ADAPTATION OF THE 6-SULPHATOXYMELATONIN RHYTHM IN SHIFTWORKERS ON OFFSHORE OIL INSTALLATIONS DURING A 2-WEEK 12-H NIGHT-SHIFT

The circadian rhythms of most shiftworkers do not adapt to night shift . We have studied oil workers on a rotating system involving 2 weeks d ay shift (0600-1800 h) and 2 weeks night shift (1800-0600 h) throughou t a day and night shift sequence. Urine samples were collected 3-hourl y whilst awake, with an over-sleep collection, for the measurement of 6-sulphatoxymelatonin by radioimmunoassay. In three separate groups re sults showed adaptation by delay of the 6-sulphatoxymelatonin rhythm i n the first week of night shift. The rates of phase shift (mean +/- SE M) were 1.51 +/- 0.16 h/day (n = 5), 1.32 +/- 0.41 h/day (n = 5) and 1 .77 +/- 0.31 h/day (n = 17). Specific environmental and social factors together with the shift schedule on oil rigs may facilitate adaptatio n to a 12 h night shift within a week. (C) 1998 Elsevier Science Irela nd Ltd.