Is academic mobility good for you? A case report on the effects of frequent, two-weekly travel across one time zone on sleep-wake indices

The aim of the present study was to investigate the actigraphic sleep-wake and light exposure patterns of a 48-y-old healthy woman who travelled across one time zone (Italy to UK and vice versa) every two weeks for over 2.5 years (i.e. 852 night of sleep data, with 80% of recorded days retained for analysis after exclusion of travel and non-UK/Italy stays; 58% of time spent in Italy), and reported early evening somnolence and unpleasantly early wake-up time in the UK, especially immediately after travelling. She therefore started to wear an actigraph to monitor rest-activity and light exposure. Compared to Italy, UK-based recordings showed a significantly earlier midsleep (02:46 ± 01:00 vs. 03:02 ± 01:07 local clock time; p < 0.01) and more wake after sleep onset (WASO, 57.4 ± 29.7 vs. 46.5 ± 30.3 min; p < 0.001). Time spent above the 1000 lux threshold, used as a reference for outdoor light exposure, was significantly greater in the UK (92 ± 82 min vs. 56 ± 78 min, p < 0.001). Higher daytime light exposure was associated with earlier midsleep and reduced sleep fragmentation, as indicated by lower WASO. In conclusion, frequent travel across one time zone resulted in prolonged sleep-wake disturbance, with no obvious pattern of resolution after the flight.