Figure 2. Sleep duration, time to loss of consciousness, and time to return of consciousness as a function of age in those volunteers 65 yr and younger after a propofol bolus dose of 2 mg/kg. The sleep duration is the time to return of consciousness (lower panel) minus the time of loss of consciousness (middle panel). Volunteers older than 65 yr received a reduced bolus dose because of safety concerns, and for this reason they were not included here. The participant who did not fall asleep after the bolus dose was not included in this part of the analysis.