Shift work, Sleep and health POST, UK PARLIAMENT

Dr Sarah Bunn, Lef Apostolakis | Parliamentary Office of Science and Technology

Sleep is as essential to life as food and water. So why don’t we treat it as such? Sleep problems may affect up to a third of the population and most sleep-wake disorders are likely to be underdiagnosed. Research also suggests that long-term sleep problems may be a factor in many physical and mental health conditions. On the 16th of October 2018, POST in collaboration with the Nuffield Foundation, invited experts from medicine, research, and occupational sectors to highlight the latest research and discuss the implications for policy. On this page you will find a record of the oral presentations from the day, on sleep and health. A second page presents oral presentation on shift work, sleep and health.

Professor Derk-Jan Dijk

Derk-Jan is Professor of Sleep and Physiology and Director of the Surrey Sleep Research Centre at the University of Surrey. His research focusses on sleep and circadian rhythms and the impact of their disturbances (which are common in shift work) on waking performance. He has served as the Editor in Chief of the Journal of Sleep Research and has published more than 240 research papers and reviews.

What is shift work?

While there is no specific definition of shift work in law, the Health and Safety Executive defines standard work/standard daytime hours as a work schedule that involves activity during the day, commonly for an eight-hour period between 7.00am and 7.00pm. Shift work can be considered as:

  • work activity outside standard daytime hours, where there may be a handover of duty from one individual or work group to another.
  • a pattern of work where one employee replaces another on the same job within a 24 hour period.
  • starting work between 2.00pm and 6.30am.

Despite the lack of a legal definition, different types of shift work have some common characteristics. These include work during the afternoon, night or weekend, with periods of the work scheduled outside daytime hours; extended work periods of longer than twelve hours often associated with a compressed working week; rotating hours; split shifts; overtime and standby or on-call duties. Within these are other features: shift pattern (permanent or rotating, forward and backward), shift rotation (fast or slow), shift timing, shift duration, and rest breaks between shifts.

Shift work is prevalent across a range of industries, however the variety in working patterns makes it difficult to determine how challenging it is. Assessment will consider many factors such as how long the employee has been awake for, how long the shift has been, how many breaks taken were taken, whether the breaks were paid or not, and so on.

According to the European Working Conditions Survey, 22% of UK employees work shifts, while 22% of UK employees report having worked at least one night-shift a month. The Trades Union Congress (TUC) estimated that there were 3.2m night workers in the UK in 2017 (equivalent to 11.7% of the working age population).

Shift work prevalence varies by country. Within the EU for example it can reach 40% of the population (Croatia). In the US in 2010 according to the National Health Interview Survey, 29% of workers work hours outside 6.00a.m and 6.00pm.

Shift work prevalence also varies by profession. Survey data of the nursing workforce collected by the Royal College of Nursing (pdf) showed that 57% worked shifts, with 10% working permanent nights and 58% on rotating shifts.

It should be noted that precise figures of shift work prevalence are hard to come by, as estimates vary depending on how shift work is defined (by different sectors and between countries). However, it is unlikely that these figures will go down, which is why gaining insight into the health consequences of shift work is important.

Image: Tim Vrtiska

With such a large part of the population engaged in some type of shift-work, evidence on health outcomes has been accumulating and it strongly suggests an association with adverse outcomes. Sleep disruption and deprivation are primary factors but other factors such as lifestyle are also relevant. When are shift-workers eating or exercising? Does the temporal structure of these activities correspond with those of non-shift workers?

In 2016 the literature on the topic amounted to 38 meta-analyses, 24 systematic reviews, and a number of narrative reviews and articles outlining possible mechanisms (according to one systematic review). In terms of the underlying physiology and the impact of waking functioning and overall health, the sleep-wake cycle is influenced by the homeostat (sleep-wake history) circadian timing (itself influenced by the light-dark cycle), genetic variation and individual factors. Shift schedules will drive sleep-wake cycles, and sleep debts can accumulate as a consequence of shift work.

Accidents and sleepiness

A systematic review of shift work and long working hours, found that in both cases, the accident rate increased by between 50 and 100%. Sleepiness during shifts is common, and Shift Work Sleep Disorder is a recognised condition (listed in the International Classification of Sleep Disorders); clinical features include insomnia/excessive sleepiness and reduced total sleep time, with symptoms lasting at least three months. Estimated prevalence is between 10% and 23%.

Consequences of accidents can be serious. For example, the Croydon tram crash in 2016 resulted from the driver experiencing a microsleep during a 49 second period in which the tram passed through three tunnels in the hours of darkness. Inspectors said it was possible that a sleep debt accumulated by the driver – who was regularly sleeping less than six hours before waking at 3.20am to get to work – could have made him fatigued.

Furthermore, sleep-breaks while working shifts tends to have limited benefits. Data on people’s subjective experience of sleep-breaks is that they are non-refreshing and that waking up is difficult. Perceptions of sleep duration during sleep breaks differ from objective data, with individuals feeling like they've slept on average 30 minutes to an hour less than they actually have. Short recovery times between shifts and fast shift rotations, can intensify these negative effects. While shift-workers overall make up for the lost sleep on recovery days, at least in terms of quantity, they can still experience chronic sleep disturbances (risk ratio of 1.16), such as insomnia symptoms.

Impact of shift work on health

Apart from sleep disorders, it has been suggested that shift work can lead to a range of other negative health outcomes from cardiovascular disease to cancer.

Cardiovascular Disease – 34 observational studies of over two million people, suggest that shift work is associated with increased risk of myocardial infarction (pooled risk ratio 1.23) and ischaemic stroke (pooled risk ratio of 1.05). The highest risk is associated with night shifts (risk ratio 1.41). There is no significant risk from evening shifts.

Metabolic Disorders – Shift work is associated with obesity and weight gain (with one estimate of risk ratio at 1.14), and impaired glucose tolerance. For type 2 diabetes data from cohort studies puts the risk ratio between 1.12 and 1.15. These are not large effects but are significant.

Cancer – In 2007 The International Agency for Research on Cancer stated that shift work probably increases the risk of breast cancer. Since 2007, three other reviews have concluded that there is insufficient or limited evidence. Four reviews have reported that long exposure to shifts (>20 years) is associated with elevated risk for breast cancer with risk ratios ranging from 1.06 to 1.20. For prostate cancer, a meta-analysis based on eight studies found that the risk ratio is 1.24, with a 2.8% increase in risk for each five year’s duration of night shift work. For colorectal cancer the available evidence paints a similar picture: a meta-analysis of six studies reported an odds ratio of 1.32, with an 11% increase in risk for every five years of night shift work.

Today, research is being conducted on several other areas of interest centred on other consequences including life expectancy, cognitive decline, depression, multiple sclerosis and overall quality of life. Other research looks at individual differences and how sex, age, and chronotype (whether one is a morning or evening person) can affect the risk of negative outcomes.

Effects on genes and other processes – The effects of mistimed sleep (through shift work or jet lag for example) on peripheral circadian rhythm disruption have also been characterised at the molecular level, as seen in gene expression studies. Genes and processes at the core of circadian rhythm generation and gene expression were reduced significantly, although the centrally driven circadian rhythm of melatonin is not affected. Research at the molecular level adds important insights to the overall biology of sleep and the effects of sleep disruption.

Dr Michael Farquhar

Mike is a Consultant in Sleep Medicine at Evelina London Children’s Hospital, Guy’s and St Thomas’ NHS Foundation Trust. He trained in Glasgow, Nottingham, Sydney, and London, taking up post at Evelina London in 2012. Evelina London provides assessment and management for children with complex, rare, and refractory sleep problems, and is one of the UK’s busiest diagnostic sleep labs. Mike has an interest in the impact of sleep deprivation and fatigue in the context of shift-working.

Managing shift work

Mike is interested in mitigating the adverse consequences of shift work, particularly in the healthcare sector. One of the main challenges is the lack of good quality evidence and the fact that shift work is defined differently between studies. In addition, there are very few studies that look at interventions for shift work in real life, and the sample sizes in studies tend to be small. Therefore approaches tend to be based on what we think makes sense, rather than on the evidence. To further complicate things, individual differences play a huge role in mitigation approaches. Chronotype differences for example create two groups – morning and night people – which eliminates the possibility of a universal solution.

Still, it is important for those who employ shift workers, to acknowledge the negative health outcomes this type of work is associated with, and think of ways to manage the wellbeing of their staff. Knowing the risks is crucial so that employers can put appropriate support in place. Mike believes that the NHS has ignored this issue for a long time and could adopt several approaches to address the impacts of shift work:

  1. Educating and informing people about health in relation to shift work, such as educating shift workers about good sleep routines, including how to compensate for lost sleep and how to get back into day-mode after shift work at night. Research in a cohort of London junior doctors showed that 76% found education alone improved outcomes either by improving their core sleep, how they worked at night, or both. This is an intervention that really brings into focus the impact of messaging. Mike thinks that promoting the idea of coping with shifts is unhelpful and we should not expect people to perform to super-human standards. At the end of the day, shift workers are not super-human but have the same physiology as everybody else.
  2. Creating appropriate shift schedules: while these will differ for different people in different situations, it should be acknowledged that workers need a higher degree of control of individual working patterns. Intelligent rostering software can take individual preferences into account.
  3. Considering lighting: lighting is a powerful tool that can modulate shift work consequences.
  4. Promoting rest and breaks: there is currently a wide range of what we think is acceptable in terms of break timings and durations but there are likely to be benefits from a more considered approach. For example, there might be different break periods needed between professions, for example between heavy goods vehicle (HGV) drivers and medical consultants.
  5. Provision of facilities: it is especially important to have access to high quality food, including the ability to take a proper break in a well-designed space with adequate rest facilities. This type of space is provided for flight crew by some airlines.
  6. Proactive screening: since shift work is likely to cause sleep disruption, and as a consequence a range of resulting health outcomes, access to at least annual health checks is important.
  7. Challenging misconceptions: communication is key in many public health interventions. Changing the language around shift work and endurance, moving away from referring to shift workers as ‘superheroes’ for working at night or not taking breaks, can take some pressure off shift work.
  8. Medication: Using medication should not be routine unless absolutely necessary (for example the use of drugs such as modafinil to stimulate attention). While there may be a role for some medications, such as melatonin, this decision should be made after consulting with a trained healthcare professional. Interventions should assess the overall health and specific circumstances of a person. Medications should not be used as a blanket approach to managing shift work.
  9. Preventing driving when tired: driving home after night shifts can lead to accidents that can be lethal. It should be the responsibility of employers to ensure that their staff can get home safely. Junior doctors now benefit from being given a bed to sleep in at work, if they are too tired to drive home and every employer should be considering ways to manage similar risks in their sector.

Managing the negative health outcomes of shift work is an emerging field and there is still a lot of work that needs to be done to fill existing knowledge gaps, alongside a wider discussion on the impacts of expectations. For example, the increasing emphasis on the night time economy and the London Mayor’s vision for a 24-hour city. While there are financial incentives to shift work, there is often a human cost.

Dr Rob Hunter

Rob is Head of Flight Safety for the British Airline Pilots’ Association and he bis also a Transport Safety Commissioner. He is a qualified GP, a consultant specialist in aviation medicine, and a pilot on Boeing and Airbus types. He manages a department that is researching “how tired is too tired” for airline pilots to undertake their work.

Industry insights: British Airline Pilots’ Association

Shift work is integral to the smooth operations of many industries, so it should come as no surprise that often important insights come from within industry. A great example is the work carried out by the British Airline Pilots’ Association (BALPA), a professional association and trade union for British pilots. While this is a tightly regulated sector that limits flight times for pilots, tension does exist between increasing productivity and increasing safety. Of course the first priority for the sector is safety, and aviation is indeed a very safe sector. Still, some taboos around shift work remain.

For example, let's take the sector's system determining pilots’ fitness to fly, which takes tiredness into account. Pilots’ working hours are controlled through European regulation (and deregulation) which comprise two main components:

  1. The prescriptive rule-set which is a complex set of rules defining quantitatively what is allowed: for example, a maximum of 900 hours per year. This rule-set can “allow” very fatiguing rosters to be created.
  2. An overarching rule-set that pilots must not fly when “too fatigued” and airlines must not roster pilots to do fatiguing duties.

These systems create a catch 22 situation: pilots need to carry out a number of tasks that make them tired, but are not permitted to carry out these tasks if they're "too tired". But how tired is too tired? There is an exemption from the prescriptive rule set to allow bespoke assessments of the risk, through so called Fatigue Risk Management Systems (FRMS), but these are vulnerable to conflicting interests. Adding to the complexity of this assessment system, pilots report finding it less tiring to put up with something rather than to go through the process of reporting instances of where fatigue has been an issue.

For example, pilots can decline work due to fatigue. But there are precedents of airlines contesting pilots' assessments and subjecting pilots to disciplinary action. In one such case, data on effectiveness showed that the pilot’s level of fatigue on the declined day of duty was equivalent to being four times the legal limit for drinking alcohol.

Aviation accidents

The Air Accidents Investigation Branch (AAIB) examines all aviation incidents. Fatigue is a significant avenue for investigation for the AAIB, and a report on a serious occurrence in 2013 revealed the impact of rostering for standby duties can impact on a pilot’s fitness to operate safely in subsequent scheduled duties.

Along similar lines, a BALPA poll of 500 airline pilots in 2011 found that 43% reported having fallen asleep on the flight deck during operations where two crew were on the flight deck. When asked if they had woken to find the other pilot asleep, 31% reported yes. Involuntary sleep on the flight deck must be reported to the Civil Aviation Authority (CAA). However, between 1984 and 2014 only two such reports were made, equivalent to one in 100,000,000 flying hours. Clearly there is a discrepancy in what pilots are saying about involuntary sleep when surveyed (roughly equivalent to one in 20 flight hours) versus what is recorded by the regulator.

Along similar lines, a body of research from 2003 investigated crew sleep patterns in the cockpit on transatlantic flights. Figures showed periods of alertness and sleep in both the captain and the first officer. The captain’s scheduled nap provides rest to allow them to be well rested for landing at GMT 11.30. Despite this, both pilots were flying through the circadian load and there were several instances where neither pilot was fully alert.

The question then arises as to how aviation is so safe, given the commonplace experience of fatigue on the flight deck? Let's look at this video describing a recent near miss in 2017 as an Air Canada plane began to land on a runway where four other full passenger aircraft were taxiing for take-off. The Air Canada plane came within 13 feet of the other aircraft. The subsequent investigation found that the captain of the Air Canada flight had been awake continuously for 19 hours. A crash was averted through a set of established safety procedures instigated by air traffic control and auto-pilot safety functions in the aircraft, and to some degree, luck.

Martin Brown

Martin is the Health and Safety Director for Crossrail. Coming from a background in Mechanical Engineering and Industrial Relations, he started his work with health and safety in 1979, joining the HM Factory Inspectorate in the Health and Safety Executive. Since, he has worked at the HM Railway Inspectorate, at Tube Lines as Health, Safety and Environment Director, at London Rail, where he oversaw the new London Overground railway, and at London Underground as lead for Health, Safety and Environment.

Industry insights: Crossrail

Crossrail is known for its Target Zero approach to health and safety which treats safety as a core value.

Target Zero involves three main themes: everyone has the right to go home every day unharmed, all harm is preventable, and all should work together to achieve this. Moreover health and wellbeing have been put at the centre of Crossrail’s strategy, and policies also apply to contractors and suppliers, and are referred to explicitly in contracts.

Understanding the risks and impacts of fatigue was critical for Crossrail, and was core to the project’s health and safety strategy at the outset. Martin says fatigue is implicated in 20% of rail accidents, associated with a 13% higher mortality risk, and is linked to sleep debt and the 24 hour society, without mentioning the economic costs. Causes of fatigue arise from factors linked to the environment, the workplace, and an individual’s home life. Lifestyle is an important consideration, with poor diet, excessive alcohol and caffeine all having impacts on sleep quality.

Social context

Shift work is a risk factor for poor quality sleep, particularly for those working nights. Crossrail and Transport for London research sought to examine the impact of shift work and the impact of changes to shift patterns. They examined a number of interventions that modulated shift duration and frequency. They found that people who worked shifts shorter than ten hours did not necessarily have better sleep, probably because they had more leisure time and were not prioritising sleep. This motivated a key Crossrail policy that staff “arrive at work fit and ready to work”, including not being ill, not on medication and not sleepy. Still, managing human resources in such a setting is challenging as certain policies could be argued to blur the boundaries between professional and personal life.

In summary the Crossrail working hours policy requires:

  • An uninterrupted break of one day in seven days, or two days in a 14-day period
  • A minimum rest break of 20 minutes when working more than six hours and two breaks if working twelve hours​
  • No more than twelve hours per day shift, 14 hours door to door​
  • No more than ten hours per night shift or early shift​
  • First night shift no more than eight hours​
  • A minimum of twelve hours rest between shifts, or 14 hours for consecutive nights​
  • Not to work more than 60 hours in any seven day period​
  • An uninterrupted break of one day in seven days, or two days in a 14 day period​
  • Overtime not to exceed by two hours past usual shift

Still, these rules do not guarantee optimal working conditions as shift workers' home lives might keep them from getting the rest they need. Crossrail workers have a variety of cultural backgrounds, with a significant proportion hailing from Eastern Europe, and living in multiple occupancy housing. So an employee might be coming home after a shift to sleep, as their housemates are going out. Being aware of this context helped develop resources for workers that enabled them to get the rest they needed uninterrupted. For example the development of good shower facilities and the provision of high quality food, as factors such as caffeine or alcohol consumption can impact health and safety.

While it's easier to regulate a work environment and encourage employees to use breaks effectively and help them manage high levels of physical and mental exertion, it's more difficult to mitigate home-environmental factors. Noisy neighbours, family circumstances (caring for a newborn, or dealing with a family illness), living in multiple occupancy accommodation, poor sleep habits (going late to bed and watching TV), or simply having financial or domestic worries, are all factors that can cause sleep disruptions and compromise health and safety.

Taking all the research and contextual factors into account led to Crossrail’s Fatigue Management Plan:

  1. Identify all staff who work some form of shift roster patterns
  2. Apply the HSE Index, if the pattern falls outside, re-evaluate ​​
  3. Carry out occupational health assessments for all on night shifts​
  4. Provide information and training for those ‘at risk’ to better understand lifestyle issues​
  5. Review fatigue after a month, and every three months​
  6. Include fatigue into accident investigation. If it's a root cause, further review​
  7. Undertake a management review each year

Looking at the plan it is evident that a key approach was to identify all staff working shifts and to undertake occupational health assessments for all those working nights. Fatigue is assessed after a month and every three months thereafter. Regular screening is also picking up other health conditions. All incident investigations have to assess whether fatigue was a factor.

Points for Further Consideration

The HSE Fatigue and risk index tool fails to address the non-work context. Research highlighted differences, questioning some changes to shift length. Non-rostered work is a difficult policy area but a key element of possible fatigue and support areas. Crossrail developed its own fatigue risk assessment in conjunction with the Epworth Sleepiness Score. Providing information about how to cope with shift work and how to recognise fatigue is effective and makes a difference. Occupational health assessments have highlighted symptoms of fatigue-related illness, however there is more to do in assessing fatigue in incidents.

Crossrail’s Toolkit for Crossrail Contractors can be found on the Crossrail Learning Legacy website, as the project has a commitment to share everything they have learnt. The website has numerous resources on risk assessment, incident investigation, training, work scheduling, health assessments, and monitoring checklists.

Created By
Lef Apostolakis

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