Maternal obesity in pregnancy and respiratory health in early childhood

Obesity is associated with systemic inflammation, immunological changes, increased risk of respiratory infections and chronic respiratory illness. Maternal obesity in pregnancy increases the risk of pregnancy complications, caesarean sections and adverse birth outcomes, which have in turn been associated with respiratory illness in children. To our knowledge, the possible influence of maternal obesity in pregnancy on respiratory illness in early childhood beyond the newborn period has not been explored. We examined the relationship between a high maternal body mass index (BMI) in pregnancy and lower respiratory tract infections and wheeze up to 18 months of age in the Norwegian Mother and Child Study (MoBa), a population-based cohort study that includes 100,000 pregnant women, conducted at the Norwegian Institute of Public Health. We analysed data from the first 33 192 children, born between 1999 and 2005. In unadjusted analyses maternal obesity in pregnancy was related to both respiratory infections and wheeze in the children. In multivariable analyses, only an effect on wheeze remained. The risk of wheeze increased linearly with maternal BMI in pregnancy, and was 3.3% higher [95% CI 1.2, 5.3] for children with mothers who were obese during pregnancy, than for children of mothers with normal BMI. This effect was not mediated through obesity-related pregnancy complications, low birthweight, preterm birth or caesarean section.

T-bet expression is regulated by EGR1-mediated signaling in activated T cells

T-bet is a Th1-specific transcription factor that is directly involved in three important pathways for Th1 cell differentiation, namely TCR signaling, and the IFN-gamma-STAT1 and IL-12-STAT4 pathways. A recent study also showed that T-bet plays a vital role in innate immunity. However, the molecular mechanism responsible for transcriptional activation of T-bet during T cell development is not yet known. Here, we characterize the essential human T-bet promoter elements and show that binding of EGR1 to this promoter induces T-bet transcription. Notably, overexpression of EGR1 transactivates and, synergistically in concert with TCR signaling, induces T-bet expression in activated T cells. In contrast, depletion of EGR1 significantly decreases T-bet induction. Finally, we report a positive correlation between EGR1 and T-bet expression during T helper cell differentiation. Collectively, these findings provide molecular insight into T-bet transcription and suggest that EGR1 is an upstream regulator of T-bet induction.

Smoke exposure interacts with ADAM33 polymorphisms in the development of lung function and hyperresponsiveness

INTRODUCTION

ADAM33 is the first identified asthma gene by positional cloning, especially asthma combined with bronchial hyperresponsiveness (BHR). Moreover, ADAM33 is associated with early-life lung function and decline of forced expiratory volume in 1 s (FEV(1)) in the general population. In utero and postnatal cigarette smoke exposure (CSE) are associated with reduced lung function, and development of BHR and asthma. We hypothesized that this may occur via interaction with ADAM33.

AIM

To replicate the role of ADAM33 in childhood lung function and development of BHR and asthma. Furthermore, we investigated gene-environment interaction of ADAM33 with in utero and postnatal CSE in the Dutch PIAMA cohort.

METHODS

Six ADAM33 single-nucleotide polymorphisms (SNPs) were genotyped. Rint was measured at age 4 and 8 years, FEV(1) and BHR at age 8 years; asthma was based on questionnaire data at age 8.

RESULTS

In the total cohort, the rs511898 A, rs528557 C, and rs2280090 A alleles increased the risk to develop asthma (+BHR). There existed interaction between in utero but not postnatal CSE and the rs528557 and rs3918396 SNPs with respect to development of BHR, the rs3918396 SNP with Rint at age 8 and the rs528557 SNP with FEV(1)% predicted.

CONCLUSIONS

We confirm associations between ADAM33 and the development of asthma (+BHR). This is the first study suggesting that interaction of in utero CSE with ADAM33 results in reduced lung function and the development of BHR, which needs further confirmation.

Natural history of lung function in health and diseases

PURPOSE OF REVIEW

To outline major advances in the understanding of factors that influence lung function development through childhood.

RECENT FINDINGS

New study approaches such as adjusting for 'tracking' or analysing without predefined phenotypes suggest that reduced lung function reported with several pre or coexisting features such as lower respiratory tract infections and early allergic sensitization may be spurious rather than causative. Also, two large, recent studies have clearly demonstrated that living close to major roads causes significant lung function deficits in school children, with the possible long-term impact this can have on health in adult life. Furthermore, it is becoming clear that we need to focus upon early life events that can cause harm as well as have a potential for catch-up growth or development in postnatal life.

SUMMARY

The implications of these findings are clearly that there is a potential for intervening in a potential pathological development. Furthermore, there is a clear need to focus research upon early life events that can improve lung growth in the damaged lung and prevent damage to the potentially healthy lung at the very start of life.

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.

Lung function at 10 yr is not impaired by early childhood lower respiratory tract infections

The causal relationship between lower respiratory tract infections (LRIs) in early life and reduced lung function later in childhood is unsettled. Therefore, we assessed whether LRIs the first 2 yr of life influenced lung function development from birth to school age. In the prospective Oslo birth cohort, 'the Environment and Childhood Asthma (ECA) study' lung function was measured at birth in 802 infants by tidal flow volume loops and in 664 infants by passive respiratory mechanics and half yearly questionnaires, including LRI questions, were completed until 2 yr of age. The present study includes 607 children with information about LRIs the first 2 yr of life and successfully forced expiratory flow (FEF) volume measurements at the 10-yr follow-up assessment. At 10 yr of age, FEF at 50% of forced vital capacity (FEF(50)) (mean 95% confidence interval) was reduced in children with at least one bronchiolitis (85.0, 80.6-89.5, p = 0.020) or bronchitis (86.2, 82.6-89.8, p = 0.030) or > or =3 LRIs (83.4, 78.1-88.8, p = 0.017) when compared with no LRIs (90.6, 88.8-92.5) by 2 yr of life. The effects were significant in girls only when stratifying for gender. Among girls with later bronchiolitis compliance of the respiratory system (3.64, 3.17-4.10 vs. 4.18, 3.98-4.37, p = 0.031) and the ratio of time to peak tidal expiratory flow to total expiratory time (t(PTEF)/t(E)) measured at birth was significantly reduced (0. 26, 0.23-0.29 vs. 0.32, 0.30-0.33, p = 0.005) when compared with children with no LRIs. Change in lung function from birth (by t(PTEF)/t(E)) to 10 yr of age was not significantly associated with LRIs the first 2 yr of life, and LRIs by 2 yr of life were not significantly associated with lung function at 10 yr of age in regression analyses including lung function at birth and other possible predictors of lung function at 10 yr. In our study, LRIs during the first 2 yr of life did not impair lung function development from birth until 10 yr of age.

Non-atopic intrinsic asthma and the 'family tree' of chronic respiratory disease syndromes

We present a scheme below in which the most common forms of inflammatory diseases of the respiratory tract, notably atopic and non-atopic asthma and COPD, are depicted as separate offshoots from a common 'at-risk' pathway underpinned by genotypes related to aberrations in control of host defence and tissue repair mechanisms. We propose that entrance into this pathway is initially programmed by environmental experience during infancy and early childhood, in particular by severe lower respiratory tract infection, and that further progression towards expression of specific disease phenotype(s) is determined by the nature, timing and frequency of additional environmental insults subsequently encountered. At the one extreme, early sensitization of at-risk subjects to aeroallergens can potentially drive rapid progression towards expression of the atopic asthmatic phenotype under the dual onslaught of inflammatory responses to allergens/pathogens. At the opposite end of the spectrum the drip-feed effects of occasional infections on respiratory function(s) are amplified over a longer time frame by inflammation resulting from exposure to tobacco smoke and/or related chemical pollutants. Non-atopic asthma is envisaged to fit between these two extremes, being driven essentially by the downstream effects of respiratory infections alone in at-risk subjects. An important common factor in all three disease phenotypes is that acute exacerbations are typically driven by infections, the host responses to which display a characteristic T-helper type 2-like footprint, which in our view points to underlying genotype(s) which result in unbalanced host responses to respiratory pathogens.

Markers of early disease and prognosis in COPD

COPD is a complex disease with multiple pathological components, which we unfortunately tend to ignore when spirometry is used as the only method to evaluate the disorder. Additional measures are needed to allow a more complete and clinically relevant assessment of COPD. The earliest potential risk factors of disease in COPD are variations in the genetic background. Genetic variations are present from conception and can determine lifelong changes in enzyme activities and protein concentrations. In contrast, measurements in blood, sputum, exhaled breath, broncho-alveolar lavage, and lung biopsies may vary substantially over time. This review explores potential markers of early disease and prognosis in COPD by examining genetic markers in the α₁-antitrypsin, cystic fibrosis transmembrane conductance regulator (CFTR), and MBL-2 genes, and by examining the biochemical markers fibrinogen and C-reactive protein (CRP), which correlate with degree of pulmonary inflammation during stable conditions of COPD. Chronic lung inflammation appears to contribute to the pathogenesis of COPD, and markers of this process have promising predictive value in COPD. To implement markers for COPD in clinical practice, besides those already established for the α₁-antitrypsin gene, further research and validation studies are needed.

TBX21 gene variants increase childhood asthma risk in combination with HLX1 variants

BACKGROUND

The T cell-specific T-box transcription factor (TBX21) plays a crucial role in the regulation of the immune system because this factor induces the differentiation of T(H)1 and blocks T(H)2 commitment together with the homeobox transcription factor HLX1.

OBJECTIVE

The role of genetic variants in TBX21 alone and in combination with HLX1 polymorphisms was investigated in the development of T(H)2-associated atopy and asthma.

METHODS

The TBX21 gene was resequenced in 37 adult volunteers. Polymorphisms identified were genotyped in a cross-sectional (N = 3099) and nested asthma case-control population (N = 1872) using mainly matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Effects of promoter polymorphisms on TBX21 gene expression were studied by reporter gene assays. Furthermore, the impact of combinations of TBX21 and HLX1 polymorphisms on the development of asthma was assessed by using a risk score model. Statistical analyses were performed by using SAS/Genetics.

RESULTS

Forty-three polymorphisms were identified in the TBX21 gene. Considering a minor allele frequency of at least 10%, single nucleotide polymorphisms were assigned to 7 linkage disequilibrium blocks. Three tagging single nucleotide polymorphisms increased childhood asthma risk significantly (odds ratio [OR], 2.60, 95% CI, 1.34-5.03, P = .003; OR, 1.39, 95% CI, 1.02-1.90, P = .039; and OR, 1.97, 95% CI, 1.18-3.30, P = .009). TBX21 promoter polymorphisms contained in 2 blocks significantly influenced TBX21 promoter activity. In a risk score model, the combination of TBX21 and HLX1 polymorphisms increased the asthma risk by more than 3-fold.

CONCLUSIONS

These data suggest that TBX21 polymorphisms contribute to the development of asthma, potentially by altering TBX21 promoter activity. A risk score model indicates that TBX21 and HLX1 polymorphisms may have synergistic effects on asthma risk.

Brief bout of exercise alters gene expression in peripheral blood mononuclear cells of early- and late-pubertal males

Peripheral blood mononuclear cells (PBMCs) are stimulated by exercise and contribute not only to host defense, but also to growth, repair, and disease pathogenesis. Whether PBMC gene expression is altered by exercise in children is not known. Ten early pubertal boys (8-12 y) and 10 late pubertal boys (15-18 y) performed ten 2-min bouts of strenuous, constant work rate exercise with 1-min rest intervals. PBMCs were isolated before and after exercise and microarray (Affymetrix U133 + 2 chips) analyzed. Statistical criterion to identify gene expression changes was less than 5% false discovery rate (FDR) with 95% confidence interval. One thousand two hundred forty-six genes were altered in older boys (517 up, 729 down), but only 109 were altered in the younger group (79 up, 30 down). In older boys, 13 gene pathways (using Expression Analysis Systematic Explorer, p < 0.05) were found (e.g. natural killer cell cytotoxicity, apoptosis). Epiregulin gene expression (EREG, a growth factor involved in wound healing) increased in older boys. In older boys exercise altered genes such as TBX21, GZMA, PGTDR, and CCL5 also play roles in pediatric inflammatory diseases like asthma. Sixty-six genes were changed significantly in both groups. The pattern of PBMC gene expression suggests the initiation of an immunologic "danger" signal associated with a sudden change in energy expenditure.

What have we learned from prospective cohort studies of asthma in children?

Prospective cohort studies have provided a useful tool for the study of the natural history of asthma and lung function and for the development of concepts of asthma phenotypes during childhood. However, although observational epidemiology has indicated a large number of credible associations between environmental variables and asthma onset in childhood, it can be argued that it has yet to fulfill the promise of identifying modifiable, causal risk factors that are amenable to intervention for the primary or secondary prevention of disease. The development of efficient, high-throughput genotyping that can be applied to large, longitudinal cohorts with detailed data on exposures and phenotypic outcomes, opens the way for studies of genetic effects and gene-environment interactions that may come closer to identifying causal pathways between exposure and disease. Therefore, there continues to be an important role for large-scale, observational studies with careful attention to definition and evaluation of outcomes and plausible risk factors.

Norwegian adolescents with asthma are physical active and fit

BACKGROUND

Evidence regarding habitual physical activity levels and aerobic fitness of asthmatic compared to nonasthmatic children and adolescents is contradictory, and it is unclear if low physical activity levels can contribute to asthma development. The present study therefore aimed to determine whether adolescents with asthma have reduced physical activity levels and aerobic fitness, or increased energy intake and body fat compared to controls.

METHODS

From the environment and childhood asthma study in Oslo, 174 (13- to 14-year old) adolescents, 95 (66 boys) with and 79 (41 boys) without asthma performed maximal running on a treadmill with oxygen consumption measurement (aerobic fitness) and had the sum of four skinfolds and waist circumference recorded (body fat), followed by wearing an activity monitor and registering diet for four consecutive days. Asthma was defined by at least two of the following three criteria fulfilled: (1) dyspnoea, chest tightness and/or wheezing; (2) a doctor's diagnosis of asthma; (3) use of asthma medication. Participants with asthma used their regular medications.

RESULTS

Neither aerobic fitness, total energy expenditure nor hours in moderate to very vigorous intensity physical activity during week and weekend differed between adolescents with and without asthma. Energy intake and body fat was similar in both groups.

CONCLUSIONS

Total energy expenditure, aerobic fitness and hours in moderate to very vigorous intensity physical activity were not reduced and energy intake and body fat measured with skinfolds not increased among Norwegian adolescents with asthma.

A genome-wide association study in chronic obstructive pulmonary disease (COPD): identification of two major susceptibility loci

There is considerable variability in the susceptibility of smokers to develop chronic obstructive pulmonary disease (COPD). The only known genetic risk factor is severe deficiency of alpha(1)-antitrypsin, which is present in 1-2% of individuals with COPD. We conducted a genome-wide association study (GWAS) in a homogenous case-control cohort from Bergen, Norway (823 COPD cases and 810 smoking controls) and evaluated the top 100 single nucleotide polymorphisms (SNPs) in the family-based International COPD Genetics Network (ICGN; 1891 Caucasian individuals from 606 pedigrees) study. The polymorphisms that showed replication were further evaluated in 389 subjects from the US National Emphysema Treatment Trial (NETT) and 472 controls from the Normative Aging Study (NAS) and then in a fourth cohort of 949 individuals from 127 extended pedigrees from the Boston Early-Onset COPD population. Logistic regression models with adjustments of covariates were used to analyze the case-control populations. Family-based association analyses were conducted for a diagnosis of COPD and lung function in the family populations. Two SNPs at the alpha-nicotinic acetylcholine receptor (CHRNA 3/5) locus were identified in the genome-wide association study. They showed unambiguous replication in the ICGN family-based analysis and in the NETT case-control analysis with combined p-values of 1.48 x 10(-10), (rs8034191) and 5.74 x 10(-10) (rs1051730). Furthermore, these SNPs were significantly associated with lung function in both the ICGN and Boston Early-Onset COPD populations. The C allele of the rs8034191 SNP was estimated to have a population attributable risk for COPD of 12.2%. The association of hedgehog interacting protein (HHIP) locus on chromosome 4 was also consistently replicated, but did not reach genome-wide significance levels. Genome-wide significant association of the HHIP locus with lung function was identified in the Framingham Heart study (Wilk et al., companion article in this issue of PLoS Genetics; doi:10.1371/journal.pgen.1000429). The CHRNA 3/5 and the HHIP loci make a significant contribution to the risk of COPD. CHRNA3/5 is the same locus that has been implicated in the risk of lung cancer.

Lung volume, breathing pattern and ventilation inhomogeneity in preterm and term infants

Background

Morphological changes in preterm infants with bronchopulmonary dysplasia (BPD) have functional consequences on lung volume, ventilation inhomogeneity and respiratory mechanics. Although some studies have shown lower lung volumes and increased ventilation inhomogeneity in BPD infants, conflicting results exist possibly due to differences in sedation and measurement techniques.

Methodology/Principal Findings

We studied 127 infants with BPD, 58 preterm infants without BPD and 239 healthy term-born infants, at a matched post-conceptional age of 44 weeks during quiet natural sleep according to ATS/ERS standards. Lung function parameters measured were functional residual capacity (FRC) and ventilation inhomogeneity by multiple breath washout as well as tidal breathing parameters. Preterm infants with BPD had only marginally lower FRC (21.4 mL/kg) than preterm infants without BPD (23.4 mL/kg) and term-born infants (22.6 mL/kg), though there was no trend with disease severity. They also showed higher respiratory rates and lower ratios of time to peak expiratory flow and expiratory time (t_PTEF/t_E) than healthy preterm and term controls. These changes were related to disease severity. No differences were found for ventilation inhomogeneity.

Conclusions

Our results suggest that preterm infants with BPD have a high capacity to maintain functional lung volume during natural sleep. The alterations in breathing pattern with disease severity may reflect presence of adaptive mechanisms to cope with the disease process.

Pharmaceutical treatment strategies for childhood asthma

PURPOSE OF REVIEW

Although great improvement has been obtained in quality of life and mastering of illness by asthmatic children over recent decades, controversies still exist related to asthma treatment. The objective of the present article is to discuss such controversies.

RECENT FINDINGS

Results from recent publications related to childhood asthma treatment question existing dogmas. Important for prescribing correct treatment to children is correct diagnosis. Phenotypes of childhood asthma related to treatment decisions are discussed. Early use of inhaled steroids in young children is still debated as well as the preference of inhaled long-acting beta2-agonists versus leukotriene receptor antagonists as add on to inhaled steroids. When present, both allergic rhinitis and asthma should be treated to obtain improved control. Also as regards the treatment of exercise-induced asthma in children, new results concerning use of leukotriene receptor antagonists is discussed as well as the acute treatment in infants with bronchial obstruction.

SUMMARY

There are still several controversies regarding treatment of the asthmatic child. New studies designed specifically for children are needed to solve these questions. One cannot rely on studies performed in adults for treatment in children. New studies designed for childhood asthma are needed to solve these controversies.

Is there an increased frequency of food allergy in children delivered by caesarean section compared to those delivered vaginally?

AIM

Allergic diseases are increasing. At the same time an increasing number of children are delivered by caesarean section. These children do not get the same contact with their mother's gut flora as babies delivered vaginally. Theoretically, lack of exposure to maternal vaginal and perineal bacteria might change the gut flora, with secondary changes in the immune system. The aim of this study was to investigate whether children delivered by caesarean section were more prone to develop food allergy.

METHODS

Six hundred and nine children were included at birth. At 2-year follow-up, 512 children participated, 171 delivered by caesarean section, 341 born vaginally. The children reported to have symptoms consistent with possible food allergy, were examined at the outpatient clinic. The diagnosis was based on the history, skin prick test (SPT), specific IgE, elimination/challenge test and double blind placebo controlled challenge.

RESULTS

Thirty-five (6.8%) children were diagnosed with adverse reactions to food, 27 with non-IgE-mediated and eight with IgE-mediated allergy. There was no over representation of children born by caesarean section.

CONCLUSION

In this study there seems to be no increased risk for food allergy in the first 2 years of life in children delivered by caesarean section.

Detecting shared pathogenesis from the shared genetics of immune-related diseases

Recent genetic studies have revealed shared immunological mechanisms in several immune-related disorders that further our understanding of the development and concomitance of these diseases. Our Review focuses on these shared aspects, using the novel findings of recently performed genome-wide association studies and non-synonymous SNP scans as a starting point. We discuss how identifying new genes that are associated with more than one autoimmune or chronic inflammatory disorder could explain the genetic basis of the shared pathogenesis of immune-related diseases. This analysis helps to highlight the key molecular pathways that are involved in these disorders and the potential roles of novel genes in immune-related diseases.

A TLR2 polymorphism is associated with type 1 diabetes and allergic asthma

Type 1 diabetes (T1D) and allergic asthma are immune-mediated diseases. Pattern recognition receptors are proteins expressed by cells in the immune system to identify microbial pathogens and endogenous ligands. Toll-like receptors (TLRs) and CD14 are members of this family and could represent a molecular link between microbial infections and immune-mediated diseases. Diverging hypotheses regarding whether there exists a common or inverse genetic etiology behind these immune-mediated diseases have been presented. We aimed to test whether there exist common or inverse associations between polymorphisms in the pattern recognition receptors TLR2, TLR4 and CD14 and T1D and allergic asthma. Eighteen single nucleotide polymorphisms (SNPs) were genotyped in TLR2 (2), TLR4 (12) and CD14 (4) in 700 T1D children, 357 nuclear families with T1D children and 796 children from the 'Environment and Childhood Asthma' study. Allele and haplotype frequencies were analyzed in relation to diseases and in addition transmission disequilibrium test analyses were performed in the family material. Both T1D and allergic asthma were significantly associated with the TLR2 rs3804100 T allele and further associated with the haplotype including this SNP, possibly representing a susceptibility locus common for the two diseases. Neither TLR4 nor CD14 were associated with T1D or allergic asthma.

Effect of breastfeeding duration on lung function at age 10 years: a prospective birth cohort study

INTRODUCTION

The protective effects of breastfeeding on early life respiratory infections are established, but there have been conflicting reports on protection from asthma in late childhood. The association of breastfeeding duration and lung function was assessed in 10-year-old children.

METHODS

In the Isle of Wight birth cohort (n = 1456), breastfeeding practices and duration were prospectively assessed at birth and at subsequent follow-up visits (1 and 2 years). Breastfeeding duration was categorised as "not breastfed" (n = 196); "<2 months" (n = 243); "2 to <4 months" (n = 142) and ">or=4 months" (n = 374). Lung function was measured at age 10 years (n = 1033): forced vital capacity (FVC), forced expiratory volume in 1 s (FEV(1)), FEV(1)/FVC ratio and peak expiratory flow (PEF). Maternal history of asthma and allergy was assessed at birth. The effect of breastfeeding on lung function was analysed using general linear models, adjusting for birth weight, sex, current height and weight, family social status cluster and maternal education.

RESULTS

Compared with those who were not breastfed, FVC was increased by 54.0 (SE 21.1) ml (p = 0.001), FEV(1) by 39.5 (20.1) ml(p = 0.05) and PEF by 180.8 (66.1) ml/s (p = 0.006) in children who were breastfed for at least 4 months. In models for FEV(1) and PEF that adjusted for FVC, the effect of breastfeeding was retained only for PEF (p = 0.04).

CONCLUSIONS

Breastfeeding for at least 4 months enhances lung volume in children. The effect on airflow appears to be mediated by lung volume changes. Future studies need to elucidate the mechanisms that drive this phenomenon.

Role of TNF-alpha gene variation in idiopathic childhood ischemic stroke: a case-control study

Etiology of the idiopathic childhood stroke remains unknown. In previous studies, the immunologic process may be involved in the idiopathic stroke. Tumor necrosis factor- alpha (TNF-alpha), an important immune mediator, may contribute to the initiation and progression in the stroke. The main purpose of this study was to investigate correlation of TNF-alpha genetic variation and idiopathic childhood ischemic stroke. Using the direct DNA sequencing method, polymorphisms in the TNF-alpha promoter region were genotyped in 67 Chinese patients with idiopathic childhood stroke and 70 controls. Among totally 7 single nucleotide polymorphisms identified in the TNF-alpha promoter region, the variant of the -863C/A is associated with increased risk of idiopathic childhood ischemic stroke in our study group. TNF-alpha molecule may have genetically as well as functionally an important role in the pathogenesis of idiopathic childhood ischemic stroke in the Chinese population.

New insights into mechanisms of immunoregulation in 2007

Substantial progress in understanding the mechanisms of immune regulation in allergic diseases and asthma has been made during the last year. In asthma, rhinitis, and atopic dermatitis the immune system is activated by allergens, autoantigens, and components of superimposed infectious agents. Immune regulation in the lymphatic organs and in the tissue has an important role in the control and suppression of allergic disease in all stages of the inflammatory process, such as cell migration to tissues, cells gaining an inflammatory and tissue-destructive phenotype in the tissues, and their interaction with resident tissue cells to augment the inflammation. After the discovery of regulatory T cells, the importance of their unique suppressive capacity was strongly emphasized for the suppression of effector T-cell responses. However, it seems that all 3 subsets of effector T(H)1, T(H)2, and T(H)17 cells, as well as regulatory T cells, regulate each other at the level of transcription, major cytokines, and surface molecules. This review highlights key advances in immune regulation that were published in the Journal of Allergy and Clinical Immunology.

Restoration of T-box-containing protein expressed in T cells protects against allergen-induced asthma

BACKGROUND

A T(H)1-specific transcription factor, T-box-containing protein expressed in T cells (T-bet), controls the production of both T(H)1 and T(H)2 cytokines in T(H) cell differentiation by means of distinct mechanisms. T-bet-deficient mice overproduce T(H)2 cytokines and have spontaneous airway inflammation.

OBJECTIVES

We tested whether T-bet overexpression could protect against the development or progression of asthma.

METHODS

We generated a T cell-specific and inducible line of T-bet-transgenic mice on a T-bet-deficient genetic background and used it to study the function of T-bet in an ovalbumin (OVA)-induced asthma model.

RESULTS

Induction of T-bet in a T cell-specific manner in an OVA model of asthma concomitant with OVA injection prevented airway hyperresponsiveness, eosinophilic and lymphocytic inflammation, and IL-5 and IL-13 production in bronchoalveolar lavage fluid and also reduced serum IgE and T(H)2 cytokine production by peripheral T cells. Even when T-bet expression was induced during later stages of asthma progression, T-bet overexpression still attenuated airway hyperresponsiveness and goblet cell hyperplasia, as well as T(H)2 cytokine production.

CONCLUSIONS

Our results suggest that T-bet expression in T cells can prevent the initiation of airway inflammation and progression of chronic inflammation and might be extrapolated to human asthma.

The prevalence of allergic diseases in an unselected group of 6-year-old children. The DARC birth cohort study

This study determines the prevalence of atopic dermatitis, asthma, rhinoconjunctivitis, food hypersensitivity and urticaria and the frequency of sensitization in children with and without clinical allergic disease. In an ongoing prospective non-interventional birth cohort study of 562 unselected children, 404 children were subjected to interview, clinical examination, lung function measurements and allergy testing at 6 yr of age. Sensitization measured by skin prick test (SPT) and specific immunoglobulin E (S-IgE) was determined for 24 different allergens. The 1-yr period prevalence of atopic dermatitis, asthma and rhinoconjunctivitis was 14.4%, 6.2% and 13.6%. 25.7% of the children suffered from at least one of the three diseases. The frequency of sensitization in children with no disease (controls), any allergic disease, atopic dermatitis, asthma and rhinoconjunctivitis was 17%, 45%, 47%, 56% and 55% (defined as SPT >or=3 mm and/or S-IgE >or=0.35 kU/l for at least one allergen). Symptoms were linked to sensitization for 44% in the asthma group and 42% in the rhinoconjunctivitis group, whereas sensitization could not be linked to worsening of the eczema in any cases of atopic dermatitis. Overlap between the three diseases was significantly more frequent in sensitized children than in non-sensitized (19/46 = 41% vs. 9/58 = 16%, p = 0.004). The prevalence of food hypersensitivity and urticaria was 1.2% and 5.4% respectively. In unselected 6 yr old children, approximately half of the children with atopic dermatitis, asthma or rhinoconjunctivitis are IgE-sensitized. Sensitization tends to link these diseases to each other.

Differing lung function development in infants with univentricular hearts compared with healthy infants

AIM

To compare the difference in lung function development of healthy controls and patients with univentricular hearts from birth prior to surgery and during the first year of life when cardiac shunt procedures and the cavopulmonary connection are required.

METHODS

Tidal flow-volume measurements and single-occlusion tests were performed from birth serially up to 18 months of age on 28 unsedated spontaneously breathing infants with univentricular hearts and 58 healthy control infants.

RESULTS

Infants with univentricular heart physiology had low tidal volumes, low compliance of the respiratory system and high respiratory rate at birth, which over time normalized, whereas the peak expiratory flow increased during the study period. The lung function measured at birth was predictive of later lung function measurements.

CONCLUSION

The pattern of lung function development is different in the patients with univentricular hearts compared to healthy controls. Lung function measured at birth is predictive of later lung function.

HLX1 gene variants influence the development of childhood asthma

BACKGROUND

Major transcription factors controlling T(H)1 and T(H)2 development, such as T-box transcription factor and GATA3, might be centrally involved in asthma and atopic diseases. Only recently, the homeobox transcription factor H.20-like homeobox 1 (HLX1), interacting closely with T-box transcription factor, has been identified as an important regulator of T(H)1 differentiation and suppressor of T(H)2 commitment.

OBJECTIVE

We investigated whether genetic variations in the HLX1 gene exist and whether these could affect the development of childhood asthma.

METHODS

The HLX1 gene was resequenced in 80 chromosomes. Associations between identified polymorphisms, asthma, and atopic diseases were investigated in German children (total n = 3099) from the cross-sectional International Study of Asthma and Allergy in Childhood phase II. Functional properties of polymorphisms were studied by using luciferase reporter gene assays and electrophoretic mobility shift assays in T cells. All statistical analyses were performed with SAS/Genetics software (SAS Institute, Inc, Cary, NC).

RESULTS

Nineteen polymorphisms were identified in the HLX1 gene, and 2 tagging single nucleotide polymorphisms representing 7 polymorphisms were associated with childhood asthma in our study population. Two promoter polymorphisms, C-1407T and C-742G, contained in 1 tagging block were associated with asthma (odds ratio, 1.44; 95% CI, 1.11-1.86; P = .0061), significantly decrease promoter transactivation, and disrupt specificity protein-transcription factor binding in in vitro experiments.

CONCLUSIONS

Our data suggest that polymorphisms in the HLX1 gene increase the risk for childhood asthma. On the cellular level, altered binding of specificity protein-transcription factors to the HLX1 promoter and subsequent changes in HLX1 gene expression might contribute to these effects.

Associations of wheezing phenotypes in the first 6 years of life with atopy, lung function and airway responsiveness in mid-childhood

BACKGROUND

Patterns of wheezing during early childhood may indicate differences in aetiology and prognosis of respiratory illnesses. Improved characterisation of wheezing phenotypes could lead to the identification of environmental influences on the development of asthma and airway diseases in predisposed individuals.

METHODS

Data collected on wheezing at seven time points from birth to 7 years from 6265 children in a longitudinal birth cohort (the ALSPAC study) were analysed. Latent class analysis was used to assign phenotypes based on patterns of wheezing. Measures of atopy, airway function (forced expiratory volume in 1 s (FEV(1)), mid forced expiratory flow (FEF(25-75))) and bronchial responsiveness were made at 7-9 years of age.

RESULTS

Six phenotypes were identified. The strongest associations with atopy and airway responsiveness were found for intermediate onset (18 months) wheezing (OR for atopy 8.36, 95% CI 5.2 to 13.4; mean difference in dose response to methacholine 1.76, 95% CI 1.41 to 2.12 %FEV(1) per mumol, compared with infrequent/never wheeze phenotype). Late onset wheezing (after 42 months) was also associated with atopy (OR 6.6, 95% CI 4.7 to 9.4) and airway responsiveness (mean difference 1.61, 95% CI 1.37 to 1.85 %FEV(1) per mumol). Transient and prolonged early wheeze were not associated with atopy but were weakly associated with increased airway responsiveness and persistent wheeze had intermediate associations with these outcomes.

CONCLUSIONS

The wheezing phenotypes most strongly associated with atopy and airway responsiveness were characterised by onset after age 18 months. This has potential implications for the timing of environmental influences on the initiation of atopic wheezing in early childhood.

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

RATIONALE

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

OBJECTIVES

To relate AR in infancy to asthma in childhood.

METHODS

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

MEASUREMENTS AND MAIN RESULTS

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

CONCLUSIONS

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

Early identification of atopy in the prediction of persistent asthma in children

The long-term solution to the asthma epidemic is thought to be prevention, and not treatment of established disease. Atopic asthma arises from gene-environment interactions, which mainly take place during a short period in prenatal and postnatal development. These interactions are not completely understood, and hence primary prevention remains an elusive goal. We argue that primary-care physicians, paediatricians, and specialists lack knowledge of the role of atopy in early life in the development of persistent asthma in children. In this review, we discuss how early identification of children at high risk is feasible on the basis of available technology and important for potential benefits to the children. Identification of an asthmatic child's atopic status in early life has practical clinical and prognostic implications, and sets the basis for future preventative strategies.

High prevalence of allergic diseases and sensitization in a low allergen country

BACKGROUND

The prevalence of adult atopic diseases in Iceland is lower than in other West European countries, despite an affluent lifestyle, but limited data are available on children. The main aim of this study was to investigate the prevalence of atopic diseases and sensitivity to common allergens in 10- to 11-year-old Icelandic schoolchildren as part of phase II of the International Study of Asthma and Allergies in Children (ISAAC).

METHODS

Nine hundred and forty-six children and their parents answered a questionnaire about atopic diseases. Skin prick tests with six allergens were performed on 773 children and they were examined for signs of atopic dermatitis (AD).

RESULTS

The 12-month prevalence of allergic rhinoconjunctivitis and asthma was 11.5% and 8.9% respectively. The reported prevalence of AD was 27%, but only 9.2% had signs when inspected. A positive skin prick test (SPT) was found in 24.4% of the children, that is 18.8% to grass, 12.9% to cat, 3.6% to trees, 3.0% to Dermatophagoides pteronyssinus, 1.4% to D. farinae and 0.5% to Alternaria.

CONCLUSION

The high prevalence of atopic diseases in children at 10-11 years is surprising, as the prevalence in adults is low in Iceland. The findings resemble those in developing countries. Iceland has had an affluent lifestyle for a considerable time, but the absence of dust mites, low pet ownership and relatively low pollen counts in the country raise doubts about the role of exposure levels in the development of sensitization and atopic diseases.

Severe asthma in childhood: assessed in 10 year olds in a birth cohort study

BACKGROUND

Limited information is available regarding the prevalence of severe asthma in children. The present study aimed at investigating the prevalence of severe asthma in an urban child population; secondarily evaluating the applicability of the chosen definition by clinical characteristics.

METHODS

Children enrolled in the prospective birth cohort; the Environment and Childhood Asthma Study in Oslo; were reinvestigated at the age of 10 years (n = 1019). A representative population based cohort of 616 children [mean age 10.9 (SD 0.9) years] with lung function measurements at birth was used for prevalence estimates, whereas all 1019 children (154 with current asthma) attending the 10-year follow-up were included for verification of the definition of severe asthma. Clinical investigations included spirometry, tests of bronchial hyperresponsiveness, skin prick tests and exhaled nitric oxide. Severe asthma was defined as poorly controlled asthma despite treatment with > or = 800 microg budesonide or equivalent; assessed by a detailed structured interview.

RESULTS

The population point prevalence at age 10 years of current severe asthma was 0.5% (three of 616) and among children with current asthma 4.5% (three of 67). The 10/154 children identified as suffering from severe asthma more often had severe bronchial hyperresponsiveness (PD(20) methacholine <1 micromol) (60%vs 22%, P = 0.015), lower median forced expiratory volume in 1 s/forced vital capacity ratio (93%vs 99%, P = 0.04) and higher body mass index (mean BMI 22.3 vs 18.3, P < 0.001) than nonsevere current asthmatics.

CONCLUSIONS

The prevalence of severe asthma was 0.5% in all 10-year olds, and 4.5% among current asthmatics. The severe asthma definition applied in this study is supported by results of clinical investigations.

New visions in respiratory allergy (asthma and allergic rhinitis): an iPAC summary and future trends

In many aspects, respiratory allergies, i.e., allergic asthma and rhinitis, represent the hallmarks of allergy. Epidemiologic data highlight their large prevalence of most parts of the world, socioeconomic analysis reveal their large impact on global health and the large number of scientific publications in this field regularly brings to light many new aspects of these diseases. However, the current understanding of respiratory allergies, in particular in children remains scarce. How can we efficiently prevent respiratory allergies in allergy-prone infants? How can we prevent the progression of the disease? What therapeutic strategies could efficiently address efficient immunomodulation? the international Pediatric Allergy and Asthma Consortium, addressed these issues by a thorough review of the literature providing a state-of-the-art current knowledge in respiratory allergy, and identified a series of needs to be addressed in future studies.

Increasing burden and risk factors for bronchiolitis-related medical visits in infants enrolled in a state health care insurance plan

OBJECTIVES

The goals were to estimate the year-round burden of health care visits attributable to bronchiolitis and to identify risk factors for bronchiolitis in term healthy infants.

METHODS

We conducted a population-based, retrospective cohort study of 103 670 term, non-low birth weight infants enrolled in Tennessee Medicaid in 1995-2003. We monitored infants through the first year of life. Risk factors for bronchiolitis during infancy and rates of inpatient, emergency department, and outpatient visits during the study period were calculated by using claims data.

RESULTS

Over the 9 study years, rates of bronchiolitis visits were 238 outpatient visits per 1000 infant-years, 77 emergency department visits per 1000 infant-years, and 71 hospitalizations per 1000 infant-years. Average annual rates of bronchiolitis visits increased 41%, from 188 visits per 1000 infant-years to 265 visits per 1000 infant-years, from 1996-1997 to 2002-2003. Analysis of the linear trend in 500-g increments demonstrated a negative association between increasing birth weight and bronchiolitis diagnosis. There was a significant negative trend between maternal age and infant bronchiolitis diagnosis. Compared with infants of mothers 20 to 29 years of age, infants of mothers 15 to 19 years of age had a small increase in risk of having a bronchiolitis visit, whereas infants of older mothers (30-39 or 40-44 years of age) were less likely to have a visit.

CONCLUSIONS

The disease burden of bronchiolitis is substantial, with increasing rates of all types of visits among term, otherwise-healthy infants enrolled in Tennessee Medicaid between 1995 and 2003. Protective factors in this cohort of term infants included higher birth weight and older maternal age.

Wheezing rhinovirus illnesses in early life predict asthma development in high-risk children

RATIONALE

Virus-induced wheezing episodes in infancy often precede the development of asthma. Whether infections with specific viral pathogens confer differential future asthma risk is incompletely understood.

OBJECTIVES

To define the relationship between specific viral illnesses and early childhood asthma development.

METHODS

A total of 259 children were followed prospectively from birth to 6 years of age. The etiology and timing of specific viral wheezing respiratory illnesses during early childhood were assessed using nasal lavage, culture, and multiplex reverse transcriptase-polymerase chain reaction. The relationships of these virus-specific wheezing illnesses and other risk factors to the development of asthma were analyzed.

MEASUREMENTS AND MAIN RESULTS

Viral etiologies were identified in 90% of wheezing illnesses. From birth to age 3 years, wheezing with respiratory syncytial virus (RSV) (odds ratio [OR], 2.6), rhinovirus (RV) (OR, 9.8), or both RV and RSV (OR , 10) was associated with increased asthma risk at age 6 years. In Year 1, both RV wheezing (OR, 2.8) and aeroallergen sensitization (OR, 3.6) independently increased asthma risk at age 6 years. By age 3 years, wheezing with RV (OR, 25.6) was more strongly associated with asthma at age 6 years than aeroallergen sensitization (OR, 3.4). Nearly 90% (26 of 30) of children who wheezed with RV in Year 3 had asthma at 6 years of age.

CONCLUSIONS

Among outpatient viral wheezing illnesses in infancy and early childhood, those caused by RV infections are the most significant predictors of the subsequent development of asthma at age 6 years in a high-risk birth cohort.

Asthma year in review 2006-7

This review focuses on papers published between September 2006 and September 2007 that either answer important clinical questions, or signpost important areas for future research.

Airway modeling and remodeling in the pathogenesis of asthma

PURPOSE OF REVIEW

Asthma remains a severe health problem since current therapies are directed to suppressing, rather than preventing or reversing, the primary disease process. Clearly, a greater understanding of the pathogenesis of asthma is critical to the development of better therapeutic modalities. In this review, we discuss the recent advancements in research targeting the role of airway remodeling in asthma.

RECENT FINDINGS

Epithelial fragility and abnormalities are being recognized as important facets of asthma, as are other features of remodeling such as angiogenesis, goblet cell hyperplasia and thickened lamina reticularis. Significantly, these anomalies occur early in disease pathogenesis. However, their impact on disease severity remains unclear.

SUMMARY

Although an altered immune response is undoubtedly important to the pathogenesis of asthma, there is increasing evidence that the tissue-specific manifestations occur independently of inflammation and significantly impact on disease development and severity.

Prevalence and risk factors of asthma and allergic diseases among schoolchildren in Bolu, Turkey

AIM

In this study we aimed to detect the prevalence and risk factors of asthma and allergic diseases in children aged between 7 and 14 years old at rural and urban areas of Bolu, Turkey.

METHODS

Questionnaire of International Study of Asthma and Allergies in Childhood (ISAAC) phase one and questionnaire including questions about family, demographic, socio-economic characteristics of children were applied to 931 schoolchildren who were selected by randomized sampling.

RESULTS

In children, the prevalence of diseases and symptoms were as follows: wheeze ever: 15.5%, asthma: 5.6%, nasal symptoms ever: 41.4%, allergic rhinitis: 23.2%, itchy rash ever: 5.9% and eczema: 5.0%. In multivariate regression analysis, presence of allergic disease in the family was risk factor for wheezing (OR=1.74, 95% CI=1.19-2.76), asthma (OR=2.19, CI=1.06-4.52), allergic rhinitis (OR=2.68, CI=1.80-3.98) and eczema (OR=2.33, CI=1.17-4.65); living in shanties was risk factor for allergic rhinitis (OR=5.26, CI=2.1-13.16); a monthly income below $300 was risk factor for asthma (OR=2.54, CI=1.06-6.08).

CONCLUSION

It was detected that the prevalence of allergic rhinitis and its symptoms was more common in schoolchildren living in Bolu. Presence of allergic disease in fathers or mothers and low socio-economic level increase the risk of asthma and other allergic diseases in children.

Asthmatic symptoms, physical activity, and overweight in young children: a cohort study

OBJECTIVE

Prevalence of asthma and overweight has increased simultaneously during the past decades. Several studies have reported an association between these two health problems, but it is unclear whether this relation is causal. We hypothesize that children with asthmatic symptoms are less physically active, which may contribute to the development of overweight.

PATIENTS AND METHODS

The study included children from the KOALA Birth Cohort Study who were invited at 4 to 5 years of age to wear an Actigraph accelerometer for 5 days (n = 305; 152 boys). Information on wheezing was gathered by repeated questionnaires completed by parents at child ages 7 months and 1, 2, and 4 to 5 years. Questionnaires on physical activity were completed at child age 4 to 5 years, and height, weight, and abdominal circumference were measured. Accelerometer data were expressed as mean counts per minute, minutes per day performing vigorous activity, and moderate-to-vigorous physical activity during > or = 1 minute.

RESULTS

Children who had wheezed in the last 12 months showed very similar activity levels compared with children who had never wheezed. By contrast, boys who had wheezed at least once but not in the last 12 months were more physically active than boys who had never wheezed (geometric mean: 694 vs 625 cpm; adjusted geometric mean ratio: 1.11). This was not found for girls. Similar results were found in parent-reported physical activity data. No association was found between wheezing at any age and overweight at the age of 4 to 5 years.

CONCLUSIONS

These results do not support our hypothesis and previous studies that showed that wheezing children are less physically active. Our data provide no evidence that asthmatic symptoms induce a lower physical activity level and more overweight. Additional research could concentrate on the effect of physical activity and overweight on the development of asthmatic symptoms.

Interpatient variability in rates of asthma progression: can genetics provide an answer?

Asthma is a heterogeneous disorder with a variable natural history. In children 3 patterns of the natural history of asthma have been described: early onset but transient, persistent, and later onset, with only the former leading to persistent asthma later in childhood. In adults a range of different asthma phenotypes differing in their environmental, inflammatory, and prognostic characteristics have also been described. These extend beyond allergic (extrinsic) and nonallergic (intrinsic) asthma to include persistent airflow obstruction and accelerated decrease in lung function over time. Asthma progression can be defined as the change in an individual's phenotype along a continuum ranging from nonasthmatic to asthmatic and subsequent development of severe chronic disease. It is clear that for prevention of asthma progression in patients, there is a need for both better understanding of the pathophysiology of asthma and identification of predictors of progression. Interpatient genetic variability has been shown to affect multiple facets of asthma progression, including increased susceptibility to atopy and subsequent asthma, progression to severe disease, and modification of the response to treatment. Thus genetic testing might provide a means for predicting the likely progression of an individual along the continuum, allowing targeting of preventative treatment. However, the prospect of the use of genetic information in clinical practice raises important social and ethical issues that will need to be addressed before genetic testing can be used to inform the preventative treatment of patients to prevent the development of progression of asthma in individuals.

The hypothalamic-pituitary-adrenal axis in asthmatic children

Reduced responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis in patients with various chronic allergic inflammatory disorders and a blunted HPA axis response of poorly controlled asthmatics before long-term treatment with inhaled corticosteroids (ICS) have been reported. It seems that pro- and anti-inflammatory cytokines might be involved in the attenuation of cortisol and adrenocorticotropic hormone (ACTH) responses to stress in these patients. Although long-term ICS treatment might produce mild adrenal suppression in some asthmatic children, improvement of adrenal function has been detected in the majority of cases. We postulate that the anti-inflammatory effects of ICS result both in asthma remission and HPA axis improvement. Adrenal suppression of some asthmatic patients on maintenance ICS seems to be a separate phenomenon, possibly constitutionally or genetically determined.

Impact of gender on asthma in childhood and adolescence: a GA2LEN review

A number of studies have shown gender differences in the prevalence of wheeze and asthma. The aim of this review was to examine published results on gender differences in childhood and adolescent asthma incidence and prevalence, define current concepts and to identify new research needs. A Medline search was performed with the search words (gender OR sex) AND (child OR childhood OR adolescence) AND (asthma). Articles that reported on absence or presence of gender differences in asthma were included and reviewed, and cross-references were checked. Boys are consistently reported to have more prevalent wheeze and asthma than girls. In adolescence, the pattern changes and onset of wheeze is more prevalent in females than males. Asthma, after childhood, is more severe in females than in males, and is underdiagnosed and undertreated in female adolescents. Possible explanations for this switch around puberty in the gender susceptibility to develop asthma include hormonal changes and gender-specific differences in environmental exposures. This aspect needs consideration of the doctors and allergists who diagnose and treat asthmatic individuals. In conclusion, sex hormones are likely to play an important role in the development and outcome of the allergic immune response and asthma in particular. By obtaining functional data from appropriate models, the exact underlying mechanisms can be unravelled. To examine the effect of gender-specific differences in environmental exposures and changes of asthma prevalence and severity in puberty, larger populations may need to be investigated.