Genetics of the apnea hypopnea index in Caucasians and African Americans: I. Segregation analysis

Differences in age of presentation and anatomic risk factors for obstructive sleep apnea (OSA) in Caucasians and African Americans suggest possible racial differences in the genetic underpinnings of the disorder. In this study, we assess transmission patterns in a Caucasian sample consisting of 177 families (N = 1,195) and in an African American sample consisting of 125 families (N = 720) for two variables: 1) apnea hypopnea index (AHI) log transformed and adjusted for age, and 2) AHI log transformed and adjusted for age and body mass index (BMI). We allowed for residual familial correlations and sex-specific means in all models. Analysis of the Caucasian sample showed transmission patterns consistent with that of a major gene that were stronger in the age-adjusted variable than in the age- and BMI-adjusted variable. However, in the African American families, adjusting for BMI in addition to age gave stronger evidence for segregation of a codominant gene with an allele frequency of 0.14, accounting for 35% of the total variance. These results provide support for an underlying genetic basis for OSA that in African Americans is independent of the contribution of BMI.