The aims of this study are to compare 3 different treatments for circadian adjustment to a laboratory protocol which will mimic westward air travel across 8 time zones. One treatment will involve simply following the new schedule for 3 days. Another treatment will also involve exposure to bright light for 1 hour per day. A third treatment will involve exposure to bright light + exercise for 1 hour per day + consuming a melatonin tablet. Adjustment to the shifted schedule will be assessed by comparing measures of sleep, mood, mental performance, physical performance, and timing of melatonin across the 3 treatment conditions.
Design Overview. Following a 1 week home baseline, N=36 young adults will spend 6 days in the laboratory (Figure 3 and Table 1). Following am 8 h baseline polysomnographic recording (PSG) on Night 1, participants will undergo a 26 h baseline circadian assessment via an ultrashort sleep-wake protocol involving 2 h wake intervals and 1 h sleep intervals, repeated throughout the protocol. Following baseline circadian assessment, participants will be placed on a 16 h wake-8 h sleep schedule in which the wake-sleep and light-dark schedule is delayed 8 h for 3 days (analogous to traveling 8 time zones west). Participants will be randomized to one of 3 treatments (n=12 per treatment) administered each of the 3 days of the shifted schedule: (1) placebo control, (2) bright light, and (3) bright light + exercise + melatonin. PSG recording will occur on the last night of the shifted schedule, followed by an end-of-study 26 h ultrashort sleep wake schedule. On baseline Day 1 and Days 2-3 of the shifted schedule, sleepiness, mood, and mental performance will be assessed every 3 h during wake. During all four 8 h sleep periods, sleep will also be recorded with the Z-machine, which assesses sleep stages from 3 EEG electrodes. During the ultrashort sleep-wake schedules, mental performance, physiological performance, urinary aMT6s, mood, and sleepiness will be measured around-the-clock.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
SINGLE
3 consecutive days of 1 hour bright light
3 consecutive days of bright light, exercise, and melatonin
3 consecutive days of dim red light + light stretching + placbo
Center Sleep and Circadian Sciences
Tucson, Arizona, United States
RECRUITINGChange (shift) in the acrophase of urinary 6-sulphatoxymelatonin (aMT6s) excretion
Change (shift) in the cosine fitted peak for the assessments (every 90 min) during lab days 2-3 compared with the assessments taken during days 6-7
Time frame: 6.5 days
Change (shift) in the acrophase of the rhythm of the median reaction time
Change (shift) in the cosine fitted peak for the assessments (psychomotor vigilance, every 3 h) taken during days 2-3 compared with the assessments taken during days 6-7
Time frame: 6.5 days
Change in sleep duration
Change in total sleep time assessed during night one in the lab and night 5 in the lab duration
Time frame: 5 days
Change (shift) in the acrophase of the Total Mood Disturbance composite scale of on the Profile of Mood States questionnaire
Change (shift) in the cosine-fitted peak of the rhythm of total mood disturbance assessed during days 2-3 compared with total mood disturbance assessed during days 6-7
Time frame: 5 days
Change (shift) in the acrophase of the Stanford Sleepiness Scale
Change (shift) in the cosine-fitted peak of the rhythm of the Stanford Sleepiness Scale assessed during days 2-3 compared with the Stanford Sleepiness Scale mood disturbance assessed during days 6-7
Time frame: 5 days
Change (shift) in the acrophase of the Wingate Anaerobic Performance Test
Change (shift) in the cosine-fitted peak of the rhythm of the Wingate Anaerobic Performance Test assessed on days 2-3 and day 6-7.
Time frame: 5 days
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Enrollment
36
Change in sleep recorded with z-machine
Z machine recorded sleep with electrodes on the mastoid bones. Change in sleep assessed in eight 1-h sleep intervals on days 2-3 and days 6-7
Time frame: 5 days