Flowchart displaying the analysis plan undertaken.

<p>In the first step separate SNP-traffic exposure GWIS of the EA and AA cohorts was performed. Following this suggestive (P < 1x10<sup>-5</sup>) results were examined for replication via a meta-analysis of both cohorts using METAL[<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0152670#pone.0152670.ref031" target="_blank">31</a>]. Finally step 3 involved an examination of suggestive results from a meta-analysis of all the interactions.</p>