Sleepiness and days of recovery

In the literature recovery after work is taken for granted – one has 16 h off between work bouts and one has 36 h off each weekend. However, the situation for those working irregular work hours may be quite different because of night work, long shifts, or long sequences of working days. Strictly speaking we don't have any scientific support for theories on how recovery days should be patterned. This paper, therefore, brings together data from a series of our own studies that involve irregular work hours, with the specific purpose of looking at the recovery process. The results show that for the average normal office week worker two days of recovery are normally sufficient. For those who work long shifts in long sequences three days are needed for normalization, whereas 12 h shifts in 2–3 day sequences seem not to cause accumulated fatigue. Interestingly, fatigue/sleepiness is often at its peak during the first day of recovery – not the last day of the working week. Air crew and oil rig workers take a longer time to recover, probably because of too much adjustment of the biological clock. As a rule, long haul air crew is usually much more fatigued than short haul crew during their days off, despite the fact that long haul flying is voluntary and opted for by those who fly it. Also train drivers are affected during their days off by their irregular work hours – in particular backwards rotating schedules seem to cause accumulation of fatigue. The results suggest that one day of recovery never is sufficient, two days usually is, whereas 3–4 days are necessary after periods of severely disturbed circadian rhythmicity.