Genetic variants and risk of asthma in an American Indian population.

BACKGROUND: Asthma is recognized as a complex, multifactorial disease with a genetic component that is well recognized. Certain genetic variants are associated with asthma in a number of populations. OBJECTIVE: To determine whether the same variants increase the risk of asthma among American Indian children. METHODS: The electronic medical records of an Indian Health Service facility identified all children between 6 and 17 years of age with case-defining criteria for asthma (n = 108). Control children (n = 216), matched for age, were also identified. Real-time polymerase chain reaction assays were used to genotype 10 single-nucleotide polymorphisms (SNPs) at 6 genetic loci. Genotypic distributions among cases and controls were evaluated by χ2 and logistic regression methods. RESULTS: A variant at 5q22.1 revealed a statistically significant imbalance in the distribution of genotypes between case-control pairs (rs10056340, P < .001). In logistic regression analyses, the same variant at 5q22.1 and a variant at 17q21 were associated with asthma at P < .05 (rs10056340 and rs9303277). Inclusions of age, body mass index, and atopy in multivariate models revealed significant associations between rs10056340 (odds ratio, 2.020; 95% confidence interval, 1.283-3.180; P = .002) and all 5 17q21 SNPs and asthma in this population. In analyses restricted to atopic individuals, the association of rs10056340 was essentially unchanged, whereas among nonatopic individuals the trend was in the same direction but nonsignificant. The reverse was true for the 17q21 SNPs. CONCLUSION: These findings demonstrate that many variants commonly associated with asthma in other populations also accompany this condition among American Indian children. American Indian children also appear to have an increased risk of asthma associated with obesity.