Although we limited analyses to African-American participants, it remains possible that population structure may be confounding the results. Within the African-American subsample, there is undoubtedly variation in the amount of African and Caucasian ancestry between individuals. We were not able to test for genetic ancestry, and thus results should be interpreted with caution. However, because the design of the study involved randomizing participants to intervention conditions, we believe population stratification may be less of an issue than in case-control designs in which participants are selected based on the presence or absence of a disease or disorder. In the present study, variation in genetic ancestry is more likely to be divided equally between groups in the randomization process. Future studies with larger sample sizes and that examine compute genetic ancestry will be required to test this.
