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Rationale: Adverse effects of exposures to ambient air pollution on lung function are well documented, but evidence in racial/ethnic minority children is lacking., Objectives: To assess the relationship between air pollution and lung function in minority children with asthma and possible modification by global genetic ancestry., Methods: The study population consisted of 1,449 Latino and 519 African American children with asthma from five different geographical regions in the mainland United States and Puerto Rico. We examined five pollutants (particulate matter ≤10 μm and ≤2.5 μm in diameter, ozone, nitrogen dioxide, and sulfur dioxide), derived from participant residential history and ambient air monitoring data, and assessed over several time windows. We fit generalized additive models for associations between pollutant exposures and lung function parameters and tested for interaction terms between exposures and genetic ancestry., Measurements and Main Results: A 5 μg/m(3) increase in average lifetime particulate matter less than or equal to 2.5 μm in diameter exposure was associated with a 7.7% decrease in FEV1 (95% confidence interval = -11.8 to -3.5%) in the overall study population. Global genetic ancestry did not appear to significantly modify these associations, but percent African ancestry was a significant predictor of lung function., Conclusions: Early-life particulate exposures were associated with reduced lung function in Latino and African American children with asthma. This is the first study to report an association between exposure to particulates and reduced lung function in minority children in which racial/ethnic status was measured by ancestry-informative markers.

Background: Atopy varies by ethnicity, even within Latino groups. This variation might be due to environmental, sociocultural, or genetic factors., Objective: We sought to examine risk factors for atopy within a nationwide study of US Latino children with and without asthma., Methods: Aeroallergen skin test responses were analyzed in 1830 US Latino subjects. Key determinants of atopy included country/region of origin, generation in the United States, acculturation, genetic ancestry, and site to which subjects migrated. Serial multivariate zero-inflated negative binomial regressions stratified by asthma status examined the association of each key determinant variable with the number of positive skin test responses. In addition, the independent effect of each key variable was determined by including all key variables in the final models., Results: In baseline analyses African ancestry was associated with 3 times (95% CI, 1.62-5.57) as many positive skin test responses in asthmatic participants and 3.26 times (95% CI, 1.02-10.39) as many positive skin test responses in control participants. Generation and recruitment site were also associated with atopy in crude models. In final models adjusted for key variables, asthmatic patients of Puerto Rican (exp[β] [95% CI], 1.31 [1.02-1.69]) and mixed (exp[β] [95% CI], 1.27 [1.03-1.56]) ethnicity had a greater probability of positive skin test responses compared with Mexican asthmatic patients. Ancestry associations were abrogated by recruitment site but not region of origin., Conclusions: Puerto Rican ethnicity and mixed origin were associated with degree of atopy within US Latino children with asthma. African ancestry was not associated with degree of atopy after adjusting for recruitment site. Local environment variation, represented by site, was associated with degree of sensitization., (Copyright © 2013 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.)

Rationale: Air pollution is a known asthma trigger and has been associated with short-term asthma symptoms, airway inflammation, decreased lung function, and reduced response to asthma rescue medications., Objectives: To assess a causal relationship between air pollution and childhood asthma using data that address temporality by estimating air pollution exposures before the development of asthma and to establish the generalizability of the association by studying diverse racial/ethnic populations in different geographic regions., Methods: This study included Latino (n = 3,343) and African American (n = 977) participants with and without asthma from five urban regions in the mainland United States and Puerto Rico. Residential history and data from local ambient air monitoring stations were used to estimate average annual exposure to five air pollutants: ozone, nitrogen dioxide (NO₂), sulfur dioxide, particulate matter not greater than 10 μm in diameter, and particulate matter not greater than 2.5 μm in diameter. Within each region, we performed logistic regression to determine the relationship between early-life exposure to air pollutants and subsequent asthma diagnosis. A random-effects model was used to combine the region-specific effects and generate summary odds ratios for each pollutant., Measurements and Main Results: After adjustment for confounders, a 5-ppb increase in average NO₂ during the first year of life was associated with an odds ratio of 1.17 for physician-diagnosed asthma (95% confidence interval, 1.04-1.31)., Conclusions: Early-life NO₂ exposure is associated with childhood asthma in Latinos and African Americans. These results add to a growing body of evidence that traffic-related pollutants may be causally related to childhood asthma.

Motivation: Local ancestry analysis of genotype data from recently admixed populations (e.g. Latinos, African Americans) provides key insights into population history and disease genetics. Although methods for local ancestry inference have been extensively validated in simulations (under many unrealistic assumptions), no empirical study of local ancestry accuracy in Latinos exists to date. Hence, interpreting findings that rely on local ancestry in Latinos is challenging., Results: Here, we use 489 nuclear families from the mainland USA, Puerto Rico and Mexico in conjunction with 3204 unrelated Latinos from the Multiethnic Cohort study to provide the first empirical characterization of local ancestry inference accuracy in Latinos. Our approach for identifying errors does not rely on simulations but on the observation that local ancestry in families follows Mendelian inheritance. We measure the rate of local ancestry assignments that lead to Mendelian inconsistencies in local ancestry in trios (MILANC), which provides a lower bound on errors in the local ancestry estimates. We show that MILANC rates observed in simulations underestimate the rate observed in real data, and that MILANC varies substantially across the genome. Second, across a wide range of methods, we observe that loci with large deviations in local ancestry also show enrichment in MILANC rates. Therefore, local ancestry estimates at such loci should be interpreted with caution. Finally, we reconstruct ancestral haplotype panels to be used as reference panels in local ancestry inference and show that ancestry inference is significantly improved by incoroprating these reference panels., Availability and Implementation: We provide the reconstructed reference panels together with the maps of MILANC rates as a public resource for researchers analyzing local ancestry in Latinos at http://bogdanlab.pathology.ucla.edu, Supplementary Information: Supplementary data are available at Bioinformatics online.

Motivation: It is becoming increasingly evident that the analysis of genotype data from recently admixed populations is providing important insights into medical genetics and population history. Such analyses have been used to identify novel disease loci, to understand recombination rate variation and to detect recent selection events. The utility of such studies crucially depends on accurate and unbiased estimation of the ancestry at every genomic locus in recently admixed populations. Although various methods have been proposed and shown to be extremely accurate in two-way admixtures (e.g. African Americans), only a few approaches have been proposed and thoroughly benchmarked on multi-way admixtures (e.g. Latino populations of the Americas)., Results: To address these challenges we introduce here methods for local ancestry inference which leverage the structure of linkage disequilibrium in the ancestral population (LAMP-LD), and incorporate the constraint of Mendelian segregation when inferring local ancestry in nuclear family trios (LAMP-HAP). Our algorithms uniquely combine hidden Markov models (HMMs) of haplotype diversity within a novel window-based framework to achieve superior accuracy as compared with published methods. Further, unlike previous methods, the structure of our HMM does not depend on the number of reference haplotypes but on a fixed constant, and it is thereby capable of utilizing large datasets while remaining highly efficient and robust to over-fitting. Through simulations and analysis of real data from 489 nuclear trio families from the mainland US, Puerto Rico and Mexico, we demonstrate that our methods achieve superior accuracy compared with published methods for local ancestry inference in Latinos.

Background: The effects of in utero tobacco smoke exposure on childhood respiratory health have been investigated, and outcomes have been inconsistent., Objective: To determine if in utero tobacco smoke exposure is associated with childhood persistent asthma in Mexican, Puerto Rican, and black children., Patients and Methods: There were 295 Mexican, Puerto Rican, and black asthmatic children, aged 8 to 16 years, who underwent spirometry, and clinical data were collected from the parents during a standardized interview. The effect of in utero tobacco smoke exposure on the development of persistent asthma and related clinical outcomes was evaluated by logistic regression., Results: Children with persistent asthma had a higher odds of exposure to in utero tobacco smoke, but not current tobacco smoke, than did children with intermittent asthma (odds ratio [OR]: 3.57; P = .029). Tobacco smoke exposure from parents in the first 2 years of life did not alter this association. Furthermore, there were higher odds of in utero tobacco smoke exposure in children experiencing nocturnal symptoms (OR: 2.77; P = .048), daily asthma symptoms (OR: 2.73; P = .046), and emergency department visits (OR: 3.85; P = .015) within the year., Conclusions: Exposure to tobacco smoke in utero was significantly associated with persistent asthma among Mexican, Puerto Rican, and black children compared with those with intermittent asthma. These results suggest that smoking cessation during pregnancy may lead to a decrease in the incidence of persistent asthma in these populations.

Objective: A recent admixture mapping analysis identified interleukin 6 (IL6) and IL6 receptor (IL6R) as candidate genes for inflammatory diseases. In the airways during allergic inflammation, IL6 signaling controls the production of proinflammatory and anti-inflammatory factors. In addition, albuterol, a commonly prescribed asthma therapy, has been shown to influence IL6 gene expression. Therefore, we reasoned that interactions between the IL6 and IL6R genes might be associated with bronchodilator drug responsiveness to albuterol in asthmatic patients., Methods: Four functional IL6 single nucleotide polymorphisms (SNPs) and a nonsynonymous IL6R SNP were genotyped in 700 Mexican and Puerto Rican asthma families and in 443 African-American asthma cases and controls. Both family-based association tests and linear regression models were used to assess the association between individual SNPs and haplotypes with bronchodilator response. Gene-gene interactions were tested by using multiple linear regression analyses., Results: No single SNP was consistently associated with drug response in all the three populations. However, on the gene level, we found a consistent IL6 and IL6R pharmacogenetic interaction in the three populations. This pharmacogenetic gene-gene interaction was contextual and dependent upon ancestry (racial background). This interaction resulted in higher drug response to albuterol in Latinos, but lower drug response in African-Americans. Herein, we show that there is an effect modification by ancestry on bronchodilator responsiveness to albuterol., Conclusion: Genetic variants in the IL6 and IL6R genes act synergistically to modify the bronchodilator drug responsiveness in asthma and this pharmacogenetic interaction is modified by the genetic ancestry.

Rationale: Independent replication of genetic associations in complex diseases, particularly in whole-genome association studies, is critical to confirm the association., Objectives: A whole-genome association study identified ORMDL3 as a promising candidate gene for asthma in white populations. Here, we attempted to confirm the role of ORMDL3 genetic variants in asthma in three ethnically diverse populations: Mexican, Puerto Rican, and African American., Methods: We used family-based analyses to test for association between seven candidate single-nucleotide polymorphisms (SNPs) in and around the ORMDL3 gene and asthma and related phenotypes in 701 Puerto Rican and Mexican parent-child trios. We also evaluated these seven SNPs and an additional ORMDL3 SNP in 264 African American subjects with asthma and 176 healthy control subjects., Measurements and Main Results: We found significant associations between two SNPs within ORMDL3 (rs4378650 and rs12603332) and asthma in Mexicans and African Americans (P = 0.028 and 0.001 for rs4378650 and P = 0.021 and 0.001 for rs12603332, respectively), and a trend toward association in Puerto Ricans (P = 0.076 and 0.080 for SNPs rs4378650 and rs12603332, respectively). These associations became stronger among Mexican and Puerto Rican subjects with asthma with IgE levels greater than 100 IU/ml. We did not find any association between ORMDL3 SNPs and baseline lung function or response to the bronchodilator albuterol., Conclusions: Our results confirm that the ORMDL3 locus is a risk factor for asthma in ethnically diverse populations. However, inconsistent SNP-level results suggest that further studies will be needed to determine the mechanism by which ORMDL3 predisposes to asthma.

Socioeconomic and environmental differences do not fully explain differences in asthma prevalence, morbidity, and mortality among Puerto Ricans, African Americans, and Mexican Americans. Differences in response to albuterol may be a factor. We compared bronchodilator responsiveness between these three populations. All groups demonstrated below expected responsiveness. Puerto Ricans of all ages and African American children with moderate-to-severe asthma demonstrated the lowest responsiveness overall. Among subjects with moderate-to-severe asthma, children were even less likely than adults to show the expected bronchodilator response. We conclude that ethnic-specific differences in bronchodilator drug responsiveness exist between Mexicans, Puerto Ricans, and African Americans with asthma. This may be of importance in asthma management.

Background: High levels of IgE are associated with asthma. Whether higher levels of IgE are associated with more severe asthma is still unclear., Objective: To determine whether IgE is associated with asthma severity among Latino and African American subjects with asthma., Methods: We assessed lung function and asthma severity among African American, Mexican, and Puerto Rican patients with asthma with high IgE levels (> or =100 IU/mL; n = 492) and compared these values to those of patients with asthma with low IgE levels (<100 IU/mL; n = 247). We also examined IgE as a continuous variable among these groups., Results: Patients with asthma with high IgE had a lower mean FEV(1) (87.6 +/- 17.1, percent of predicted) than patients with asthma with low IgE (91.5 +/- 17.0; P = .031). Regardless of race and ethnicity, baseline FEV(1), forced expiratory flow, and FEV(1)/forced vital capacity were lower among subjects with high IgE than among subjects with low IgE (P = .031, P < .0001, P = .0001, respectively). In addition, 54.7% of patients with asthma with high IgE had been previously hospitalized, compared with 44.1% of patients with asthma with low IgE (odds ratio, 1.33; 95% CI, 1.04-1.71)., Conclusion: Higher IgE is associated with lower baseline lung function and more severe asthma among these populations., Clinical Implications: Among patients with asthma from 3 ethnically distinct groups, total IgE levels are inversely correlated with baseline lung function and asthma severity.

Background: The prostanoid DP receptor (PTGDR) gene on chromosome 14q22.1 has been identified as an asthma susceptibility gene. A haplotype with decreased transcription factor binding and transcription efficiency was associated with decreased asthma susceptibility in African American and white subjects. The significance of PTGDR gene variants in asthma has yet to be determined in Latinos, the largest US minority population, nor has the association been replicated in other populations., Objective: To determine the role of PTGDR gene variants in asthma susceptibility and asthma-related traits among the Mexican, Puerto Rican, and African American populations., Methods: We determined whether single nucleotide polymorphisms (SNPs) and haplotypes in PTGDR were associated with asthma and asthma-related traits by family-based and cross-sectional cohort analyses in 336 Puerto Rican and 273 Mexican asthmatic trios and by case-control analysis among African American subjects with asthma and healthy controls (n = 352)., Results: We identified 13 SNPs in the PTGDR gene, and 6 were further analyzed. There was no significant association between PTGDR variants and asthma by family-based or case-control analyses. SNPs -441C and -197C and haplotype TTT showed marginal association with asthma-related traits in Mexican subjects. SNP -441 genotype TT (P = .05) and haplotype TTT (P = .02) were associated with increased IgE levels in African Americans., Conclusion: We conclude that the PTGDR gene is not a significant risk factor for asthma among Puerto Ricans, Mexicans, or African Americans., Clinical Implications: Asthma candidate genes provide insights to pathophysiology and potentially new therapeutic targets, although the PTGDR gene was not found to be a significant risk factor for asthma in 3 populations.

Background: Puerto Ricans, an admixed population of African, European, and Native American ancestries, have the highest asthma prevalence, morbidity, and mortality rates of any United States' population. Although socioeconomic status (SES) is negatively correlated with asthma incidence in most populations, no such relationship has been identified among Puerto Ricans. We hypothesized that, in this admixed population, the association between SES and asthma may interact with genetic ancestry., Methods: We analyzed 135 Puerto Rican subjects with asthma and 156 control subjects recruited from six different recruitment centers in Puerto Rico. Individual ancestry for each subject was estimated using 44 ancestry informative markers. SES was assigned using the census tracts' median family income. Analyses of SES were based on the SES of the clinic site from which the subjects were recruited and on a subset of individuals on whom home address-based SES was available., Results: In the two (independent) analyses, we found a significant interaction between SES, ancestry, and asthma disease status. At lower SES, European ancestry was associated with increased risk of asthma, whereas African ancestry was associated with decreased risk. The opposite was true for their higher SES counterparts., Conclusions: The observed interaction may help to explain the unique pattern of risk for asthma in Puerto Ricans and the lack of association with SES observed in previous studies when not accounting for varying proportions of ancestry.

In the United States, asthma prevalence and mortality are the highest among Puerto Ricans and the lowest among Mexicans. Case-control association studies are a powerful strategy for identifying genes of modest effect in complex diseases. However, studies of complex disorders in admixed populations such as Latinos may be confounded by population stratification. We used ancestry informative markers (AIMs) to identify and correct for population stratification among Mexican and Puerto Rican subjects participating in case-control studies of asthma. Three hundred and sixty-two subjects with asthma (Mexican: 181, Puerto Rican: 181) and 359 ethnically matched controls (Mexican: 181, Puerto Rican: 178) were genotyped for 44 AIMs. We observed a greater than expected degree of association between pairs of AIMs on different chromosomes in Mexicans (P < 0.00001) and Puerto Ricans (P < 0.00002) providing evidence for population substructure and/or recent admixture. To assess the effect of population stratification on association studies of asthma, we measured differences in genetic background of cases and controls by comparing allele frequencies of the 44 AIMs. Among Puerto Ricans but not in Mexicans, we observed a significant overall difference in allele frequencies between cases and controls (P = 0.0002); of 44 AIMs tested, 8 (18%) were significantly associated with asthma. However, after adjustment for individual ancestry, only two of these markers remained significantly associated with the disease. Our findings suggest that empirical assessment of the effects of stratification is critical to appropriately interpret the results of case-control studies in admixed populations.

Genetic association studies in admixed populations may be biased if individual ancestry varies within the population and the phenotype of interest is associated with ancestry. However, recently admixed populations also offer potential benefits in association studies since markers informative for ancestry may be in linkage disequilibrium across large distances. In particular, the enhanced LD in admixed populations may be used to identify alleles that underlie a genetically determined difference in a phenotype between two ancestral populations. Asthma is known to have different prevalence and severity among ancestrally distinct populations. We investigated several asthma-related phenotypes in two ancestrally admixed populations: Mexican Americans and Puerto Ricans. We used ancestry informative markers to estimate the individual ancestry of 181 Mexican American asthmatics and 181 Puerto Rican asthmatics and tested whether individual ancestry is associated with any of these phenotypes independently of known environmental factors. We found an association between higher European ancestry and more severe asthma as measured by both forced expiratory volume at 1 second (r=-0.21, p=0.005) and by a clinical assessment of severity among Mexican Americans (OR: 1.55; 95% CI 1.25 to 1.93). We found no significant associations between ancestry and severity or drug responsiveness among Puerto Ricans. These results suggest that asthma severity may be influenced by genetic factors differentiating Europeans and Native Americans in Mexican Americans, although differing results for Puerto Ricans require further investigation., (Copyright (c) 2005 Wiley-Liss, Inc.)

Background: In the United States, Puerto Ricans and Mexicans have the highest and lowest asthma prevalence, morbidity, and mortality, respectively. Ethnic-specific differences in the response to drug treatment may contribute to differences in disease outcomes. Genetic variants at the beta(2)-adrenergic receptor (beta(2)AR) may modify asthma severity and albuterol responsiveness. We tested the association of beta(2)AR genotypes with asthma severity and bronchodilator response to albuterol in Puerto Ricans and Mexicans with asthma., Methods: We used both family-based and cross-sectional tests of association with 8 beta(2)AR single nucleotide polymorphisms in 684 Puerto Rican and Mexican families. Regression analyses were used to determine the interaction between genotype, asthma severity, and bronchodilator drug responsiveness., Results: Among Puerto Ricans with asthma, the arginine (Arg) 16 allele was associated with greater bronchodilator response using both family-based and cross-sectional tests (p = 0.00001-0.01). We found a strong interaction of baseline FEV(1) with the Arg16Glycine (Gly) polymorphism in predicting bronchodilator response. Among Puerto Ricans with asthma with baseline FEV(1) < 80% of predicted, but not in those with FEV(1) > 80%, there was a very strong association between the Arg16 genotype and greater bronchodilator responsiveness. No association was observed between Arg16Gly genotypes and drug responsiveness among Mexicans with asthma., Conclusions: Ethnic-specific pharmacogenetic differences exist between Arg16Gly genotypes, asthma severity, and bronchodilator response in Puerto Ricans and Mexicans with asthma. These findings underscore the need for additional research on racial/ethnic differences in asthma morbidity and drug responsiveness.