Asthma in farm children is more determined by genetic polymorphisms and in non-farm children by environmental factors

BACKGROUND

The asthma syndrome is influenced by hereditary and environmental factors. With the example of farm exposure, we study whether genetic and environmental factors interact for asthma.

METHODS

Statistical learning approaches based on penalized regression and decision trees were used to predict asthma in the GABRIELA study with 850 cases (9% farm children) and 857 controls (14% farm children). Single-nucleotide polymorphisms (SNPs) were selected from a genome-wide dataset based on a literature search or by statistical selection techniques. Prediction was assessed by receiver operating characteristics (ROC) curves and validated in the PASTURE cohort.

RESULTS

Prediction by family history of asthma and atopy yielded an area under the ROC curve (AUC) of 0.62 [0.57-0.66] in the random forest machine learning approach. By adding information on demographics (sex and age) and 26 environmental exposure variables, the quality of prediction significantly improved (AUC = 0.65 [0.61-0.70]). In farm children, however, environmental variables did not improve prediction quality. Rather SNPs related to IL33 and RAD50 contributed significantly to the prediction of asthma (AUC = 0.70 [0.62-0.78]).

CONCLUSIONS

Asthma in farm children is more likely predicted by other factors as compared to non-farm children though in both forms, family history may integrate environmental exposure, genotype and degree of penetrance.

An approach to the asthma-protective farm effect by geocoding: Good farms and better farms

BACKGROUND

The highly consistent association of growing up on a farm with a reduced asthma risk has so far been attributed to direct farm exposure. In contrast, geographic determinants of the larger environment have never been assessed. In this study, the effects of proximity to farms and environmental variables in relation to the residential address on asthma and atopy were assessed.

METHODS

Addresses of 2265 children of the Bavarian arm of the GABRIELA study were converted into geocodes. Proximity to the nearest cow farm was calculated, and environmental characteristics were derived from satellite data or terrestrial monitoring. Bacterial diversity in mattress dust samples was assessed in 501 children by sequencing of the 16S rRNA amplicons. Logistic regression models were used to calculate associations between outcomes and exposure variables.

RESULTS

Asthma and atopy were inversely associated with the presence of a farm within a radius of maximum 100 m. The environmental variables greenness, tree cover, soil sealing, altitude, air pollution differed not only between farm and non-farm children but also between farm children with and without another farm nearby. The latter distinction revealed strong associations with characteristics of traditional farms including a broader diversity of microbial exposure, which mainly contributed to the protective effect on asthma. In non-farm children, the protective effect of a farm nearby was completely explained by consumption of farm milk.

CONCLUSIONS

Clustering of farms within a neighborhood of 100 m is strongly associated with the protective effect on asthma and may represent a more traditional style of farming with broader microbial exposure.

Identification of fungal candidates for asthma protection in a large population-based study

BACKGROUND

Exposure to molds has been related to asthma risk both positively and negatively, depending on the environmental setting. The pertinent results are based on generic markers or culturing methods although the majority of present fungi cannot be cultured under laboratory conditions. The aim of the present analysis was to assess environmental dust samples for asthma-protective fungal candidates with a comprehensive molecular technique covering also non-cultivable and non-viable fungi.

METHODS

Mattress dust samples of 844 children from the GABRIELA study were analyzed by polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) of the fungus-specific internal transcribed spacer (ITS) region. Known asthma candidate species were tested for their associations with asthma, and further gel positions were sought to explain the above. As a second, data-driven, analysis, we tested the association of each individual gel position with asthma.

RESULTS

In the hypothesis-driven approach, Penicillium chrysogenum emerged with an odds ratio of 0.80 (95% confidence interval 0.66-0.96; p = 0.020). The effect size was changed by 39% toward the null when adjusting for the two bands 683 (DNA of Metschnikowia sp., Aureobasidium spp.) and 978 (DNA of Epicoccum spp., Galactomyces spp., uncultured Penicillium). The data-driven approach yielded an additional band (containing DNA of Pseudotaeniolina globosa) with reduced risk of asthma (OR = 0.80 [0.66-0.96], p = 0.012).

CONCLUSIONS

A large population-based study revealed several fungal taxa with inverse associations with childhood asthma. Molds produce a variety of bioactive compounds with detrimental but also beneficial immunoregulatory capacities, which renders them promising targets for further asthma research.

Safety and efficacy of pimecrolimus in atopic dermatitis: a 5-year randomized trial

BACKGROUND AND OBJECTIVES

Atopic dermatitis (AD) primarily affects infants and young children. Although topical corticosteroids (TCSs) are often prescribed, noncorticosteroid treatments are needed because compliance with TCSs is poor due to concerns about their side effects. In this longest and largest intervention study ever conducted in infants with mild-to-moderate AD, pimecrolimus 1% cream (PIM) was compared with TCSs.

METHODS

A total of 2418 infants were enrolled in this 5-year open-label study. Infants were randomized to PIM (n = 1205; with short-term TCSs for disease flares) or TCSs (n = 1213). The primary objective was to compare safety; the secondary objective was to document PIM's long-term efficacy. Treatment success was defined as an Investigator's Global Assessment score of 0 (clear) or 1 (almost clear).

RESULTS

Both PIM and TCSs had a rapid onset of action with >50% of patients achieving treatment success by week 3. After 5 years, >85% and 95% of patients in each group achieved overall and facial treatment success, respectively. The PIM group required substantially fewer steroid days than the TCS group (7 vs 178). The profile and frequency of adverse events was similar in the 2 groups; in both groups, there was no evidence for impairment of humoral or cellular immunity.

CONCLUSIONS

Long-term management of mild-to-moderate AD in infants with PIM or TCSs was safe without any effect on the immune system. PIM was steroid-sparing. The data suggest PIM had similar efficacy to TCS and support the use of PIM as a first-line treatment of mild-to-moderate AD in infants and children.

Asthma and allergies: is the farming environment (still) protective in Poland? The GABRIEL Advanced Studies

BACKGROUND

Evidence exists that a farming environment in childhood may provide protection against atopic respiratory disease. In the GABRIEL project based in Poland and Alpine regions of Germany, Austria and Switzerland, we aimed to assess whether a farming environment in childhood is protective against allergic diseases in Poland and whether specific exposures explain any protective effect.

METHODS

In rural Poland, 23 331 families of schoolchildren completed a questionnaire enquiring into farming practices and allergic diseases (Phase I). A subsample (n = 2586) participated in Phase II involving a more detailed questionnaire on specific farm exposures with objective measures of atopy.

RESULTS

Farming differed between Poland and the Alpine centres; in the latter, cattle farming was prevalent, whereas in Poland 18% of village farms kept ≥1 cow and 34% kept ≥1 pig. Polish children in villages had lower prevalences of asthma and hay fever than children from towns, and in the Phase II population, farm children had a reduced risk of atopy measured by IgE (aOR = 0.72, 95% CI 0.57, 0.91) and skin prick test (aOR = 0.65, 95% CI 0.50, 0.86). Early-life contact with grain was inversely related to the risk of atopy measured by IgE (aOR = 0.66, 95% CI 0.47, 0.92) and appeared to explain part of the farming effect.

CONCLUSION

While farming in Poland differed from that in the Alpine areas as did the exposure-response associations, we found in communities engaged in small-scale, mixed farming, there was a protective farming effect against objective measures of atopy potentially related to contact with grain or associated farm activities.

The combined effects of family size and farm exposure on childhood hay fever and atopy

BACKGROUND

Exposure to farming environments and siblings is associated with reduced risks of childhood hay fever and atopy. We explored the independence and interaction of these protective effects in the GABRIELA study.

METHODS

Questionnaire surveys on farming, asthma, and allergies were conducted in four central European areas among 79,888 6-12-yr-old children. Aeroallergen-specific serum IgE was measured in a stratified sample of 8,023 children. Multiple logistic regression was used to compare gradients in allergy prevalence by sibship size across three categories of exposure to farming environments.

RESULTS

The prevalence of hay fever ranged from 2% (95% confidence interval 1.6%; 2.7%) among farmers' children with more than two siblings to 12% (11.2%; 13.0%) among children with no farm exposure and no siblings. Farming families were larger on average. More siblings and exposure to farming environments independently conferred protection from hay fever and atopy. There was no substantial effect modification between family size and exposure to farming environments. The odds ratios for hay fever per additional sibling were 0.79 among unexposed non-farm children, 0.77 among farm-exposed non-farm children, and 0.72 among children from farming families (2df interaction test: p = 0.41).

CONCLUSION

The inverse association of exposure to farming environments with hay fever is found in all sizes of family, with no substantial tendency to saturation or synergism. This suggests that different biological mechanisms may underlie these two protective factors. Combinations of a large family and exposure to farming environments markedly reduce the prevalence of hay fever and indicate the strength of its environmental determinants.

Farming environments and childhood atopy, wheeze, lung function, and exhaled nitric oxide

BACKGROUND

Previous studies have demonstrated that children raised on farms are protected from asthma and allergies. It is unknown whether the farming effect is solely mediated by atopy or also affects nonatopic wheeze phenotypes.

OBJECTIVE

We sought to study the farm effect on wheeze phenotypes and objective markers, such as lung function and exhaled nitric oxide, and their interrelation with atopy in children.

METHODS

The GABRIEL Advanced Studies are cross-sectional, multiphase, population-based surveys of the farm effect on asthma and allergic disease in children aged 6 to 12 years. Detailed data on wheeze, farming exposure, and IgE levels were collected from a random sample of 8023 children stratified for farm exposure. Of those, another random subsample of 858 children was invited for spirometry, including bronchodilator tests and exhaled nitric oxide measurements.

RESULTS

We found effects of exposure to farming environments on the prevalence and degree of atopy, on the prevalence of transient wheeze (adjusted odds ratio, 0.78; 95% CI, 0.64-0.96), and on the prevalence of current wheeze among nonatopic subjects (adjusted odds ratio, 0.45; 95% CI, 0.32-0.63). There was no farm effect on lung function and exhaled nitric oxide levels in the general study population.

CONCLUSIONS

Children living on farms are protected against wheeze independently of atopy. This farm effect is not attributable to improved airway size and lung mechanics. These findings imply as yet unknown protective mechanisms. They might include alterations of immune response and susceptibility to triggers of wheeze, such as viral infections.

Protection from childhood asthma and allergy in Alpine farm environments-the GABRIEL Advanced Studies

BACKGROUND

Studies on the association of farm environments with asthma and atopy have repeatedly observed a protective effect of farming. However, no single specific farm-related exposure explaining this protective farm effect has consistently been identified.

OBJECTIVE

We sought to determine distinct farm exposures that account for the protective effect of farming on asthma and atopy.

METHODS

In rural regions of Austria, Germany, and Switzerland, 79,888 school-aged children answered a recruiting questionnaire (phase I). In phase II a stratified random subsample of 8,419 children answered a detailed questionnaire on farming environment. Blood samples and specific IgE levels were available for 7,682 of these children. A broad asthma definition was used, comprising symptoms, diagnosis, or treatment ever.

RESULTS

Children living on a farm were at significantly reduced risk of asthma (adjusted odds ratio [aOR], 0.68; 95% CI, 0.59-0.78; P< .001), hay fever (aOR, 0.43; 95% CI, 0.36-0.52; P< .001), atopic dermatitis (aOR, 0.80; 95% CI, 0.69-0.93; P= .004), and atopic sensitization (aOR, 0.54; 95% CI, 0.48-0.61; P< .001) compared with nonfarm children. Whereas this overall farm effect could be explained by specific exposures to cows, straw, and farm milk for asthma and exposure to fodder storage rooms and manure for atopic dermatitis, the farm effect on hay fever and atopic sensitization could not be completely explained by the questionnaire items themselves or their diversity.

CONCLUSION

A specific type of farm typical for traditional farming (ie, with cows and cultivation) was protective against asthma, hay fever, and atopy. However, whereas the farm effect on asthma could be explained by specific farm characteristics, there is a link still missing for hay fever and atopy.

The GABRIEL Advanced Surveys: study design, participation and evaluation of bias

Exposure to farming environments has been shown to protect substantially against asthma and atopic disease across Europe and in other parts of the world. The GABRIEL Advanced Surveys (GABRIELA) were conducted to determine factors in farming environments which are fundamental to protecting against asthma and atopic disease. The GABRIEL Advanced Surveys have a multi-phase stratified design. In a first-screening phase, a comprehensive population-based survey was conducted to assess the prevalence of exposure to farming environments and of asthma and atopic diseases (n = 103,219). The second phase was designed to ascertain detailed exposure to farming environments and to collect biomaterial and environmental samples in a stratified random sample of phase 1 participants (n = 15,255). A third phase was carried out in a further stratified sample only in Bavaria, southern Germany, aiming at in-depth respiratory disease and exposure assessment including extensive environmental sampling (n = 895). Participation rates in phase 1 were around 60% but only about half of the participating study population consented to further study modules in phase 2. We found that consenting behaviour was related to familial allergies, high parental education, wheeze, doctor diagnosed asthma and rhinoconjunctivitis, and to a lesser extent to exposure to farming environments. The association of exposure to farm environments with asthma or rhinoconjunctivitis was not biased by participation or consenting behaviour. The GABRIEL Advanced Surveys are one of the largest studies to shed light on the protective 'farm effect' on asthma and atopic disease. Bias with regard to the main study question was able to be ruled out by representativeness and high participation rates in phases 2 and 3. The GABRIEL Advanced Surveys have created extensive collections of questionnaire data, biomaterial and environmental samples promising new insights into this area of research.

Gene-environment interaction for childhood asthma and exposure to farming in Central Europe

BACKGROUND

Asthma is a disease in which both genetic and environmental factors play important roles. The farming environment has consistently been associated with protection from childhood asthma and atopy, and interactions have been reported with polymorphisms in innate immunity genes.

OBJECTIVE

To detect gene-environment interactions for asthma and atopy in the farming environment.

METHODS

We performed a genome-wide interaction analysis for asthma and atopy by using 500,000 genotyped single nucleotide polymorphisms (SNPs) and farm-related exposures in 1708 children from 4 rural regions of Central Europe. We also tested selectively for interactions between farm exposures and 7 SNPs that emerged as genome-wide significant in a large meta-analysis of childhood asthma and 5 SNPs that had been reported previously as interacting with farm exposures for asthma or atopy.

RESULTS

Neither the asthma-associated SNPs nor the SNPs previously published for interactions with asthma showed significant interactions. The genome-wide interaction study did not reveal any significant interactions with SNPs within genes in the range of interacting allele frequencies from 30% to 70%, for which our study was well powered. Among rarer SNPs, we identified 15 genes with strong interactions for asthma or atopy in relation to farming, contact with cows and straw, or consumption of raw farm milk.

CONCLUSION

Common genetic polymorphisms are unlikely to moderate the protective influence of the farming environment on childhood asthma and atopy, but rarer variants, particularly of the glutamate receptor, metabotropic 1 gene, may do so. Given the limited statistical power of our study, these findings should be interpreted with caution before being replicated in independent farm populations.

Opinions of children about participation in medical genetic research

AIMS

The objective was to evaluate children's opinions about their participation in a large research project.

METHODS

Polish children between 6 and 14 years of age completed a questionnaire about their participation in the Polish Gabriel study (which aims to identify genetic and environmental causes of asthma). In total 706 questionnaires were collected.

RESULTS

Children's main motivation for participation was wanting to know whether they were healthy or not. Most children could think of no reasons to reconsider participation. Children aged 6-10 years might reconsider participating because they did not know what was going to happen. A third of the children were not informed by anybody about the study. Especially the youngest children indicated a need for a tailored letter (42%). The youngest children were less often asked for their opinion about participation. All children preferred that both parents and children are asked for consent or assent. Children who were not informed or not asked for their opinion seemed less emotionally involved in the study.

CONCLUSION

While researchers and parents tend to focus their information provision to older children and include them in decision-making, especially the younger children expressed a need for more tailored information and involvement in their participation in research.

Atopy and asthma in rural Poland: a paradigm for the emergence of childhood respiratory allergies in Europe

BACKGROUND

We hypothesized that, in south-west Poland, a 'rural' protective effect on atopy and respiratory allergies would be most pronounced among children but that at all ages would be stronger among those with a rural background.

METHODS

A cross-sectional survey of the inhabitants (age >5 years, n = 1657) of Sobotka, a town of 4000 people in south-west Poland: and seven neighbouring villages. We measured and analysed responses to skin prick tests (atopy) and to a standard questionnaire (asthma and hayfever).

RESULTS

Atopy was very uncommon (7%) among villagers at all ages but not among townspeople (20%, P < 0.001); the differences were most marked among those aged under 40 years. Asthma and hayfever were similarly distributed, both being very rare among villagers. The differences appear to be explained by the cohort effect of a communal move away from rural life. This interpretation is supported by an ecological correlation (rho = -0.59) between rural populations and childhood wheeze in 22 European countries.

CONCLUSION

The very striking differences in the prevalence of allergy between these two neighbouring communities of central Europe reflect the pan-continental population movements that may have been responsible for the emergence of childhood allergies in Europe.

Tacrolimus ointment does not affect the immediate response to vaccination, the generation of immune memory, or humoral and cell-mediated immunity in children

BACKGROUND

Concern exists that the prolonged application of immunomodulators to treat atopic dermatitis may cause systemic immunosuppression.

AIMS

In a 7-month, multicentre, randomised, controlled trial, we investigated the equivalence of response to vaccination against meningococcal serogroup C disease with a protein-conjugate vaccine in children (2-11 years) with moderate to severe atopic dermatitis, by applying either 0.03% tacrolimus ointment (TAC-O; n = 121[corrected]) or a hydrocortisone ointment regimen (HC-O; n = 111).

METHODS

TAC-O was applied twice daily (bid) for 3 weeks, and thereafter daily until clearance. 1% hydrocortisone acetate (HA) for head/neck and 0.1% hydrocortisone butyrate ointment for trunk/limbs was applied bid for 2 weeks; thereafter HA was applied bid to all affected areas. At week 1, patients were vaccinated with protein-conjugate vaccine against meningococcal serogroup C, and challenged at month 6 with low dose meningococcal polysaccharide vaccine. The control group (44 non-atopic dermatitis children) received the primary vaccination and challenge dose. Assessments were made at baseline, weeks 1 and 5, and months 6 and 7. The primary end point was the percentage of patients with a serum bactericidal antibody (SBA) titre > or = 8 at the week 5 visit.

RESULTS

The response rate (patients with SBA titre > or = 8) was 97.5% (confidence interval (CI) approximately 97.3 to 100), 99.1% (94.8 to 100) and 97.7% (93.3 to 100) in the TAC-O, HC-O and control groups, respectively.

CONCLUSIONS

The immune response to vaccination against meningococcal serogroup C in children with atopic dermatitis applying either 0.03% TAC-O or HC is equivalent. Ointment application does not affect the immediate response to vaccination, generation of immune memory or humoral and cell-mediated immunity.