NIGHT-SHIFT WORK IN ANTARCTICA - SLEEP CHARACTERISTICS AND BRIGHT LIGHT TREATMENT

Changes in sleep parameters during and after night-shift and the effec ts of bright white (2500-3000 lx) and dim red (> 500 lx) light treatme nt on re adaptation after night-shift during winter were studied in 14 men on the British Antarctic Survey Base of Halley (75 degrees south) . Subjects kept daily sleep diaries and mood ratings from one week bef ore to three weeks after night-shift and received either full-spectrum white or dim red light treatment from 1100 to 1300 h daily during the first week after night-shift. Plasma melatonin (for 24 h at the end o f weeks 1, 2 and 4), and urinary 6-sulfatoxymelatonin (aMT6s, for 48 h weekly) were measured. A significant (MANOVA; p < 0.05) improvement i n sleep was seen during night shift (latency and duration) and with br ight light treatment (latency). Melatonin and aMT6s rhythms delayed by 7-8 h during night-shift. The white light group readapted slowly, app arently by phase delay, as assessed by aMT6s measurement. The red ligh t group readapted slightly, but significantly (ANOVA, p < 0.01) faster than the white light group.