title: Melatonin and cortisol assessment of circadian shifts in astronauts before flight.
abstract: Melatonin and cortisol were measured in saliva and urine samples to assess the effectiveness of a 7-day protocol combining bright-light exposure with sleep shifting in eliciting a 12-hr phase-shift delay in eight U.S. Space Shuttle astronauts before launch. Baseline acrophases for 15 control subjects with normal sleep-wake cycles were as follows: cortisol (saliva) at 0700 (0730 in urine); melatonin (saliva) at 0130 (6-hydroxymelatonin sulfate at 0230 in urine). Acrophases of the astronaut group fell within 2.5 hr of these values before the treatment protocols were begun. During the bright-light and sleep-shifting treatments, both absolute melatonin production and melatonin rhythmicity were diminished during the first 3 treatment days; total daily cortisol levels remained constant throughout the treatment. By the fourth to sixth day of the 7-day protocol, seven of the eight crew members showed phase delays in all four measures that fell within 2 hr of the expected 11- to 12-hr shift. Although cortisol and melatonin rhythms each corresponded with the phase shift, the rhythms in these two hormones did not correspond with each other during the transition.
authors.affiliation: Medical Sciences Division, NASA/Johnson Space Center, Houston, TX 77058, USA.
authors.forename: P A
authors.initials: PA
authors.lastname: Whitson
authors.forename: L
authors.initials: L
authors.lastname: Putcha
authors.forename: Y M
authors.initials: YM
authors.lastname: Chen
authors.forename: E
authors.initials: E
authors.lastname: Baker
mesh_terms: D018480:Astronauts; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism* / Q000652:urine; D008027:Light; D008297:Male; D008550:Melatonin / Q000031:analogs & derivatives / Q000378:metabolism* / Q000652:urine; D010870:Pineal Gland / Q000502:physiology; D011863:Radioimmunoassay; D012463:Saliva / Q000378:metabolism; D012890:Sleep; D013026:Space Flight
chemical_list: D008550:Melatonin; C012365:6-hydroxymelatonin; D006854:Hydrocortisone