Hoshikawa, M, Uchida, S, and Dohi, M. Intervention for reducing sleep disturbances after a 12-time zone transition. J Strength Cond Res 34(7): 1803-1807, 2020-The purpose of this study was to examine the effect of an intervention consisting of bright light exposure, sleep schedule shifts, and ramelteon on sleep disturbances after a transition of 12 time zones. Two groups, which flew from Tokyo to Rio, participated in this study. The experimental group received the treatment, whereas the control group did not receive any treatment. The experimental group members were exposed to bright light at night and their sleep-wake schedules were gradually delayed for 4 days before their flight. They also took 8 mg of ramelteon once a day for 5 days from the day of their first flight. Both groups departed Tokyo at 14:05, transiting through Frankfurt and arriving in Rio at 05:05. In Rio, it was recommended that they go to bed earlier than usual if they experienced sleepiness. Nocturnal sleep variables measured by wristwatch actigraphy and subjective morning tiredness were compared between groups. Statistical analysis revealed shorter sleep onset latencies (SOLs) in the experimental group (p < 0.01). The SOLs in Rio were 7.7 ± 2.5 minutes for the experimental group and 16.3 ± 3.7 minutes for the control group (d = 0.89, effect size: large). Sleep efficiency for the first 3 nights in Rio was 88.5 ± 1.2% for the experimental group and 82.9 ± 3.0% for the control group (p < 0.01, d = 1.09, effect size: large). These results suggest that the intervention reduced sleep disturbances in Rio. Our intervention may increase the options for conditioning methods for athletic events requiring time zone transitions.