (atopy), modulated by environmental factors, exposure to allergens, infections and irritants, among others. A confounding element is the fact that the concept of allergic diseases encompasses phenotypes of rhinitis, atopic dermatitis or asthma in which no IgE-mediated atopic mechanism is demonstrated, and which can manifest in a way similar to true allergic phenotypes. Differentiation between the two is difficult to establish on the basis of self-administered questionnaires alone, in the absence of a precise etiological diagnosis. The present article reviews the numerous factors suggested to be responsible for the increase in allergic diseases recorded in the last few decades, and for the differences in prevalence observed among centres. For most of these factors the results published in the literature are contradictory, in some cases due to a lack of control of the associated interacting or confounding factors. Consensus exists for only some of these causal factors, such as the established parallelism between the increase in allergic diseases and the reduction in infectious processes on one hand, and the increase in particles generated by diesel fuel combustion on the other. In addition, the implicated factors could act differently (and in some cases even antagonically) upon atopy and on the different disease phenotypes, thereby complicating the study of these interactions even further.

Ambient formaldehyde levels and allergic disorders among Japanese pregnant women: baseline data from the Osaka maternal and child health study

PURPOSE

The effects of formaldehyde (FA) exposure on allergic disorders are not clearly understood. This cross-sectional study examined the relationship between FA exposure and the prevalence of allergic disorders in Japan.

METHODS

Subjects were 998 pregnant women. Participants were considered to have asthma, atopic eczema, or allergic rhinitis (including cedar pollinosis) if they had received any medical treatment for any of these allergic disorders during the previous 12 months. Passive air sampling tubes were worn for 24 hours and analyzed for FA.

RESULTS

When FA levels were categorized into four groups, there was a tendency for a positive exposure-response relationship between FA levels and the prevalence of atopic eczema, although the adjusted odds ratio for highest vs. lowest FA categories did not reach statistical significance. When FA levels were categorized into two groups to assess the effects of exposure to high levels of FA on allergic disorders, FA levels of 47 ppb or more were independently associated with an increased prevalence of atopic eczema (adjusted odds ratio = 2.25; 95% confidence interval, 1.01-5.01). The positive association was more pronounced in women with a negative familial allergic history than in those with a positive familial allergic history. No clear association was found between FA levels and the prevalence of asthma or allergic rhinitis.

CONCLUSIONS

FA exposure may be associated with an increased prevalence of atopic eczema in Japanese pregnant women.

The role of T cells in the enhancement of respiratory syncytial virus infection severity during adult reinfection of neonatally sensitized mice

Respiratory syncytial virus (RSV) is the major cause of infantile bronchiolitis and hospitalization. Severe RSV disease is associated with the development of wheezing in later life. In a mouse model of the delayed effects of RSV, the age at primary infection determines responses to reinfection in adulthood. During primary RSV infection, neonatal BALB/c mice developed only mild disease and recruited CD8 cells that were defective in gamma interferon production. Secondary reinfection of neonatally primed mice caused enhanced inflammation and profuse lung T-cell recruitment. CD4 cell depletion during secondary RSV challenge attenuated disease (measured by weight loss); depletion of CD8 cells also markedly attenuated disease severity but enhanced lung eosinophilia, and depletion of both CD4 and CD8 cells together completely abrogated weight loss. Depletion of CD8 (but not CD4) cells during primary neonatal infection was protective against weight loss during adult challenge. Therefore, T cells, in particular CD8 T cells, play a central role in the outcome of neonatal infection by enhancing disease during secondary challenge. These findings demonstrate a crucial role for T cells in the regulation of immune responses after neonatal infection.

Life history theory and the immune system: steps toward a human ecological immunology

Within anthropology and human biology, there is growing interest in immune function and its importance to the ecology of human health and development. Biomedical research currently dominates our understanding of immunology, and this paper seeks to highlight the potential contribution of a population-based, ecological approach to the study of human immune function. Concepts from life-history theory are applied to highlight the major challenges and demands that are likely to shape immune function in a range of ecological contexts. Immune function is a major component of maintenance effort, and since resources are limited, trade-offs are expected between investment in maintenance and other critical life-history functions involving growth and reproduction. An adaptationist, life-history perspective helps make sense of the unusual developmental trajectory of immune tissues, and emphasizes that this complex system is designed to incorporate information from the surrounding ecology to guide its development. As a result, there is substantial population variation in immune development and function that is not considered by current biomedical approaches. In an attempt to construct a framework for understanding this variation, immune development is considered in relation to the competing life-history demands that define gestation, infancy, childhood, adolescence, and adulthood. Each life stage poses a unique set of adaptive challenges, and a series of hypotheses is proposed regarding their implications for immune development and function. Research in human ecological immunology is in its earliest stages, but this is a promising area of exploration, and one in which anthropology is well-positioned to make important contributions.

The potential biases in studying the relationship between asthma and microbial infection

OBJECTIVE

To assess bias in parent reports of asthma status of children and detection bias of medical records-based asthma ascertainment and to examine effects of such bias on the association between asthma status and infections.

METHODS

A prospective cohort study was conducted to compare the correlations between the frequency of acute illnesses and that of medical evaluations between children with or without asthma according to parental report and medical record review by following a group of children who were enrolled in the Mayo Clinic Sick Child Care Program in Rochester, Minnesota. Parents completed a self-administered questionnaire to determine asthma status of their child. Also, comprehensive medical record reviews were conducted to determine asthma status of each subject by applying predetermined criteria for asthma.

RESULTS

A convenience sample of 115 parents and their children participated in this study. The mean age of the parents who participated in the study was 32.8 years (standard deviation: 5.4 years); 93% were female (mothers); and 90% were white. Of the 115 children who participated in this study, 84% were reported to be white and 49% were female. The mean age of the children was 2 years (standard deviation: 1.0 year). Parents whose children had asthma by report appeared to be less likely to seek medical evaluations (Spearman's rho: 0.42,p = 0.11) when their children had acute illnesses, compared to those of non-asthmatic children (rho: 0.64,p < 0.001). Concerns that asthmatic patients (rho: 0.62,p < 0.001) are more likely to see health care providers and undergo medical evaluations and laboratory tests when they have acute illnesses than non-asthmatic patients (rho: 0.64,p < 0.001) are not supported by our study.

CONCLUSION

Parental report bias needs to be considered carefully when studying the relationship between asthma and microbial infection.

Cytokine production from peripheral blood mononuclear cells of mite allergen-sensitized atopic adults stimulated with respiratory syncytial virus and mite allergen

BACKGROUND

The interaction between viral respiratory tract infection and allergen sensitization in allergic asthma is unclear. Respiratory syncytial virus (RSV) has attracted attention as an important lower respiratory pathogen during childhood, while recent evidence indicates that RSV is also an important lower respiratory pathogen for adults. Immunity against RSV differs between children and adults. Several reports suggest that RSV infection in children results in a Th2-skewed immune response. The purpose of the present study was to determine the effects of RSV infection in adults who had previously been sensitized with a common aeroallergen.

METHODS

Peripheral blood mononuclear cells (PBMCs) isolated from 9 mite-sensitized atopic subjects and 11 healthy nonatopic subjects were exposed to live or UV-inactivated RSV concomitant to incubation with or without mite allergen, and the subsequent production of cytokines - interleukin (IL)-5, interferon (IFN)-gamma, IL-10 and IL-12p70 - was measured.

RESULTS

Mite allergen significantly increased IL-5 production in atopic PBMCs. RSV infection significantly increased IFN-gamma production from healthy and atopic PBMCs; the levels of IFN-gamma were significantly higher for atopic PBMCs. Live RSV infection significantly attenuated IL-5 production from mite allergen-stimulated atopic PBMCs. UV-inactivated RSV, but not live RSV, significantly enhanced allergen-specific IL-10 production in atopic PBMCs. IL-12 could not be detected in the present study.

CONCLUSION

The present findings suggest that RSV infection did not simply enhance allergen-specific Th2-like response in atopic adults. Live RSV-induced IFN-gamma and RSV protein-induced IL-10 appear to play important roles in the regulation of allergic airway inflammation in atopic adults.

Comparison of allergic diseases, symptoms and respiratory infections between Finnish and Russian school children

BACKGROUND

Little is known about differences in allergic and respiratory diseases between the Finnish and Russian populations.

METHODS

We conducted a population-based cross-sectional study to compare the occurrence of allergic diseases and respiratory infections among school children in the towns of Imatra in Finland and Svetogorsk in Russia on either side of the common border. The study population consisted of 512 Finnish and 581 Russian school children aged 7-16 years (response rate 79%). We used multiple logistic regression analysis to calculate odds ratios adjusting for age and gender.

RESULTS

The prevalences of asthma (6.7 vs. 3.9%, adjusted odds ratio (OR) 1.54, 95% confidence interval (CI 0.87-2.71), allergic rhinitis (15.2 vs. 8.8%, OR 1.81, 1.22-2.68), allergic conjunctivitis (4.7 vs. 3.2%, 1.33, 0.70-2.53), and atopic dermatitis (10.5 vs. 5.9%, 1.78, 1.12-2.83) were substantially higher among school children in Imatra compared to those in Svetogorsk, but the symptoms were more severe among allergic Russian children. Tonsillitis (adjusted OR 0.11, 95% CI 0.07-0.17), sinusitis (0.39, 0.24-0.63), bronchitis (0.41, 0.27-0.62) and pneumonia (0.19, 0.04-0.90) occurred less frequently in the Finnish children, whereas otitis media (2.37, 1.55-3.62) and common cold (4.07, 3.12-5.31) were more frequent in Finland.

CONCLUSIONS

Allergic diseases are more common in Finnish than Russian school children, but the symptoms are more severe among allergic Russian children. Respiratory infections are in general more frequent in Russian children. "Western" lifestyle habits, differences in diagnostic procedures and environmental factors, and availability of health care and medications are discussed as possible explanations for the observed differences.

Diagnosis and treatment of asthma in childhood: a PRACTALL consensus report

Asthma is the leading chronic disease among children in most industrialized countries. However, the evidence base on specific aspects of pediatric asthma, including therapeutic strategies, is limited and no recent international guidelines have focused exclusively on pediatric asthma. As a result, the European Academy of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma and Immunology nominated expert teams to find a consensus to serve as a guideline for clinical practice in Europe as well as in North America. This consensus report recommends strategies that include pharmacological treatment, allergen and trigger avoidance and asthma education. The report is part of the PRACTALL initiative, which is endorsed by both academies.

The genetic and environmental basis of atopic diseases

The prevalence of atopic diseases has increased abruptly in recent years in most Westernized societies, making the question why this happened the topic of a heated debate. The best paradigm available to date to explain this steep rise, the 'hygiene hypothesis', supports that it is the excess 'cleanliness' of our environments that has led to the decline in the number of infectious stimuli that are necessary for the proper development of our immune system. Recent findings support that it is the combined effect that not only pathogenic, but also non-pathogenic microorganisms, and even their structural components,can exert on the immune system that deters from the development of atopic responses. Adding to these results are intriguing new findings on the effect different gene polymorphisms can have on an individual's predisposition to allergic diseases. The most important linkages produced, to date, include those among the genes for IL-4, IL-13, HLA-DRB, TNF, LTA,FCER1B, IL-4RA, ADAM33, TCR alpha/delta, PHF11, GPRA, TIM, p40, CD14, DPP10, T-bet, GATA-3, and FOXP3 and allergic disorders. The two parallel research efforts, epidemiologic and genetic, are only recently starting to converge,producing fascinating results on the effect particular gene-environment interactions might have in the development of atopy.The most important lesson learned through this tremendous research effort is that not only a small number but thousands and millions of separate risk factors act in concordance in the production of the allergic phenotype.

Helicobacter pylori colonisation and eczema

The hygiene hypothesis postulates that the increase in atopic diseases may in part be due to diminished exposure to microorganisms. But it is unknown which type of infection does render protection. An epidemiological study was conducted in Leipzig, Germany, and its rural county, involving 3347 school starters. Two types of infection were considered: (1) gastrointestinal colonisation (Helicobacter pylori detection using in vivo [(13)C] urea breath test) and (2) respiratory infections (physician-diagnosed lower (bronchitis) and upper (common cold) respiratory infections). H pylori colonisation was selected because it is very common and plays an important role in gastrointestinal disorders. Atopic eczema was selected as the (allergic) target variable because of its high frequency in the age of the study participants. The results, adjusted for relevant confounders, showed a significant inverse association between H pylori infection and eczema (adjusted odds ratio (aOR) = 0.31, p = 0.006) in children not predisposed to atopy. In contrast, bronchitis increased the risk of eczema (aOR = 1.98, p<0.001). Bacterial digestive tract colonisation (infection) seems to protect against eczema in comparison with the effect of respiratory tract infections. The hygiene hypothesis may be better explained when gastrointestinal and respiratory infections are subtly differentiated.

Helicobacter pylori colonisation and eczema

The hygiene hypothesis postulates that the increase in atopic diseases may in part be due to diminished exposure to microorganisms. But it is unknown which type of infection does render protection. An epidemiological study was conducted in Leipzig, Germany, and its rural county, involving 3347 school starters. Two types of infection were considered: (1) gastrointestinal colonisation (Helicobacter pylori detection using in vivo [(13)C] urea breath test) and (2) respiratory infections (physician-diagnosed lower (bronchitis) and upper (common cold) respiratory infections). H pylori colonisation was selected because it is very common and plays an important role in gastrointestinal disorders. Atopic eczema was selected as the (allergic) target variable because of its high frequency in the age of the study participants. The results, adjusted for relevant confounders, showed a significant inverse association between H pylori infection and eczema (adjusted odds ratio (aOR) = 0.31, p = 0.006) in children not predisposed to atopy. In contrast, bronchitis increased the risk of eczema (aOR = 1.98, p<0.001). Bacterial digestive tract colonisation (infection) seems to protect against eczema in comparison with the effect of respiratory tract infections. The hygiene hypothesis may be better explained when gastrointestinal and respiratory infections are subtly differentiated.

[Incidence of asthma and risk factors in a cohort of schoolchildren aged from 6-7 years old to 14-15 years old in Castellón (Spain) following the International Study of Asthma and Allergies in Childhood (ISAAC)]

BACKGROUND AND OBJECTIVE

To estimate the incidence of asthma in schoolchildren from 6-7 years old to 14-15 years old and associated risk factors.

POPULATION AND METHOD

A cohort study, with the ISAAC phases I and III in 1994 and 2002, respectively, was carried out in Castellón, and the nearby towns Vila-real, Almassora, Benicàssim, El Grau de Castelló, Borriol, and L'Alcora. In 1992, 3,607 schoolchildren aged 6-7 years old took part, of whom 1,805 were again studied in 2002, at the age of 14-15. New cases of asthma were defined following the ISAAC questionnaire. Poisson regression was used in the analysis of asthma risk factors.

RESULTS

Participation was 50.0%. The cumulative incidence of asthma was 6.4% during the 8 years of study, 108 new cases of 1,698 schoolchildren free of asthma at beginning. Incidence was greater in boys than girls, and in 14-year old teenagers compared to 15-year olds, although differences were not significant. Risk factors associated with the incidence of asthma were: family history of asthma, history of allergic rhinitis, history of bronchitis and upper-middle compared to lower social class.

CONCLUSIONS

A low incidence of asthma was found in schoolchildren from Castellón, Spain, in comparison with other cohort studies. Estimated risk factors were generally in accordance with incidence studies.

Environmental factors and allergic disorders

Despite numerous studies on possible associations between environmental exposure and allergic disorders, any conclusions made remain a matter of controversy. We conducted a review of evidence in relation to environmental and nutritional determinants and wheeze, asthma, atopic dermatitis, and allergic rhinitis. Identified were 263 articles for analysis after consideration of 1093 papers that were published since 2000 and selected by electronic search of the PubMed database using keywords relevant to epidemiological studies. Most were cross-sectional and case-control studies. Several prospective cohort studies revealed inconsistent associations between various environmental factors and the risk of any allergic disorder. Therefore, the evidence was inadequate to infer the presence or absence of a causal relationship between various environmental exposures and allergic diseases. However, evidence is suggestive of positive associations of allergies with heredity. Because almost all the studies were performed in Western countries, the application of these findings to people in other countries, including Japan, may not be appropriate. Further epidemiological information gained from population-based prospective cohort studies, in particular among Japanese together with other Asians, is needed to assess causal relationships between various environmental factors and allergic diseases.

Intranasal delivery of whole influenza vaccine prevents subsequent allergen-induced sensitization and airway hyper-reactivity in mice

BACKGROUND

Infection with influenza virus has been associated with seemingly opposing effects on the development of asthma. However, there are no data about the effects of mucosal vaccination with inactivated influenza on the inception of allergic asthma.

OBJECTIVE

To assess the immunological effects of inhaled inactivated influenza vaccine, using two different types of flu vaccines, on the inception of allergic sensitization and allergen-mediated airway disease in a mouse model.

METHODS

BALB/c mice were intranasally or intratracheally vaccinated with whole or split influenza virus vaccine (days -1 or -1, 27) before systemic sensitization with ovalbumin (OVA) (days 1, 14) and repeated airway allergen challenges (days 28-30). Allergen sensitization (IgE serum levels), airway inflammation (differential cells in bronchoalveolar lavage fluid) and airway hyper-reactivity (AHR) (in vivo lung function) were analysed.

RESULTS

The intranasal instillation of whole influenza vaccine before allergen sensitization significantly reduced the serum levels of total and OVA-specific IgE as well as allergen-induced AHR. Prevention was due to an allergen-specific shift from a predominant T helper (Th)2- towards a Th1-immune response. Application of split influenza vaccine did not show the same preventive effect.

CONCLUSION

Intranasal administration of inactivated whole influenza vaccine reduced subsequent allergen sensitization and prevented allergen-induced AHR. Our results show that the composition of the influenza vaccine has a major influence on subsequent development of allergen-induced sensitization and AHR, and suggest that mucosal inactivated whole influenza vaccination may represent a step towards the development of a preventive strategy for atopic asthma.

Early childhood lower respiratory illness and air pollution

BACKGROUND

Few studies of air pollutants address morbidity in preschool children. In this study we evaluated bronchitis in children from two Czech districts: Teplice, with high ambient air pollution, and Prachatice, characterized by lower exposures.

OBJECTIVES

Our goal was to examine rates of lower respiratory illnesses in preschool children in relation to ambient particles and hydrocarbons.

METHODS

Air monitoring for particulate matter < 2.5 microm in diameter (PM(2.5)) and polycyclic aromatic hydrocarbons (PAHs) was conducted daily, every third day, or every sixth day. Children born May 1994 through December 1998 were followed to 3 or 4.5 years of age to ascertain illness diagnoses. Mothers completed questionnaires at birth and at follow-up regarding demographic, lifestyle, reproductive, and home environmental factors. Longitudinal multivariate repeated-measures analysis was used to quantify rate ratios for bronchitis and for total lower respiratory illnesses in 1,133 children.

RESULTS

After adjustment for season, temperature, and other covariates, bronchitis rates increased with rising pollutant concentrations. Below 2 years of age, increments in 30-day averages of 100 ng/m(3) PAHs and of 25 microg/m(3) PM(2.5) resulted in rate ratios (RRs) for bronchitis of 1.29 [95 % confidence interval (CI), 1.07-1.54] and 1.30 (95% CI, 1.08-1.58), respectively; from 2 to 4.5 years of age, these RRs were 1.56 (95% CI, 1.22-2.00) and 1.23 (95% CI, 0.94-1.62), respectively.

CONCLUSION

Ambient PAHs and fine particles were associated with early-life susceptibility to bronchitis. Associations were stronger for longer pollutant-averaging periods and, among children > 2 years of age, for PAHs compared with fine particles. Preschool-age children may be particularly vulnerable to air pollution-induced illnesses.

Decreased markers of atopy in children with presumed early exposure to allergens, unhygienic conditions, and infections

BACKGROUND

Several risk factors for the development of asthma and atopic disease in children have been described. Furthermore, there is consistent evidence that the prevalence of atopy increases with higher socioeconomic status. The knowledge about risk factors and preventive factors for atopy needs to be improved.

OBJECTIVE

To compare 2 child populations (foster care and reference children) with different risk and protective factors for the development of atopy.

METHODS

The study group consisted of 415 children, living in all 10 community foster homes in Lodz, a large industrial city in Poland. The study was performed from April 2, 2004, to April 30, 2006. The reference group consisted of 500 children, living with their parents at home, recruited from primary care centers. The primary outcome measures were skin prick test results and specific IgE in serum. Secondary outcomes included symptoms of allergic diseases and family history, including life conditions in early childhood.

RESULTS

The full analysis set included 408 study children and 402 reference children. Significant differences were observed in the prevalence of atopy between the study and reference groups (11.3% vs 25.9%). We observed more positive skin prick test results in children from the reference group than in study children. To explain this phenomenon, we selected 16 variables that differ in both groups in early life and relate these to atopy. We found that the more cumulative features characteristic of the foster home population (poor living conditions), the lower the risk of atopy.

CONCLUSION

Extremely unfavorable environmental circumstances, which are characteristic of the foster home population during early childhood, might prevent from atopy.

Microbial manipulation of immune function for asthma prevention: inferences from clinical trials

The "hygiene hypothesis" proposes that the increase in allergic diseases in developing countries reflects a decrease in infections during childhood. Cohort studies suggest, however, that the risks of asthma are increased in children who suffer severe illness from a viral respiratory infection in infancy. This apparent inconsistency can be reconciled through consideration of epidemiologic, clinical, and animal studies. The elements of this line of reasoning are that viral infections can predispose to organ-specific expression of allergic sensitization, and that the severity of illness is shaped by the maturity of immune function, which in turn is influenced by previous contact with bacteria and viruses, whether pathogenic or not. Clinical studies of children and interventional studies of animals indeed suggest that the exposure to microbes through the gastrointestinal tract powerfully shapes immune function. Intestinal microbiota differ in infants who later develop allergic diseases, and feeding Lactobacillus casei to infants at risk has been shown to reduce their rate of developing eczema. This has prompted studies of feeding probiotics as a primary prevention strategy for asthma. We propose that the efficacy of this approach depends on its success in inducing maturation of immune function important in defense against viral infection, rather than on its effectiveness in preventing allergic sensitization. It follows that the endpoints of studies of feeding probiotics to infants at risk for asthma should include not simply tests of responsiveness to allergens, but also assessment of intestinal flora, immune function, and the clinical response to respiratory viral infection.

Prevalence of allergy, patterns of allergic sensitization and allergy risk factors in rural and urban children

BACKGROUND

We aimed to compare the prevalence of allergic diseases and sensitization in children living in urban and rural areas and to identify potential risk/protection factors associated with allergy.

METHODS

School children 12-16 years old, from urban community (n = 201) and rural area (n = 203) were recruited. The data obtained by questionnaire were referred to doctors' diagnosis, skin prick tests (SPTs), and serum specific and total IgE assessment.

RESULTS

The prevalence of allergic diseases in urban children was significantly higher as compared with rural children [asthma 16.42%vs 1.97% (P < 0.001) allergic rhinitis 38.81%vs 10.84% (P < 0.001)]. Positive SPTs to at least one allergen was found in 63.7% of urban and 22.7% rural children (P < 0.001). Significantly higher percentage of allergic rural than urban children were monosensitized or sensitized to 2-4 allergens, but almost a fourfold higher percentage of allergic urban children was found to be sensitized to five or more allergens (P < 0.0001). The history of frequent upper respiratory factor (URT) infections, antibiotic therapy, tonsiltectomy/adenoidectomy were positively associated with development of atopy and sensitization.

CONCLUSION

Our findings confirm that residence of rural area is associated with a significant lower prevalence of allergic sensitization and symptoms in school children. Several risk and protective factors related to environment and style of life could be identified in both environments.

IL-10 and RANTES are elevated in nasopharyngeal secretions of children with respiratory syncytial virus infection

BACKGROUND

Respiratory syncytial virus (RSV) infection causes asthma-like symptoms in infants and young children. Although an increase in several mediators in the airway during RSV infection has been reported, the mechanisms involved in airway inflammation are not fully understood. The aim of this study was to investigate the immunological deviation associated with airway inflammation by measuring cytokine and chemokine levels in the airway during RSV infection.

METHODS

One hundred and ten children under 3 years of age with respiratory symptoms were enrolled in this study from November 2004 through January 2005. Nasopharyngeal secretions (NPAs) were gently aspirated and analyzed with RSV antigen, thereafter the concentrations of IL-4, IL-10, IFN-gamma, and RANTES were measured using an ELISA kit. We also investigated the prognosis of each child after 1 year by reference to clinical records or by interviews and re-evaluated the cytokine and chemokine levels.

RESULTS

Of the subjects, 70 children were RSV positive and 40 were negative. Only 4 children were given a diagnosis of asthma by the pediatrician when NPAs were collected. The levels of IL-4, IL-10, and RANTES were significantly higher in the RSV-positive patients than RSV-negative patients with P values at 0.0362, 0.0007, and 0.0047, respectively. In contrast, there was no significant difference in the levels of IFN-gamma. Furthermore, there was a significant positive correlation between IL-10 and RANTES.

CONCLUSIONS

The increased production of IL-4, IL-10, and RANTES in the airway may play an important role in the pathophysiological mechanisms of RSV infection.

Dishing the dirt on asthma: What we can learn from poor hygiene

Allergic asthma continues to represent a huge health burden worldwide and is largely treated by non-selective immunosuppressive drugs, which often prove ineffective. The hygiene hypothesis proposes that the increased incidence of allergy and asthma in Western countries observed in the last 50 years is due to environmental changes that include improved hygiene and a lack of infections. The immunological mechanisms that must underpin such an environmental impact on immune regulation remain to be defined, making it difficult to identify specific ways of preventing development of allergy and asthma in early life. In this article we will seek to review some of the pathways that might underlie the hygiene hypothesis in an attempt to provide targets for future asthma prevention.

High-throughput, sensitive, and accurate multiplex PCR-microsphere flow cytometry system for large-scale comprehensive detection of respiratory viruses

Human respiratory viruses are a diverse group of pathogens composed of hundreds of virus strains, and this presents a major challenge for diagnostic laboratories. To efficiently detect numerous viruses in a large epidemiologic study, we developed a fast, multitarget, sensitive, and specific assay named the Respiratory MultiCode-PLx Assay (RMA). The RMA utilizes improved multiplex PCR chemistry (EraGen MultiCode-PLx technology) coupled with high-throughput microsphere flow cytometry (Luminex). Eighteen sets of virus-specific multiplex PCR primers were developed based on the conserved sequences of all available respiratory-virus sequences for eight distinct groups: human rhinovirus (HRV), respiratory syncytial virus (RSV), parainfluenza virus (PIV), influenza virus (InfV), metapneumovirus, adenovirus (Ad), coronavirus, and enterovirus. Each primer set detected 20 cDNA copies of the intended target per sample and had no reaction with 60,000 copies of human genomic DNA. The accuracy and sensitivity of the RMA for detecting respiratory viruses in human samples were tested with two sets of clinical specimens. First, 101 nasal-wash specimens that were positive for HRV, RSV, InfV, PIV, or Ad by traditional techniques were reanalyzed by RMA, and all target viruses were detected with an overall sensitivity of 94% and specificity of 99%. Second, 103 nasal-wash samples from 5-year-old children with asthma and respiratory symptoms were analyzed; RMA detected viruses in 74 specimens (71.8%) compared to only 24 (23.3%) by traditional culture and immunofluorescent-staining techniques. These results show that RMA is an accurate, sensitive, and practical test for respiratory-virus infections.

The effects of maternal employment on child injuries and infectious disease

This article presents estimates of effects of maternal paid work and nonmaternal child care on injuries and infectious disease for children aged 12 to 36 months. Mother-child fixed-effects estimates are obtained by using data from the NICHD Study of Early Child Care. Estimates indicate that maternal employment itself has no statistically significant adverse effects on the incidence of infectious disease and injury. However, greater time spent by children in center-based care is associated with increased rates of respiratory problems for children aged 12 to 36 months and increased rates of ear infections for children aged 12 to 24 months.

High prevalence of atopy, but not of asthma, among children in an industrialized area in North Italy: the role of familial and environmental factors--a population-based study

The prevalence of atopy and asthma, and their association with familial and environmental factors were investigated among 13- to 14-yr-old children living in Brescia, an industrialized town in North Italy. All the 1450 children attending primary school in the town were invited to participate, and 967 of them (66.7%, 493 males) provided a valid questionnaire filled in by their parents at home. We used a modified version of the questionnaire adopted in the Italian Study of Respiratory Disorders in Childhood and Environment, which is an extended version of the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. Six hundred and twenty-eight subjects underwent skin prick test (SPT), and 308 of them (49%) were positive for at least one of the 12 allergen extracts commonly employed. Ninety-nine children (10.2%) had a physician's diagnosis of asthma - 12.4% of the males and 8.0% of the females (p = 0.03). The prevalence of wheezing in the past 12 months was 6.2%. Atopy was found in 76.8% of the subjects with, and in 45.6% of those without physician's diagnosis of asthma (p < 0.001). Analysis by multiple logistic regression showed an inverse association between physician-diagnosed asthma and female sex (odds ratio, OR = 0.5); presence of relatives in the bedroom in initial years of life (OR = 0.6); attending day care (OR = 0.4) and infant school (OR = 0.4); a positive association with parental history of wheezing (OR = 2.5) and asthma (OR = 3.8); and the child's history of asthmatic bronchitis (OR = 31.9) and atopic eczema (OR = 3.8) in the first 2 yr of life. The strength of the associations did not change when restricting the analysis to atopic asthma. In conclusion, atopy and clinical asthma among 13- to 14-yr-old adolescents are significantly associated with some familial and environmental factors, providing further support for the hygiene hypothesis. Prevalence of atopy, but not of asthma, is high in this industrialized area. The strong association found between atopy and clinical asthma suggests that atopy may play a role in causing asthma in genetically predisposed children only.

The relation of adult bronchial responsiveness to serious childhood respiratory illness in the ECRHS

BACKGROUND

Respiratory symptoms in adulthood have been found to be associated with childhood respiratory infection, but few studies have analyzed adult bronchial responsiveness (BHR) with adequate adjustment for known risk factors.

OBJECTIVE

To estimate the relation of BHR with serious childhood respiratory infections in a large population study.

METHODS

The European Community Respiratory Health Survey (ECRHS) was a cross-sectional population-based survey in 34 centers. Data on serious respiratory infections before the age of 5 years and possible confounders were obtained from a questionnaire administered in the clinic. Blood samples were taken for measurement of total immunoglobulin E (IgE) and specific IgE to four common allergens, and spirometry and bronchial challenge with methacholine were performed. A continuous measure of BHR was analyzed by multiple regression, in 11,282 participants, in relation to serious respiratory infection and other potential risk factors, adjusted for center and major determinants of adult BHR.

RESULTS

Those reporting a serious childhood respiratory infection had greater BHR, by an amount corresponding to approximately 0.23 doubling doses (95% confidence interval 0.02-0.44) of the amount of methacholine causing a 20% fall (PD(20)) in forced expiratory volume in 1s (FEV(1)). All childhood factors explained less than 0.3% of variation in BHR in addition to over 20% by factors measured in adulthood. The relation of BHR to BMI was confined to smokers.

CONCLUSIONS

We found an effect of serious childhood respiratory infection on adult BHR, but this was small in comparison to relations of BHR to IgE-sensitization and airway caliber.

Allergies, infections and the hygiene hypothesis--the epidemiological evidence

The 'hygiene hypothesis' was first proposed by Strachan in 1989 suggesting that infections and unhygienic contact with older siblings or through other exposures may confer protection from the development of allergic illnesses. This hypothesis has evolved in various ways exploring the role of overt viral and bacterial infections, the significance of environmental exposure to microbial compounds, and their effect on underlying responses of innate and adaptive immunity. So far a truly unifying concept is still lacking, but various pieces of a complex interplay between a host's immune response, characteristics of the invading microorganism, the level and variety of the environmental exposure, and the interactions between a genetic background and a range of exposures become apparent. All these pieces eventually assemble to the clinical presentation of a complex syndrome namely of asthma and allergic illnesses. Even if today practical implications cannot directly be deduced from these findings, there is great potential for the development of novel preventive and therapeutic strategies in the future based on the concepts of the 'hygiene hypothesis'.

Viral infections and allergies

Respiratory viral infections have been implicated in the origin of, protection from and exacerbation of allergy-related symptoms in a variety of ways. Viral infections are closely linked to infantile wheezing. Severe bronchiolitis in early infancy may predispose to chronic childhood asthma as well as allergic sensitization; alternatively it could represent a marker of susceptible individuals. In contrast, repeated mild infections in early life may have a protective role in the development of asthma or atopy by driving the immune system towards Th1 responses. However, evidence on this hypothesis is not consistent as far as respiratory viruses are concerned. Several factors, including the presence of an atopic environment, timing of exposure and severity of the infection, interactively contribute to the allergy-infection relationship. In the present report, recent data on the role of viral infections in the development and progression of allergy and asthma are reviewed.

Increased risk of childhood asthma from antibiotic use in early life

BACKGROUND

To address the major methodological issues of reverse causation and selection bias in epidemiologic studies of antibiotic use in early life and the development of asthma, we undertook a cohort study of this association in a complete population of children.

METHODS

Using the health-care and prescription databases of Manitoba, Canada, this longitudinal study assessed the association between antibiotic prescription use during the first year of life and asthma at age 7 years in a 1995 birth cohort of 13,116 children.

RESULTS

Independent of well-known asthma risk factors, asthma was significantly more likely to develop in children who had received antibiotics in the first year of life at age 7 years. The association with asthma was observed for antibiotic use in non-respiratory tract infections (adjusted odds ratio [OR], 1.86; 95% confidence interval [CI], 1.02 to 3.37). The risk of asthma was highest in children receiving more than four courses of antibiotics (adjusted OR, 1.46; 95% CI, 1.14 to 1.88), especially among rural children, and in the absence of maternal asthma or a dog in the birth year. Broad-spectrum (BS) cephalosporin use was more common in these subpopulations of children.

CONCLUSIONS

Antibiotic use in early life was associated with the development of childhood asthma, a risk that may be reduced by avoiding the use of BS cephalosporins.

Living at high altitude and risk of hospitalisation for atopic asthma in children: results from a large prospective birth-cohort study

BACKGROUND

Asthma is among the most common chronic diseases in childhood and is steadily increasing in prevalence. Better characterisation of factors that determine the risk of hospitalisation for atopic asthma in childhood may help design prevention programmes and improve our understanding of disease pathobiology. This study will focus on the altitude of residence.

METHODS

This is an ongoing prospective birth-cohort study that enrolled all live-born infants in the Tyrol. Between 1994 and 1999, baseline data were collected for 33 808 infants. From 2000 to 2005, all children hospitalised for atopic asthma at the age of > or =6 years (n = 305) were identified by a careful search of hospital databases. Disease status was ascertained from the typical medical history, a thorough examination and proof of atopy.

RESULTS

Living at higher altitude was associated with an enhanced risk of hospitalisation for atopic asthma (multivariate RRs (95% confidence interval 2.08 (1.45 to 2.98) and 1.49 (1.05 to 2.11) for a comparison between altitude categories > or =1200 m and 900-1199 m versus <900 m; p<0.001). This finding applied equally to hospital admissions in spring, summer, autumn and winter. When altitude of residence was analysed as a continuous variable, the risk for asthma hospitalisation increased by 7% for each 100-m increase in altitude (p = 0.013).

CONCLUSIONS

This large prospective study shows a significant association between the risk of hospitalisation for atopic asthma and altitude of residence between 450 and 1800 m. The underlying mechanisms remain to be elucidated, but it is tempting to speculate about a role for altitude characteristics such as the decline in outdoor temperature and air humidity and increase in ozone levels, which may trigger airway hyper-responsiveness and attenuate lung function.

Interactions between breast-feeding, specific parental atopy, and sex on development of asthma and atopy

BACKGROUND

The influence of breast-feeding on the risk of developing atopy and asthma remains controversial.

OBJECTIVE

To examine asthma and atopy outcomes by sex, reported specific parental history of atopy, and breast-feeding.

METHODS

In a birth cohort, we examined childhood asthma and atopy (positive skin prick tests) by sex and breast-feeding in relation to maternal and paternal atopy. Interactions were explored in logistic regression models.

RESULTS

For boys, breast-feeding (odds ratio [OR], 1.63; 95% CI, 0.93-2.87; P = .09) and maternal atopy (OR, 1.95; 95% CI, 0.93-4.08; P = .08) were each associated with atopy at age 13 years. Breast-feeding increased the risk for atopy among boys with paternal atopy (OR, 7.39; 95% CI, 2.21-24.66) compared with non-breast-fed boys with paternal atopy, but did not significantly further increase risk among subjects with maternal atopy. For girls, breast-feeding (OR, 0.74; 95% CI, 0.41-1.31) and maternal and paternal atopy were not independent risk factors for atopy at age 13 years. However, breast-feeding increased the risk for atopy in girls with maternal atopy (OR, 3.13; 95% CI, 1.20-8.14) compared with non-breast-fed girls with maternal atopy. There was no such effect among subjects with paternal atopy. Results for the outcome of asthma followed a similar pattern.

CONCLUSION

The influence of breast-feeding on development of atopy and asthma differs by sex and by maternal and paternal atopy, and is most significant among subjects at lower baseline risk.

CLINICAL IMPLICATIONS

Analyses of environmental risk factors for asthma and atopy should be stratified by specific parental atopy and sex.

Recorded infections and antibiotics in early life: associations with allergy in UK children and their parents

BACKGROUND

It is suggested that the inverse relationship between allergic disease and family size reflects reduced exposure to early life infections, and that antibiotic treatment in childhood diminishes any protective effect of such infection.

METHODS

A birth cohort study was undertaken in 642 children recruited before birth and seen annually until the age of 8 years. Reported infections and prescribed antibiotics by the age of 5 years were counted from GP records and comparisons were made with a previous study of their parents.

RESULTS

At the age of 8 years, 104 children (19%) were atopic, 79 (13%) were currently wheezy and 124 (21%) had seasonal rhinitis. 577 children (97%) had at least three infections recorded by age 5, a figure much higher than that of their parents (69%). By the age of 5 only 11 children (2%) had never received a prescription for antibiotics; the corresponding figure for the parents was 24%. Higher numbers of infections were recorded for firstborn children. After adjusting for parental atopy and birth order, there was no association between infection counts and atopy (OR 1.01 (95% CI 0.99 to 1.03) per infection). Significant positive associations were found for wheeze and seasonal rhinitis. An increased risk of current wheeze was found for each antibiotic prescription (adjusted OR 1.07 (95% CI 1.03 to 1.10)) but not for atopy. This was primarily explained by prescriptions for respiratory infections. Similar patterns were observed for seasonal rhinitis.

CONCLUSIONS

Despite very high rates of recorded early life infections and antibiotic prescriptions, no plausibly causative relationships were found with subsequent respiratory allergies.

Clinical sepsis in neonates is responsible for the lower prevalence of developing allergy

BACKGROUND

The hygiene hypothesis proposes an association between the change in exposure to microbes and the increased incidence of atopic disease. The purpose of the present study was to perform a prospective epidemiological study of the effect of perinatal infection on the development of allergy.

METHODS

Eight hundred and ten children were born at Umeda Gynecological Hospital in Yamaguchi prefecture in Japan between April 1997 and March 1998. A questionnaire survey on the development of allergic diseases was sent by mail in 2002. The presence or absence of neonatal infectious disease (clinical sepsis) and maternal complications during the gestational period and delivery, and the incidence of bacterial infection during the perinatal period, were investigated by examining hospital records.

RESULTS

Data were obtained for 410 children (51%). One hundred and forty-eight children (36.1%) developed allergic diseases. Among children whose mothers had allergies, the percentage of children who developed allergic disease(s) was significantly lower in children who had had clinical sepsis in the neonatal period than in those without clinical sepsis (26.1% vs 49.7%, P < 0.03).

CONCLUSIONS

Clinical sepsis in neonates might reduce the risk of developing allergic diseases in early childhood in children whose mothers have allergies.

Prospectively assessed incidence, severity, and determinants of respiratory symptoms in the first year of life

Respiratory symptoms are common in infancy. Nevertheless, few prospective birth cohort studies have studied the epidemiology of respiratory symptoms in normal infants. The aim of this study was to prospectively obtain reliable data on incidence, severity, and determinants of common respiratory symptoms (including cough and wheeze) in normal infants and to determine factors associated with these symptoms. In a prospective population-based birth cohort, we assessed respiratory symptoms during the first year of life by weekly phone calls to the mothers. Poisson regression was used to examine the association between symptoms and various risk factors. In the first year of life, respiratory symptoms occurred in 181/195 infants (93%), more severe symptoms in 89 (46%). The average infant had respiratory symptoms for 4 weeks and 90% had symptoms for less than 12 weeks (range 0 to 23). Male sex, higher birth weight, maternal asthma, having older siblings and nursery care were associated with more, maternal hay fever with fewer respiratory symptoms. The association with prenatal maternal smoking decreased with time since birth. This study provides reliable data on the frequency of cough and wheeze during the first year of life in healthy infants; this may help in the interpretation of published hospital and community-based studies. The apparently reduced risk in children of mothers with hayfever but no asthma, and the decreasing effect of prenatal smoke exposure over time illustrate the complexity of respiratory pathology in the first year of life.