Designing better shift systems

The results of some intervention studies on the effects of the change from weekly rotating to quicker rotating shift systems are presented. Consequently, the following recommendations for the design of shift systems according to physiological, psychological and social criteria are discussed: (1) Nightwork should be reduced as much as possible. If this is not possible, quickly rotating shift systems are preferable to slowly rotating ones. Permanent nightwork does not seem to be recommendable for the majority of shiftworkers. (2) Extended workdays (9-12 hours) should only be contemplated when the nature of work and the workload are suitable for extended working hours, and the shift system is designed to minimize the accumulation of fatigue and toxic exposure is limited. (3) An early start for the morning shift should be avoided. Flexible working time arrangements can be achieved in all shift systems. The highest flexibility is possible in the so-called 'time autonomous groups'. (4) Quick changeovers (e.g. from night shift to afternoon shift on the same day) should be avoided. The number of consecutive working days should be limited to five-seven. Every shift system should include some free weekends with at least two consecutive days off. (5) The forward rotation (phase delay, clockwise rotation: morning/evening/night shift) would seem to be most preferred.     

Optimization of shift work: physiological contributions

Abstract

Healthy subjects (n= 62) with different circadian phase positions worked up to six weeks in different shift systems. Rotation speed was experimentally varied. On shift days all subjects worked in the Institute but spent their leisure time as usual.

In order to minimize bias through masking effects, ‘control days’ were interpolated (twice a week) into the shift periods. On these control days subjects remained on bedrest for 24 hours under constant conditions.

Results were as follows:

(i) The earlier the circadian phase position the poorer the adaptation to night-shifts. In particular, morning types were not able to adapt even to permanent night-shifts.

(ii) Evening types were able to adjust their circadian systems to a slowly rotating shift system (rotation speed seven days) and a 25 h-sliding system though they failed to do so with more quickly rotating systems. Whereas indifferent subjects were not able to adjust to even the slowly rotating system.

(iii) When stable phase shifts occurred in response to altered working hours they always amounted to about one hour per day if the working hours were not coherent with the usual environmental zeitgebers.

It is concluded that, on physiological criteria, very slow rotating shift systems or permanent night-shifts seem to be acceptable for evening types, but not for morning types who may require special health care in these conditions.     

Time-budget studies of policemen in weekly or swiftly rotating shift systems

For 8 days 120 policemen kept special diaries including working time, travelling to and from work, leisure time and sleeping time. By analysing the data of leisure and sleep in relation to the time of day and the type of shift it is possible to find out critical points within a shift system.

The mean duration of sleep was reduced before morning shifts, between night shifts and after a morning shift that was followed by a night shift on the same day. The leisure time was limited in connection with afternoon shifts and between the combined morning and night shift. It is recommended not to have double shifts on one day.

Rapidly rotated shift systems had more advantages referring to the total amount of night sleep than weekly rotated shift systems. The backward rotation of shifts was unfavourable because of the short time off between the last afternoon shift and the first morning shift. Furthermore, short nightwork periods and a start of the morning shift which is not too early seem to be preferable.     

What roles do team climate,roster control,and work life conflict play in shiftworkers' fatigue longitudinally?

The study aimed to examine shiftworkers fatigue and the longitudinal relationships that impact on fatigue such as team climate, work life conflict, control of shifts and shift type in shift working nurses. We used a quantitative survey methodology and analysed data with a moderated hierarchical multiple regression. After matching across two time periods 18 months apart, the sample consisted of 166 nurses from one Australian hospital. Of these nurses, 61 worked two rotating day shifts (morning & afternoon/evening) and 105 were rotating shiftworkers who worked three shifts (morning afternoon/evening and nights). The findings suggest that control over shift scheduling can have significant effects on fatigue for both two-shift and three-shift workers. A significant negative relationship between positive team climate and fatigue was moderated by shift type. At both Time 1 and Time 2, work life conflict was the strongest predictor of concurrent fatigue, but over time it was not.     

Changing the speed of shift rotation: a field study

Abstract

A group of 33 controllers of an emergency service were studied before and after a change in shift roster. The original roster was the traditional weekly rotating type of three shifts, morning, afternoon and night in that direction, in which controllers worked seven consecutive shifts of the same type. This was changed to a rapidly rotating roster of shifts with no more than three consecutive night shifts. The direction of shift change remained the same. Sleep and meal diaries were kept by all controllers for 2 weeks before the roster change. Self-report measures were taken of health, social drug consumption and work variables, an anxiety inventory, the State-Train Anxiety Inventory and the Work Environment Scale were administered both before and 5 months after the roster change. Significant improvements were found after the shift roster change on almost all measures with the exception of self-reported nervousness and loss of appetite and a number of items in the Work Environment Scale. This finding provides some evidence from the field for the argument that rapidly rotating shifts may be the optimal form of shift system.     

How fast should the night shift rotate?

Claims are frequently made that changing from morning to afternoon to night shift at about two- to three-day intervals (rapid rotation) is the best way of organizing 24h staffing. A critical analysis is made of the grounds for these assertion, followed by a review of evidence bearing upon the issue of whether longer periods of rotation are to be preferred. The conclusion is that permanent (zero rotation), fixed-night systems are superior on most counts, and should be implemented for night work, leaving the option of rapid rotation to cover the two (morning and afternoon) day shifts. This said, the multiplicity of shift systems and settings means that this will not always be the method of choice. Furthermore the recommendation should be regarded as provisional pending a search for more data directly comparing the two systems.     

How fast should the night shift rotate?

Claims are frequently made that changing from morning to afternoon to night shift at about two- to three-day intervals (rapid rotation) is the best way of organizing 24h staffing. A critical analysis is made of the grounds for these assertions, followed by a review of evidence bearing upon the issue of whether longer periods of rotation are to be preferred. The conclusion is that permanent (zero rotation), fixed-night systems are superior on most counts, and should be implemented for night work, leaving the option of rapid rotation to cover the two (morning and afternoon) day shifts. This said, the multiplicity of shift systems and settings means that this will not always be the method of choice. Furthermore the recommendation should be regarded as provisional pending a search for more data directly comparing the two systems.     

Re-entrainment of Body Temperature in Experimental Shift-Work Studies

In a series of experimental shift work studies six subjects worked on continuous night shift for three weeks, four subjects worked on a 1-1-1 shift system (1st day morning shift, 2nd day afternoon shift, 3rd day night shift, 4th day off), and two subjects worked on an 2-2-2 shift system (the ‘metropolitan rota’). Rectal temperature was continuously recorded in each experiment.

The greatest changes in the circadian rhythm of body temperature occurred on the second night shift day, and during the first week of continuous night shift working. The changes involved both shifts in the phasing of the rhythm, and alterations in its form. The re-entrainment of the rhythm to its normal phasing took two or more days after two or more successive night shifts, but only one day after a single night shift. Considerable individual differences in the rhythm adjustment to night work were observed.

In a field validation of these findings, 34 shiftworkers in municipal gas and water supply undertakings measured their oral temperature every 2h both on and off duty. Although only very few temperature readings were obtained during sleep periods, the results confirmed, in general, those of the experimental studies.     

Effect of time of day on height loss response variability in asymptomatic participants on two consecutive days

Abstract

Ergonomists measure height loss in relation to loads imposed on the spine. It is difficult to interpret whether height loss responses recorded on different days are accurate due to natural daily fluctuations in height loss and measurement variability. The objective of this research was to investigate whether the variability of height loss in the sitting position is affected by time of day and to analyse day-to-day variability in asymptomatic participants. Fifty asymptomatic participants attended two sessions (morning and afternoon) of stadiometry testing on four separate days. The results showed that a variability of height loss response changes in excess of 0.886?mm in morning and 1.128?mm in afternoon between days indicates that an intervention itself has influenced height loss. Future investigations on height loss in sitting should take these results into consideration to confidently state that an intervention has influenced height loss response at each time of day.

Practitioner summary: Daily fluctuation creates difficulties when interpreting whether height losses recorded on different days and times are intervention related. Seated stadiometry measures on different days and times of day demonstrated specific levels of natural variation. Changes above 0.886?mm (morning) and 1.128?mm (afternoon) can be attributed to intervention effects.

Abbreviations: LBP: low back pain; SEM: standard error of measurement; MeanSDs: means of standard deviations     

Experimental Studies of Shift-Work I: A Comparison of ‘ Rotating ’ and ‘ Stabilized ’ 4-hour Shift Systems

Abstract

Efficiency at ‘ mental ’ tasks was observed when performed according to a time schedule imposed by following one of two different 4-hour shift systems for a period of 12 consecutive days. Twenty-eight subjects were assigned either to a ‘ rotating ’ system, in which each 4-hour period of the 24 hours was worked once every 72 hours in a repeating cycle, or to a ‘ stabilized ’ system, in which the work periods were from 1230 to 1630 and 2400-0400 each day. In the rotating system, alterations in the level of several aspects of performance at different times of day were found to be related quite closely to concurrent fluctuations in body temperature arising from its natural circadian rhythm. A shift in the phase of this rhythm in response to the now sleep/waking cycle imposed by the stabilized system was accompanied by a corresponding change in the relative levels of performance observed in the two work periods. Thus in both systems body temperature was, in effect, a predictor of performance efficiency. Some implications for the organization of shift working are discussed     

Productivity on a weekly rotating shift system: circadian adjustment and sleep deprivation effects?

Abstract

There is little doubt that productivity and safety can be impaired on the night shift. Two main factors have been identified that may be responsible for this. On the one hand, the circadian rhythm in performance on at least simple tasks is at a low ebb at night, and adjusts only slowly over a span of night shifts. On the other, the day sleeps of shift workers taken between night shifts are of a reduced duration, and thus a cumulative sleep debt may accrue over successive night shifts. The former thus predicts that productivity should improve over a span of night duty, while the latter predicts that it should decline. We have examined the productivity of 53 female shift workers, and the sleeping habits of a sub-sample of 30 of them, on a weekly rotating shift system in order to assess the relative contribution of these two factors. Our results suggest that circadian adjustment to night work is the dominant factor for the first three or four successive nights shifts, but that sleep deprivation effects may then result in a decrease in productivity over subsequent nights. They also indicate that sleep deprivation, but not circadian adjustment, may affect the productivity of some workers when on the morning shift.     

Diurnal variations of cloud activity in Bangladesh and north of the Bay of Bengal in 2000

The Japanese Geostationary Meteorological Satellite (GMS-5) high resolution (10 km mesh) hourly data are sampled in 1°×1° grid boxes in the domain of 600×600 km over Bangladesh (land) and the north part of the Bay of Bengal (ocean) to obtain diurnal cycle of cloud activity. The cloud embedded area (CEA) shows afternoon (∼1700 LST) and morning (∼0003 LST) peaks over land typically composed of relatively small deep (<214 K) and large shallow (<243 K) convective cloud systems. In contrast, only afternoon (1400-1600 LST) peak is observed over ocean typically composed of small shallow and large deep convective cloud systems. Meanwhile the frequency of the cloud systems exhibits the clear afternoon (∼1600 LST) peak over the land and the ocean that indicates that afternoon is the initiation times of land-based clusters over Bangladesh and water-based clusters in the analyzed ocean (87.44-93.33°E; 15.7-21.08°N).Radar data from Bangladesh Meteorological Department (BMD) for consecutive 135 days from 16 April 2000 over Bangladesh are utilized to obtain the diurnal variations and characteristics of precipitation in relation to cloud activity. The nature of the diurnal cycle of precipitation in Bangladesh is that there is a morning peak at 0600 LST with minimum at noon. The frequency of the echoes exhibits two peaks—one in the afternoon (∼1500 LST) and the other in the morning (0600 LST) hours. The smaller echoes dominate in the afternoon while larger echoes develop in the early morning. The shape, lifetime, horizontal length and movement of the precipitation features in Bangladesh are also investigated using radar data.     

Shiftwork and work injuries in an iron and steel mill

A study on work injuries that occurred over a five-year period was conducted in an iron and steel mill employing over 1000 workers. Of all the 921 injuries which required more than one day's sick leave, over 40% (383 cases) happened during the morning shift (0700-1500 hours), 210 cases occurred in the afternoon shift (1500-2300 hours) and only 150 cases were reported during the night shift. There were two injury peaks throughout the day, one at mid-morning (between 0900 and 1000 hours) and the other towards the mid-afternoon (1400-1500 hours). It was observed that hand injuries were more common during the morning and afternoon shifts and foot injuries normally occurred at night. 'Fall' was one of the main causes of accidents at night, whereas 'struck by' heavy objects and 'burn' were more common during the day. Although there were more accidents during the morning and afternoon shifts, work injuries which occurred at night generally required a longer duration of sick leave. This suggests that accidents which happened at night were more serious. It is believed that the work habits, shift systems and work environment have a substantial influence on these accidents.     

Inviting Strangers to Participate in Collaborative Consumption through Mobile App

ABSTRACT

Mobile technology has facilitated an emerging form of consumption practices called collaborative consumption. In this study, we investigate one such manifestation whereby merchants send group discount coupons to nearby consumers and encourage them to invite surrounding people to enjoy the discount together. We are interested to know if timing (morning vs. afternoon) and message framing (active vs. passive mutual helping tone) would increase the chance of an individual deciding to invite strangers (and invite a higher proportion of strangers if they did) to participate in the collaborative consumption. Facilitating the participation among strangers can help elevate the reach and influence of collaborative consumption, allowing its potential to be better exploited. Our field experiment findings show that in general people are more likely to invite strangers (and also a higher proportion of strangers in all their invitations) in the morning than in the afternoon. In addition, a message framed to ask the focal individual to actively help others enjoy the deal (active tone) is more effective than a message framed passively, i.e., to let others help him/her (passive tone) in the morning. However, passive tone framing can induce individuals to invite a higher proportion of strangers in the afternoon if they did invite others. These findings have important implications to merchants and app providers on how to more fully tap into the potential of collaborative consumption via mobile technology.     

Is there a 'best compromise' shift system?

In his review Wilkinson considers the question 'How fast should the night shift rotate? He concludes quite strongly that with the possible exception of social factors, most of the evidence favours the use of prolonged or permanent night shifts. In this reply I argue that in reaching this conclusion Wilkinson has (i) overestimated the problems associated with rapidly-rotating shift systems; and (ii) underestimated the problems that might be encountered in trying to implement effective permanent night shift systems. The evidence on the various problems reviewed by Wilkinson is reconsidered. Other aspects of shift systems that were ignored by Wilkinson are then also taken into account. It is concluded that the evidence does not allow a general choice to be made between the use of either permanent night shifts or rapidly rotating, delaying, shift system. Rather the choice between them would appear to depend on the relative importance attached to safety and social problems in any given workplace.     

On the implications of user variability in open systems An overview of the little we know and of the lot we have to find out

Abstract

As the use of computers increases, the cost of educating computer users rises. Therefore the need for extensive education of users should be avoided as much as possible. Instead computer systems should be adapted to the requirements and characteristics of computer users. Hereby the need to identify user characteristics arises. The less computer educated the users, the more their requirements of the systems will differ. Where user characteristics are difficult to change, it will be worthwhile to attend to user differences in the design of systems. The implications of user differences may vary depending upon the type of task to be performed. The present paper presents an analysis of different user characteristics and their possible interactions with different task requirements. Hereby some recommendations regarding the need to educate users or adapt systems to the user were derived.     

What is the evidence for less shift work tolerance in older workers?

This paper explores the suggestion that older people would be less tolerant to shift work. Field studies on age-shift work interaction effects on sleep, fatigue, performance, accidents and health were reviewed. Studies on age-shift (morning, afternoon, night) and age-shift system (roster) interactions were also reviewed. In nine studies, shift and day workers were compared and interactions with age were addressed. Two studies reported more problems in older people, four studies reported opposite results, while in five studies no significant age-shift work interaction was observed. From across-shift comparisons (six studies), it was deduced that older compared with younger workers have more sleep problems with night shifts, while the opposite is true for morning shifts. This review did find some differences between older and younger workers, but did not find evidence for the suggestion of more shift work problems in older workers. STATEMENT OF RELEVANCE: This systematic review reveals the limited evidence that exists concerning shift work tolerance in older workers, highlighting an area for future research. Some interactions between age and shift type and shift system have been found, however. In view of these, it is argued that age-specific aspects should be considered in shift work planning.     

Police officers attitude to different shift systems: association with age, present shift schedule, health and sleep/wake complaints

It is often claimed that shift workers give priority to long series of days off and therefore prefer compressed work schedules at the expense of what is optimal for long-term health. The aim of the present study was to evaluate the attitude to six new shift systems among a randomly selected sample of police officers. The results showed that the most popular shift system was a rapidly, forward, rotating schedule with at least 16 h of rest between shifts, despite that it had fewer days off compared with some of the compressed shift systems. However, the individual differences were large and many individuals (32%) disliked the rapidly rotating shift system. Young age was associated with a positive attitude to the rapidly rotating shift system. The attitude to the shift system was also influenced by the present schedule, and shift systems that were similar to the present work hours received more positive evaluation. Sleep and health complaints showed no association with the attitude to the shift systems. In conclusion, the shift workers attitude to the new schedules was partly in agreement with the ergonomic recommendations of the design of three-shift systems that will facilitate sufficient sleep and minimize negative health consequences.     

The Cost of Work in Medical Nursing

Abstract

The physiological cost of work was measured on the nursing staff of a general medical ward. Fourteen subjects took part in the study. Heart rates were measured during work and sleep on 13 nurses, and oxygen consumption measurements were made on 12, using the Miser Respirometer. In addition, maximum aerobic capacity was estimated on eight of the subjects

Mean heart rates during work were 93 ± SD 10 bt min^-1 significantly higher on the late than the early shift. The mean rate of energy expenditure was 147 ± SD 31 W. and was significantly higher in the morning than the afternoon or the evening

The mean relative work toad was 22% ± SD5%. The mean individual relative heart rate was 26% ± SD 9% and the mean ratio of work : sleep heart rates was 145 ± SDO-19 The findings placed medical nursing in the same category as light industrial work.     

Hourly trends in workers' compensation claims

Very few studies have investigated the variations in occupational injuries throughout the day. The main objective of this study was to examine hourly trends in reported claims of occupational injuries and illnesses and their associated cost, with special emphasis on low-back disorders (LBDs) and cumulative trauma disorders (CTDs). The data were obtained from the records of a major insurance carrier. The results showed that the number of claims per hour exhibited a Gaussian-like distribution with highest reported numbers occurring between 07:00 and 11:00 h. There was an observed increase in LBD claims during the morning hours when compared to the afternoon. In addition, there was a pronounced increase in the number of CTD claims at 09:00 h indicating a possible carry-over effect from nocturnal and early morning pain commonly experienced in CTD sufferers. More revealing, normalized claims (per number of people working at a given hour) showed a dramatic increase during the evening and early morning hours when compared to normal working hours. For both the overall and LBD claims, the rates during the night and early morning periods were up to three times higher than during the typical day-time working hours. However, this trend was not as pronounced for the CTD claims. Most of the hourly cost trends were similar to those observed for the claims trends. However, cost information may reveal further insights about the severity of injuries, especially for CTDs. The findings of the study indicate that special attention should be paid to activities and work processes performed during night and early morning hours of the day. It should be noted that this study focused on the 'recording' of time of injury which may or may not correspond to the ‘true’ time of occurrence of an injury or a symptom. Further studies are needed to assess the agreement between the recorded and the actual time of occurrence of an incident, and to better understand the underlying reasons behind the variation in the time of injuries.