Jet lag and shiftwork : their effects on sleep & sleepiness

Sammanfattning: The aim of the studies was to describe the detailed sleep/wake patterns before, during, and after a period of work that forces individuals to deviate from their normal sleep/wake pattern. Possible countermeasures to experienced problems was evaluated in intervention designs. Measures of sleep included activity monitoring, sleep and wake diaries and questionnaires. Also performance measures during work were obtained.It was found that in connection to both a westbound and an eastbound flight almost all subjects adapted to local bed times on layover. This increased the wake span during outward and homeward flight days to between 21-28 hours. During flight days napping was found to be very common, especially during flights. Sleep efficiency dropped below 90% during layover in both flight directions, disturbed by awakenings, and gradually returned to normal across four recovery days. Sleepiness symptoms increased during layover, peaked to encompass 25% of the return flight day and gradually decreased across recovery days. The eastbound flight was shown to contain more sleep difficulties and to be more dependent on nap sleep.A possible countermeasure to jet lag was tested in an intervention study, letting crews retain their home-base sleep/wake pattern on layover after westward flight. This reduced jet lag symptoms and sleepiness on layover but not at home. Another intervention was evaluated when a group of shift workers changed from rotating three shift (8-hour) to a 12-hour shift schedule. The data showed that quick changes (8h rest) in the 8-hour schedule increased sleep problems and fatigue. Health, perceived accident risk or reaction time performance was not negatively affected; alertness improved and subjective recovery time after night work decreased in the 12-hour schedule. It was concluded that the change was positive in most respects, possibly due to shorter sequences of work days, longer sequences of consecutive days off, and the elimination of quick changes.A detailed analysis of morning work including use of polysomnography (EEG) showed that preceding sleep was reduced to 5 hours and 12 minutes. Subjective ratings demonstrated that morning work was associated with more apprehension of difficulties in awakening and insufficient sleep.The present studies demonstrate that sleep related problems are frequent for both shift workers and air crew. The particular characteristic of each work schedule pose different problems, either it involves night work, quick changes, early morning work, time zone crossings or long work hours. The studies further demonstrate that a change of either work hours or sleep strategies can decrease some of these problems.