Review and special articleShifting Schedules: The Health Effects of Reorganizing Shift Work
Introduction
Shift work is an increasingly common form of work organization. Approximately one fifth of workers are engaged in some kind of shift work.1 Technologic advances, changes in the economy, and the emergence of 24-hour societies2, 3 mean that shift work is no longer confined to the manufacturing and industrial sectors, and it is now an important aspect of employment in the retail and service sectors. Shift work continues to be commonplace among healthcare and emergency-services personnel, with up to 50% of hospital staff working on shifts.4 However, shift work remains socially patterned, with a higher prevalence among lower socioeconomic groups,5 so it is they who most experience the adverse consequences of shift work on health and work–life balance.
The possible negative effects of shift work on health and work–life balance are well known.1, 6, 7, 8 Reported health problems include sleep disturbances, fatigue, digestive problems, emotional problems, and stress-related illnesses, as well as increases both in general morbidity and in sickness absence.9 These problems may derive from disruption to physiologic, psychological, and social circadian rhythms.6, 7 Shift work, particularly night work, disrupts the natural circadian rhythm, requiring people to be active at times when they would normally be sleeping, and vice versa.7 This leads to problems with sleep (e.g., when natural alerting mechanisms such as the cortisol surge and temperature rise interrupt it) as well as with daytime functioning (when wakefulness at night is reduced by temperature drops and melatonin surges). Sudden changes in schedule can therefore have an effect akin to jet lag. Disruption of the circadian rhythm can also lead to disharmony within the body, as some functions (e.g., heart rate) adapt more quickly than others (typically the endogenous functions such as body temperature and melatonin production). This leads to desynchronization, which itself can result in psychological malaise, fatigue, and gastrointestinal problems. Realignment can take several weeks.7
Previous studies have explored associations between the physiological and psychological aspects of long-term exposure to shift work and health issues such as cardiovascular problems, pre-term births, or breast cancer.10, 11, 12 Shift work may also involve increased risk of injuries and accidents as performance fluctuates.13, 14 For example, a review of injuries related to shift work concluded that workers on rotating shift work had a higher risk of injury than workers on fixed shifts, that there was a greater risk of injury on shifts that rotated more frequently, and that longer workdays were no more hazardous than the more usual 8-hour workday.13
Most existing research emphasizes the physiological changes that shift work induces, but shift work also involves considerable social desynchronization, involving working at times and on days that may make it difficult to maintain a balanced domestic and social life.15 The Work Foundation defines work–life balance as people having a measure of control over when, where, and how they work. It is achieved when an individual’s right to a fulfilled life inside and outside paid work is accepted and respected as the norm to the mutual benefit of the individual, business, and society.16 It has been suggested that work–life imbalance can lead to poorer health. For example, a study of the Swedish working population found that a majority of employees experienced work–life imbalance, and that this was due to work interfering with nonwork activities. Self-reported health on the General Health Questionnaire (GHQ) was significantly worse among employees who experienced work–life imbalance.17
A range of interventions has been suggested to address the negative effects of shift work.1 These include interventions at the individual level: exposure to bright light or napping; training; counseling and education; countermeasures against sleep problems and problems with appetite and digestion; educational interventions (e.g., to help workers to cope with shift work); regular medical surveillance and pharmaceutical interventions (e.g., melatonin administration); and selection strategies to remove the most vulnerable.7, 18, 19 At the organizational level, interventions include decreased shift length (especially on night shift); redesign of shift work schedules (according to ergonomic criteria or to increase flexibility); improvements in working conditions (reducing noise or improving unfavorable working environments); and legislation that limits working hours or exposure to shift work (e.g., the European Union’s Working Time Directive, and its subsequent revisions).1
The effects of some of these interventions on health and work–life balance have been evaluated in primary studies. This article presents the results of a systematic review of the health and work–life balance impacts of organizational-level changes to shift work and any differential impacts by social group. The review was conducted between October 2005 and November 2006. Although previous literature reviews exist in the area of shift work and health, they often concentrate on observational epidemiologic studies (descriptive or comparative) rather than evaluative intervention studies; tend to cover only individual-level interventions; focus on certain occupational groups; or have not been conducted using full systematic review methodology.1, 4, 8, 9, 13, 20
Section snippets
Inclusion and Exclusion
The review sought to identify all primary empirical studies that examined the effects of organizational-level interventions on the health and work–life balance of shift workers and their families. It excluded studies of controlled exposure to darkness and light, as it defined those as individual-level, rather than organizational-level, interventions within its context. It also excluded selection strategies, as these interventions seem to be primarily focused on characteristics of the individual
Results
Twenty-six studies of organizational-level interventions were synthesized. These covered a diverse range of interventions: changes to the speed, direction, and use of rotation; changes to night work; later start and finish times; changes to weekend working; decreased shift lengths; and self-scheduling.25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 (Some studies are reported in more than one publication.) One study was a
Effects of the Interventions
Overall, most types of organizational shift work intervention examined in this systematic review appear to have either positive or neutral effects on health and work–life balance (Appendix G). No one type of organizational intervention was found to be consistently harmful to workers (although this may be due to publication bias or methodologic problems; see below). Three types of intervention, however, were reported to have beneficial effects: switching from slow to fast rotation, changing from
Conclusion
The results of this systematic review of intervention studies supports the results of descriptive epidemiologic research and laboratory-based studies that have suggested that slow-to-fast rotation and backward-to-forward rotation are less harmful to the health and work–life balance of shift workers.1, 7, 14, 48, 52, 53, 54 The review reinforces previous research showing that increased control at work, in this case via self-scheduling, can be beneficial to the health and work–life balance of
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