Shiftwork and health

Industrial and commercial activities that operate outside normal work hours have become widespread in recent years; services such as banking, communications, transport, catering and retailing are routinely available during evening hours, and often round-the-clock. Consequently, the work patterns of a substantial proportion of the population now extend beyond regular daytime working hours; variable schedules (often including evening or night work) and rotating shifts are both widespread. In a recent European survey, 28% of the workforce had variable work patterns, 10% had evening or night schedules, while 17% worked two-shift or three-shift rotating schedules (Boisard et al., 2003). Further analyses showed that the proportion of shift workers remained relatively constant up to age 45 years, but fell sharply at higher ages, particularly over 55 years (European Foundation for the Improvement of Living and Working Conditions, 2003), reflecting older workers’ difficulties in adjusting to shiftwork. Similarly, analyses of US survey data showed that, in 1997, 27.6% of the workforce had flexible work schedules, while 16.8% of full-time employees had ‘alternative’ schedules involving work outside normal daytime hours (06.00–18.00 hrs), 6.4% of whom worked night or rotating shifts (Beers, 2000). These proportions varied by occupation; rotating shifts were particularly common in security services (16.3%), mining (12.5%) and catering (8.7%), but infrequent among professionals and managers (1.7%). Night work was prevalent in healthcare, manufacturing, and manual occupations. Global trends towards a ‘24-hour society’ suggest that these proportions are likely to rise; thus, the implications of shiftwork for physical and mental health are not only a matter of current concern but are also likely to become increasingly important in the future (Costa, 2001; Rajaratnam & Arendt, 2001).