Increased risk of asthma in overweight children born large for gestational age

BACKGROUND

Being born large for gestational age (LGA) is a marker of increased growth velocity in fetal life and a risk factor for childhood overweight. Both being born LGA and childhood overweight may influence the development of asthma, although the role of overweight in the association between LGA and childhood asthma is unclear. Importantly, recent studies have suggested that the association between overweight and asthma may be related to non-allergic pathways. If this also applies to the association between LGA and asthma, the association between being born LGA and asthma may be different for atopic and non-atopic children.

OBJECTIVE

We investigated the association of being LGA with the prevalence of asthma at age 8 in atopic and non-atopic children and the role of overweight in this association.

METHODS

Complete data on asthma, anthropometry and atopy at age of 8 years, and potential confounders were available for 1608 participants of the PIAMA birth cohort. Odds ratios for the association between LGA and asthma in atopic and non-atopic children were estimated by logistic regression analysis adjusting for potential confounders. Overweight was assessed as a potential modifier of the association between LGA and asthma.

RESULTS

Being born LGA was not significantly associated with asthma at age of 8 in atopic and non-atopic children. However, overweight at age of 8 years modified the association between asthma at age of 8 and LGA. In non-atopic children, children who were born LGA and were overweight at age of 8 years had a significantly increased odds of asthma compared to non-LGA, non-overweight children (adj OR 7.04; 95% CI 2.2-24).

CONCLUSIONS

We observed that non-atopic children born LGA, who were overweight by 8 years have an increased risk of asthma. If confirmed, these findings suggest that non-atopic children born LGA may be identified early in life as a high-risk group for asthma.

The sex-shift in single disease and multimorbid asthma and rhinitis during puberty - a study by MeDALL

BACKGROUND

Cross-sectional studies suggested that allergy prevalence in childhood is higher in boys compared to girls, but it remains unclear whether this inequality changes after puberty. We examined the sex-specific prevalence of asthma and rhinitis as single and as multimorbid diseases before and after puberty onset in longitudinal cohort data.

METHODS

In six European population-based birth cohorts of MeDALL, we assessed the outcomes: current rhinitis, current asthma, current allergic multimorbidity (ie, concurrent asthma and rhinitis), puberty status and allergic sensitization by specific serum antibodies (immunoglobulin E) against aero-allergens. With generalized estimating equations, we analysed the effects of sex, age, puberty (yes/no) and possible confounders on the prevalence of asthma and rhinitis, and allergic multimorbidity in each cohort separately and performed individual participant data meta-analysis.

FINDINGS

We included data from 19 013 participants from birth to age 14-20 years. Current rhinitis only affected girls less often than boys before and after puberty onset: adjusted odds ratio for females vs males 0.79 (95%-confidence interval 0.73-0.86) and 0.86 (0.79-0.94), respectively (sex-puberty interaction P = .089). Similarly, for current asthma only, females were less often affected than boys both before and after puberty onset: 0.71, 0.63-0.81 and 0.81, 0.64-1.02, respectively (sex-puberty interaction P = .327). The prevalence of allergic multimorbidity showed the strongest sex effect before puberty onset (female-male-OR 0.55, 0.46-0.64) and a considerable shift towards a sex-balanced prevalence after puberty onset (0.89, 0.74-1.04); sex-puberty interaction: P < .001.

INTERPRETATION

The male predominance in prevalence before puberty and the "sex-shift" towards females after puberty onset were strongest in multimorbid patients who had asthma and rhinitis concurrently.

Paving the way of systems biology and precision medicine in allergic diseases: the MeDALL success story: Mechanisms of the Development of ALLergy; EU FP7-CP-IP; Project No: 261357; 2010-2015

MeDALL (Mechanisms of the Development of ALLergy; EU FP7-CP-IP; Project No: 261357; 2010-2015) has proposed an innovative approach to develop early indicators for the prediction, diagnosis, prevention and targets for therapy. MeDALL has linked epidemiological, clinical and basic research using a stepwise, large-scale and integrative approach: MeDALL data of precisely phenotyped children followed in 14 birth cohorts spread across Europe were combined with systems biology (omics, IgE measurement using microarrays) and environmental data. Multimorbidity in the same child is more common than expected by chance alone, suggesting that these diseases share causal mechanisms irrespective of IgE sensitization. IgE sensitization should be considered differently in monosensitized and polysensitized individuals. Allergic multimorbidities and IgE polysensitization are often associated with the persistence or severity of allergic diseases. Environmental exposures are relevant for the development of allergy-related diseases. To complement the population-based studies in children, MeDALL included mechanistic experimental animal studies and in vitro studies in humans. The integration of multimorbidities and polysensitization has resulted in a new classification framework of allergic diseases that could help to improve the understanding of genetic and epigenetic mechanisms of allergy as well as to better manage allergic diseases. Ethics and gender were considered. MeDALL has deployed translational activities within the EU agenda.

Residential greenness is differentially associated with childhood allergic rhinitis and aeroallergen sensitization in seven birth cohorts

BACKGROUND

The prevalence of allergic rhinitis is high, but the role of environmental factors remains unclear. We examined cohort-specific and combined associations of residential greenness with allergic rhinitis and aeroallergen sensitization based on individual data from Swedish (BAMSE), Australian (MACS), Dutch (PIAMA), Canadian (CAPPS and SAGE), and German (GINIplus and LISAplus) birth cohorts (n = 13 016).

METHODS

Allergic rhinitis (doctor diagnosis/symptoms) and aeroallergen sensitization were assessed in children aged 6-8 years in six cohorts and 10-12 years in five cohorts. Residential greenness was defined as the mean Normalized Difference Vegetation Index (NDVI) in a 500-m buffer around the home address at the time of health assessment. Cohort-specific associations per 0.2 unit increase in NDVI were assessed using logistic regression models and combined in a random-effects meta-analysis.

RESULTS

Greenness in a 500-m buffer was positively associated with allergic rhinitis at 6-8 years in BAMSE (odds ratio = 1.42, 95% confidence interval [1.13, 1.79]) and GINI/LISA South (1.69 [1.19, 2.41]) but inversely associated in GINI/LISA North (0.61 [0.36, 1.01]) and PIAMA (0.67 [0.47, 0.95]). Effect estimates in CAPPS and SAGE were also conflicting but not significant (0.63 [0.32, 1.24] and 1.31 [0.81, 2.12], respectively). All meta-analyses were nonsignificant. Results were similar for aeroallergen sensitization at 6-8 years and both outcomes at 10-12 years. Stratification by NO2 concentrations, population density, an urban vs rural marker, and moving did not reveal consistent trends within subgroups.

CONCLUSION

Although residential greenness appears to be associated with childhood allergic rhinitis and aeroallergen sensitization, the effect direction varies by location.

Association of season of birth with DNA methylation and allergic disease

BACKGROUND

Season of birth influences allergy risk; however, the biological mechanisms underlying this observation are unclear. The environment affects DNA methylation, with potentially long-lasting effects on gene expression and disease. This study examined whether DNA methylation could underlie the association between season of birth and allergy.

METHODS

In a subset of 18-year-old participants from the Isle of Wight (IoW) birth cohort (n = 367), the risks of birth season on allergic outcomes were estimated. Whole blood epigenome-wide DNA methylation was measured, and season-associated CpGs detected using a training-and-testing-based technique. Validation method examined the 8-year-old Prevention and Incidence of Asthma and Mite Allergy (PIAMA) cohort. The relationships between DNA methylation, season of birth and allergy were examined. CpGs were analysed in IoW third-generation cohort newborns.

RESULTS

Autumn birth increased risk of eczema, relative to spring birth. Methylation at 92 CpGs showed association with season of birth in the epigenome-wide association study. In validation, significantly more CpGs had the same directionality than expected by chance, and four were statistically significant. Season-associated methylation was enriched among networks relating to development, the cell cycle and apoptosis. Twenty CpGs were nominally associated with allergic outcomes. Two CpGs were marginally on the causal pathway to allergy. Season-associated methylation was largely absent in newborns, suggesting it arises post-natally.

CONCLUSIONS

This study demonstrates that DNA methylation in adulthood is associated with season of birth, supporting the hypothesis that DNA methylation could mechanistically underlie the effect of season of birth on allergy, although other mechanisms are also likely to be involved.

Classroom ventilation and indoor air quality-results from the FRESH intervention study

Inadequate ventilation of classrooms may lead to increased concentrations of pollutants generated indoors in schools. The FRESH study, on the effects of increased classroom ventilation on indoor air quality, was performed in 18 naturally ventilated classrooms of 17 primary schools in the Netherlands during the heating seasons of 2010-2012. In 12 classrooms, ventilation was increased to targeted CO2 concentrations of 800 or 1200 ppm, using a temporary CO2 controlled mechanical ventilation system. Six classrooms were included as controls. In each classroom, data on endotoxin, β(1,3)-glucans, and particles with diameters of <10 μm (PM10 ) and <2.5 μm (PM2.5 ) and nitrogen dioxide (NO2 ) were collected during three consecutive weeks. Associations between the intervention and these measured indoor air pollution levels were assessed using mixed models, with random classroom effects. The intervention lowered endotoxin and β(1,3)-glucan levels and PM10 concentrations significantly. PM10 for instance was reduced by 25 μg/m³ (95% confidence interval 13-38 μg/m³) from 54 μg/m³ at maximum ventilation rate. No significant differences were found between the two ventilation settings. Concentrations of PM2.5 and NO2 were not affected by the intervention. Our results provide evidence that increasing classroom ventilation is effective in decreasing the concentrations of some indoor-generated pollutants.

The independent role of prenatal and postnatal exposure to active and passive smoking on the development of early wheeze in children

Maternal smoking during pregnancy increases childhood asthma risk, but health effects in children of nonsmoking mothers passively exposed to tobacco smoke during pregnancy are unclear. We examined the association of maternal passive smoking during pregnancy and wheeze in children aged ≤2 years.Individual data of 27 993 mother-child pairs from 15 European birth cohorts were combined in pooled analyses taking into consideration potential confounders.Children with maternal exposure to passive smoking during pregnancy and no other smoking exposure were more likely to develop wheeze up to the age of 2 years (OR 1.11, 95% CI 1.03-1.20) compared with unexposed children. Risk of wheeze was further increased by children's postnatal passive smoke exposure in addition to their mothers' passive exposure during pregnancy (OR 1.29, 95% CI 1.19-1.40) and highest in children with both sources of passive exposure and mothers who smoked actively during pregnancy (OR 1.73, 95% CI 1.59-1.88). Risk of wheeze associated with tobacco smoke exposure was higher in children with an allergic versus nonallergic family history.Maternal passive smoking exposure during pregnancy is an independent risk factor for wheeze in children up to the age of 2 years. Pregnant females should avoid active and passive exposure to tobacco smoke for the benefit of their children's health.

Phenotyping asthma, rhinitis and eczema in MeDALL population-based birth cohorts: an allergic comorbidity cluster

BACKGROUND

Asthma, rhinitis and eczema often co-occur in children, but their interrelationships at the population level have been poorly addressed. We assessed co-occurrence of childhood asthma, rhinitis and eczema using unsupervised statistical techniques.

METHODS

We included 17 209 children at 4 years and 14 585 at 8 years from seven European population-based birth cohorts (MeDALL project). At each age period, children were grouped, using partitioning cluster analysis, according to the distribution of 23 variables covering symptoms 'ever' and 'in the last 12 months', doctor diagnosis, age of onset and treatments of asthma, rhinitis and eczema; immunoglobulin E sensitization; weight; and height. We tested the sensitivity of our estimates to subject and variable selections, and to different statistical approaches, including latent class analysis and self-organizing maps.

RESULTS

Two groups were identified as the optimal way to cluster the data at both age periods and in all sensitivity analyses. The first (reference) group at 4 and 8 years (including 70% and 79% of children, respectively) was characterized by a low prevalence of symptoms and sensitization, whereas the second (symptomatic) group exhibited more frequent symptoms and sensitization. Ninety-nine percentage of children with comorbidities (co-occurrence of asthma, rhinitis and/or eczema) were included in the symptomatic group at both ages. The children's characteristics in both groups were consistent in all sensitivity analyses.

CONCLUSION

At 4 and 8 years, at the population level, asthma, rhinitis and eczema can be classified together as an allergic comorbidity cluster. Future research including time-repeated assessments and biological data will help understanding the interrelationships between these diseases.

Early-life house dust mite allergens, childhood mite sensitization, and respiratory outcomes

BACKGROUND

Exposure to indoor allergens during early life may play a role in the development of the immune system and inception of asthma.

OBJECTIVE

To describe the house dust mite (HDM) allergen concentrations in bedroom dust during early life and to evaluate its associations with HDM sensitization, wheezing, and asthma, from birth to school age, in 5 geographically spread European birth cohorts.

METHODS

We included 4334 children from INMA-Menorca (Spain), BAMSE (Sweden), LISAplus and MAS (Germany), and PIAMA-NHS (the Netherlands). Dust samples were collected from bedrooms during early life and analyzed for Dermatophagoides pteronyssinus (Der p1) and Dermatophagoides farinae (Der f1). HDM concentrations were divided into four categories. Sensitization was determined by specific IgE. Wheezing and asthma information up to 8/10 years was collected through questionnaires. We performed mixed-effects logistic regression models and expressed associations as odds ratios with 95% confidence intervals.

RESULTS

House dust mite concentrations varied across cohorts. Mean allergen concentrations were highest in INMA-Menorca (geometric mean (GM) Der p1 = 3.3 μg/g) and LISAplus (GM Der f1 = 2.1 μg/g) and lowest in BAMSE (GM Der p1 = 0.1 μg/g, Der f1 = 0.3 μg/g). Moderate and high HDM concentrations were significantly (P-values < 0.05) associated with 50-90% higher prevalence of HDM sensitization. No significant associations were observed with respiratory outcomes.

CONCLUSION

Our study based on geographically spread regions, a large sample size, and a wide range of allergen concentration shows that HDM allergen concentrations vary across regions and that exposure during early life plays a role in the development of allergic sensitization but not in the development of respiratory outcomes.

Associations of sugar-containing beverages with asthma prevalence in 11-year-old children: the PIAMA birth cohort

BACKGROUND/OBJECTIVES

Recently, a few studies have linked soft drink consumption to increased asthma risk, but the contribution of different types of soft drinks is unknown. We investigated cross-sectional associations between six different types of soft drinks and asthma in 11-year-old children.

SUBJECTS/METHODS

We analyzed data of 2406 children participating in the Dutch Prevention and Incidence of Asthma and Mite Allergy birth cohort. At age 11, children self-reported consumption of sugar-added drinks, diet drinks, sweetened milk drinks, 100% fruit juice, energy drinks and sport drinks. The definition of asthma was based on parental reports of wheezing, prescription of inhaled corticosteroids and doctor's diagnosis of asthma.

RESULTS

The prevalence of asthma in this study was 5.8%. In adjusted logistic regression analyses, asthma risk was increased for high (⩾10 glasses/week (gl/wk) versus low (<4 gl/wk) consumption of 100% fruit juice (odds ratio (OR): 2.09, 95% confidence interval (CI): 1.21-3.60), sugar-added drinks (OR: 1.56, 95%CI: 0.95-2.56) and for very high (>21.5 gl/wk) versus low (<12.5 gl/wk) total sugar-containing beverage (SCB) consumption (OR: 1.91, 95%CI: 1.04-3.48). Consumption of other beverages and consumption of fruit were not associated with increased asthma risk. No evidence for mediation of the observed associations by body mass index was found.

CONCLUSIONS

This study indicates that high consumption of 100% fruit juice and total SCBs is associated with increased asthma risk in children. The positive association between consumption of 100% fruit juice and asthma is an unexpected finding that needs confirmation in future studies.

Quantity and diversity of environmental microbial exposure and development of asthma: a birth cohort study

Background

Early-life exposure to environmental microbial agents may be associated with the development of allergies. The aim of the study was to identify better ways to characterize microbial exposure as a predictor of respiratory symptoms and allergies.

Methods

A birth cohort of 410 children was followed up until 6 years of age. Bacterial endotoxin, 3-hydroxy fatty acids, N-acetyl-muramic acid, fungal extracellular polysaccharides (EPS) from Penicillium and Aspergillus spp., β-D-glucan, ergosterol, and bacterial or fungal quantitative polymerase chain reactions (qPCRs) were analyzed from dust samples collected at 2 months of age. Asthma, wheezing, cough, and atopic dermatitis were assessed using repeated questionnaires. Specific IgEs were determined at the age of 1 and 6 years.

Results

Only few associations were found between single microbial markers and the studied outcomes. In contrast, a score for the total quantity of microbial exposure, that is, sum of indicators for fungi (ergosterol), Gram-positive (muramic acid) bacteria, and Gram-negative (endotoxin) bacteria, was significantly (inverted-U shape) associated with asthma incidence (P < 0.001): the highest risk was found at medium levels (adjusted odds ratio (aOR) 2.24, 95% confidence interval (95% CI) 0.87–5.75 for 3rd quintile) and the lowest risk at the highest level (aOR 0.34, 95% CI 0.09–1.36 for 5th quintile). The microbial diversity score, that is, sum of detected qPCRs, was inversely associated with risk of wheezing and was significantly (inverted-U shape) associated with sensitization to inhalant allergens.

Conclusion

Score for quantity of microbial exposure predicted asthma better than single microbial markers independently of microbial diversity and amount of dust. Better indicators of total quantity and diversity of microbial exposure are needed in studies on the development of asthma.

Perinatal risk factors for wheezing phenotypes in the first 8 years of life

BACKGROUND

A novel data-driven approach was used to identify wheezing phenotypes in pre-schoolchildren aged 0-8 years, in the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort. Five phenotypes were identified: never/infrequent wheeze, transient early wheeze, intermediate onset wheeze, persistent wheeze and late onset wheeze. It is unknown which perinatal risk factors drive development of these phenotypes.

OBJECTIVE

The objective of the study was to assess associations of perinatal factors with wheezing phenotypes and to identify possible targets for prevention.

METHODS

In the PIAMA study (n = 3963), perinatal factors were collected at 3 months, and wheezing was assessed annually until the age of 8 years. Associations between perinatal risk factors and the five wheezing phenotypes were assessed using weighted multinomial logistic regression models. Odds ratios were adjusted for confounding variables and calculated with 'never/infrequent wheeze' as reference category.

RESULTS

Complete data were available for 2728 children. Risk factors for transient early wheeze (n = 455) were male gender, maternal and paternal allergy, low maternal age, high maternal body mass index, short pregnancy duration, smoking during pregnancy, presence of older siblings and day-care attendance. Risk factors for persistent wheeze (n = 83) were male gender, maternal and paternal allergy, and not receiving breastfeeding for at least 12 weeks. Intermediate onset wheeze (n = 98) was associated with a lower birth weight and late onset wheeze (n = 45) with maternal allergy.

CONCLUSION AND CLINICAL RELEVANCE

We identified different risk factors for specific childhood wheezing phenotypes. Some of these are modifiable, such as maternal age and body mass index, smoking, day-care attendance and breastfeeding, and may be important targets for prevention programmes.

Dampness and moulds in relation to respiratory and allergic symptoms in children: results from Phase Two of the International Study of Asthma and Allergies in Childhood (ISAAC Phase Two)

BACKGROUND

Many studies report that damp housing conditions are associated with respiratory symptoms. Less is known about mechanisms and possible effect modifiers. Studies of dampness in relation to allergic sensitization and eczema are scarce.

OBJECTIVE

We study the influence of damp housing conditions world-wide on symptoms and objective outcomes.

METHODS

Cross-sectional studies of 8-12-year-old children in 20 countries used standardized methodology from Phase Two of the International Study of Asthma and Allergies in Childhood (ISAAC). Symptoms of asthma, rhinitis and eczema, plus residential exposure to dampness and moulds, were ascertained by parental questionnaires (n = 46 051). Skin examination, skin prick tests (n = 26 967) and hypertonic saline bronchial challenge (n = 5713) were performed. In subsamples stratified by wheeze (n = 1175), dust was sampled and analysed for house dust mite (HDM) allergens and endotoxin.

RESULTS

Current exposure to dampness was more common for wheezy children (pooled odds ratio 1.58, 95% CI 1.40-1.79) and was associated with greater symptom severity among wheezers, irrespective of atopy. A significant (P < 0.01) adverse effect of dampness was also seen for cough and phlegm, rhinitis and reported eczema, but not for examined eczema, nor bronchial hyperresponsiveness. HDM sensitization was more common in damp homes (OR 1.16, 1.03-1.32). HDM-allergen levels were higher in damp homes and were positively associated with HDM-sensitization, but not wheeze.

CONCLUSION

A consistent association of dampness with respiratory and other symptoms was found in both affluent and non-affluent countries, among both atopic and non-atopic children. HDM exposure and sensitization may contribute, but the link seems to be related principally to non-atopic mechanisms.

Endotoxin, extracellular polysaccharides, and β(1-3)-glucan concentrations in dust and their determinants in four European birth cohorts: results from the HITEA project

Early-life exposure to microbial agents may play a protective role in asthma and allergies development. Geographical differences in the prevalence of these diseases exist, but the differences in early-life indoor microbial agent levels and their determinants have been hardly studied. We aimed to describe the early-life levels of endotoxin, extracellular polysaccharides (EPS), and β(1-3)-glucans in living room dust of four geographically spread European birth cohorts (LISA in Germany, PIAMA in the Netherlands, INMA in Spain, and LUKAS2 in Finland) and to assess their determinants. A total of 1572 dust samples from living rooms of participants were analyzed for endotoxin, Penicillium/Aspergillus EPS, and β(1-3)-glucans. Information on potential determinants was obtained through questionnaires. Concentrations of endotoxin, EPS, and β(1-3)-glucans were different across cohorts. Concentrations of endotoxin and EPS were respectively lower and higher in INMA than in other cohorts, while glucans were higher in LUKAS2. Season of sampling, dog ownership, dampness, and the number of people living at home were significantly associated with concentrations of at least one microbial agent, with heterogeneity of effect estimates of the determinants across cohorts. In conclusion, both early-life microbial exposure levels and exposure determinants differ across cohorts derived from diverse European countries.

PRACTICAL IMPLICATIONS

This study adds evidence of variability in the levels of indoor endotoxin, extracellular polysaccharide, and β(1-3)-glucans across four geographically spread European regions. Furthermore, we observed heterogeneity across regions in the effect of exposure determinants. We hypothesize that the variations observed in our study may play a role in the differences in asthma and allergies prevalences across countries.

Glutathione-S-transferase P1, early exposure to mould in relation to respiratory and allergic health outcomes in children from six birth cohorts. A meta-analysis

BACKGROUND

There are conflicting study results regarding the association of exposure to visible mould and fungal components in house dust with respiratory and allergic diseases in children. It has been suggested that functional polymorphisms of the GSTP1 gene may influence the risk for allergic disorders through an impaired defence against oxidant injury.

METHODS

We examined in six birth cohorts of over 14 000 children whether the association between early exposure to reported mould at home in relation to respiratory and allergic diseases is modified by a single nucleotide polymorphism of the GSTP1 gene.

RESULTS

We observed a positive association of mould exposure with nasal symptoms (2-10 year) aOR: 1.19 (1.02-11.38). Further, there was a borderline significant increased risk of rhinoconjunctivitis (6-8 year) in children homozygous for the minor allele Val/Val, aOR: 1.25 (0.98-1.60). In stratified analyses, subjects homozygous for the minor allele and exposed to mould at home were at increased risk for early wheezing aOR: 1.34 (1.03-1.75), whereas the major allele may confer susceptibility for later nasal outcomes, (6-8 year) aOR: 1.20 (1.00-1.45) and (2-10 year) aOR: 1.30 (1.04-1.61), respectively. For none of the health outcomes studied, we found gene by environment interactions.

CONCLUSION

A genetic influence of the GSTP1 gene cannot be ruled out, but the magnitude of the effect is a matter of further research. In conclusion, the interplay between gene and environments is complex and remains subject of further study.

Exposure to microbial agents in house dust and wheezing, atopic dermatitis and atopic sensitization in early childhood: a birth cohort study in rural areas

BACKGROUND

Early-life exposure to environmental microbial agents may be associated with development of wheezing and allergic diseases.

OBJECTIVE

To assess the association of microbial exposure in rural homes with the risk of asthma, wheezing, atopic dermatitis and sensitization.

METHODS

Birth cohorts of rural children (n = 1133), half from farmer families, were followed up from birth to 2 years of age by questionnaires in five European centres. Endotoxin and extracellular polysaccharides (EPS) of Penicillium and Aspergillus spp. were determined from living room floor and mother's mattress dust samples collected at 2 months of age. Specific IgE against 19 allergens was measured at 1 year of age. Discrete-time hazard models, generalized estimations equations (GEE) and logistic regression were used for statistical analyses.

RESULTS

The incidence of asthma was inversely associated with the amount of dust (adjusted odds ratio (aOR) 0.73, 95% CI 0.58-0.93) and the loads (units/m(2)) of EPS (aOR 0.75, 95% CI 0.55-1.04) and endotoxin (aOR 0.79, 95% CI 0.60-1.05) in the mother's mattress. Similar associations were seen with wheezing and with living room floor dust. The microbial markers were highly correlated and their effects could not be clearly separated. The inverse associations were seen especially among non-farmers. The risk of sensitization to inhalant allergens increased with increasing endotoxin exposure from mattress dust. No associations were observed with concentrations (units/g) or with atopic dermatitis.

CONCLUSION AND CLINICAL RELEVANCE

The amount and microbial content of house dust were inversely associated with asthma and wheezing, but due to high correlations between microbial agents and amount of dust, it was not possible to disentangle their individual effects. New ways to better measure and represent exposure to environmental microbes, including indexes of biodiversity, are needed especially among farmers.

The 8-year follow-up of the PIAMA intervention study assessing the effect of mite-impermeable mattress covers

BACKGROUND

Exposure to high levels of house dust mite (HDM) allergens is associated with the development of allergic sensitization to HDM, a risk factor for the development of asthma, rhinitis, and allergic dermatitis. We studied the effect of an early intervention with mite-impermeable mattress covers on HDM allergen levels and the development of asthma and mite allergy throughout the first 8 years of life.

METHODS

High-risk children (allergic mother) were prenatally recruited and randomly allocated to two groups receiving mite allergen-impermeable (n = 416) and placebo mattress covers (n = 394) or no intervention (n = 472). Asthma and allergies were assessed yearly by questionnaire. Specific immunoglobulin E and bronchial hyper-responsiveness were measured at the age of 8 years. Mattress dust samples collected at different time points were analyzed for HDM allergens.

RESULTS

At the age of 8 years, levels of HDM allergen Der f1 but not Der p1 were lower in the active than the placebo mattress cover group. In repeated measures analyses, we found a temporary decreased risk of asthma symptoms at the age of 2 years in the intervention group compared to the placebo group and a temporary association between higher HDM allergen exposure at the age of 3 months and more asthma symptoms.

CONCLUSION

Early intervention with mite-impermeable mattress covers is successful in reducing exposure to Der f1; it only temporarily reduces the risk of asthma symptoms and does not reduce the risk of hay fever, eczema, and allergic sensitization.

Meta-analysis of mould and dampness exposure on asthma and allergy in eight European birth cohorts: an ENRIECO initiative

BACKGROUND

Several cross-sectional studies during the past 10 years have observed an increased risk of allergic outcomes for children living in damp or mouldy environments.

OBJECTIVE

The objective of this study was to investigate whether reported mould or dampness exposure in early life is associated with the development of allergic disorders in children from eight European birth cohorts.

METHODS

We analysed data from 31 742 children from eight ongoing European birth cohorts. Exposure to mould and allergic health outcomes were assessed by parental questionnaires at different time points. Meta-analyses with fixed- and random-effect models were applied. The number of the studies included in each analysis varied based on the outcome data available for each cohort.

RESULTS

Exposure to visible mould and/or dampness during first 2 years of life was associated with an increased risk of developing asthma: there was a significant association with early asthma symptoms in meta-analyses of four cohorts [0-2 years: adjusted odds ratios (aOR), 1.39 (95% CI, 1.05-1.84)] and with asthma later in childhood in six cohorts [6-8 years: aOR, 1.09 (95% CI, 0.90-1.32) and 3-10 years: aOR, 1.10 (95% CI, 0.90-1.34)]. A statistically significant association was observed in six cohorts with symptoms of allergic rhinitis at school age [6-8 years: aOR, 1.12 (1.02-1.23)] and at any time point between 3 and 10 years [aOR, 1.18 (1.09-1.28)].

CONCLUSION

These findings suggest that a mouldy home environment in early life is associated with an increased risk of asthma particularly in young children and allergic rhinitis symptoms in school-age children.

Childhood overweight and asthma symptoms, the role of pro-inflammatory proteins

BACKGROUND

Systemic inflammation is suggested as a mechanism by which overweight might induce asthma. However, few studies have linked childhood overweight, inflammation and asthma.

OBJECTIVE

To study the association between body mass index (BMI), asthma symptoms and pro-inflammatory proteins.

METHODS

High-sensitivity C-reactive protein (hs-CRP), complement factor 3 (C3) and 4 (C4) concentrations, and body weight and height were available for 359 4-year-old children participating in the Prevention and Incidence of Asthma and Mite Allergy birth cohort study. Data on asthma symptoms were obtained by yearly questionnaires. Logistic regression and generalized estimating equations were used to analyse the cross-sectional and prospective associations between BMI, asthma symptoms and pro-inflammatory proteins.

RESULTS

BMI was associated with asthma symptoms {odds ratio [OR] 1.43 [95% confidence interval (CI): 1.08-1.88] per BMI standard deviation scores [SDS]}. The inclusion of hs-CRP, C3 and C4 in the statistical models did not change this association. C3 was cross-sectionally associated with frequent asthma symptoms [OR per interquartile range of C3: 1.97 (95% CI: 1.20-3.24)] and prospectively with asthma symptoms [OR: 1.48 (95%CI: 1.04-2.09)], independent of BMI SDS.

CONCLUSIONS AND CLINICAL RELEVANCE

We showed no evidence for a role of hs-CRP, C3 and C4 in the association between BMI and asthma symptoms. C3 concentrations were associated with (frequent) asthma symptoms, independent of BMI.

Respiratory health in children, and indoor exposure to (1,3)-β-D-glucan, EPS mould components and endotoxin

For a long time, exposure to mould and dampness-derived microbial components was considered a risk factor for the development of respiratory diseases and symptoms. Some recent studies suggested that early childhood exposure to mould components, such as (1,3)-β-D-glucan and extracellular polysaccharides (EPSs), may protect children from developing allergy. We investigated the association of exposure to (1,3)-β-D-glucan, EPS and endotoxin with asthma and allergies in 6-yr-old children. This investigation was the follow-up to a nested case-control study among three European birth cohorts. Children from two ongoing birth cohort studies performed in Germany (n = 358) and one in the Netherlands (n = 338) were selected. Levels of (1,3)-β-D-glucan, EPS and endotoxin were measured in settled house dust sampled from children's mattresses and living-room floors when the children were, on average, 5 yrs of age. At the age of 6 yrs, health outcome information was available for 678 children. In the two German subsets, domestic EPS and endotoxin exposure from children's mattresses were significantly negatively associated with physician-diagnosed asthma (OR per interquartile range increase 0.60 (95% CI 0.39-0.92) and 0.55 (95% CI 0.31-0.97), respectively). In addition, EPS exposure was inversely related to physician-diagnosed allergic rhinitis (OR 0.50, 95% CI 0.31-0.81). For the Dutch population, no associations were observed between exposure to microbial agents and respiratory health outcomes. We found inverse associations between domestic exposure to EPS and endotoxin from children's mattresses, and doctor-diagnosed asthma and rhinitis in German, but not in Dutch, school children. The reasons for the differences between countries are not clear.

Toll-like receptor 2 and 4 genes influence susceptibility to adverse effects of traffic-related air pollution on childhood asthma

BACKGROUND

Epidemiological studies have reported adverse effects of ambient air pollution on the prevalence of asthma. Laboratory studies have suggested that innate immune responses are involved.

OBJECTIVE

A study was undertaken to determine whether the Toll-like receptor 2 and 4 genes (TLR2 and TLR4) influence the susceptibility to adverse effects of traffic-related air pollution with respect to the prevalence of childhood asthma.

METHODS

Haplotype tagging single nucleotide polymorphisms (SNPs) in the TLR2 (n=4) and TLR4 genes (n=9) were genotyped in 916 children from the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort. Exposure to particulate matter (PM(2.5)), soot and nitrogen dioxide (NO(2)) at the birth address was estimated by land use regression models. Interactions between levels of pollutants and SNPs in relation to annual questionnaire reports of asthma diagnosis and symptoms from birth up to 8 years of age were analysed longitudinally by generalised estimating equations.

RESULTS

Two TLR2 SNPs and four TLR4 SNPs significantly modified the effect of air pollution on the prevalence of doctor-diagnosed asthma from birth up to 8 years of age. The risk of having doctor-diagnosed asthma increased with increasing PM(2.5) levels in children with at least one copy of the TLR2 rs4696480 A allele (OR 2.0 (95% CI 1.2 to 3.1) for an interquartile range increase in exposure). Similar observations were present with the following TLR4 genotypes: rs2770150 TC (OR 2.0 (95% CI 1.1 to 3.6)), rs10759931 GG (OR 2.6 (95% CI 1.4 to 4.9)), rs6478317 GG (OR 2.2 (95% CI 1.2 to 4.3)), rs10759932 CT or CC (OR 2.9 (95% CI 1.2 to 6.9)) and rs1927911 TT (OR 4.4 (95% CI 1.7 to 11.7)).

CONCLUSIONS

Variant alleles of TLR2 and TLR4 genes influence the susceptibility to adverse effects of traffic-related air pollution on childhood asthma.

Asthma and allergic symptoms in relation to house dust endotoxin: Phase Two of the International Study on Asthma and Allergies in Childhood (ISAAC II)

BACKGROUND

Several studies have consistently reported inverse associations between exposure to endotoxin in house dust and atopy. With regard to the association between house dust endotoxin and asthma, the results are inconsistent.

OBJECTIVES

To study the association between house dust endotoxin levels and respiratory symptoms and atopy in populations from largely different countries.

METHODS

Data were collected within the International Study on Asthma and Allergies in Childhood Phase Two, a multi-centre cross-sectional study of 840 children aged 9-12 years from six centres in the five countries of Albania, Italy, New Zealand, Sweden and the United Kingdom. Living room floor dust was collected and analysed for endotoxin. Health end-points and demographics were assessed by standardized questionnaires. Atopy was assessed by measurements of allergen-specific IgE against a panel of inhalant allergens. Associations between house dust endotoxin and health outcomes were analysed by logistic regression. Odds ratios (ORs) were presented for an overall interquartile range increase in exposure.

RESULTS

Many associations between house dust endotoxin in living room floor dust and health outcomes varied between countries. Combined across countries, endotoxin levels were inversely associated with asthma ever [adjusted OR (95% confidence interval (CI)) 0.53 (0.29-0.96) for endotoxin levels per m(2) of living room floor] and current wheeze [adjusted OR (95% CI) 0.77 (0.64-0.93) for endotoxin levels per gram of living room floor dust]. There were inverse associations between endotoxin concentrations and atopy, which were statistically significant in unadjusted analyses, but not after adjustment for gender, parental allergies, cat and house dust mite allergens. No associations were found with dust quantity and between endotoxin exposure and hayfever.

CONCLUSION

These findings suggest an inverse association between endotoxin levels in living room floor dust and asthma in children.

Repeated measurements of mite and pet allergen levels in house dust over a time period of 8 years

BACKGROUND

Studies of the association between indoor allergen exposure and the development of allergic diseases have often measured allergen exposure at one point in time.

OBJECTIVE

We investigated the variability of house dust mite (Der p 1, Der f 1) and cat (Fel d 1) allergen in Dutch homes over a period of 8 years.

METHODS

Data were obtained in the Dutch PIAMA birth cohort study. Dust from the child's mattress, the parents' mattress and the living room floor was collected at four points in time, when the child was 3 months, 4, 6 and 8 years old. Dust samples were analysed for Der p 1, Der f 1 and Fel d 1 by sandwich enzyme immuno assay.

RESULTS

Mite allergen concentrations for the child's mattress, the parents' mattress and the living room floor were moderately correlated between time-points. Agreement was better for cat allergen. For Der p 1 and Der f 1 on the child's mattress, the within-home variance was close to or smaller than the between-home variance in most cases. For Fel d 1, the within-home variance was almost always smaller than the between-home variance. Results were similar for allergen levels expressed per gram of dust and allergen levels expressed per square metre of the sampled surface. Variance ratios were smaller when samples were taken at shorter time intervals than at longer time intervals.

CONCLUSION

Over a period of 4 years, mite and cat allergens measured in house dust are sufficiently stable to use single measurements with confidence in epidemiological studies. The within-home variance was larger when samples were taken 8 years apart so that over such long periods, repetition of sampling is recommended.

Bacteria and mould components in house dust and children's allergic sensitisation

It has been suggested that early childhood exposure to microbial agents decreases the risk of allergies in children. The current authors studied the association between microbial agents in house dust and allergic sensitisation in children aged 2-4 yrs. Nested case-control studies were performed within ongoing birth cohort studies in Germany, the Netherlands and Sweden and approximately 180 sensitised and 180 nonsensitised children were selected per country. Levels of bacterial endotoxin, beta(1,3)-glucans and fungal extracellular polysaccharides (EPS) were measured in dust samples from the children's mattresses and the living-room floors. Combined across countries, higher amounts of mattress dust and higher mattress dust loads of endotoxin, beta(1,3)-glucans and EPS were associated with a significantly decreased risk of sensitisation to inhalant allergens. After mutual adjustment, only the protective effect of the amount of mattress dust remained significant (odds ratio (95% confidence interval) 0.57(0.39-0.84)). Higher amounts of mattress dust may decrease the risk of allergic sensitisation to inhalant allergens. The effect might be partly attributable to endotoxin, beta(1,3)-glucans and extracellular polysaccharides, but could also reflect (additional) protective effects of (microbial) agents other than the ones measured. It is not possible to distinguish with certainty which component relates to the effect, since their levels are highly correlated.

Determinants of house dust endotoxin in three European countries - the AIRALLERG study

The comparison of endotoxin levels between study populations and countries is limited as a result of differences in sampling, extraction, and storage procedures. The objective of this study is to assess the levels and determinants of endotoxin in mattress and living room floor dust samples from three European countries, namely, Germany, the Netherlands, and Sweden, using a standardized sampling, storage, and analysis protocol. The mattress and living room floor dust was collected from the homes of 1065 German, Dutch, and Swedish (pre-)school children. All the samples were collected in the cool season and analyzed for endotoxin in a central laboratory. The determinants were assessed by a standardized questionnaire. The endotoxin concentrations in mattress and living room floor dust were found to be the highest in German homes and lowest in the Swedish ones. Differences between the geometric means were small (factor 1.1-1.7). Most of the associations between endotoxin concentrations and potential determinants were not statistically significant and heterogeneous across countries. However, keeping pets and having more than four persons living in the home were consistently associated with up to 1.7-fold higher endotoxin concentrations in mattress and floor dust. Furthermore, having carpets or rugs, and opening the windows frequently was associated with up to 3.4-fold and 1.3-fold higher endotoxin concentrations in living room floor dust, respectively. The proportion of variance explained by the questionnaire variables was generally low. In conclusion, the data on housing characteristics did not accurately predict the endotoxin concentrations in house dust, and could only partly explain the differences between countries.

PRACTICAL IMPLICATIONS

The differences between the endotoxin concentrations in German, Dutch, and Swedish homes are small. House dust endotoxin concentrations are associated with a number of housing factors, such as pet-ownership, floor cover, number of persons living in the home, and ventilation. The variability of the endotoxin levels between homes and countries can only be partly explained by these factors.

Respiratory health and individual estimated exposure to traffic-related air pollutants in a cohort of young children

OBJECTIVES

To estimate long-term exposure to traffic-related air pollutants on an individual basis and to assess adverse health effects using a combination of air pollution measurement data, data from geographical information systems (GIS) and questionnaire data.

METHODS

40 measurement sites in the city of Munich, Germany were selected at which to collect particulate matter with a 50% cut-off aerodynamic diameter of 2.5 microm (PM2.5) and to measure PM2.5 absorbance and nitrogen dioxide (NO2). A pool of GIS variables (information about street length, household and population density and land use) was collected for the Munich metropolitan area and was used in multiple linear regression models to predict traffic-related air pollutants. These models were also applied to the birth addresses of two birth cohorts (German Infant Nutritional Intervention Study (GINI) and Influence of Life-style factors on the development of the Immune System and Allergies in East and West Germany (LISA)) in the Munich metropolitan area. Associations between air pollution concentrations at birth address and 1-year and 2-year incidences of respiratory symptoms were analysed.

RESULTS

The following means for the estimated exposures to PM2.5, PM2.5 absorbance and NO2 were obtained: 12.8 microg/m3, 1.7x10(-5) m(-1) and 35.3 mug/m3, respectively. Adjusted odds ratios (ORs) for wheezing, cough without infection, dry cough at night, bronchial asthma, bronchitis and respiratory infections indicated positive associations with traffic-related air pollutants. After controlling for individual confounders, significant associations were found between the pollutant PM2.5 and sneezing, runny/stuffed nose during the first year of life (OR 1.16, 95% confidence interval 1.01 to 1.34) Similar effects were observed for the second year of life. These findings are similar to those from our previous analysis that were restricted to a subcohort in Munich city. The extended study also showed significant effects for sneezing, running/stuffed nose. Additionally, significant associations were found between NO2 and dry cough at night (or bronchitis) during the first year of life. The variable "living close to major roads" (<50 m), which was not analysed for the previous inner city cohort with birth addresses in the city of Munich, turned out to increase the risk of wheezing and asthmatic/spastic/obstructive bronchitis.

CONCLUSIONS

Effects on asthma and hay fever are subject to confirmation at older ages, when these outcomes can be more validly assessed.

Comparison of parental reports of smoking and residential air nicotine concentrations in children

BACKGROUND

Using questionnaires to assess children's residential exposure to environmental tobacco smoke (ETS) may result in misclassification from recall and response bias. Questionnaire data have frequently been validated against urinary cotinine measurements, but rarely against actual measurements of residential air nicotine.

OBJECTIVE

To compare questionnaire reported smoking with air nicotine concentrations in a large population of children and with urinary cotinine levels in a subpopulation; and to assess the potential impact of the symptom status of the children on the agreement between different measures of exposure.

METHODS

The authors assessed residential exposure to ETS in 347 German, 335 Dutch, and 354 Swedish preschool and schoolchildren by questionnaire and air nicotine measurements, and in a subset of 307 German children by urinary cotinine measurements. They then compared the different measures of ETS exposure.

RESULTS

In all countries, air nicotine concentrations increased with increasing questionnaire reported smoking in a dose-response fashion. Specificity and negative predictive values of questionnaire reports for nicotine concentrations were excellent. Sensitivity and positive predictive values were moderate to good. Excluding occasional smokers, the overall percentage of homes misclassified was 6.9%, 6.7%, and 5.1% in Germany, the Netherlands, and Sweden, respectively. Similar results were found for the agreement of urinary cotinine concentrations with questionnaire reports and air nicotine levels. There was no indication of underreporting by parents of symptomatic children.

CONCLUSION

Despite some misclassification, questionnaire reports are an inexpensive and valid estimate of residential ETS exposure among preschool and school children.

Parental education and children's respiratory and allergic symptoms in the Pollution and the Young (PATY) study

Inequalities in health between socio-economic groups are a major public health concern. The current authors studied associations between parental socio-economic status (SES) and children's respiratory and allergic symptoms in 13 diverse countries, including the Russian Federation, North America (Canada and the USA), and countries across Eastern and Western Europe. Data of 57,000 children aged 6-12 yrs, originating from eight cross-sectional studies, were analysed. SES was defined by parental education. Respiratory and allergic symptoms were defined by parental questionnaire reports. Multiple logistic regressions showed that low parental education was associated with a decreased risk of inhalant allergy and itchy rash in school children. Furthermore, low parental education was associated with an increased prevalence of wheeze and nocturnal dry cough. No clear association was found between parental education and prevalence of doctor-diagnosed asthma and bronchitis. Part of the difference between socio-economic groups with regard to their children's symptoms was explained by established risk factors, such as parental allergy, smoking during pregnancy, pet ownership, crowding, mould/moisture in the home, use of gas for cooking, and air pollution (particulate matter with a diameter of <10 microm). However, differences remained after adjusting for these variables. Children's health was associated with parental education. The association could not fully be explained by established risk factors.

Exposure to traffic related air pollutants: self reported traffic intensity versus GIS modelled exposure

BACKGROUND

In epidemiological studies of the potential health effects of traffic related air pollution, self reported traffic intensity is a commonly used, but rarely validated, exposure variable.

METHODS

As part of a study on the impact of Traffic Related Air Pollution on Childhood Asthma (TRAPCA), data from 2633 and 673 infants from the Dutch and the German-Munich cohorts, respectively, were available. Parents subjectively assessed traffic intensity at the home address. Objective exposures were estimated by a combination of spatial air pollution measurements and geographic information system (GIS) based modelling using an identical method for both cohorts.

RESULTS

The agreement rates between self reported and GIS modelled exposure--accumulated over the three strata of self assessed traffic intensity--were 55-58% for PM(2.5), filter absorbance (PM(2.5) abs), and nitrogen dioxide in Munich and 39-40% in the Netherlands. Of the self reported low traffic exposed group, 71-73% in Munich and 45-47% in the Netherlands had low modelled exposure to these three air pollutants. Of the self assessed high exposed subgroups in Munich (15% of the total population) and the Netherlands (22% of the total population), only 22-33% and 30-32% respectively had high modelled exposure to the three air pollutants. The subjective assessments tend to overestimate the modelled estimates for PM(2.5) and NO2 in both study areas. When analysis was restricted to the portion of the Dutch cohort living in non-urban areas, the agreement rates were even lower.

CONCLUSIONS

Self reported and modelled assessment of exposure to air pollutants are only weakly associated.

Are house dust mite allergen levels influenced by cold winter weather?

BACKGROUND

Moisture is vitally important for house dust mites and they cannot survive in cold or hot-dry climates.

AIMS OF THE STUDY

To investigate the influence of two extraordinarily cold and dry winters in 1995/1996 and 1996/1997 on house dust mite levels in German homes.

METHODS

Dust samples were collected between June 1995 and December 2001 on the mattresses of 655 adults and 454 schoolchildren living in five different areas of Germany. We compared house dust mite allergen Dermatophagoides pteronyssinus (Der p 1) levels before and during the winters of 1995/1996 and 1996/1997 with levels after these winters.

RESULTS

D. pteronyssinus (Der p 1) levels in samples taken after the cold winters of 1995/1996 and 1996/1997 were approximately two times lower than Der p 1 levels in dust samples collected before or during these respective winters (Geometric means: Erfurt 89 vs 33 ng/g; Hamburg 333 vs 219 ng/g; Bitterfeld, Hettstedt, and Zerbst 296 vs 180 ng/g). Except for Hamburg, the decrease in Der p 1 levels was statistically significant. D. pteronyssinus levels measured in dust samples collected in 2001 (i.e. 3 years after the two cold winters) show a statistically non-significant increase (Geometric means: Erfurt 33 vs 39 ng/g; Hamburg 219 vs 317 ng/g), suggesting that it may take a long time for mite allergen levels to increase again after a sudden decrease.

CONCLUSION

We conclude that Der p 1 levels in German mattress dust samples have been approximately reduced by a factor of three to four by the two consecutive cold winters of 1995/1996 and 1996/1997.

Exposure to house dust endotoxin and allergic sensitization in adults

BACKGROUND

It has been suggested that exposure to elevated levels of endotoxin decreases the risk of allergic sensitization.

OBJECTIVE

To examine the associations between current exposure to bacterial endotoxin in house dust and allergic sensitization in adults.

METHODS

In 1995-1996, we conducted a nested case-control study following a cross-sectional study performed within the European Community Respiratory Health Survey (ECRHS). Data of 350 adults aged 25-50 years was analysed. Allergic sensitization was assessed by measurement of specific immunoglobulin E (IgE) against several inhalant allergens. Living room floor dust samples were taken. The endotoxin content was quantified using a chromogenic kinetic Limulus amoebocyte lysate test.

RESULTS

Multiple logistic regression analysis showed a negative association between exposure to house dust endotoxin and severe allergic sensitization. Odds ratios (95% CI) adjusted for place of residence, gender, age, and 'caseness' were 0.80 (0.64-1.00) for sensitization to >/=1 allergen and 0.72 (0.56, 0.92) for sensitization to >/=2 allergens using 3.5 kU/l as a cut-off value for sensitization. With regard to single allergens, the protective effect of endotoxin was strongest for pollen sensitization [aOR (95% CI) = 0.74 (0.58, 0.93)].

CONCLUSION

Our results indicate that current exposure to higher levels of house dust endotoxin might be associated with a decreased odds of allergic sensitization in adults.

Levels and predictors of endotoxin in mattress dust samples from East and West German homes

East-West differences in prevalence of asthma and allergies were suggested to be associated with lifestyle factors. To describe endotoxin levels in mattress dust samples from East and West German homes collected approximately 10 years after reunification. To identify factors that may account for an East-West difference. Dust was collected from mattresses of 2157 infants and 2108 mothers living in Leipzig (former East Germany) and Munich (West Germany). Endotoxin was measured using a chromogenic kinetic Limulus amoebocyte lysate test. Data on bedding, dwelling, and housing characteristics, and occupants' behavior were collected using a self-administered questionnaire. Endotoxin levels were significantly higher in Leipzig compared with Munich for the infants' mattresses but not for the mothers' mattresses. Apart from this, predictors for the mothers' and the infants' mattresses were very similar. Pet-ownership and contact with animals outside the home were most influential. Endotoxin levels in mattress dust were highest in summer and increased with the number of persons living in the household. The overall percentage of variability in endotoxin levels explained by these factors was low. Endotoxin levels were associated with lifestyle factors discussed within the framework of the hygiene hypothesis. None of these factors explains the difference in infant's mattress dust endotoxin between Leipzig and Munich or could be used as a surrogate for endotoxin.

PRACTICAL IMPLICATIONS

Endotoxin levels in mattress dust are associated with a number of factors discussed in the framework of the hygiene hypothesis; among other things they are associated with pet-ownership, contact with pets and number of persons living in the home. However, none of these factors and not even a combination of factors explains the variability of endotoxin levels between homes.

The influence of air conditioning, humidity, temperature and other household characteristics on mite allergen concentrations in the northeastern United States

BACKGROUND

Information about the influence of housing and occupant characteristics on mite allergen concentrations is crucial to determine which methods could be used to decrease exposure of susceptible subjects.

OBJECTIVES

To identify housing and occupant characteristics that are associated with mite allergen concentrations in house dust collected from living rooms and mattresses.

METHODS

We collected dust samples from 750 homes in the northeastern US. The influence of various characteristics on concentrations of mite allergens (Der p 1 and Der f 1) was studied using multiple linear regression analysis.

RESULTS

Some characteristics, like absence of air conditioners, the presence of mold or mildew, and a lower temperature were consistently associated with higher concentrations of both mite allergens in dust from all sampling locations. However, none of these factors changed Der p 1 or Der f 1 concentrations by more than a factor of 2. People of white ethnic background had roughly two times higher mite allergen concentrations, while family income, family size, and education level only marginally influenced mite allergen concentrations.

CONCLUSIONS

Various housing characteristics have some influence on mite allergen concentrations, and could possibly be used to decrease exposure of susceptible subjects. However, only a limited percentage of the variation in mite allergen concentrations was explained by these characteristics.

The effect of storage on allergen and microbial agent levels in frozen house dust

BACKGROUND

House dust samples collected for exposure studies are often stored for variable time periods until analysis. However, there is currently no information on the effects of dust storage on the content of biocontaminants. Therefore, associations were analysed between the levels of mite allergens (Der p 1, Der f 1), cat allergen (Fel d 1) and microbial components (endotoxin, beta(1-->3)-glucan) on the one hand and the storage duration of dust samples at -20 degrees C on the other hand.

METHODS

Within the framework of a study on the influences of INdoor factors and Genetics on Asthma (INGA), dust samples were collected from living room floors between June 1995 and August 1998 and extracted according to a standardized protocol. The concentrations of Der p 1, Der f 1, Fel d 1 and beta(1-->3)-glucan were determined with specific enzyme immunoassays. Endotoxin content was quantified using a chromogenic kinetic Limulus amoebocyte lysate (LAL) test. All concentrations were expressed per gram of dust

RESULTS

Dust samples (n = 1236) were obtained from 655 homes in Hamburg, Hettstedt, Zerbst and Bitterfeld. Storage duration (range 8-298 days) was grouped into four categories (<or= 60 d; 61-90 d; 91-120 d; > 120 d). After adjustment for city of residence and season of dust sampling, means ratios comparing categories 2-4 to the first category were not statistically significant for Der p 1, Der f 1, endotoxin and beta(1-->3 glucan). However, Fel d 1 concentrations significantly declined with increased storage times of dust samples.

CONCLUSIONS

Storage of house dust at -20 degrees C for up to 10 months has no effect on mite allergen, endotoxin and beta(1-->3)-glucan levels. A potential loss of Fel d 1 during storage of frozen dust samples needs further investigations by repeated measurements of allergen in identical dust samples.

Predictors of cat allergen (Fel d 1) in house dust of German homes with/without cats

BACKGROUND

Exposure to cat allergen is a major risk factor for sensitization and the development of asthma in many parts of the world. The study was designed to examine the levels of cat allergen (Fel d 1) in homes of two German cities and to detennine predictors of Fel d 1 exposure.

METHODS

We collected dust samples from 405 randomly selected homes in Hamburg (n = 201) and Erfurt (n = 204). In each apartment dust samples were taken from living room floor (LR), bedroom floor (BR), and mattress surface (MA) using vacuum sampling and analyzed by two-site monoclonal antibody ELISA. Environmental variables were assessed by questionnaire to obtain information on factors supposed to have an impact on the Fel d 1 levels in house dust. The effects of possible predictors of Fel d 1 were assessed by multiple linear regression models.

RESULTS

Fel d 1 was present in 98% of the homes (395/405), ranging from 0.015 to 7.278 microg/g dust (GM 0.486 microg/g). The levels were similar in floors (GM for LR 0.575 microg/g and BR 0.469 microg/g) and in MA (GM 0.424 microg/g). Higher allergen concentrations (> 2 microg/g) were detected in 99% of the homes keeping cats, in 55% of homes that had had a cat during the last year, and in 28% of the homes without a cat. Fel d 1 levels were significantly higher in homes with a cat (628-682-fold, MA, floor) and in homes in which a cat had previously lived (11-12-fold, floor, MA) than in homes that never had a cat. Furthermore, after controlling for possible other confounders, Fel d 1 levels were significantly higher in summer and in homes with low frequency of cleaning and low ventilation rate.

CONCLUSION

It could be confirmed that keeping a cat has the highest impact on Fel d 1 concentration. Besides, a continuous influx of Fel d 1 in homes without cat, as a result of direct or indirect cat contact outside the home, is likely. High frequencies of dusting and ventilation might reduce cat allergens in homes with and without cats.

Traffic-related air pollution and respiratory health during the first 2 yrs of life

As part of an international collaborative study on the impact of Traffic-Related Air Pollution on Childhood Asthma (TRAPCA), the health effects associated with long-term exposure to particles with a 50% cut-off aerodynamic diameter of 2.5 microm (PM2.5), PM2.5 absorbance, and nitrogen dioxide (NO2) were analysed. The German part of the TRAPCA study used data from subpopulations of two ongoing birth cohort studies (German Infant Nutrition Intervention Programme (GINI) and Influences of Lifestyle Related Factors on the Human Immune System and Development of Allergies in Children (LISA)) based in the city of Munich. Geographic information systems (GIS)-based exposure modelling was used to estimate traffic-related air pollutants at the birth addresses of 1,756 infants. Logistic regression was used to analyse possible health effects and potential confounding factors were adjusted for. The ranges in estimated exposures to PM2.5, PM2.5 absorbance, and NO2 were 11.9-21.9 microg m(-3), 1.38-4.39 x 10(-5) m(-1), and 19.5-66.9 microg x m3, respectively. Significant associations between these pollutants and cough without infection (odds ratio (OR) (95% confidence interval (CI)): 1.34 (1.11-1.61), 1.32 (1.10-1.59), and 1.40 (1.12-1.75), respectively) and dry cough at night (OR (95% CI): 1.31 (1.07-1.60), 1.27 (1.04-1.55), and 1.36 (1.07-1.74), respectively) in the first year of life were found. In the second year of life, these effects were attenuated. There was some indication of an association between traffic-related air pollution and symptoms of cough. Due to the very young age of the infants, it was too early to draw definitive conclusions from this for the development of asthma.

Predictors of high endotoxin concentrations in the settled dust of German homes

Endotoxin concentrations in settled house dust were measured within the collaborative study named INGA (Indoor Exposure and Genetics in Asthma) together with other asthma-related indoor factors in 405 randomly selected homes in two German cities. Endotoxin was assayed using the quantitative kinetic chromogenic Limulus Amebocyte Lysate (LAL) method. The mean concentration of 2,274 ng endotoxin/g dust in living rooms is about two orders of magnitude below mean occupational exposure (e.g. agriculture). Endotoxin concentrations are higher in old buildings (means ratio = (MR) 1.52, 95% C.I.: 1.14; 2.04), and in the lower storey of the dwelling (MR = 1.30, 95% C.I.: 1.04; 1.62). Furthermore, higher endotoxin concentrations are associated with longer occupancy in the apartment (MR = 1.63, 95% C.I.: 1.21; 2.18), high utilisation of the apartment during the sampling period (MR = 2.52, 95% C.I.: 1.42; 4.47), infrequent vacuum cleaning of the carpets (MR = 1.67; 95% C.I.: 1.10; 2.54), an indifferent attitude to ventilation (MR = 1.37; 95% C.I.: 1.03; 1.82), keeping cats (MR = 1.91; 95% C.I.: 1.43; 2.55) and dogs (1.57; 95% C.I.: 1.08; 2.30), as well as the occurrence of mice (MR = 1.39; 95% C.I.: 1.00; 1.93). The season and indoor climate (operative temperature and relative humidity) did not effect endotoxin concentration. These results indicate that high endotoxin concentration in settled dust is an indicator of poor hygienic conditions in homes.

Maternal compliance with nutritional recommendations in an allergy preventive programme

AIMS

To assess maternal compliance with nutritional recommendations in an allergy preventive programme, and identify factors influencing compliance behaviour.

METHODS

Randomised double-blind intervention study on the effect of infant formulas with reduced allergenicity in healthy, term newborns at risk of atopy. Maternal compliance with dietary recommendations concerning milk and solid food feeding was categorised.

RESULTS

A total of 2252 newborns were randomised to one of four study formulas. The drop out rate during the first year of life was 13.5% (n = 304). The rates of high, medium, and low compliance to milk feeding during weeks 1-16 were 83.4%, 4.0%, and 7.5%; the corresponding rates to solid food feeding during weeks 1-24 were 60.0%, 12.1%, and 22.9%. In 5.1% of subjects no nutritional information was available. Low compliance was more frequent among non-German parents, parents with a low level of education, young mothers, smoking mothers, and those who weaned their infant before the age of 2 months.

CONCLUSIONS

Evaluation of allergy preventive programmes should take into account non-compliance for assessing the preventive effectiveness on study outcome.

Pets and vermin are associated with high endotoxin levels in house dust

BACKGROUND

Previous studies have shown that the risk for allergic sensitization is lower in children who grew up on farms and in young adults who were exposed to dogs in early childhood. A higher microbial exposure in general and in particular to endotoxin in early childhood might contribute to this lower risk of atopy.

OBJECTIVE

We examined whether the presence of pets or vermin in the home is associated with higher endotoxin concentrations in settled house dust.

METHODS

House dust was sampled in a standardized manner on the living room floors of 454 homes of German children aged 5-10 years (participation rate 61%). Endotoxin was assessed with a quantitative kinetic chromogenic Limulus Amebocyte Lysate (LAL) method. Associations between endotoxin levels, pets and vermin are presented as ratios of the crude and confounder adjusted geometric means (means ratios) in the category of study vs. a reference category using multiple linear regression models.

RESULTS

Endotoxin concentrations in living room floor dust sampled in homes without pets and vermin were lower (1246 ng per square meter, 1519 ng endotoxin/g dust, n = 157) than those sampled in homes with pets or vermin (2267 ng per square meter, 2200 ng endotoxin/g dust, n = 296). After adjustment for city of residence, season of dust sampling, age of the building and story of the dwelling, means ratios for endotoxin expressed per gram of dust were statistically significantly increased for dog (1.64, 95% CI 1.09-2.46), for cat (1.50, 95% CI 1.03-2.18) and for cockroach (3.01, 95% CI 1.37-6.60), whereas no major statistically significant associations were found for other pets, ants and mice.

CONCLUSION

Keeping a dog or a cat in the home is consistent with higher exposure to endotoxin and might therefore contribute to the lower risk of atopy in later life.

Exposure to endotoxin decreases the risk of atopic eczema in infancy: a cohort study

BACKGROUND

Previous studies have shown a protective effect of early exposure to cats and dogs on the development of atopic eczema, asthma, allergic rhinitis, and atopic sensitization in later life. In particular, a higher microbial exposure to endotoxin in early childhood might contribute to this effect.

OBJECTIVE

We examined the associations between bacterial endotoxin in house dust and atopic eczema, infections, and wheezing during the first year of life in an ongoing birth cohort study (LISA).

METHODS

Data of 1884 term and normal-weight neonates with complete information on exposure to biocontaminants and confounding variables were analyzed. House dust from the mothers' and the children's mattresses was sampled 3 months after birth. Endotoxin content was quantified by using a chromogenic kinetic limulus amoebocyte lysate test.

RESULTS

During the first 6 months of life, the risk of atopic eczema was significantly decreased by endotoxin exposure in dust from mothers' mattresses in the fifth quintile (odds ratio [OR], 0.50; 95% CI, 0.28-0.88), whereas the risk was increased for respiratory infections (OR, 1.69; 95% CI, 1.25-2.28) and cough with respiratory infection, bronchitis, or both (OR, 1.73; 95% CI, 1.28-2.33). The risk of wheezing was also significantly increased during the first 6 months of life (OR, 2.37; 95% CI, 1.40-4.03). For the entire first year of life, these associations attenuated, except for the risk of wheezing, which remained significant (OR, 1.60; 95% CI, 1.10-2.30).

CONCLUSION

Our findings support the hygiene hypothesis that exposure to high concentrations of endotoxin very early in life might protect against the development of atopic eczema within the first 6 months of life, along with an increased prevalence of nonspecific respiratory diseases.

Molecular characterization of a phosphatidylcholine-hydrolyzing phospholipase C

While searching for a phospholipase C (PLC) specific for phosphatidylcholine in mammalian tissues, we came across such an activity originating from a contamination of Pseudomonas fluorescens. This psychrophilic bacterium was found to contaminate placental extracts upon processing in the cold. The secreted phosphatidylcholine-hydrolyzing PLC was purified by a combination of chromatographic procedures. As substrates, the enzyme preferred dipalmitoyl-phosphatidylcholine and 1-palmitoyl-2-arachidonoyl-phosphatidylcholine over phosphatidylinositol. The active enzyme is a monomer of approximately 40 kDa. As for other bacterial PLCs, the enzyme requires Ca2+ and Zn2+ for activity; dithiothreitol affected the activity due to its chelation of Zn2+, but this inhibition could be compensated for by addition of ZnCl2. The compound D609, described to selectively inhibit phosphatidylcholine-specific PLCs, caused half-inhibition of the P. fluorescens enzyme at approximately 420 microM, while 50-fold lower concentrations similarly affected PLCs from Bacillus cereus and Clostridium perfringens. Partial peptide sequences obtained from the pure P. fluorescens enzyme after tryptic cleavage were used to clone a DNA fragment of 3.5 kb from a P. fluorescens gene library prepared from our laboratory isolate. It contains an ORF of 1155 nucleotides encoding the PLC. There is no significant sequence homology to other PLCs, suggesting that the P. fluorescens enzyme represents a distinct subclass of bacterial PLCs. The protein lacks cysteine residues and consequently contains no disulfide bonds. Interestingly, P. fluorescens reference strain DSMZ 50090 is devoid of the PLC activity described here as well as of the relevant coding sequence.

Respiratory symptoms in relation to indoor exposure to mite and cat allergens and endotoxins. Indoor Factors and Genetics in Asthma (INGA) Study Group

The authors investigated the relationship between respiratory symptoms in adults and exposure to mite and cat allergens, the role of endotoxins in house dust, the effects of mixtures of several allergens, and interactions between allergen exposure and allergic sensitization. Within a nested case-control study, 405 subjects aged 25-50 yrs from two German cities answered a standardized questionnaire. Allergen-specific immunoglobulin-E was measured. Dust samples were taken from the subjects' homes to determine exposure to mite (Dermatophagoides pteronyssinus antigen 1 Der p 1) and (D. farinae antigen 1 Der f l) and cat (cat antigen d1 Fel d 1) allergen and endotoxin content in settled house dust. Exposure to Der f 1 and Der p 1 plus Der f 1 >10 microg x g(-1) of mattress dust, respectively, increased the risk of wheeze and breathlessness (odds ratios (OR): 4.04, 95% confidence interval (CI): 1.53-10.64, OR: 2.78, 95% CI: 1.06-7.28). Fel d 1 >8 microg x g(-1) was positively associated with cough at night (OR: 2.74, 95%, CI: 1.22-.17), noteworthy also in the nonsensitized subjects. Subjects exposed to elevated concentrations of more than one allergen had an up to seven-fold increase in the risk of respiratory symptoms, compared to nonexposed subjects. Sensitized subjects exposed to elevated concentrations of Der f 1 or Fel d 1 were found to have the highest risk of asthma attacks and respiratory symptoms. No statistically significant association was found between exposure to endotoxins and respiratory health. Indoor exposure to Dermatophagoides farinae antigen 1 and cat antigen d1 is a risk factor for respiratory symptoms in adults, and for cat antigen d 1 even in nonsensitized subjects. The risk is increased if subjects are exposed to a mixture of allergens or if they are sensitized in addition to high exposure.

The impact of draught related to air velocity, air temperature and workload

This experimental study was designed to test the hypotheses that the effects of draught increase with higher air velocity, with lower air temperature, and with lower workload. Thirty healthy young males were exposed to horizontal draught during 55 min while they operated an arm ergometer in a standing posture. Air velocity, air temperature, and workload were varied in 3 steps each, between 11 and 23 degrees C, 0.1 and 0.3 m/s, and 104 to 156 W/m2, respectively. The 27 combinations were distributed over subjects in a fractional factorial 3(3)-design. The participants were clothed for thermal neutrality. Workload was measured at the end of the sessions by respirometry. Draught-induced annoyance was determined every 5 min, separately for 10 body sites. Corresponding skin temperature was also recorded. The hypotheses were verified for the influence of air velocity and air temperature. Regarding workload, local heat production is probably decisive, meaning that draft-induced local annoyance is inversely related to workload in active but independent from workload in non-active body areas. To improve the situation for the workers concerned it is suggested to apply protective gloves that cover an as great area of the forearms as possible and to limit airflows to mean velocities of less than 0.2 m/s (with turbulence intensities of 50%).

Prospective cohort studies using hydrolysed formulas for allergy prevention in atopy-prone newborns: a systematic review

The aim of this study is to give a systematic overview on publications having investigated the allergy preventive effect of extensively and/or partially hydrolysed infant formulas. Publications were searched by several strategies. Inclusion criteria were: prospective cohort study, randomisation, family history of atopy of the subjects, follow-up for at least the 1st year of life. Studies were described systematically as to methods, study participants, interventions and co-interventions, and study outcomes. The methodological quality was judged according to an instrument assessing the reduction of bias (score between 0 and 7 points). Data of studies having examined partial hydrolysates are presented as odds ratios. Of 16 studies found, 10 fulfilled the inclusion criteria. Study designs showed considerable differences as to methods, intervention and co-intervention procedures and definition of outcomes. Methodological quality varied between 0 and 6 points. The comparison of exclusively test- and control formula-fed groups showed a uniform tendency towards allergy protection in studies with partial hydrolysates. Study results on the effect of extensive hydrolysates were not comparable because of major differences in study designs.

CONCLUSION

More well-designed studies with an adequate statistical power are needed to compare the allergy preventive effect of partially and extensively hydrolysed formulas with a standard infant formula.

Transcriptional activation by the human Hsp70-associating protein Hap50

We investigated human Hap50, the large isoform of the previously characterized Hsp70/Hsc70-associating protein Hap46, also called BAG-1, for effects on transcriptional activities. Overproduction by transient transfection led to enhanced expression of reporter gene constructs in various cell types using different promoters, suggesting independence of promoter type. Similarly, overexpression of Hap50 resulted in increased levels of poly(A)(+)mRNAs in HeLa, COS-7, 3T3 and HTC cells. Concomitantly, the expression of some selected endogenous genes, such as those coding for c-Jun and the glucocorticoid receptor, was enhanced significantly relative to actin. Nuclear runoff transcription assays using HeLa cells showed that the effect is caused by increased transcription rates rather than mRNA stabilization. Activation of transcription by Hap50 occurred at 37 degrees C and did not require prior thermal stress, as is the case for Hap46. In accordance with these biological effects, Hap50 is localized exclusively in the nuclear compartment of different cell types, whereas Hap46 is mostly cytoplasmic in unstressed cells, as revealed by use of fusion constructs with green fluorescent protein. High cellular levels of Hap50 were found to make cells less susceptible to adverse environmental effects such as heat stress. Our data suggest that Hap50 is a nuclear protein that acts in cells to increase the transcription of various genes.