Sleep and occupational performance are inseparable: Why occupational therapy practice and research should consider sleep and circadian rhythm

Sleep is essential for human health, and recovery from injury and disease. Inadequate sleep is linked to worse physical and mental health, from increased diabetes risk, to worse cognitive decline (Chaput et al., 2020). Sleep is of particular relevance to occupational functioning; it affects cognitive performance, from alertness and attention, to executive functioning and learning (Tkachenko & Dinges, 2018), and affects physical performance from basic cardiorespiratory functioning to sports performance (Charest & Grandner, 2020). Sleep timing and patterns also affect social inclusion and occupational routines; predictably timed nocturnal sleep is usually preferable, whilst erratically timed or reversed sleep can interfere with people’s ability to make social or work plans (Faulkner & Bee, 2017).

Normal sleep is characterised by a cessation of activity, dramatic changes in brain activity and loss of conscious awareness of external stimuli (although the right stimuli will still wake the person). Core body temperature and heart rate drop especially during slow wave sleep (deep sleep), and during Rapid Eye Movement (REM) there is muscle atonia, which prevents people from acting out their dreams (Roehrs & Roth, 2019). Healthy sleep-wake cycles follow a circadian rhythm (as do many other biological processes), this rhythm is set by the circadian clock (in mammals, the suprachiasmatic nucleus, SCN), which controls timed changes in production of neurotransmitters, including a rise in melatonin in the evening before sleep. This internal pacemaker produces an approximately 24h rhythm which continues in the absence of any environmental cues, and which synchronises with the external time of day through regular light exposure (Roenneberg & Merrow, 2016).

Sleep pressure, or sleep drive, builds up with longer time spent awake (Milinski et al., 2021), but this sleep drive can be resisted for some time in situations of acute stress. Although this was no doubt useful during our evolution, many modern sources of stress are not improved by remaining awake and vigilant. Stress can lead to short term insomnia. Insomnia may then be maintained by changes to behaviour such as extending time in bed, cancelling daytime activities and coping strategies such as caffeine use (Perlis et al., 2010).

Sleep can also be disturbed due to circadian dysregulation; regular daylight exposure and darkness at night is needed for good circadian entrainment, and this can be lacking when spending most time indoors in artificial lighting. Circadian dysregulation does not just affect shift-workers, but can affect teenagers (whose natural rhythm is later), older people (whose natural rhythm can become less robust) and people with particular neuropsychiatric diagnoses which appear linked to poorer circadian rhythm (such as schizophrenia) (Jagannath et al., 2013). Poor circadian entrainment can affect people who because of illness or disability find it difficult to get outdoors on a regular basis, and who may have limited ‘social cues’ (such as work or social commitments) to promote a regular rhythm.

Sleep is a relevant consideration for occupational therapists on two levels; firstly, sleep knowledge should inform occupational therapy practice and research across specialities, and secondly, sleep treatment should become more established as a specialism for occupational therapists. Sleep is intrinsically linked to many areas which occupational therapists are well equipped to address, such as the physical and social environment, the timing and type of activities undertaken and optimising performance capacity, see Figure 1. These areas all provide potential targets for occupational therapy interventions for sleep improvement. Furthermore, it is relevant for us to understand the interactions of sleep with these areas, in order to avoid unintended consequences.

Figure 1.

Impact of occupational therapy interventions on sleep and occupational performance.

Some examples of how sleep knowledge is relevant for occupational therapists in ‘non-sleep’ specialities are now explored. Firstly, a person’s performance in assessments may be affected by whether they are sleep deprived, and whether they have recently woken up and are experiencing sleep inertia (Werts et al., 2006). Without such awareness functional assessments may be inaccurate. Secondly, recovery will be optimised by promoting a good sleep environment, and practices. For example, enforced early morning bathing for all on hospital wards should be questioned by occupational therapists, more personalised timing may better promote independence and enhance recovery. Thirdly, occupational therapists in a range of fields are well placed to identify sleep difficulties; excessive sleepiness may be picked up during functional assessment, prompting screening or referral for sleep apnoea assessment. Insomnia, problems with sleep hygiene or maladaptive sleep behaviours, may be picked up when assessing daily routines, occupational therapists might signpost clients, refer for treatment, or provide self-help advice. Fourthly, failure to recognise possible sleep difficulties may lead to waste of resources, trying to treat the problems caused by poor sleep, as though they are caused by other factors.

Occupational therapists have a relevant contribution to make to the development, testing and delivery of biopsychosocial treatments to improve sleep. Cognitive Behavioural Therapy for insomnia (CBTi) has been successfully delivered by occupational therapists (Eakman et al., 2022). Occupational therapists have relevant skills for delivering CBTi and related behavioural sleep interventions, for instance CBTi calls for restricting time in bed, avoiding non-sleep activities in bed, and avoiding napping (Perlis et al., 2010) – the ability to work with clients to address the type, timing and location of activities is very relevant to supporting these goals (e.g. avoiding napping is easier when engaging in activity). Occupational therapists can use their skills in environmental assessment and adaptation to optimise the sleep environment (temperature, safety, toileting needs, and positional supports), to improve daytime light exposure and reduce evening and nighttime light. Many components of existing sleep interventions involve behaviour changes which are easy to specify, but hard to initiate for clients. They might involve doing the opposite of what the sleep deprived person feels like doing, and changing longstanding habits can be challenging. Many occupational therapists are well practiced in use of behaviour change techniques such as graded goal setting, use of environmental supports, motivational work, and using personalisation to make goals relevant and meaningful.

Occupational therapy research about sleep fits in one way or another with each of the top 10 research priorities (Royal College of Occupational Therapists and James Lind Alliance, 2020). For instance, priority 6 – addressing sleep may be a means of being more inclusive of both physical and mental health, and priority 8 – improving sleep may reduce hospital admissions in people whose conditions are exacerbated by poor sleep. There are a many potentially fruitful areas of research in which occupational therapists could have a useful contribution; such as research on interventions to increase physical activity to improve sleep. Research in mice has demonstrated that the content of wake time alters sleep drive, with more engaging exploratory activity producing more sleep drive than a repetitive compulsive activity (Milinski et al., 2021). Occupational therapists may be well positioned to contribute toward research to identifying the characteristics of daytime activity in humans which best promotes healthy build-up of sleep drive, so that this knowledge can be incorporated in future sleep interventions.

Research on light exposure interventions to improve sleep has so far been focused on use of light boxes, and with little attention to how this fits within the person’s daily routine, and little personalisation in terms of utilising occupational opportunities to obtain light exposure. This might make these light exposure treatment protocols unsustainable (Faulkner et al., 2020). Occupational therapists are well placed to develop and test personalisable occupationally embedded protocols to improve daily light exposure.

Research on sleep and circadian rhythm has moved on a huge amount in the last 20 years, for example, the retinal cells responsible for detection of light by the circadian system (distinct from the vision-producing rods and cones) were only discovered in 2002 (Hattar et al., 2002). In order to remain evidence based in our practice, it is necessary to have a current and active engagement with research evidence. Occupational therapists should not be satisfied with basic general knowledge of sleep; an in-depth understanding of normal sleep, circadian rhythm and insomnia processes are relevant to support expert clinical practice in most if not all occupational therapy specialities. There is a lot to know about sleep, circadian rhythm, and its interactions with the environment and our habits and routines, and occupational therapists are ideally placed to both use and create this knowledge.

ORCID iD

Sophie Faulkner https://orcid.org/0000-0003-1549-0922