Sleep and Fatigue Offshore: Investigating subjective and objective parameters on sleep, fatigue, health, safety and performance.

Fatigue has been described to be a multi-dimensional, complex construct with
effects on cognitive and task performance which influence safety outcomes.2
Fatigue includes behavioral, physiological, emotional and cognitive
components.3 Experiences of fatigue have been noted to be very common on
worksites with an estimated prevalence of 22% in Dutch populations.4 Resnick
(2006) found that self-reported fatigue is associated with higher body mass
index5 and fatigue in general has been linked to ill-health6,7 and safety
outcomes such as accidents, injuries8 and reduced performance.3,9 The extensive
effect of fatigue on health and safety outcomes can be partly explained by the
influence fatigue has on decreasing cognitive processing speed. Decreased
cognitive processing speed has been shown to be associated with increased
reaction times, tunnel vision, inattentiveness and lower vigilance and
concentration10 which in turn increase the chances of accidents (at work).
Further, the link between increased fatigue and accident involvement has been
explained by the depletion of required cognitive resources due to physical
exertion or sleep deprivation.11 Dawson and Reid (1997) found that the
cognitive processing deficits of individuals with moderate sleep deprivation
were analogous to those experienced by individuals with blood alcohol levels
above the legal driving limit.12

In the offshore oil and gas industry, safety is taken very seriously because of
the potential hazards stemming from the oil and gas production. A pilot study
among Dutch offshore workers found that 73% of workers reported severe fatigue
levels and sleeping difficulties. Further, the study found that 41% of workers
experienced a physical and mental dip at some point during their fortnight
shift, which could be detrimental to health and safety aspects offshore. The
majority of workers (60%) reported this dip to occur on the 10th or 11th day,
whilst being offshore. In the UK, Ross (2009) found that one of the major
health concerns among offshore workers were sleeping problems.1 Understanding
and improving sleep, fatigue and dip experiences is crucial to prevent
accidents like the Macondo disaster close to the Gulf of Mexico in 2010 or the
Piper Alpha disaster which took place close to the coast of Aberdeen in 1988.

It has been suggested that there is a gained benefit of using subjective and
objective measures together to investigate several health behaviors.13
Especially for fatigue, it has been noted that subjective measures alone are
not sufficient for the thorough investigation of fatigue. Subjective estimates
are prone to bias and are often inaccurate.14 However, perceived sleep is
important and individual differences in sensitivity to the effects of sleep
loss constitute key considerations in the prediction of fatigue. Therefore,
programs should investigate both objective and subjective measures.

To our knowledge, no studies exist on offshore workers working in the Dutch
North
Sea sector and only a handful UK offshore studies exist investigating the
health of offshore workers. Overall, only a few offshore studies conducted in
other countries exist, that looked at the effects of physical and (psycho)
social work environments on workers* health status. A recent systematic review
on the effect of offshore shift work on health found that shift workers
reported more sleep problems than day workers.15 Although sleeping problems
offshore have been reported by the authors no explanations were given with
regard to etiology and consequences. For example, the previously investigated
Dutch offshore population did not have a permanent shift work schedule and yet
they still reported severe fatigue and sleeping difficulties. The outcomes of
the proposed study will help to clarify which factors constitute the sleep and
fatigue problems offshore and will shed light on how sleep and fatigue problems
affect health and safety parameters offshore. Moreover the data will help us
identify which factors constitute the dip that workers reported in the pilot
study.

Primary Objective:
To objectively and subjectively investigate sleep and fatigue among Dutch and
British offshore workers and their influence on health safety and performance.

Secondary Objective(s):
• To examine the course of cortisol, cotison and melatonin levels during a
fortnight offshore shift
• To examine links between the dip indication and objective (cortisol and
melatonin) and subjective (sleep diary) measures
• To examine the sleep/wake cycle of offshore workers as indicated by actigraph
data
• To examine the course of reaction times of PVT outcomes during a fortnight
offshore shift as indicated by number of lapses and mean reaction time
• To relate fatigue and sleep parameters with health, safety and performance
outcomes
• To compare Dutch and British offshore workers on the parameters mentioned
above
• To compare subjective and objective sleep and fatigue indications

This study is a repeated measures design conducted over the course of four
weeks in two different countries (the Netherlands and the UK).

The majority of measurements will be conducted during working hours offshore.
The measurements cover a period of four weeks and the accumulated time
investment needs to be taken into account: Baseline questionnaire 20 min.;
sleep diary 28 x 10 min.; saliva samples on 3 days x (5 x 5 min).; PVT 28 x 10
min.; Closing questionnaire 10 min.. On average on a day with biomarker testing
an individual will spend 55 min on the research. On a day without biomarker
testing: 30 min. To our knowledge, there are no known risks of the involved
measurements.