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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.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service toour customers we are providing this early version of the manuscript. The manuscript will undergocopyediting, typesetting, and review of the resulting proof before it is published in its final form. Pleasenote that during the production process errors may be discovered which could affect the content, and alllegal disclaimers that apply to the journal pertain.
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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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