This study finds less dramatic associations than Retey et al. Comparing carriers to non-carriers, a difference was only seen among the group of carriers that had consumed caffeine — when compared to caffeine-consuming non-carriers, carriers had lower sleep latency, higher sleep efficiency percentage, more REM sleep and fewer minutes awake. This may indicate carriers are less susceptible to sleep disruptive effects of caffeine.
However, there was no significant differences found between carriers and non-carriers in various self-reported traits (caffeine intake, restless legs syndrome, insomnia, sleep-promoting drugs). Also, the authors monitored arousals per hour for the subjects and found no significant difference between carriers and non-carriers (which contrasts with the self-reported data from Retey et al.). Findings may be less dramatic in this study because the subjects represent a highly heterogeneous epidemiological group.