Rapid adaptation to night work at an oil platform, but slow readaptation after returning home.

Previous research indicates that night workers' circadian rhythms do not adapt to night work and that disturbed sleep and wakefulness persist, even after weeks of working on night shift. We studied adjustment to 14 days of consecutive night work at an oil platform and the readjustment to day life at home, using the Karolinska sleep/wake diary. The platform workers adapted to night work within a few days, as indicated by the rapid reduction of night-work sleepiness, and by the gradual delay of bedtime to an hour commensurate with the behavior of day workers. Readaptation to day life was slower and more difficult, adding evidence of a complete adaptation to night work. We conclude that the lack of conflicting exposure to daylight in the morning may have facilitated the rapid adjustment to night work.