Residential outdoor air pollution and allergen sensitization in schoolchildren in Oslo, Norway

BACKGROUND: Epidemiological studies that have investigated the association between air pollution and atopy have found inconsistent results. Furthermore, often exposure to outdoor air pollution has had limited quality, and more individual exposure is needed. OBJECTIVE: To investigate the relations between early and lifetime exposure to residential outdoor air pollution and allergen sensitization in 9-10-year-old children in Oslo, Norway. METHODS: Sensitization to common allergens was measured by skin prick tests (SPTs), which were performed in 2244 children who had lived in Oslo since birth. Several definitions of positive SPT were used. Information on potential confounding variables was collected by a parental questionnaire. Exposure to outdoor air pollution was assessed by the EPISODE dispersion model, which calculates hourly concentrations of nitrogen dioxide (NO2), particulate matter (PM) with aerodynamic diameter <10 microm (PM10) and <2.5 microm (PM2.5), respectively. RESULTS: We found no associations between long-term air pollution exposure and sensitization to any allergen, any indoor or any pollen allergen. However, lifetime air pollution exposure was associated with sensitization to the house dust mite Dermatophagoides farinae. One interquartile increase of lifetime exposure to NO2, PM10 and PM2.5 was associated with 1.88 (adjusted odds ratio) (1.02, 3.47) [95% confidence interval (CI)], 1.61 (0.96, 2.72) and 1.46 (0.96, 2.22), respectively, for D. farinae. Lifetime exposure was also associated with sensitization to cat in a subpopulation. Both associations diminished after adjusting for a contextual socio-economic factor. CONCLUSION: Long-term exposure to traffic-related pollutants was generally not associated with allergen sensitization in 9-10-year-old Oslo children. However, lifetime exposure was associated with sensitization to D. farinae, and with sensitization to cat in a subpopulation, which may be explained by socio-economic confounding or multiple comparisons. The air pollution levels in Oslo may be too low to reveal associations with sensitization.     

Prevalence of food allergy and its relationship to asthma and allergic rhinitis in schoolchildren

BACKGROUND: Food allergy (FA) is an important health problem. However, epidemiological studies at the population level are scarce. We assessed the prevalence of FA and its associations with respiratory manifestations among schoolchildren. METHODS: A total of 6672 schoolchildren aged 9-11 years recruited from 108 randomly chosen schools in six French cities underwent a clinical examination including skin prick test (SPT) to common food and aeroallergens and the standardized protocol of the run test to assess exercise-induced bronchial hyper-responsiveness (EIB). Asthma, allergic rhinitis (AR) and clinical symptoms of FA were determined using a standardized questionnaire completed by parents. RESULTS: About 2.1% of the children reported symptoms of FA, 1.9% were sensitized to food allergens, and 0.1% had SP-tested FA. The AR was more prevalent than asthma (20.0% lifetime, 11.9% past year vs 9.8%, 8.7% respectively). Reported FA, food sensitization and SP-tested FA were all positively associated with asthma and AR (P < 0.001). These associations persisted also for FA not manifesting as respiratory symptoms (P < 0.001). Asthma and AR remained significantly associated with reported symptoms of FA and allergic sensitization to food allergens after adjustment for confounders as well as for sensitization to aeroallergens. No relationship existed between EIB (9.0%) and FA. CONCLUSION: The relationships between FA and asthma and AR could be totally explained neither by the existence of respiratory manifestations of FA nor by sensitization to aeroallergens. The FA might intervene differently in asthma and AR.     

Interactions Between Innate Immunity Genes and Early-Life Risk Factors in Allergic Rhinitis

Purpose

Allergic rhinitis (AR) is a common chronic disease. Many factors could affect the development of AR. We investigated early-life factors, such as delivery mode, feeding method, and use of antibiotics during infancy, which could affect the development of AR. In addition, how interactions between these factors and innate gene polymorphisms influence the development of AR was investigated.

Methods

A cross-sectional study of 1,828 children aged 9-12 years was conducted. Three early-life factors and AR were assessed by a questionnaire. Skin prick tests were done. Polymorphisms of TLR4 (rs1927911) and CD14 (rs2569190) were genotyped.

Results

Use of antibiotics during infancy increased the risk of AR (aOR [95% CI] 1.511 [1.222-2.037]) and atopic AR (aOR [95% CI], 1.565 [1.078-2.272]). There were synergistic interactions between caesarean delivery, formula feeding, and use of antibiotics in the rate of atopic AR (aOR [95% CI], 3.038 [1.256-7.347]). Additional analyses revealed that the risk for the development of AR or atopic AR subjects with the TLR4 CC genotype were highest when all the 3 early-life factors were present (aOR [95% CI], 5.127 [1.265-20.780] for AR; 6.078 [1.499-24.649] for atopic AR). In addition, the risk for the development of AR or atopic AR in subjects with the CD14 TT genotype were highest when all the 3 early-life factors were present (aOR [95% CI], 5.960 [1.421-15.002] for AR; 6.714 [1.440-31.312] for atopic AR).

Conclusions

Delivery mode, feeding method, and use of antibiotics during infancy appeared to have synergistic interactions in the development of AR. Gene-environment interactions between polymorphism of innate genes and early- life risk factors might affect the development of AR.     

Skin prick test can identify eczematous infants at risk of asthma and allergic rhinitis

BACKGROUND: Assessment of allergic sensitization is not routinely performed in infants and young children with eczema. OBJECTIVE: To determine whether infants who have atopic eczema (with sensitization) are at a greater risk of developing asthma and allergic rhinitis (AR) than those with non-atopic eczema (without concurrent sensitization). METHODS: The presence of eczema was prospectively documented until 2 years of age in a birth cohort of 620 infants with a family history of atopic disease. Sensitization status was determined by skin prick tests (SPTs) at 6, 12, and 24 months using six common allergens. Interviews were conducted at 6 and 7 years to determine the presence of asthma and AR. RESULTS: Within the first 2 years of life, 28.7% of the 443 children who could be classified had atopic eczema: 20.5% had non-atopic eczema, 19.0% were asymptomatic but sensitized and 31.8% were asymptomatic and not sensitized. When compared with children with non-atopic eczema in the first 2 years of life, children with atopic eczema had a substantially greater risk of asthma [odds ratio (OR)=3.52, 95% confidence interval=1.88-6.59] and AR (OR=2.91, 1.48-5.71). The increased risk of asthma was even greater if the infant had a large SPT (OR=4.61, 2.34-9.09) indicative of food allergy. There was no strong evidence that children with non-atopic eczema had an increased risk of asthma or AR compared with asymptomatic children. CONCLUSION: In children with eczema within the first 2 years of life, SPT can provide valuable information on the risk of childhood asthma and AR.     

Atopic disease and its determinants – a focus on the potential role of childhood infection

BACKGROUND: Atopic diseases develop on a genetic background and are modulated by environmental factors among which some infectious diseases are thought to have a protective influence. OBJECTIVE: The aim of this study was to determine the influence of infectious diseases in younger ages, bacterial and viral, on atopic diseases and sensitization to aero- and food-allergens in adults. METHODS: A population-based sample of 4262 subjects aged 25-74 years were interviewed concerning their history of infectious disease within the first 18 years of life. Information about allergic disease, including atopic eczema, allergic rhinitis (AR), and asthma was obtained. A blood sample was drawn and analysed for allergen-specific IgE antibodies against food- and aero-allergens. RESULTS: Multiple logistic regression analyses identified viral infection to be associated with AR (adjusted odds ratio (OR) = 1.39; 95% confidence interval (95% CI): 1.13-1.72) and sensitization to aeroallergens (OR = 1.21; 95% CI: 1.05-1.41). Bacterial disease was a negative predictor for atopy development in the subgroup of patients sensitized to nutritional allergens with concomitant atopic eczema (OR = 0.34; 95% CI: 0.11-0.99), AR (OR = 0.67; 95% CI: 0.42-1.07), or asthma (OR = 0.41; 95% CI: 0.19-0.87). Influences of viral and bacterial infection on AR differed with regard to family history of atopic disease. CONCLUSION: In our study population, history of viral infection was consistently positively associated with AR. Our data suggests that bacterial infections might be preventive for specific subgroups of atopy.     

Air pollution and seasonal asthma during the pollen season. A cohort study in Puertollano and Ciudad Real (Spain)

BACKGROUND: Many studies have demonstrated a positive association between air pollutants and emergency visits for asthma. However, few studies have included pollen when analysing this relationship in mild-moderate asthmatic patients. OBJECTIVE: To determine the importance of the pollutants such as ozone (O(3)), particles (PM(10)), nitrogen dioxide (NO(2)) and sulphur dioxide (SO(2)) in the clinical course of mild-moderate pollen-allergic asthmatic patients from two Spanish towns in La Mancha: Puertollano (high pollution levels) and Ciudad Real (low pollution levels). METHODS: We used a Poisson regression model to study a cohort of 137 patients from Puertollano and Ciudad Real during two pollen seasons (2000-2001) and analysed the relationship between air pollutant and pollen levels and daily symptoms, the medication used and peak-flow measurements. RESULTS: The number of asthma symptoms and the mean values of the PM(10), SO(2) and NO(2) levels were higher in Puertollano than in Ciudad Real. In Puertollano, the risk of asthma increased by 6% with a 3-day lag for PM(10), by 8% with a 3-day lag for O(3), by 4% with a 1-day lag for SO(2) and by 15% with a 3-day lag for O(3) when its values exceeded the health threshold (P < 0.05). CONCLUSIONS: The air pollution levels in Puertollano were associated with an increased risk of asthma symptoms in pollen-allergic asthmatic patients com pared with a similar group from Ciudad Real.     

Infectious and uterus related complications during pregnancy and development of atopic and nonatopic asthma in children

BACKGROUND: It has been suggested that environmental factors early in life, particularly related to hygiene and infections, seem to be involved in the increase of asthma and allergic disease observed recently in developed countries. The possible effect of these factors also in utero have yet to be completely clarified. The aim of this study was to investigate the association between infective and uterus related complications during pregnancy, as well as related drug factors, with atopic and nonatopic asthma in children. METHODS: This was a case-controlled study enrolling 338 children with asthma and 467 controls, who had never suffered from wheeze or asthma. Fever episodes, flu episodes, threatened abortions and related drug factors were retrospectively assessed by parental report via a standardized questionnaire. Atopy was determined by skin-prick tests to 10 prevalent allergens at the time of examination. RESULTS: Flu episodes during pregnancy were significantly associated with development of asthma in children [adjusted odds ratio (aOR) 1.91; 95% confidence interval (95% CI) 1.1-3.2], mainly with nonatopic asthma. Fever episodes showed similar results (aOR 2.16; 95% CI 1.2-3.9), but were associated with both atopic and nonatopic asthma. The effect seems mainly due to flu and fever episodes contracted in the third trimester. Exposure to isoxsuprine was significantly associated with asthma (aOR 1.54; 95% CI 1.08-2.19) while threatened abortions were more frequent in the asthma group than in controls, although the difference was statistically significant only when such events occurred in the second trimester (aOR 2.06; 95% CI 1.07-3.94). Both threatened abortions and exposure to isoxsuprine were associated only with nonatopic asthma. CONCLUSIONS: This study confirms that prenatal infective complications may contribute to the development of asthma in children and show a possible role for a new risk factor for asthma, that is exposure to isoxsuprine. Therefore, larger prospective studies, capable of separating atopic and nonatopic asthma, would serve to confirm these results and to explain the possible mechanism through which these factors may act.     

Temporal relationship between air pollution and hospital admissions for asthmatic children in Hong Kong

BACKGROUND: Many epidemiological studies have shown positive association between respiratory health and current levels of outdoor air pollution in Europe and America. OBJECTIVE: The aim of this study was to investigate the association between air pollution and the number of childhood admissions for asthma in Hong Kong. METHODS: Daily counts of childhood admission for asthma to a large teaching Hospital were obtained from the computerized database for the period 1993-1994. A Poisson regression allowing for seasonal patterns and meteorological conditions was used to assess the associations between the number of Hospital admissions and the three pollutants: nitrogen dioxide, sulphur dioxide and inhalable particles (measured as PM10, particles < 10 microm in aerodynamic diameter). RESULTS: A total of 1217 children under 15 years of age were admitted for asthma during the study period. The calculated annual hospitalization rates were 283 and 178 per 100 000 for boys and girls, respectively. The mean PM10, NO2 and SO2 levels were 44.1 microg/m3, 43.3 microg/m3, and 12.2 microg/m3, respectively. Daily admission for asthma increased significantly with increasing ambient level of nitrogen dioxide (relative risk (RR) = 1.08 per 10 microg/m3 increase), sulphur dioxide (RR = 1.06) and inhalable particles (RR = 1.03). No association was found between hospital admission and humidity, temperature or atmospheric pressure. CONCLUSION: This is the first daily time series study of childhood admissions for asthma and air pollution in Hong Kong. The results support that current levels of air pollution contribute to the respiratory morbidity in asthmatic children in Hong Kong.     

Associations of urban greenness with asthma and respiratory symptoms in Mexican American children

Background

Evidence on the association between residential surrounding greenness (RSG) in urban areas with asthma and asthma symptoms is inconsistent.

Outcome in adulthood of asymptomatic airway hyperresponsiveness to histamine and exercise-induced bronchospasm in childhood.

BACKGROUND: Studies of the clinical outcome in adulthood of asymptomatic airway hyperresponsiveness (AHR) to histamine or exercise-induced bronchospasm (EIB) detected in childhood in general population samples are sparse and have produced conflicting results. OBJECTIVE: To describe the outcome of asymptomatic AHR to histamine and EIB. METHODS: Data from a 12-year follow-up study of a random population sample of individuals aged 7 to 17 years at enrollment were analyzed; only individuals without asthma at enrollment were included in the analysis. AHR to inhaled histamine, EIB, lung function, and sensitization to aeroallergens were measured. RESULTS: Among the 281 nonasthmatic participants studied, 58 (22%) had AHR to histamine, 33 (12%) had EIB, and 82 (29%) had AHR to histamine and/or EIB. At follow-up, 37.9% of individuals with AHR to histamine and 30% of individuals with EIB had developed current asthma, compared with only 5% of individuals in whom these test results were negative. In patients with AHR to histamine, parental asthma (odds ratio [OR], 12.6; 95% confidence interval [CI], 1.5-108.5), furred pets ownership (OR, 6.0; 95% CI, 1.2-19.6), and dermatitis and/or rhinitis in childhood (OR, 2.2; 95% CI, 1.1-5.1) predicted the subsequent development of asthma, whereas no risk factors for the development of asthma could be identified in individuals with EIB CONCLUSION: Asymptomatic AHR to histamine and EIB in childhood predict the subsequent development of asthma in adulthood. A genetic disposition to asthma, furred pets ownership, and concomitant rhinitis or dermatitis increase the risk of asthma development in individuals with AHR to histamine.     

Perinatal influences on the development of asthma and atopy in childhood

BackgroundIn most children with asthma and atopy, onset of disease occurs early in life, indicating a crucial role of in utero and early childhood environment. However, only a small part of this burden of disease established early in life has been explained.ObjectiveTo examine the effects of early environmental exposures on the development of asthma and atopy within the setting of an affluent urban population.MethodsThe authors followed 526 German children from birth to 5 years of age. Parental interviews in pregnancy and then yearly assessed the health of the child and environmental characteristics. Endotoxin and allergens in house dust were measured at 3 months. Atopic sensitization was assessed at 1 and 5 years.ResultsIn atopic mothers, acute atopic symptoms during pregnancy were associated with increased risk of early atopic dermatitis (adjusted odds ratio [aOR] 1.74, 95% confidence interval [CI] 1.00–3.02) and allergic rhinitis at 5 years (aOR 2.11, 95% CI 1.01–4.41). Further, maternal illnesses during pregnancy (ie, repeated common colds) increased the risk of asthma at 5 years (aOR 2.31, 95% CI 1.12–4.78). Endotoxin in the child's mattress was inversely associated with atopic sensitization (aOR 0.79, 95% CI 0.64–0.97) and asthma (aOR 0.71, 95% CI 0.55–0.93). A contrasting effect of early endotoxin and mite exposure was observed for mite sensitization: mite exposure increased the risk of mite sensitization at 5 years (aOR 1.30, 95% CI 1.11–1.53), whereas endotoxin exposure was inversely associated with mite sensitization (aOR 0.73, 95% CI 0.57–0.95).ConclusionFactors affecting the in utero environment, such as maternal atopy and infections, and bacterial exposure in pregnancy or early life may act as immunomodulators enhancing or inhibiting the development of asthma and atopy in childhood.     

Association between air pollution and asthma admission among children in Hong Kong

OBJECTIVE: To examine the association of air pollutants with hospital admission for childhood asthma in Hong Kong. METHODS: Data on hospital admissions for asthma, influenza and total hospital admissions in children aged < or =18 years at all Hospital Authority hospitals during 1997-2002 were obtained. Data on daily mean concentrations of particles with aerodynamic diameter <10 microm (i. e. PM10) and <2.5 microm (i. e. PM2.5), nitrogen dioxide (NO2), sulphur dioxide (SO2), and ozone (O3) and data on meteorological variables were associated with asthma hospital admissions using Poisson's regression with generalized additive models for correction of yearly trend, temperature, humidity, day-of-week effect, holiday, influenza admissions and total hospital admission. The possibility of a lag effect of each pollutant and the interaction of different pollutants were also examined. RESULTS: The association between asthma admission with change of NO2, PM10, PM2.5 and O3 levels remained significant after adjustment for multi-pollutants effect and confounding variables, with increase in asthma admission rate of 5.64% (3.21-8.14) at lag 3 for NO2, 3.67% (1.52-5.86) at lag 4 for PM10, 3.24% (0.93-5.60) at lag 4 for PM2.5 and 2.63% (0.64-4.67) at lag 2 for O3. Effect of SO2 was lost after adjustment. CONCLUSION: Ambient levels of PM10, PM2.5) NO2 and O3 are associated with childhood asthma hospital admission in Hong Kong.     

Maternal fish intake during pregnancy and atopy and asthma in infancy

BACKGROUND: There is growing evidence that n-3 fatty acids have anti-inflammatory properties and may modulate immune response. Dietary intake of these nutrients during pregnancy could play a role in the risk of asthma and atopy in the offspring. METHODS: Using data from a cohort of women (n=462) enrolled during pregnancy and whose offspring were followed up to 6 years, we evaluated the impact of fish consumption during pregnancy on the incidence of atopy and asthma. Dietary intake was assessed by food frequency questionnaire (42 items) applied by an interviewer. RESULTS: Thirty-four percent of infants had a medical diagnosis of eczema at age 1 year, 14.3% of the children were atopic [based on skin prick test (SPT) at 6 years], and 5.7% had atopic wheeze at age 6 years. After adjusting for potential confounding factors, fish intake during pregnancy was protective against the risk of eczema at age 1 year, a positive SPT for house dust mite at age 6 years and atopic wheeze at age 6 years [odds ratio (OR)=0.73 95% confidence interval (CI) 0.55-0.98, OR=0.68, 95% CI 0.46-1.01 and OR=0.55, 95% CI 0.31-0.96, respectively]. For an increase in fish intake from once per week to 2.5 times per week, the risk of eczema at age 1 year decreased by 37%, and the risk of positive SPT at age 6 years by 35%. Stratification by breastfeeding showed that fish intake was significantly related to a decrease risk in persistent wheeze among non-breastfed children (P for interaction<0.05). No protective effect was observed among breastfed children. CONCLUSION: Our data suggest a protective effect of fish intake during pregnancy on the risk of atopy-related outcomes.     

Exposure to air pollution during different gestational phases contributes to risks of low birth weight

BACKGROUND: Although there have been growing concerns about the adverse effects of air pollution on birth outcomes, little is known about which specific exposure times of specific pollutants contribute to low birth weight (LBW). METHODS: We evaluated the relationships between LBW and air pollution exposure levels in Seoul, Korea. Using the air pollution data, we estimated the exposure during each trimester and also during each month of pregnancy on the basis of the gestational age and birth date of each newborn. Generalized additive logistic regression analyses were conducted considering infant sex, birth order, maternal age, parental education level, time trend, and gestational age. RESULTS: The monthly analyses suggested that the risks for LBW tended to increase with carbon monoxide (CO) exposure between months 2-5 of pregnancy, with exposure to particles <10 micro m (PM(10)) in months 2 and 4, and for sulphur dioxide (SO(2)) and nitrogen dioxide (NO(2)) exposure between months 3-5. CONCLUSIONS: This study suggests that exposure to CO, PM(10,) SO(2) and NO(2) during early to mid pregnancy contribute to risks for LBW.     

Effects of air pollution on asthma hospitalization rates in different age groups in Hong Kong

AIMS: To assess the relationship between levels of ambient air pollutants and hospitalization rates for asthma in Hong Kong (HK). METHODS: This is a retrospective ecological study. Data of daily emergency hospital admissions to 15 major hospitals in HK for asthma and indices of air pollutants [sulphur dioxide (SO(2)), nitrogen dioxide (NO(2)), ozone (O(3)), particulates with an aerodynamic diameter of <10 microm particulate matter (PM(10)) and 2.5 microm (PM(2.5))] and meteorological variables from January 2000 to December 2005 were obtained from several government departments. Analysis was performed by the generalized additive models with Poisson distribution. The effects of time trend, season, other cyclical factors, temperature and humidity were adjusted. Autocorrelation and overdispersion were corrected. RESULTS: Altogether, 69 716 admissions were assessed. Significant associations were found between hospital admissions for asthma and levels of NO(2), O(3), PM(10) and PM(2.5). The relative risks (RR) for hospitalization for every 10 microg/m(3) increase in NO(2), O(3), PM(10) and PM(2.5) were 1.028, 1.034, 1.019 and 1.021, respectively, at a lag day that ranged from cumulative lag 0-4 to 0-5. In a multi-pollutant model, O(3) was significantly associated with increased admissions for asthma. The younger age group (0-14 years) tended to have a higher RR for each 10 microg/m(3) increase in pollutants than those aged 15-65 years. The elderly (aged >/=65 years) had a shorter 'best' lag time to develop asthma exacerbation following exposure to pollutants than those aged <65 years. CONCLUSION: Adverse effects of ambient concentrations of air pollutants on hospitalization rates for asthma are evident. Measures to improve air quality in HK are urgently needed.     

Effect of body mass on exercise-induced bronchospasm and atopy in African children

BACKGROUND: Sensitization to allergen is common in rural populations in less affluent countries, but atopic disease is less frequent than in richer countries. Variables explaining this dichotomy may provide insight into underlying mechanisms of atopic diseases like asthma. OBJECTIVE: To test whether risk of exercise-induced bronchospasm (EIB) in urbanized African populations is increased in association with greater skin sensitivity or increased body mass. METHODS: A total of 3322 children were enrolled in a prevalence survey of EIB in urban and rural South Africa. Children responding positively to an exercise challenge and a random sample of children responding negatively were recruited into a case-control study (393 controls, 380 cases). Subjects were investigated by using allergen skin prick testing, anthropometry, and assay of IgE. Stools were analyzed for parasite infestation. RESULTS: The prevalence of EIB was higher in urban (14.9%) than rural (8.9%) areas (P < .0001). The difference in risk of EIB between urban and rural subjects was associated with atopy (odds ratio [OR] for upper tertile of skin wheal diameter, 2.65; 95% CI, 1.43-4.89; P < .0001), increasing weight (OR for upper tertile of body mass index [BMI], 2.17; 95% CI, 1.45-3.26; P = .001), and affluence. Increasing BMI was also associated with a greater strength of association between specific IgE and the corresponding skin test (Dermatophagoides pteronyssinus, OR for a positive skin test result in presence of specific IgE: heavier subjects, OR, 34.6; 95% CI, 0.9-109.3; P < .0001; lighter subjects, OR, 8.05; 95% CI, 2.74-23.6; P < .001). CONCLUSION: Increases in BMI of rural children in subsistence economies may lead to an increased prevalence of atopic disease. This observation merits further investigation in prospective studies.     

Allergen-specific sensitization in asthma and allergic diseases in children: the study on farmers'' and non-farmers'' children

BACKGROUND: Farmers' children are less frequently sensitized to common allergens than the non-farmers' children, but less is known about their sensitization to other allergens and its association with clinical diseases. OBJECTIVE: To examine the association of farm environment with atopic sensitization, allergic diseases, expression of allergen-induced symptoms, and the importance of specific sensitization against 'common' (timothy, dog, cat, birch, Dermatophagoides pteronyssimus, mugwort) and 'other' (cockroach, horse, Lepidoglyphus destructor, cow) allergens for asthma and allergic diseases in children. METHODS: A cross-sectional study including 344 farmers' and 366 non-farmers' children aged 6-13 years in eastern Finland, using a self-administered written questionnaire and skin prick tests against the above-mentioned allergens. RESULTS: Farmers' children had less asthma and allergic diseases and were less often sensitized against common allergens than the non-farmers' children. However, little difference was observed in sensitization against the other allergens between the farmers' (17.2%) and non-farmers (14.5%) children [adjusted odds ratios (aOR) 1.11 (0.71-1.72)]. Being sensitized against only other allergens, without sensitization against common allergens, was unrelated to asthma or allergic diseases. Among the single allergens, sensitization against pets or pollen, or against horse or cow, had the strongest association with asthma, hayfever, and atopic eczema; no such association was seen in D. pteronyssimus, mugwort, cockroach, or L. destructor. Farmers' children had significantly less often symptoms of allergic rhinitis in contact with dog (aOR 0.32%, 95% confidence interval (CI) 0.15-0.67), cat (aOR 0.45, 0.22-0.88), or pollen (aOR 0.58%, 95% CI 0.37-0.90) than the non-farmers' children. CONCLUSION: Farm environment reduces the occurrence of asthma, allergic diseases, and atopic sensitization in children, and also the occurrence of allergen-induced rhinitis. Remarkable differences were observed between single allergens in their association with allergic disease, stressing the importance of allergen selection when defining atopy in epidemiological studies.     

Environmental determinants of atopic eczema phenotypes in relation to asthma and atopic sensitization

BACKGROUND: There is still uncertainty about the determinants of atopic eczema (AE). To explain the heterogeneity of the disease, different phenotypes of AE have been suggested. METHODS: The cross-sectional PARSIFAL study included 14 893 school-age children of farmers or children attending Steiner schools and their respective reference groups. A detailed questionnaire was completed, and house dust was collected for the measurement of endotoxin and glucans. Atopic sensitization was defined by allergen-specific IgE levels in the serum. RESULTS: In multivariate analyses, helping with haying was the only variable related to a farming environment having a consistent inverse association with both current symptoms and a doctor's diagnosis of AE [aOR = 0.65 (95% CI: 0.46-0.93) and 0.73 (0.51-1.05)], respectively. Severe lower respiratory tract infections (LRTI) in the first 2 years of life and usage of antibiotics ever were found to be positively related only to asthma-associated AE, whereas the effect of LRTI on AE without asthma had an opposite effect. Levels of beta(1-->3)-glucans in mattress dust were inversely related to a doctor's diagnosis of asthma-associated AE [aOR = 0.75 (0.57-0.98)], and endotoxin levels to current symptoms of asthma-associated AE [aOR = 0.73 (0.57-0.94)]. CONCLUSIONS: The analyses of the PARSIFAL study revealed two different phenotypes of AE, depending on the association with asthma and wheezing ever. With regard to the hygiene hypothesis, help with haying, exposure to beta(1-->3)-glucans and endotoxin were found to be inversely associated with the AE phenotype associated with asthma and wheezing.     

Respiratory symptoms, bronchial hyper-responsiveness, and eosinophilic airway inflammation in patients with moderate-to-severe atopic dermatitis

BACKGROUND: Patients with atopic dermatitis (AD) often have symptoms suggestive of asthma or rhinitis. The prevalence and signs of respiratory disease in AD patients have been studied to a limited extent. OBJECTIVES: To assess the prevalence and clustering of respiratory symptoms, bronchial hyper-responsiveness (BHR), and eosinophilic airway inflammation in patients with moderate-to-severe AD. METHODS: Eighty-six consecutive patients with moderate-to-severe AD and 49 randomly selected control subjects without AD were studied by questionnaire, flow volume spirometry, histamine challenge to detect BHR, induced sputum test to detect eosinophilic airway inflammation, and skin prick tests (SPTs) and total serum immunoglobulin (Ig)E measurements to detect atopy. RESULTS: The patients with AD showed increased risk of physician-diagnosed asthma (36% vs. 2%, odds ratio (OR) 10.1, confidence interval (CI) 1.3-79.7, P=0.03), physician-diagnosed allergic rhinitis (AR) (45% vs. 6%, OR 4.5, CI 1.2-16.7, P=0.02), BHR (51% vs. 10%, OR 5.5, CI 1.5-20.1, P=0.01), and sputum eosinophilia (81% vs. 11%, OR 76.1, CI 9.3-623.5, P<0.0001) compared with the control subjects. In AD patients, elevated s-IgE and positive SPTs were associated with the occurrence of physician-diagnosed asthma and AR, BHR, and the presence of sputum eosinophilia. CONCLUSIONS: BHR and eosinophilic airway inflammation are more common in patients with AD than in control subjects. The highest prevalences were seen in patients with AD who were SPT positive and had high IgE levels. Longitudinal studies are needed to assess the outcome of patients with signs of airway disease, in order to identify those who need early initiation of asthma treatment.     

Caesarean section delivery and the risk of allergic disorders in childhood

BACKGROUND: The composition of the intestinal flora in young children, if unfavourable, may increase the susceptibility to allergic disorders. Beneficial intestinal microbes originate from the maternal vaginal tract and thus are more likely to be transferred during vaginal births than during Caesarean sections (C-sections). OBJECTIVE: To determine whether children born by C-section have a different risk of allergic disorders compared with those delivered vaginally. We also tested the hypothesis that the risk of allergic disorders is highest for children born after 'repeat C-sections'. METHODS: A retrospective cohort study of 8,953 children aged 3-10 years. Children diagnosed with allergic rhinoconjunctivitis (AR), asthma, atopic dermatitis (AD), or food allergies were identified from the Kaiser Permanente Northwest Region electronic records. The children's sex, birth weight, birth order, postnatal exposure to antibiotics as well as the mothers' age, ethnicity, education, marital status, smoking status during pregnancy, and use of asthma or hayfever medications were identified through the mothers' medical records or through the Oregon Birth Registry. RESULTS: The risk of being diagnosed with AR was significantly higher in the children born by C-section than in those delivered vaginally: adjusted odds ratio (OR)=1.37%, 95% confidence interval (CI)=1.14-1.63. Delivery by C-section was also associated with the subsequent diagnosis of asthma (OR=1.24%, 95% CI=1.01-1.53); this association was gender specific, with a positive association restricted to girls (OR for asthma in girls: OR=1.53%, 95% CI=1.11-2.10; in boys: OR=1.08%, 95% CI=0.81-1.43). There was no significant association between mode of delivery and AD. If children born in a 'repeat C-section' were considered separately the risk of being diagnosed with AR increased further (OR=1.78%, 95% CI=1.34-2.37). The same increase was noted for asthma in girls (OR=1.83%, 95% CI=1.13-2.97) but not in boys. CONCLUSION: Caesarean sections may be associated with an increased risk of developing AR in childhood.