Accepted Manuscript

Sleeping at work: not all about location, location, location

Sarah M. Jay, Brad Aisbett, Madeline Sprajcer, Sally A. Ferguson

PII: S1087-0792(14)00044-6

DOI: 10.1016/j.smrv.2014.04.003

Reference: YSMRV 806

To appear in: Sleep Medicine Reviews

Received Date: 23 November 2013

Revised Date: 28 March 2014

Accepted Date: 22 April 2014

Please cite this article as: Jay SM, Aisbett B, Sprajcer M, Ferguson SA, Sleeping at work: not all aboutlocation, location, location, Sleep Medicine Reviews (2014), doi: 10.1016/j.smrv.2014.04.003.

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Sleeping at work: not all about location, location, location.

Sarah M Jaya c

, Brad Aisbettb c

, Madeline Sprajcera c

and Sally A Fergusona c

a Central Queensland University, Appleton Institute, Adelaide, Australia

b Centre for Physical Activity and Nutrition Research, Deakin University Burwood, Australia

c Bushfire Cooperative Research Centre, Australia

Summary

Working arrangements in industries that use non-standard hours sometimes necessitate an

‘onsite’ workforce where workers sleep in accommodation within or adjacent to the

workplace. Of particular relevance to these workers is the widely held (and largely

anecdotal) assumption that sleep at home is better than sleep away, particularly when away

for work. This narrative review explores the idea that sleep outcomes in these unique work

situations are the product of an interaction between numerous factors including timing and

duration of breaks, commute length, sleeping environment (noise, movement, vibration,

light), circadian phase, demographic factors and familiarity with the sleep location. Based on

the data presented in this review, it is our contention that the location of sleep, whilst

important, is secondary to other factors such as the timing and duration of sleep periods.

We suggest that future research should include measures that allow conceptualisation of

other critical factors such as familiarity with the sleeping environment.

Keywords

Sleep, shift work, sleep loss, sleep environment, work rest facilities, non-residential

workforce, mobile workplaces

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Acknowledgements

We would like to acknowledge Professor Drew Dawson’s contributions to the manuscript.

Conflicts of Interest

None

Abbreviations

FIFO – Fly-in Fly Out

PSG – Polysomnography

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Sleep at home and away

Global industry is now well established and in order to accommodate the 24 hour society

there has been a significant shift in the organisation of work hours. A growing percentage of

the workforce no longer works a standard week. It is estimated that 16% of Australian,[1]

18% of the USA [2] and 17% of the European Union [3] workforce are involved in some form

of shift work. This shift in work patterns brings with it challenges for other aspects of life and

of particular relevance to this review is sleep. The sleep and circadian disruption associated

with shiftwork are well described [4] and inadequate sleep has adverse implications for

numerous aspects of waking function [e.g [5, 6] with ramifications for workplace

performance and safety [7, 8]. The quality and quantity of sleep that workers obtain

between consecutive work shifts is therefore paramount for safety.

Working arrangements in many industries that use non-standard hours also necessitate an

‘onsite’ workforce where workers sleep in accommodation within or adjacent to the

workplace. This is the case in mobile workplaces such as aviation, road transport, the rail

sector and maritime industry. Alternatively, the worksite may be in a remote area as in the

case of oil rigs or mine sites making recruitment of a large and specialised workforce from

the surrounding community practically impossible. In these situations, a non-residential

workforce typically travels to site for periods of work and returns home during blocks of

days off. Lastly, temporary work environments such as those involved in emergency services

or military operations also involve sleeping away from home. Given the industries described

above are high-risk, mitigation of health and safety issues related to inadequate sleep is

critical.

A widely held (and largely anecdotal) assumption is that sleep at home is better than sleep

away, particularly when away for work. To accept this would be to assume that for workers

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sleeping away from home, who are also often shift workers, the foreign or ‘away’ sleeping

location is an additional barrier to adequate sleep. An alternative view however, is that

sleeping away from home has some advantage related to fewer competing demands on

time and favorable environmental conditions. Further, in circumstances where workers are

away for significant periods at the same site, the work location may be extremely familiar.

This narrative review explores the idea that sleep in these unique work situations is

impacted by the particular shift work ‘ecosystem’. Within this ecosystem, independent

variables such as work pattern or physical environment and mediating demographic factors

such as age and general health, interact to influence the recovery value of sleep obtained

between shifts. It is our conjecture that it is the unique work/life ‘ecosystem’ that

determines how well workers sleep. We will explore each of these factors firstly by looking

at sleep in various work environments and follow with a discussion of the legitimacy of the

comparison between work and home sleep. Finally, we will discuss the extent to which these

data contribute to the notion that home sleep is always best.

Keywords were used to search the key databases, Pubmed and Googlescholar (shiftwork,

sleep, field), Bibliographies of relevant articles were scanned and used to refine the

keywords to include industries which utilise working arrangements that require sleep at

work (away from home). Where articles did not include assessment of sleep at home and at

work they were not included, unless the content was relevant for context. The authors

accessed references in the grey literature in addition to the peer-reviewed literature, as the

grey literature is an important source of field studies addressing the question of this

narrative review.

Types of work requiring ‘away’ sleep.

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Remote or isolated workplaces

The resources sector employs a large proportion of the non-residential workforce in

Australia and other resource rich countries [9]. Non-residential workforces housed in

accommodation camps are common in mining, oil and gas operations because the local

community cannot provide all of the required personnel, the worksite is remote from the

local town or because the facilities in adjacent towns are not able to cater for large numbers

of people. Such operations generally employ structured shift arrangements, and often

involve day and night shifts. Despite a proliferation of non-residential workforces in some

sectors, very few studies have compared the sleep of non-residential employees at home

and at work.

The off-shore oil rig, with reduced light exposure and social/domestic activities [10] appears

to have the makings of an ideal sleeping environment, despite being away from home.

Bjorvatn and colleagues used self-report instruments to examine the sleep of oil-rig workers

required to sleep on the rig between shifts. They showed that there were no differences in

total sleep obtained whilst away on the rigs during work periods compared to that obtained

at home during time off [11]. This was in contrast to an earlier report by Parkes and

colleagues showing that self-reported sleep on the rigs averaged 7.2 h on night shift and

6.99 h on day shift, compared to 7.7 h during leave periods at home [12]. In another study

by Bjorvatn et al [10] sleep on night shift was reported as being slightly shorter than other

studies, at 6.5 h, but longer than the same workers on day shift the following week.

Unfortunately, there was no comparison to home sleeps. The same group looked at sleep at

home and offshore on different shift patterns [13]. No difference was found in home sleep

following return from different shift patterns. As with the previous studies, work factors

were the main influence on sleep. This suite of studies on offshore workers suggests that in

some situations sleep may not be shorter in the ‘away’, work environment possibly due to

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the conditions on the oilrig. In contrast, a study of Fly-In, Fly-Out (FIFO) miners

demonstrated that despite the removal of most social and domestic activities, being away

from home did not translate into more sleep [14]. This suggests that factors other than

location are impacting on sleep (positively or negatively) in each of these environments.

The Polar Regions provide examples of isolated workplaces to which workers can be

deployed for short treks or summer camps, or for long periods at research stations [15].

While there are many unique aspects to this type of deployment, namely the extreme

physical conditions and periods of confinement [15], it is similar to the off-shore oil-rig

environment in terms of reduced light exposure (winter months) and social/domestic

activities. Weymouth et al [16] compared home sleep with sleep during a short, 12 day field

camp to Antarctica and found no differences in total sleep obtained or sleep disturbance as

measured by actigraphy, despite individuals sleeping in polar tents for the majority of the

camp. In a 13-month deployment however, marked changes in sleep as measured by

polysomnography (PSG) were observed [17], with sleep worse in all months compared to

home baseline and worsening with time. While it is clear that ‘away’ sleep was negatively

impacted, it is not possible to know how much of a role the actual conditions played

(physical conditions, work demands) and how much was due to being away from home. We

would argue that the conditions, which can be extreme, would have played a large role in

any changes to sleep. Having said that, while the 13-month deployment would have

facilitated a degree of familiarity, it is difficult to quantify ‘familiarity’ and the role it may

play in sleep outcomes. Importantly, in these particular circumstances, familiarity with the

location did not appear to benefit sleep.

Studies of the sleep of workers who slept at home between 12 h shifts have demonstrated

that workers obtain approximately 6 h sleep [18, 19]. This is similar to the amount of sleep

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miners (also working 12 h shifts) obtained when sleeping at work in purpose-built facilities

[14]. In terms of home and work comparisons, Ferguson et al [14] showed that Australian

FIFO miners got 7.3 h on days off at home, significantly more sleep than during blocks of

work sleeping away. Further, Muller et al [20] reported 6.6 hours of sleep on day shift, 6.7 h

on night shift and 8.2 h on days off. However in both studies, the comparison between away

(on-site) sleeps and home sleeps is confounded by work. The home sleeps of FIFO-based

workforces occur on days off and are thus not restricted by work hours. Ferguson and

colleagues suggested that any benefit associated with sleeping in the absence of domestic

and social distractions whilst sleeping at work, may be overridden by factors such as the

roster (specifically, the 0600 dayshift start time acting to truncate night-time sleep) and the

circadian influence on sleep propensity during day sleeps between night shifts. Well-

controlled lab studies clearly show that reduced sleep opportunity equates to less sleep [e.g.

[5] and day sleep is shorter and lighter than night sleep due to the circadian influence on

sleep [21-23]. The sleep in camps and oilrigs is thus impacted by shift factors even though

the length of the sleep opportunity (break between shifts, typically 12 h) should provide for

eight hours of sleep. Of particular interest is the way in which workers utilise their time-off

between shifts and how those choices impact on the amount of sleep they can obtain.

Typically however, this information has not been recorded. The 12 h shift rosters provide a

nominal 11-12 h sleep opportunity. Many ‘mobile’ work environments such as planes, trains

and ships are associated with work schedules that provide much shorter sleep opportunities.

Mobile workplaces

Occupations such as aviation, rail and maritime necessitate sleep in a moving vehicle due to

the long work periods (such as trans-meridian travel in aviation or freight haul operations in

rail) without any opportunity to leave the “workplace”. Australian train drivers working relay

schedules are required to sleep on the train between consecutive shifts while working an 8 h

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on/8 h off (8/8) pattern with a second crew [24-26]. During each 8 h break between shifts,

drivers sleep in customised crew rest facilities on-board the train. Three studies on three

different routes showed influence of time-of-day on sleep such that daytime sleep

opportunities were associated with less sleep than night-time opportunities of the same

duration and in the same (mobile) location. Drivers on the shortest of the three trips (40 h)

slept 3.9-4.2 h per 24 h while on trains and sleep duration varied with time of day [24][25].

Drivers working a longer 107 h round trip slept an average of 5.3h/24 h on the train with

significant time of day variation [26]. On the third route (105.8 h) drivers’ sleep was similar

to the previous two studies at 4.9 – 5.1h/24 h [24]. In all three studies, sleep on the train

was significantly shorter compared to home sleep, which was expected given the significant

confounder of work resulting in short opportunities and undesirable timing of some sleeps.

Interestingly, the shortest trip (40 h) was also associated with the least amount of sleep per

24 h. Given the similar conditions on the trains across the three trips, this suggests that

there are other factors affecting sleep. For example, greater emphasis may be placed on

sleep on longer trips given the upcoming duty requirements.

The maritime industry utilises a range of watch cycles that provide for comparatively short

periods of work and rest across extended voyages [27-31]. Broadly the length and timing of

the sleep opportunities determine sleep duration. A 4/8 watch system in one study

translated to 6.6 h of sleep per 24 h period but the sleep was divided between the two

opportunities such that blocks of sleep were predominantly less than 5 h in length [29].

These results were echoed in another study also investigating sleep on a 4/8 watch system

[31]. Harma and colleagues looked at sleep on 4/8 watches and 6/6 watches. Total sleep

during each off-watch varied with time of day but largely remained less than 5 h [28]. A

different study investigating the same watches showed that on 51% of occasions, workers

on a 4/8 watch slept in only one of their two daily opportunities: however, workers on a 6/6

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watch slept in one opportunity only 34% of the time [27]. The timing of the off-watch is a

significant factor in determining whether ANY sleep is obtained in a given rest opportunity.

For example, sleep is more likely if the timing of the off-watch coincides with the biological

night, when circadian propensity to sleep is greatest [32]. While these studies provide some

insight into factors affecting work sleep, there is no meaningful comparison to home sleep. A

study in Great Barrier Reef marine pilots examined the amount of sleep the same pilots

obtained between pilotages at home and away – both ashore [33]. Main sleeps at home

were, on average, 6.9 h in length whereas pilots obtained 6.3 h when sleeping away (ashore

in hotels or pilots houses). There was significant variation in main sleeps at both locations

but the overall mean difference amounted to more than half an hour of sleep demonstrating

that in these particular circumstances, workers slept longer when at home. Furthermore, it

is noteworthy that unlike many of the other sleeps cited thus far, these away but ashore

sleeps were not restricted by work hours.

The aviation sector requires sleep to be obtained ‘away’ in crew rest facilities on board,

particularly for long-haul flights and in hotels during layovers. Samel et al [34] demonstrated

that for two different East-West long-haul flight pairings (with flight duty periods of 11 h 45

min and 13 h 54 min), the first layover sleep was an average of 1.5 h longer than the

baseline sleep recorded at home prior to the flight. The increased homeostatic pressure

from the preceding duty requirements is likely to have facilitated long sleep. Extensive work

by the National Aeronautics and Space Administration beginning more than 30 y ago

demonstrates the difficulties flight-crew face with trans-meridian travel and/or shift-work

and the impact on sleep [35-38]. For example, local time, circadian factors and future duty

requirements were all shown to influence sleep in the layover environment [35]. Moreover,

other studies have highlighted ‘readiness to sleep’ [39] and being ‘not tired enough’ [40] as

significant factors affecting sleep in-flight, demonstrating the difficulties associated with

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sleeping when biological drive for sleep is low. This can be problematic if there is not

another opportunity to sleep for a period of time.

A unique mobile work/rest location is the space shuttle. Dijk et al [41] used PSG during space

shuttle missions to show that overall sleep structure and efficiency in-flight did not differ

from home. However, subjective sleep quality was generally rated as poorer which

reinforces the assumption among workers that sleep at home is better. Mane sleep duration

during the mission was shorter than pre-mission sleep at home. This finding implicates the

work and in particular, the restriction that work/rest cycles put on sleep opportunity as a

major difference between home and away sleep duration. Similar findings were reported in

truck drivers sleeping in cabin berths. Using objective measures, three separate studies

showed that despite sleep typically being shorter, there were minimal deviations in

objective quality measures between unrestricted home (or laboratory as was the case in one

study) and ‘work’ sleeps in cabin berths or depots [42-44]. In these cases, as in the space

shuttle example, the sleep opportunities and therefore total sleep time of away sleeps were

shorter but objective data in particular suggest that quality was comparable.

Temporary Workplaces/Camps

The final type of workplace that requires sleep away from home is temporary

accommodation such as is used in military operations or emergency services deployments.

Research into sleep in these situations is limited. Seelig and colleagues examined sleep

during military deployment and at home and showed that sleep duration during deployment

(and post-deployment) were the same as non-deployed sleep (approximately 6.5 h) [45].

However, adjusted means were lower for those individuals with combat experience and

those suffering Post Traumatic Stress Disorder. In contrast, Peterson and colleagues

assessed sleep of military personnel using self-report and showed that more than 70% of

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personnel reported reduced quality in the deployed environment compared to sleep at

home [46]. The deployment and combat environments involve various factors including

mental health (e.g. the stress of the ‘deployed’ environment, presence of Post Traumatic

Stress Disorder post-deployment), which might reasonably impact sleep independent of

location.

Emergency personnel can be required to live in temporary accommodation for many days

depending on the nature and location of natural disasters. In Australia, firefighters travel

from around the country to fight wildfire [47]. In these situations, firefighters are housed in

hotels/motels or caravan parks or temporary camps (consisting of tents) can be set up on an

oval or sports facility. In camps with tent accommodation, firefighters identified heat, light

and noise as factors affecting their sleep when sleeping on-site, particularly during the day

[47]. While some actions (e.g. situating sleeping quarters away from staging areas to

minimise noise) can be taken to mediate the physical conditions and make the sleeping

environment as comfortable as possible, some factors in the ‘tent-city’ environment

particularly heat and light are not easily controlled. However, as with a majority of the

studies discussed thus far, there was no home versus away sleep comparison.

Comparing Apples with Apples

While there are studies comparing home sleeps with away sleeps [11, 12, 14, 16, 17, 20, 24-

26, 33, 34, 41-44, 46] the confounder of work limits sleep when away but not when at home.

This makes a direct comparison impossible. A cleaner comparison would be workers

sleeping both at home and away when on the same roster. This rarely, if ever, occurs

because in many cases there is not a ‘home’ equivalent: marine pilots, flight crew, train

drivers and fishermen, for example, don’t have the option of sleeping at home during

periods of work. Even though there are workplaces where there are both on-site and

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community/home based sectors (e.g. construction [48], truck [41-43] mining [14, 49] and oil

industries [12]), there is a paucity of research that actually compares home sleeps between

work shifts and away sleeps between work shifts in these environments. The next best thing

is to examine the sleep of different individuals working the same or similar rosters sleeping

either at home or away.

Two studies have made such a comparison [12, 48]. Each compares the sleep of two sets of

workers with one group sleeping at home between shifts and the other sleeping away.

Importantly, the data show that there are positives and negatives to both home and away

working and sleeping scenarios.

The investigation by Parkes et al [12] compared home (onshore) and away (offshore) sleeps

in two groups of Control-room operators working similar rosters. Offshore workers slept

more and reported better sleep quality following night shifts than those sleeping at home.

Thus, while it is often assumed that the home environment is best for sleep, in this case the

daytime sleeping environment at work was more favorable for sleep. The lack of light in

particular and the absence of domestic distracters were thought to have been factors in the

discrepancy between the on and offshore workers’ daytime sleep. Interestingly, the

opposite was found on dayshifts. It was thought that the differing shift patterns preceding

day shifts contributed – the offshore workers started day shift immediately following a week

of night shifts, a pattern preferred by the workers to facilitate circadian adjustment to a

normal sleep-wake pattern prior to a period of leave. Not surprisingly, on days off, sleep

duration increased and sleep quality was rated more favourably in both groups. That is, not

working at all resulted in the best sleep outcomes.

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A similar home versus away comparison was made between Danish home and camp-based

construction workers by Persson and colleagues [48]. Both groups were working day shifts

but the away group worked a compressed work schedule with longer shifts and more

consecutive workdays. Nonetheless, subjective measures of sleep quality and sleepiness

across workdays suggested that there was no discernable effect of the camp environment

on sleep. Results from other, non-sleep variables however, suggested that recuperation

between shifts at the camp was not as good; for example alertness ratings during workdays

were lower and general fatigue scores were higher in the camp. While this suggests the

camp group’s sleep was affected, it is not possible to tease out whether this was to do with

physical sleep environment, difficulties ‘unwinding’, the more intensive roster or other,

unmeasured factors.

Importantly, while both these studies do compare home and away groups, neither is ideal

because not only are they comparing different (though similar) rosters, but different groups

of people as well. Importantly, the demographic characteristics of a particular individual will

also play a role in sleep, regardless of location. For example, older shift workers are

particularly susceptible to fatigue as they report shorter and more disturbed sleep than

younger shift workers (particularly night shift), for review see [50]. Torsvall et al [51] found

that the negative effects of night work on sleep were exacerbated with age. Similarly Gander

et al [52] showed that the ability to adjust to circadian change was poorer for older workers.

Indeed, in the previously discussed study by Parkes et al [12] it was concluded that older

workers experienced greater difficulty adjusting to the work patterns compared to younger

workers with age being negatively associated with sleep duration and (subjective) sleep

quality. Beyond age there are a number of individual factors that may impact sleep,

particularly in relation to shiftwork and sleeping away from home [53]. There is limited

research however examining the issue specifically.

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Unhealthy lifestyle choices can also negatively impact on sleep. Smokers for example

generally have more disturbed sleep, typically taking longer to fall asleep and experiencing

more wake time during a sleep period [54]. Conversely, healthy lifestyle choices such as

good physical fitness and a healthy diet have been reported to reduce fatigue and improve

alertness and performance in shift workers [55]. Depending on the influence of such things,

the importance of the location may be reduced. One of the most obvious factors potentially

impacting sleep away from home is the actual sleeping environment.

Beyond work hours

The timing and length of sleep opportunities between shifts are critical elements in

determining sleep duration but environmental factors also play a role, particularly for those

required to sleep in a moving environment. Movement, noise and vibration can all adversely

impact on sleep [56-59]. In a survey of the usage of aircraft bunks in flight, Rosekind et al

[39] found that flight crew listed turbulence, light, heat and random noise as factors

interfering with sleep in-flight. Further, as previously identified, heat, light and noise were all

listed as factors affecting volunteer firefighters’ sleep when sleeping in tents located near

the fireground, particularly during the day [47]. A group of Australian Truck drivers cited

noise, temperature and finding a suitable place to park as factors impacting sleep [42]. In a

survey of military personnel about sleep in combat, 57.8% reported that their Unit ‘never’

had dark and quiet areas that were designated for rest [60]. In each of the aforementioned

situations, workers are at the mercy not only of their environment but what is provided for

them. At home, people are likely to have more power to optimise their sleeping

environment. In line with this, when flight crew were asked about what would make on-

board crew rest facilities more conducive for sleep, one suggestion was better

environmental controls (humidity, ventilation and temperature) [39]. At home, controlling

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the environment might be done with greater ease and/or it may be designed to suit an

individual’s preferences.

Having the ability to control the sleeping environment might be a key element of the home-

sleep versus work-sleep distinction because work takes many workers away from home very

regularly. This means they are potentially spending as much time away as they are at home.

Miners can be away two thirds of the year (working two weeks on one week off for example)

in relatively short individual stretches compared to workers in the Polar Regions or Military

for example, who may be away for months at a time. With these types of workers in mind, it

is important to consider what factors contribute to a sense of ‘familiarity’ and how much of

a role it plays in determining sleep outcomes.

In the literature reviewed here, familiarity is not defined but as a concept, it is likely to be

multi-faceted and the frequency with which a particular environment is encountered is likely

to play a part in establishing a sense of familiarity. It is problematic to quantify familiarity in

the context of this review and while the work location might be, or become familiar, the

ability to control the physical conditions may still be limited. In addition, while workers may

be away for extended or regular periods, they may not be in exactly the same away

environment. For example, flight-crew sleep in bunks but are not always on same planes,

nor are they always in same rooms or even hotels during layovers. Arguably therefore, the

home environment is the constant in their work/life pattern even if they are spending an

equivalent amount of time away.

Even if the sleeping environment is familiar or comfortable, simply remaining in the work

environment to sleep may disturb sleep. Trying to sleep at home or away with the potential

of being woken (e.g. if on-call or for an emergency) may result in some stress and/or anxiety,

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which has been linked stress to the perception of poorer sleep [61]. Similarly, anticipation

caused by thoughts of having to wake early for a shift or being woken when on-call has been

shown to disrupt sleep with Torsvall et al [62] showing a decrease in ‘deep’ sleep when on-

call even when no calls occurred during the night. Thus, simply remaining at work to sleep,

especially if workers are not physically removed from the environment, might be akin to

being on-call in that there is no separation from work. Such feelings may reasonably be

exacerbated for those whose ‘away’ environment is actually located in the workplace such

as mobile environments (plane, truck, train, ship) and off-shore oil-rigs compared to those

such as mine sites, where the sleeping quarters are further removed (physically) from the

workspace.

While it is assumed that the physical environment can influence sleep,[63] for a majority of

studies there is no specific enquiry (subjective or objective) into the impact of the actual

environment on sleep. Rather, reasonable inferences are made about how the conditions

could positively or negatively impact on sleep [12, 24, 26, 60, 64-66]. Therefore, where

comparisons of home and away are made, they are comparisons not only between work

days and days off, as well as restricted and unrestricted opportunities and day and night

sleep opportunities but also between the physical home and away environments. It is

therefore not possible to say that home sleep is always better.

Does it matter if sleep is different at home and away?

An overarching question is whether or not differences in sleep at home and away actually

matter for performance and safety outcomes. Studies of flight-crew [40] marine pilots [67]

and train drivers [24, 25, 68] for example, all concluded that the sleep obtained at work was

sufficient to maintain safe operations as determined by measures such as reaction time

performance, sleepiness and fatigue scales. Conversely, other studies have shown work

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sleep to be insufficient. Lamond et al [69] concluded that the amount of sleep flight-crew

obtained during short layovers (<40 h) did not allow sufficient recovery of performance and

fatigue. Similarly, sleepiness levels were deemed to be excessive in certain marine industry

work scenarios like 6/6 watch systems [27, 28] and in fishermen working irregular schedules

[65]. These studies show that it is the specifics of each particular work system (including

timing, duration, location, demographics, etc) that determine the impact on sleep and that it

is less about how much sleep you get and more about whether you get enough to do the job

safely and effectively.

It is noteworthy that in the mobile workplaces previously discussed, the rosters afford

workers short sleep opportunities between consecutive shifts but the duration of shifts is

also less (e.g. 6/6, 8/8 or opportunistic sleep). If the timing of a rest break coincides with

periods of low sleep pressure such as occurs after relatively brief period of wake or during

the daytime, obtaining sleep on board may be difficult. This matches the night shift sleep

issues in camps and at home. Regardless, data show that workers do attempt sleep when

given an opportunity [24-29, 67, 70] and as Ferguson et al [67] noted, these sleeps, however

short, break up periods of continuous wake and may therefore be an effective fatigue

countermeasure during the next period of wake/work.

Location, location, location – or is it?

The preceding sections demonstrate that sleep outcomes are the product of the interaction

of numerous factors. Reduced opportunity for sleep, poor biological timing, environmental

conditions, and demographic factors can all impact on sleep in the ‘away’ environment.

Importantly, the multitude of factors means it is impossible to define the relative

contribution of any single factor, including being away from home.

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Further to this, there is no consensus on what a ‘better’ sleep actually entails in these

circumstances. Is it a quantity measure, quality measure or the worker’s perception of which

is better? Or, in work scenarios, should the measure relate to the minimum amount of sleep

required for maintenance of safe work performance? Each of these markers have been used

as valid indicators of ‘better’ sleep in this review but whether one is superior or whether a

hierarchy of measures exists is a question worthy of future consideration.

Further complicating the discussion is the fact that different factors may exert their

influence differently within the same work scenario. Gander et al [36] for example,

investigated layover sleeps of international flight crew and found circadian influence, local

time and duty requirements impacted on the sleep obtained. Importantly, the relative

contributions of each of these factors were different for the first layover sleep compared to

the second. Similarly, given the known power of natural bright light as a zeitgeber to entrain

the circadian system to the external environment [71], the annual variation of natural bright

light in the North Sea [72] might differentially impact the sleep of oil installation workers on

nightshift, despite them doing the same job and sleeping in the same environment.

Despite the complexity, there is some clarity from this literature. The first is that workers are

able to sleep, in many different locations, under a range of conditions. Secondly, of the

studies that had some kind of home comparison, a vast majority showed sleep at home to

be better; either longer, more efficient or simply rated as better quality. In these situations

however, we would argue that it was not the home location that made workers’ sleep

better. The weight of the evidence suggests that it is the factors defining the sleep

opportunity, specifically, timing and duration that will most significantly dictate the

outcomes for sleep. In line with this, in the studies that showed home sleep to be better,

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home sleep opportunities were longer and at night, and thus more likely to result in good (or

at least better) sleep outcomes, independent of location.

While the nature of these studies means we cannot isolate the ‘away’ impact, it is useful to

speculate about whether the significance of sleep location varies depending on the severity

of the other factors. For example, when sleep is being challenged by factors relating to

timing and duration, does the away location serve to worsen the situation? Alternatively,

when sleep is being challenged by factors relating to timing and duration, is the impact of

the away location reduced? In line with this second argument, provided the physical

environment is comparable to home, we would argue that it does not matter where sleep is

taken, daytime sleep will be poorer and nighttime sleep will be better. However, the nature

of many ‘away’ environments presents a sub-optimal sleeping environment. With this in

mind, optimising the physical sleep environment should be high on employers’ list of

priorities when looking to base people at work for sleeps between shifts.

Future Directions

While efforts should always be made to improve sleeping facilities at work, the timing and

duration of work hours and the impact on time available to sleep should be considered

when assessing the adequacy of work scenarios. Additionally, to better understand whether

sleeping in work facilities actually impacts sleep, subsequent research should also consider

the inclusion of home-based work groups so more accurate comparisons can be made. The

lack of home comparisons means that we do not fully understand the sleep of workers when

they are at home. For example, does the time away from their family mean reduced sleep

when they return due to a need to compensate for their absence by moving sleep down the

priority list.

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Future research should consider the inclusion of additional measures that facilitate the

conceptualisation of ‘familiarity’ in this context. As noted, many workers who sleep in work

facilities are away from home for significant periods of time. Potentially therefore, being

familiar with a specific or a general type of work sleep environment (e.g. hotel/motel room,

tent, aircraft bunk, crew rest facilities on a train) might be advantageous. In addition to how

often a particular sleeping environment is encountered, other dimensions of familiarity

might include thermal, visual, acoustic, kinesthetic and olfactory factors. Further, another

important individual difference relates to co-sleeping in the home and the effect of sleeping

alone away [73, 74]. This may have negative or positive effects on sleep and should be

included in future studies.

The sleep of workers in mobile workplaces may be influenced by factors other than noise

and light. For truck drivers seeking to sleep in their vehicles, finding a safe place may be the

most important factor in sleep quality and quantity. Another factor that may impact sleep is

the ‘first night effect’. The first night effect describes the effects on sleep of being in an

unfamiliar environment. It would be possible to review the sleep on the first night at work to

see if there are specific impacts.

Finally, while the operational fidelity of these studies is good there are significant limitations

to many of the studies and addressing these should be a priority for future inquiry in this

area. Specifically, the logistics, time and effort of conducting such research can typically

result in small sample sizes, limited objective data and large individual variability. Most

importantly in the context of assessing the ‘away’ location, the use of unequal comparisons

dominates, that is comparison of day sleeps following work with night sleeps at home, single

sleep episodes with multiple sleep episodes (summed to produce sleep/24 h), or restricted

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work sleeps with unrestricted home sleeps. As a result of these methodological limitations,

definitive conclusions cannot be drawn about differences between home and away sleeps.

Conclusions

The timing and duration of breaks in addition to commute length, sleeping environment

(noise, movement, vibration, light), circadian phase and familiarity with the away location

each need to be considered when assessing the adequacy of a particular sleeping

arrangement. Based on the data presented here, it is our contention that the location of rest

breaks, whilst important, is secondary to other factors. Specifically it appears that the way

work hours dictate both the timing and duration of sleep periods, is the most significant

determinant of sleep outcomes in these studies. That is, the ‘where’ is less important than

the ‘when’.

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Practice Points

• numerous industries use on-site workforces such that employees work and sleep at or

near the workplace

• despite the largely anecdotal view that sleep at home is better than sleep ‘away’,

employees can sleep well at ‘work’

• the amount and quality of sleep away from home are impacted by numerous factors

including timing and duration of breaks, commute length, sleeping environment,

circadian phase and demographic factors

• it might be more useful to assess any home versus away comparison in terms of

whether or not sleep was enough to maintain safe operations as determined by

performance measures and/or sleepiness and fatigue scales

Research Agenda

Subsequent research should consider the inclusion of;

• home-based groups during work days, and/or work-based groups during days off to

enable more accurate comparisons between home and away sleep

• measures that facilitate the conceptualisation of ‘familiarity’ with a particular sleep

location(s)

• a discussion about what ‘better’ sleep actually means. For example is it a measure of

quantity, quality, or the worker’s perception of which is better? Alternatively, does it

relate to a minimum required for maintenance of safe work performance?

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