ABSTRACT
For many years, shift-work has been required to provide emergency cover and essential services at all hours of the day and night, as well as for maintaining longterm industrial processes. Nevertheless, shift-work is no longer restricted to these types of occupations, but is increasingly found in modern ‘call centres’, where employees deliver financial and retail services around the clock to meet the demands of a ’24-hour’ society, in shops, and so on. It is not surprising, therefore, that approximately 13-14% of the European and South American workforce is now involved in a shift-work schedule that includes some time spent working at night (Spelten et al., 1999; Harrington, 2001; Rajaratnam and Arendt, 2001; Costa, 2003). Many employees can also be found working ‘unusual hours’; outside of the ‘normal’ 9:00 – 17:00 hour period, but not necessarily involving night work, e.g. the permanent early morning shifts worked by postal delivery personnel or the shorter morning and evening ‘split-shifts’ worked by public transport staff or office cleaners (Taylor et al., 1997).
