The effects of growing up on a farm on adult lung function and allergic phenotypes: an international population-based study.

RATIONALE: Evidence has suggested that exposure to environmental or microbial biodiversity in early life may impact subsequent lung function and allergic disease risk. OBJECTIVES: To investigate the influence of childhood living environment and biodiversity indicators on atopy, asthma and lung function in adulthood. METHODS AND MEASUREMENTS: The European Community Respiratory Health Survey II investigated ∼10 201 participants aged 26-54 years from 14 countries, including participants' place of upbringing (farm, rural environment or inner city) before age 5 years. A 'biodiversity score' was created based on childhood exposure to cats, dogs, day care, bedroom sharing and older siblings. Associations with lung function, bronchial hyper-responsiveness (BHR), allergic sensitisation, asthma and rhinitis were analysed. MAIN RESULTS: As compared with a city upbringing, those with early-life farm exposure had less atopic sensitisation (adjusted OR 0.46, 95% CI 0.37 to 0.58), atopic BHR (0.54 (0.35 to 0.83)), atopic asthma (0.47 (0.28 to 0.81)) and atopic rhinitis (0.43 (0.32 to 0.57)), but not non-atopic outcomes. Less pronounced protective effects were observed for rural environment exposures. Women with a farm upbringing had higher FEV1 (adjusted difference 110 mL (64 to 157)), independent of sensitisation and asthma. In an inner city environment, a higher biodiversity score was related to less allergic sensitisation. CONCLUSIONS: This is the first study to report beneficial effects of growing up on a farm on adult FEV1. Our study confirmed the beneficial effects of early farm life on sensitisation, asthma and rhinitis, and found a similar association for BHR. In persons with an urban upbringing, a higher biodiversity score predicted less allergic sensitisation, but to a lesser magnitude than a childhood farm environment.

The locus C11orf30 increases susceptibility to poly-sensitization.

A number of genetic variants have been associated with allergic sensitization, but whether these are allergen specific or increase susceptibility to poly-sensitization is unknown. Using data from the large multicentre population-based European Community Respiratory Health Survey, we assessed the association between 10 loci and specific IgE and skin prick tests to individual allergens and poly-sensitization. We found that the 10 loci associate with sensitization to different allergens in a nonspecific manner and that one in particular, C11orf30-rs2155219, doubles the risk of poly-sensitization (specific IgE/4 allergens: OR = 1.81, 95% CI 0.80-4.24; skin prick test/4+ allergens: OR = 2.27, 95% CI 1.34-3.95). The association of rs2155219 with higher levels of expression of C11orf30, which may be involved in transcription repression of interferon-stimulated genes, and its association with sensitization to multiple allergens suggest that this locus is highly relevant for atopy.

Intermediary quantitative traits--an alternative in the identification of disease genes in asthma?

Intermediary quantitative traits are a possible alternative for the identification of disease genes. This may be particularly relevant when diagnostic criteria are not very well defined as described for asthma. We analyzed serum samples from 944 individuals of 218 asthma families for 17 cytokines (eotaxin, GM-CSF, IFNγ, IL1B, IL1RA, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12(p40), IL-13, IL-17, IL-23, IL-33, TSLP and TNF-α) and determined the heritability. Linked chromosomal regions were identified by a genome-wide analysis using 334 autosomal microsatellite marker and association tested by further 550 SNP marker at genes implicated earlier with immune response. Heritability varied with TNF-α and IL-8 levels having the highest and TSLP having the lowest heritability. Linkage was significantly increased only for IL-12(p40) at D17S949. There were multiple significant single-nucleotide polymorphisms (SNP) associations (P<0.05) as found in the transmission disequilibrium test, whereas only a few replicated in parents or children only. These include SNPs in IL1RN that were associated with IL-33 and TSLP levels, and a SNP in NR3C2 that was associated with eotaxin, IL-13 and IFN-γ levels. Circulating level of serum cytokines exhibits genetic associations with asthma traits that are otherwise not detected using clinical diagnosis or when the clinical details are ambiguous.

Genome-wide association study of body mass index in 23 000 individuals with and without asthma.

BACKGROUND: Both asthma and obesity are complex disorders that are influenced by environmental and genetic factors. Shared genetic factors between asthma and obesity have been proposed to partly explain epidemiological findings of co-morbidity between these conditions. OBJECTIVE: To identify genetic variants that are associated with body mass index (BMI) in asthmatic children and adults, and to evaluate if there are differences between the genetics of BMI in asthmatics and healthy individuals. METHODS: In total, 19 studies contributed with genome-wide analysis study (GWAS) data from more than 23 000 individuals with predominantly European descent, of whom 8165 are asthmatics. RESULTS: We report associations between several DENND1B variants (P = 2.2 × 10(-7) for rs4915551) on chromosome 1q31 and BMI from a meta-analysis of GWAS data using 2691 asthmatic children (screening data). The top DENND1B single nucleotide polymorphisms(SNPs) were next evaluated in seven independent replication data sets comprising 2014 asthmatics, and rs4915551 was nominally replicated (P < 0.05) in two of the seven studies and of borderline significance in one (P = 0.059). However, strong evidence of effect heterogeneity was observed and overall, the association between rs4915551 and BMI was not significant in the total replication data set, P = 0.71. Using a random effects model, BMI was overall estimated to increase by 0.30 kg/m(2) (P = 0.01 for combined screening and replication data sets, N = 4705) per additional G allele of this DENND1BSNP. FTO was confirmed as an important gene for adult and childhood BMI regardless of asthma status. CONCLUSIONS AND CLINICAL RELEVANCE: DENND1B was recently identified as an asthma susceptibility gene in a GWAS on children, and here, we find evidence that DENND1B variants may also be associated with BMI in asthmatic children. However, the association was overall not replicated in the independent data sets and the heterogeneous effect of DENND1B points to complex associations with the studied diseases that deserve further study.

Low vitamin D serum level is inversely associated with eczema in children and adolescents in Germany.

BACKGROUND: Recent studies have yielded heterogeneous results regarding the relationship between vitamin D and atopic conditions. The aim of this study was to investigate the association between serum vitamin D level and the prevalence of eczema in German children and adolescents. METHODS: Data were drawn for children aged 1-17 from the German Health Interview and Examination Survey for Children and Adolescents (KiGGS), a nationwide cross-sectional representative survey. 25-hydroxyvitamin D (25(OH)D) serum concentration was measured in 9838 individuals with eczema and categorized into quartiles. We investigated the association of vitamin D level and eczema by means of logistic regression models. RESULTS: Weighted prevalence of eczema was 13.5% (95% confidence interval (CI) 12.6-14.4%). Mean vitamin D level was significantly higher in those with eczema compared with those without (P < 0.0001). Logistic regression revealed an inverse association between low levels of vitamin D and eczema (multivariate OR for quartile 1 vs quartile 2: 0.76 (95% CI 0.61-0.94)). CONCLUSIONS: This study suggests that low serum vitamin D level is inversely associated with eczema in German children and adolescents. Prospective studies are required to confirm this result, to discuss a potential opportunity for prevention of eczema.

ADRB2 Gly16Arg polymorphism, asthma control and lung function decline.

Arg/Arg homozygotes for the Gly16Arg polymorphism in the ß2-adrenoreceptor gene (ADRB2) have a reduced response to short-acting ß2-agonists but no effect has been associated with long-acting ß2-agonists (LABAs). We selected 604 subjects with current asthma from the European Community Respiratory Health Study to evaluate whether asthma control and lung function decline were associated with Gly16Arg polymorphism, and to test whether LABA or inhaled corticosteroid (ICS) use modified these effects. There was an increased risk of noncontrolled asthma (OR 1.33, 95% CI 1.01-1.75; p = 0.046) for each Arg allele. Among nonusers of ICS, the odds ratio of noncontrolled asthma among Arg/Arg versus Gly/Gly subjects was 2.73 (95% CI 1.28-5.82; p = 0.009). No increased risk of noncontrolled asthma associated with the Arg allele was observed among ICS and/or LABA users. For each Arg allele, a mean ± se decrease in decline in forced expiratory volume in 1 s of 7.7 ± 2.5 mL·yr⁻¹ was found (p-value for trend 0.003), irrespective of ICS or LABA use. Arg/Arg subjects had an increased risk of bronchial hyperresponsiveness (BHR) versus Gly/Gly subjects, with an odds ratio of 2.51 (95% CI 1.12-5.63; p = 0.025) if they did not use ICS. The Arg allele was associated with poorer asthma control, a steeper lung function decline and BHR. Absence of genotypic effects on asthma control among ICS users may be due to reversed ß2-adrenoreceptor desensitisation.

Positionally cloned genes and age-specific effects in asthma and atopy: an international population-based cohort study (ECRHS).

BACKGROUND: Several genes identified by positional cloning have been associated with asthma and atopy, but few findings have been replicated. Age at onset of asthma has been associated with different phenotypic characteristics, and with variants at chromosome 17q21 identified through genome-wide association. This study examined the associations and age-specific effects on asthma, atopy and bronchial hyper-responsiveness (BHR) of five candidate genes previously identified by positional cloning (ADAM33, PHF11, NPSR1, DPP10, SPINK5). METHODS: 51 polymorphisms from 2474 participants from 13 countries who took part in the European Community Respiratory Health Survey (1990-2000) were studied. Asthma and age at onset of asthma were assessed by questionnaire data, BHR by methacholine challenge and atopy by specific immunoglobulin E to four common allergens. RESULTS: Significant associations with asthma, atopy and particularly for asthma with atopy were observed for a large region of 47 kb in the NPSR1 gene, even after Bonferroni correction for multiple comparisons (p<0.001). The associations with NPSR1 were stronger in those reporting a first attack of asthma before the age of 15, with statistically significant interactions with age of onset found for three SNPs. The evidence for ADAM33 and BHR and for an age-specific effect of two SNPs in DPP10 and asthma was weaker. CONCLUSION: This study provides further evidence for an effect of NPSR1 on asthma, atopy and atopic asthma. In addition, this analysis suggests a role for NPSR1 in early-onset asthma driven by the strong effect of this gene on atopic asthma.

Early life origins of chronic obstructive pulmonary disease.

BACKGROUND: Early life development may influence subsequent respiratory morbidity. The impact of factors determined in childhood on adult lung function, decline in lung function and chronic obstructive pulmonary disease (COPD) was investigated. METHODS: European Community Respiratory Health Survey participants aged 20-45 years randomly selected from general populations in 29 centres underwent spirometry in 1991-3 (n = 13 359) and 9 years later (n = 7738). Associations of early life factors with adult forced expiratory volume in 1 s (FEV(1)), FEV(1) decline and COPD (FEV(1)/FVC ratio <70% and FEV(1) <80% predicted) were analysed with generalised estimating equation models and random effects linear models. RESULTS: Maternal asthma, paternal asthma, childhood asthma, maternal smoking and childhood respiratory infections were significantly associated with lower FEV(1) and defined as "childhood disadvantage factors"; 40% had one or more childhood disadvantage factors which were associated with lower FEV(1) (men: adjusted difference 95 ml (95% CI 67 to 124); women: adjusted difference 60 ml (95% CI 40 to 80)). FEV(1) decreased with increasing number of childhood disadvantage factors (> or =3 factors, men: 274 ml (95% CI 154 to 395), women: 208 ml (95% CI 124 to 292)). Childhood disadvantage was associated with a larger FEV(1) decline (1 factor: 2.0 ml (95% CI 0.4 to 3.6) per year; 2 factors: 3.8 ml (95% CI 1.0 to 6.6); > or =3 factors: 2.2 ml (95% CI -4.8 to 9.2)). COPD increased with increasing childhood disadvantage (1 factor, men: OR 1.7 (95% CI 1.1 to 2.6), women: OR 1.6 (95% CI 1.01 to 2.6); > or =3 factors, men: OR 6.3 (95% CI 2.4 to 17), women: OR 7.2 (95% CI 2.8 to 19)). These findings were consistent between centres and when subjects with asthma were excluded. CONCLUSIONS: People with early life disadvantage have permanently lower lung function, no catch-up with age but a slightly larger decline in lung function and a substantially increased COPD risk. The impact of childhood disadvantage was as large as that of heavy smoking. Increased focus on the early life environment may contribute to the prevention of COPD.

Risk factors of new-onset asthma in adults: a population-based international cohort study.

BACKGROUND: The occurrence of new-onset asthma during adulthood is common, but there is insufficient understanding of its determinants including the role of atopy. OBJECTIVE: To assess the risk factors for the development of new-onset asthma in middle-aged adults and to compare them according to atopy. METHODS: A longitudinal analysis of 9175 young adults who participated in two surveys of the European Community Respiratory Health Survey (ECRHS) conducted 9 years apart. FINDINGS: We observed 179 cases of new-onset asthma among 4588 participants who were free of asthma and reported at the beginning of the follow-up that they had never had asthma (4.5 per 1000 person-years). In a logistic regression, the following risk factors were found to increase the risk of new-onset asthma: female gender (OR: 1.97; 95% confidence interval (CI): 1.38, 2.81), bronchial hyperresponsiveness (3.25; 2.19, 4.83), atopy (1.55; 1.08, 2.21), FEV(1) < 100 % predicted (1.87; 1.34, 2.62), nasal allergy (1.98;1.39,2.84) and maternal asthma (1.91; 1.13; 3.21). Obesity, respiratory infections in early life and high-risk occupations increased the risk of new-onset asthma although we had limited power to confirm their role. Among the atopics, total IgE and sensitization to cat were independently related to the risk of new-onset asthma. The proportion of new-onset asthma attributable to atopy varied from 12% to 21%. CONCLUSION: Adults reporting that they had never had asthma were at a substantial risk of new-onset asthma as a result of multiple independent risk factors including lung function. Atopy explains a small proportion of new-onset adult asthma.

The multinational birth cohort of EuroPrevall: background, aims and methods.

BACKGROUND/AIM: The true prevalence and risk factors of food allergies in children are not known because estimates were based predominantly on subjective assessments and skin or serum tests of allergic sensitization to food. The diagnostic gold standard, a double-blind placebo-controlled food provocation test, was not performed consistently to confirm suspected allergic reactions in previous population studies in children. This protocol describes the specific aims and diagnostic protocol of a birth cohort study examining prevalence patterns and influential factors of confirmed food allergies in European children from different regions. METHODS: Within the collaborative translational research project EuroPrevall, we started a multi-center birth cohort study, recruiting a total of over 12 000 newborns in nine countries across Europe in 2005-2009. In addition to three telephone interviews during the first 30 months, parents were asked to immediately inform the centers about possible allergic reactions to food at any time during the follow-up period. RESULTS: All children with suspected food allergy symptoms were clinically evaluated including double-blind placebo-controlled food challenge tests. We assessed sensitization to different food allergens by measurements of specific serum immunoglobulin E and skin prick tests, collect blood, saliva or buccal swabs for genetic tests, breast milk for measurement of food proteins/cytokines, and evaluate quality-of-life and economic burden of families with food allergic children. CONCLUSIONS: This birth cohort provides unique data on prevalence, risk factors, quality-of-life, and costs of food allergies in Europe, leading to the development of more informed and integrated preventative and treatment strategies for children with food allergies.

Do childhood respiratory infections continue to influence adult respiratory morbidity?

The aim of the present study was to examine the influence of childhood respiratory infections on adult respiratory health. In 1992-1994, the European Community Respiratory Health Survey recruited community based samples of 20-44-yr-old people from 48 centres in 22 countries. Study participants completed questionnaires and underwent lung function testing. On average, 8.9 yrs later, 29 centres re-investigated their samples using similar methods. Mixed effects models comprising an estimate for the random variation between centres were used to evaluate the relevant associations. In total, 9,175 patients participated in both studies, of whom 10.9% reported serious respiratory infections (SRI) before 5 yrs of age and 2.8% reported hospitalisation for lung disease (HLD) before 2 yrs if age. SRI was associated with current wheeze (odds ratio (OR) 1.9, 95% confidence interval (CI) 1.7-2.2), asthma (OR 2.5, 95% CI 2.2-3.1), and lower forced expiratory volume in one second (FEV(1); 89 mL; 95% CI 54-126), forced vital capacity (FVC; 49 mL; 95% CI 8-90) and FEV(1)/FVC ratio (-1.2%; 95% CI -1.8- -0.6). Childhood respiratory infections were also associated with new asthma (OR 1.5, 95% CI 1.03-2.0), new wheeze (OR 1.5, 95% CI 1.0-2.4) and persistent wheeze (OR 2.2, 95% CI 1.4-3.6) but not with a decline in lung function. Similar findings were observed for HDL. These associations were significantly consistent across centres. SRI was associated with lower FEV(1) when excluding ever asthmatics and current wheezers. The impact of early infections was significantly larger in subjects exposed to maternal or active smoking. The impact of childhood respiratory infections on the respiratory system may not only last into adulthood but also influence development and persistence of adult respiratory morbidity.

What defines airflow obstruction in asthma?

Asthma guidelines from the Global Initiative for Asthma (GINA) and from the National Heart, Lung, and Blood Institute provide conflicting definitions of airflow obstruction, suggesting a fixed forced expiratory volume in 1 s (FEV(1))/forced vital capacity (FVC) cut-off point and the lower limit of normality (LLN), respectively. The LLN was recommended by the recent American Thoracic Society/European Respiratory Society guidelines on lung function testing. The problem in using fixed cut-off points is that they are set regardless of age and sex in an attempt to simplify diagnosis at the expense of misclassification. The sensitivity and specificity of fixed FEV(1)/FVC ratios of 0.70, 0.75 and 0.80 versus the LLN were evaluated in 815 subjects (aged 20-44 yrs) with a diagnosis of asthma within the framework of the European Community Respiratory Health Survey. In males, the 0.70 ratio showed 76.5% sensitivity and 100.0% specificity, the 0.75 ratio 100.0% sensitivity and 92.4% specificity, and the 0.80 ratio 100.0% sensitivity but 58.1% specificity. In females, the 0.70 ratio showed 57.3% sensitivity and 100.0% specificity, the 0.75 ratio 91.5% sensitivity and 95.9% specificity, and the 0.80 ratio 100.0% sensitivity but 72.9% specificity. The fixed cut-off points cause a lot of misidentification of airflow obstruction in young adults, with overestimation with the 0.80 ratio and underestimation with the 0.70 ratio. In conclusion, the GINA guidelines should change their criteria for defining airflow obstruction.

Joint effect of obesity and TNFA variability on asthma: two international cohort studies.

Obesity is a risk factor for asthma. Adipose tissue expresses pro-inflammatory molecules including tumour necrosis factor (TNF), and levels of TNF are also related to polymorphisms in the TNF-alpha (TNFA) gene. The current authors examined the joint effect of obesity and TNFA variability on asthma in adults by combining two population-based studies. The European Community Respiratory Health Survey and the Swiss Cohort Study on Air Pollution and Lung and Heart Disease in Adults used comparable protocols, questionnaires and measures of lung function and atopy. DNA samples from 9,167 participants were genotyped for TNFA -308 and lymphotoxin-alpha (LTA) +252 gene variants. Obesity and TNFA were associated with asthma when mutually adjusting for their independent effects (odds ratio (OR) for obesity 2.4, 95% confidence interval (CI) 1.7-3.2; OR for TNFA -308 polymorphism 1.3, 95% CI 1.1-1.6). The association of obesity with asthma was stronger for subjects carrying the G/A and A/A TNFA -308 genotypes compared with the more common G/G genotype, particularly among nonatopics (OR for G/A and A/A genotypes 6.1, 95% CI 2.5-14.4; OR for G/G genotype 1.7, 95% CI 0.8-3.3). The present findings provide, for the first time, evidence for a complex pattern of interaction between obesity, a pro-inflammatory genetic factor and asthma.

Serum 25-hydroxyvitamin D and IgE - a significant but nonlinear relationship.

BACKGROUND: Hormonal vitamin D system affects the determination of T-cell responses. It is unknown if there is an association between vitamin D status and allergic conditions. Our aim was to investigate differences in serum IgE concentrations by vitamin D status [measured by 25(OH)D] and by a genetic variation in a key vitamin D activation enzyme (CYP27B1) previously shown to be associated with type 1 diabetes. METHODS: 9377 participants in the 1958 British birth cohort completed a biomedical assessment at 45 years of age ; 7288 eligible participants had data on 25(OH)D and IgE, with 6429 having further information on CYP27B1 genotype ()1260C>A). RESULTS: There was a nonlinear association between 25(OH)D and IgE (P-value for curvature = 0.0001). Compared with the reference group with the lowest IgE concentrations [25(OH)D 100-125 nmol/l], IgE concentrations were 29% higher (95% CI 9-48%) for participants with the 25(OH)D <25 nmol/l, and 56% higher (95% CI 17-95%) for participants with 25(OH)D >135 nmol/l (adjusted for sex, month, smoking, alcohol consumption, time spent outside, geographical location, social class, PC/TV time, physical activity, body mass index and waist circumference). CYP27B1 genotype was associated with both 25(OH)D (difference for A vs. C allele: 1.88%, 95% CI 0.37-3.4%, P = 0.01) and IgE concentrations ()6.59%, )11.6% to )1.42%, P = 0.01). CONCLUSIONS: These data suggest that there may be a threshold effect with both low and high 25(OH)D levels associated with elevated IgE concentrations. The same CYP27B1 allele that is protective of diabetes was associated with increased IgE concentrations.

Factors influencing the incidence and prevalence of food allergy.

Food allergy is an increasing problem in Europe and elsewhere and severe reactions to food are also becoming more common. As food allergy is usually associated with other forms of allergic sensitisation it is likely that many risk factors are common to all forms of allergy. However the potential severity of the disease and the specific public heath measures required for food allergy make it important to identify the specific risk factors for this condition. Food allergy is unusual in that it often manifests itself very early in life and commonly remits with the development of tolerance. Hypotheses that explain the distribution of food allergy include specific genetic polymorphisms, the nature of the allergens involved and the unique exposure to large quantities of allergen through the gut. Progress has been made in developing more specific and testable hypotheses but the evidence for any of these is still only preliminary. Further collaborative research is required to develop an appropriate public health response to this growing problem.

Infant feeding and allergy prevention: a review of current knowledge and recommendations. A EuroPrevall state of the art paper.

The relationship between infant feeding patterns and the later development of food allergies has been the focus of much debate and research over the last decade. National recommendations have been made by many countries on how to feed infants to reduce the risk of food allergy but due to the lack of firm evidence the recommendations differ widely. This review has been developed as part of EuroPrevall, a European multicentre research project funded by the European Union, to document the differing feeding recommendations made across Europe, to investigate the current evidence base for any allergy prevention feeding recommendations and to identify areas where further research is needed. This review will also provide information which, when combined with the infant feeding data collected as part of EuroPrevall, will give an indication of compliance to national feeding guidelines which can be utilised to assess the effectiveness of current dissemination and implementation strategies.

Underestimation of airflow obstruction among young adults using FEV1/FVC <70% as a fixed cut-off: a longitudinal evaluation of clinical and functional outcomes.

BACKGROUND: Early detection of airflow obstruction is particularly important among young adults because they are more likely to benefit from intervention. Using the forced expiratory volume in 1 s (FEV(1)) to forced vital capacity (FVC) (FEV(1)/FVC) <70% fixed ratio, airflow obstruction may be underdiagnosed. The lower limit of normal (LLN), which is statistically defined by the lower fifth percentile of a reference population, is physiologically appropriate but it still needs a clinical validation. METHODS: To evaluate the characteristics and longitudinal outcomes of subjects misidentified as normal by the fixed ratio with respect to the LLN, 6249 participants (aged 20-44 years) in the European Community Respiratory Health Survey were examined and divided into three groups (absence of airflow obstruction by the LLN and the fixed ratio; presence of airflow obstruction only by the LLN; presence of airflow obstruction by the two criteria) for 1991-1993. LLN equations were obtained from normal non-smoking participants. A set of clinical and functional outcomes was evaluated in 1999-2002. RESULTS: The misidentified subjects were 318 (5.1%); only 45.6% of the subjects with airflow obstruction by the LLN were also identified by the fixed cut-off. At baseline, FEV(1) (107%, 97%, 85%) progressively decreased and bronchial hyperresponsiveness (slope 7.84, 6.32, 5.57) progressively increased across the three groups. During follow-up, misidentified subjects had a significantly higher risk of developing chronic obstructive pulmonary disease and a significantly higher use of health resources (medicines, emergency department visits/hospital admissions) because of breathing problems than subjects without airflow obstruction (p<0.001). CONCLUSIONS: Our findings show the importance of using statistically derived spirometric criteria to identify airflow obstruction.

TNFA -308G>A in two international population-based cohorts and risk of asthma.

Genetic association studies have related the tumour necrosis factor-alpha gene (TNFA) guanine to adenine substitution of nucleotide -308 (-308G>A) polymorphism to increased risk of asthma, but results are inconsistent. The aim of the present study was to test whether two single-nucleotide polymorphisms, of TNFA and of the lymphotoxin-alpha gene (LTA), are associated with asthma, bronchial hyperresponsiveness and atopy in adults, by combining the results of two large population-based multicentric studies and conducting a meta-analysis of previously published studies. The European Community Respiratory Health Survey (ECRHS) and Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults (SAPALDIA) used comparable protocols, including questionnaires for respiratory symptoms and measures of lung function and atopy. DNA samples from 11,136 participants were genotyped at TNFA -308 and LTA 252. Logistic regression employing fixed and random effects models and nonparametric techniques were used. The prevalence of asthma was 6%. The TNFA -308G>A polymorphism was associated with increased asthma prevalence and with bronchial hyperresponsiveness. No consistent association was found for atopy. The LTA 252A>G polymorphism was not associated with any of the outcomes. A meta-analysis of 17 studies showed an increased asthma risk for the TNFA -308 adenine allele. The tumour necrosis factor-alpha gene nucleotide -308 polymorphism is associated with a moderately increased risk of asthma and bronchial hyperresponsiveness, but not with atopy. These results are supported by a meta-analysis of previously published studies.

ORMDL3--guilt by association?

A recent British-German study described ORMDL3 as a new asthma gene. Although the association with chromosome 17q12 marker is plausible from earlier linkage data, it is far from being clear which gene caused the association signal, as it is derived from a large linkage disequilibrium (LD) block. Not only Aiolos and GSDML but also distant genes that are regulated by this site may be relevant. There may be even unidentified RNA transcripts requiring a much more detailed genetic and functional analysis before finding ORMDL3 guilty by association.