Fig. 1.

Study protocol. The study protocol consisted of two 12-d laboratory sessions in a cross-over design. After two baseline/habituation nights, participants were scheduled to seven consecutive sleep opportunities of 6 h in the sleep-restriction condition and seven consecutive sleep opportunities of 10 h in the control condition. Following the final sleep restriction or control sleep opportunity, participants were subjected to a period of extended wakefulness (39–41 h of total sleep deprivation), which included hourly melatonin assessments, a well-established marker of circadian phase, and three hourly RNA samplings, under constant-routine conditions. Following a 12-h recovery sleep opportunity participants were discharged from the study.