A special issue of the Brazilian Journal “ Revista de Saude Publica” is devoted to a selection of papers presented at the XVIth International Symposium on Night and Shiftwork held in Santos, Brazil, in November 2003.

At least two other recent international developments, the growth of “flexible work” and the ageing of the workforce in many countries, also present significant new challenges and opportunities for working hours research. Although workforce ageing has attracted substantial public and political attention in recent years, little systematic consideration has been given to the occupational health implications and working hours researchers, who for some time have had an interest in older workers, are in a position to provide some leadership in this regard. Various rapidly expanding forms of precarious or contingent work, particularly short-term temporary and casual work, are often promoted as “flexible” and “family-friendly”. However, this flexibility is most often organisational rather than individual, and frequently leads to more diverse, and often irregular, shift systems  and the growth of extreme work schedules that combine shiftwork with very long hours . These undesirable working hours appear to be one factor contributing to the variety of negative effects of health and safety associated with precarious employment. These developments are currently stimulating a shift away from the traditional focus of shiftwork research on full-time workers in ongoing employment toward a greater concern with workers in various forms of flexible employment.

The papers published in this issue pick up the symposium theme of equity and diversity, the ageing of the workforce and workplace flexibility. Friedhelm Nachreiner examines the topical, though still under-researched, issue of accommodating diversity in the design of work schedules. His provocative overview examines equity in relation to aspects of diversity already given some attention in working hours research (gender, marital status, social support, age and personality) and extends to others that have received somewhat less recognition (cultural values, socioeconomic differences). Several papers then examine the impact of variations in working hours on variables of long standing in shiftwork research: sleep, subjective health and wellbeing, and satisfaction.

They describe negative effects of night work on specific aspects of quality of life (Kaliterna Lipovcan, Prizmic Larsen & Zganec); the negative impact of high variability in working hours, especially company-controlled variability, on health and social lives (Janssen & Nachreiner); the disadvantage of casual (temporary) hotel workers in relation to unpredictable hours over which they had little control, work-life conflict and health (Bohle, Quinlan, Kennedy & Williamson), national differences in negative impact of night shift on perceptions of physical and mental tiredness (Tepas et al); and impact of the timing and duration of night-time naps on the sleep and performance of night workers (Takeyama et al). In the following paper, Radoševic-Vidacek and Košcec report an interesting and unusual study examining the impact of parents’ work schedules on adolescents’ sleep.

It is unusual because the students also attend school on weekly rotating morning and afternoon shifts. The results indicate that adolescents with parents in shiftwork are disadvantaged in terms of waking times, sleep duration and bedtime irregularity, particularly when they themselves were on the “morning shift”.
Four papers tdeal with aspects of what can be broadly labelled “work schedule design”. Jeppesen and colleagues examine the implications for shiftworkers applying different number of teams in the shiftwork organization. They worked in different firms, sharing the same product organization and a common corporate culture, in the same multinational company. Gärtner evaluates conflicts between employees’ preferences and ergonomic recommendations in shift scheduling. He concluded that achieving consent does not ensure ergonomically sound schedules. And procedures of risk assessment seem to be promising, but still is a difficult approach. Carsten Schomann and his colleagues describe the development of a computer programme for the design and evaluation of shift schedules. The new aspects implemented in this programme included the concept of criterion functions, resulting on the integration of workload-related aspects. Kazutaka Kogi examines industry-based guidelines on night and shift work and enterprise-level intervention projects to design a new checklist to facilitate the shiftwork interventions.

The concluding paper by Prof. Giovanni Costa, presents a reflection on the approaches and strategies to promote and to protect the shiftworkers’ health. According to Costa, a more effective and profitable adoption of preventive and compensative measures can be achieved through a systemic approach, taking into account the many domains involved on this issue.

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