Hospitalization challenges the sleep of patients in many ways. Anxiety, pain, fever, infirmity, and other discomforts can all disturb sleep, as can the noise and light of a 24-hour working facility and the need for regular day and night observation and assessment of vital signs. In turn, this disturbed sleep has the potential to adversely affect health, well-being, and recovery from illness and operation.1 Changes in cognition, mood, memory, pain perception, psychomotor function, and metabolic, inflammatory and immune markers are evident after relatively brief periods of sleep disturbance. Furthermore, preexisting sleep disorders, such as sleep-related breathing disorders, increase the risk of adverse outcomes following serious illness or postoperatively.2,3 Where sleep patterns are seriously disturbed, as can occur in intensive care unit (ICU) patients, it may take months or years for the disturbance to remit.4 Hence improving sleep in hospitalized patients has the potential to improve patient comfort, safety, and outcomes, both short and long term.
THE NATURE OF SLEEP
Sleep is a natural, readily reversible state of decreased awareness and responsiveness. It is necessary for rest and recuperation after prolonged periods of wakefulness, allowing restoration of the synaptic strength and cellular homeostasis in heavily used neural circuits.5,6 However, while restoration is an essential component, parts of the brain are active during sleep subserving other functions. These include information processing and memory consolidation, and, given the potential vulnerability of the state, monitoring vital functions and, to a limited extent, the local environment in which sleep is occurring.7
Sleep is not a homogenous state, but consists of various stages, each having distinctive electroencephalographic (EEG), electromyographic, and electrooculographic characteristics. Detailed descriptions of these stages and their structural organization (known as sleep architecture) are available elsewhere, but sleep can be broadly divided into nonrapid eye movement (nREM) and rapid eye movement (REM) sleep, with REM sleep occurring in cycles at intervals of approximately 90 minutes and occupying around 25% of sleep time in adults.8 nREM sleep consists of 3 stages: stage N1, the relatively brief period in transition from wake to sleep (“sleep onset”); stage N2, which occupies around 50% of sleep time and, with N1, is known as “light sleep”; and stage N3, which is characterized by the appearance of slow delta waves on EEG, occupies 20%–25% of sleep time in younger adults and is known as “slow wave” or “deep” sleep. While dreaming is more prevalent and better organized in REM sleep, it can occur in all sleep stages.
A feature of sleep is the muscle relaxation and decreased ventilatory drive that accompany it.9 In vulnerable individuals, these changes predispose to sleep-related upper airway obstruction (in those with narrow or floppy upper airways) or hypoventilation (in those with respiratory muscles that are weak or excessively mechanically loaded, eg, from obesity). These problems are particularly evident in REM sleep, where the sleep-related decreases in muscle activation and ventilatory drive are most profound.
Normal Sleep Requirements
Normal sleep requirement varies with age and between individuals. Normal adults require between 6 and 10 hours sleep per night, with most clustered in the recommended 7- to 9-hour range.10 The main drivers of sleep are the “homeostatic” drive that progressively increases with time spent awake, and the “circadian” drive that is determined by the internal body clock, which cyclically increases sleep propensity with the dark of night and decreases it with the light of day.
Causes of Inadequate Sleep
Sleep is readily disturbed by a variety of environmental, social, psychological, and pathologic factors.11 The causes of inadequate sleep fall into 3 broad categories: insufficient duration, inappropriate timing, and impaired quality (Figure).
Insufficient duration may occur through choice or necessity because of the competing demands of work, social, or family life; poor sleeping conditions because of environmental disturbance (light, noise, hot or cold room temperature, uncomfortable bedding); medical conditions, especially those associated with anxiety, pain, breathlessness or fever; and insomnia or other sleep disorders.12
The effects of inappropriate timing are commonly seen in relationship to shift work that intrudes on normal overnight sleep hours and jet lag. Normally, the wake–sleep cycle is dictated by the daily cycle of light and dark, with sleep optimally taken during the overnight circadian low.13
Sleep can be of apparently adequate duration and timing but be disturbed or unrefreshing because of impaired sleep quality. Factors that affect quality (and duration in some circumstances) include medical, psychological, and psychiatric disorders, medications and other substances (such as alcohol and caffeine) with the potential to disrupt sleep, or the presence of a specific sleep disorder that is associated with arousals and awakenings (such as obstructive sleep apnea [OSA] or restless legs syndrome), difficulty initiating or maintaining sleep (insomnia), or a misaligned circadian rhythm (circadian rhythm disorders).14
Apart from its overnight manifestations, inadequate sleep has daytime consequences, including sleepiness, cognitive and psychomotor impairment, mood changes, and negative physiological impacts. Paradoxically, some of the factors that disturb sleep are, in turn, aggravated by the sleep disturbance they cause. This bidirectionality is commonly seen in relationship to pain, anxiety, and depressive symptoms.15
EFFECTS OF ILLNESS AND HOSPITALIZATION ON SLEEP
The impacts of illness and hospitalization on sleep are illustrated in studies of the effects of surgery and anesthesia on the structure and duration of sleep in the postoperative period. In detailed studies of sleep architecture, using polysomnographic methods, Chung et al16 have objectively demonstrated the changing pattern of sleep in the first week following surgery. They show that, apart from a diminution in total time on the first postoperative night, the efficiency of sleep (the proportion of time allotted for sleep actually spent asleep, reflecting how disrupted it is) and the proportion of time in deep sleep and REM sleep are greatly reduced, recovering slowly over the succeeding nights toward normal on postoperative night 7.
These objective observations are consistent with subjective reports. Patients report that their sleep is substantially more restless, difficult to achieve, of lower quality, and less satisfying and refreshing in hospital than at home.11 Reasons offered for this include hospital-related factors and patient-related factors. The hospital-related factors include awakening by hospital staff for observations or other activities, the noise created by other patients, hospital staff and medical equipment, uncomfortable bedding, intrusive lighting, and overnight transfer to a different room. Among the patient-related factors identified are pain, dyspnea, anxiety, and worry about illness. Added to these are the effects on sleep of fever and infirmity.
While it might be argued that these effects are short term in their impact, study of subjective quality during recovery from critical illness demonstrates that the insomnia and sleep quality impacts can persist for weeks or months beyond the hospital stay.4
EFFECTS OF DISTURBED SLEEP ON HEALTH, WELL-BEING, RECOVERY FROM ILLNESS AND OPERATION
Disturbed sleep has substantial potential impacts on health, well-being, and recovery from illness and operation. These include its negative effects on cardiovascular, cognitive, psychomotor, psychological, metabolic, immune, inflammatory, and catabolic functions.
As little as a night or 2 of sleep restriction or deprivation can increase blood pressure in normotensive subjects as well as those with preexisting hypertension.17 This is likely to be attributable to associated sympathetic activation. Sympathetic activation occurs in settings such as sleep restriction and misalignment of the sleep–wake cycle with night and day (circadian misalignment) in otherwise healthy young adults.18 It also accompanies sleep disruption, for example, from obstructive events in OSA.19 Sympathetic activation may also be responsible for the associations between sleep disruption, from OSA and other causes, and incident atrial fibrillation. OSA is a risk factor for 30-day readmission after cardiac surgery, with atrial fibrillation the most common diagnosis on readmission; OSA is a risk factor for postoperative atrial fibrillation in this setting.20
Sleep loss is a risk factor for postoperative delirium and interventions designed to promote sleep and alignment of the circadian rhythm with night and day reduce its incidence.21 Patients with low cognitive reserve, such as the elderly and those with untreated sleep disorders, are at particular risk of postoperative delirium and attention to these matters helps both prevent and treat the problem.22,23 Untreated, delirium is a threat to well-being, with increases in falls risk, use of physical restraints, unplanned removal of catheters and devices, ventilator times, ICU and hospital length of stay, readmission rates, and mortality.24
Sleep loss and pain perception have a bidirectional relationship: pain disturbs sleep and disturbed sleep aggravates pain. This effect is readily demonstrated experimentally: pain thresholds to a variety of noxious stimuli are reduced by as little as 1 night of sleep deprivation in healthy young adults.25 Poor preoperative sleep appears to be a risk factor for postoperative pain, and postoperative sleep disruption is a credible catalyst of acute pain.26–29
Falls risk is elevated in patients with sleeping difficulties.30 This association in evident among hospitalized patients.31 Falls frequently result in injuries that increase the length and expense of hospital stay and the quality of recovery following surgery.32 Sleep disturbances are an independent risk factor for falls risk following treatment of femoral neck fractures.33
As it does with pain, sleep loss has a bidirectional relationship with depression and depressive symptoms: sleep loss aggravates depression and depression is associated with disturbed sleep. Furthermore, depressive symptoms are shared by both conditions. Increased anxiety levels are recognized as one of the most important consequences of sleep deprivation,34 with a compounding effect in settings, such as hospitalization, where both anxiety and sleep loss are common features.
Sleep loss is also associated with metabolic disturbance. Short-term sleep restriction appears to readily increase insulin resistance, more so when combined with circadian misalignment.35 Stress hyperglycemia is commonly observed in previously nondiabetic patients who have an acute illness or have undergone an aggressive invasive procedure and it increases perioperative risk.36 Sleep loss has the potential to aggravate this tendency.
Immune Dysfunction and Proinflammatory Effects
There is experimental evidence to suggest that sleep loss is associated with immune dysfunction, with a wide array of indicators affected including leukocyte migration and distribution, cytokine production, leukocyte activity and proliferation, antibody levels, complement activation, expression of cell adhesion molecules, and immune-related genes.37 Sleep disturbances, even short term, are associated with proinflammatory changes, with markers such as C-reactive protein, interleukins 6 and 7, tumor necrosis factor-α, and myeloperoxidase increasing in healthy volunteers.35,38 These effects potentially lower resistance to infection and promote systemic inflammation.37,39,40
Sleep deprivation promotes a negative nitrogen balance.41 This is consistent with the notion of a 24-hour cyclical balance of degradation and renewal, where wakeful activities favor catabolism and sleep enhances anabolism.42 Disturbance of this balance through sleep loss has the potential to augment the catabolic neuroendocrine stress response that occurs after surgery, the mitigation of which is known to enhance recovery.43
Separately and together, these effects of inadequate sleep, through reduced duration, disturbed timing, and impaired quality, are associated with physical and psychological disturbances that have potential negative impacts on the healing process. They help make the case for the future inclusion of sleep hygiene measures in enhanced recovery after surgery (ERAS) guidelines, which have been notable for their omission of such considerations.44
HOSPITALIZATION RISKS ASSOCIATED WITH PREEXISTING SLEEP DISORDERS
The challenges poor sleep poses for recovery from illness are illustrated by the hospitalization risks associated with preexisting sleep disorders.
Sleep-Related Breathing Disorders
Unrecognized OSA is associated with increased risk of adverse cardiovascular outcomes (death, myocardial injury, congestive heart failure, thromboembolism, new atrial fibrillation, and stroke) in the first 30 days postoperatively, with much of the risk concentrated in the first few days, where the challenges to safe recovery are most concentrated. The risks increase with increased OSA severity.45
Patients with obesity hypoventilation appear to be at greater postoperative risk than those with OSA alone, with risk of postoperative respiratory failure, heart failure, and ICU transfer elevated in the former relative to the latter group.46 Sleep hypoventilation from other causes, such as neuromuscular disease and advanced lung disease, is also a credible predictor of postoperative respiratory failure.47
Other Sleep Disorders
Other sleep disorders are also associated with increased postoperative risk. Insomnia patients are at increased risk of worsening symptoms postoperatively along with increased risk of delirium, as are patients with OSA.48–52 Symptomatic deterioration may occur in patients with restless legs syndrome postoperatively as a result of immobility, blood loss, iron deficiency, withdrawal of medications, and aggravating effects of other medications.53 Patients with parasomnias are at increased risk of injury.54 Narcolepsy may be aggravated and can be associated with delayed emergence or autonomic dysregulation.55
STEPS TO IMPROVE SLEEP IN HOSPITALS
Hence, disturbed sleep poses problems for safe and prompt recovery. The sleep disturbance can be based on insufficient duration, misaligned timing, or inadequate quality. The sources of these problems are often readily addressable. However, the first step in doing so is to recognize the value of adequate sleep in facilitating recovery from illness or operation and in securing it for patients as an institutional priority.
Several measures are required (Table). Noise mitigation is an obvious example, as the disrupting effects of environmental noise on sleep are well described and noise from other patients, equipment, and staff are among the most common sleep-disturbing factors reported by patients.11 Actions should include the adoption of practices by staff that are more sympathetic to patient needs, use of less intrusive monitors, and consideration of the use of ear plugs or noise-cancelling headphones by patients, where necessary.
Steps to Improve Sleep in Hospital
||Minimize overnight light levels.
||Improve comfort of bedding.
||Reduce number and impact of observations and interventions, where possible.
||Time patient movements and transfers to minimize impact on overnight sleep.
||Ensure pain control has optimization of sleep as one of its targets.
||Provide psychological support to reduce anxiety.
||Consider judicious use of nocturnal sedation in selected patients.
||Identify patients with preexisting sleep disorders for particular attention.
||Monitor sleep quality during recovery from illness or operation to ensure persistent problems are addressed.
Nighttime lighting levels are another common source of complaint, understandably enough given the sleep-disruptive effects of environmental light on sleep.56 Attention to corridor and room lighting levels to minimize their effects on sleep and circadian rhythm disruption is needed.57 The use of light-excluding eye masks should also be considered.
The comfort of hospital bedding is a further factor that affects how patients sleep in hospital.58 Attention to this issue is another step in diminishing the environmental challenges to sleep that hospitalization poses.
In addition to these general considerations, patients’ sleep is frequently punctuated by intrusive observations, treatment administration, transfer to other rooms, noisy alarm systems, and other equipments.59 Reducing the number and impact of these disruptions should be accepted as a challenge by attending staff, with an emphasis on restricting them to those that are strictly necessary and, where possible, minimizing their intrusiveness. Better timing of observations and greater use of remote monitoring can help, as can timing of interventions and patient movement and transfers to minimize impact on overnight sleep.
Uncontrolled pain is a further source of sleep disruption frequently experienced by hospitalized patients. Ensuring pain control strategies include optimization of sleep as one of their foci is an important but often inadequately considered step in addressing this problem.60
Anxiety is common among hospitalized patients and is another psychological challenge to sleep.58 Measures to address this problem through psychological support, counseling and, where necessary, anxiolytic medications will, among other benefits for well-being, assist with sleep. Benzodiazepines are effective in the treatment of acute anxiety, but they should only be used short term, because of habituation to their effects and risk of dependence. Greater care is required with their use in the elderly where confusion and falls risk may increase.61 Awareness of their potential ventilatory depressant effects, particularly in combination with opioids, is also needed in patients vulnerable to these influences.
While anxiety is a strong driver of insomnia, difficulties initiating and maintaining sleep frequently occur independent of anxiety and, apart from anxiolytics, other treatments to augment sleep have a role in patients where sleep is proving difficult to achieve.62 These include pharmacological treatments where nonpharmacological measures, such as sleep hygiene advice and cognitive behavioral approaches, are insufficient in the acute setting. Such treatments include judicious use of benzodiazepine and nonbenzodiazepine hypnotics and melatonin. Melatonin increases sleep propensity largely through its reinforcing effect on the circadian day–night, sleep–wake rhythm. It is best administered at a regular time in the evening, generally 30–60 minutes before planned sleep time, in a dose of between 1 and 5 mg. It has a lower side effect profile than many sedative drugs but is less predictably effective in promoting sleep in the short term.63
Given their potential impact on patient safety and well-being, it is important to identify patients with preexisting sleep disorders for particular attention, with continuation of their existing drug or other therapies through the perioperative period where practicable. Perioperative cessation of treatments can lead to immediate recurrence of symptoms in many sleep disorders.
Finally, sleep quality should be monitored and documented during the period of recovery from illness and operation, with identification of sleep issues made a priority for attention where new or exacerbated sleep problems are identified within and beyond the acute illness phase. Often preexisting but undiagnosed sleep problems are first identified during an in-patient stay or new sleep problems may arise. In either case, attention to these will have a long-term health and well-being benefit for the patient concerned.64
As places of healing, a reasonable expectation of hospitals is that that they provide, as best possible, the preconditions for this process. Attention to the sleep needs of patients is not always prominent among these considerations and there is accumulating evidence that it should be, both for its immediate benefits and for the longer term. Apart from their direct impacts, better sleep practices in hospitals may offer example-setting behaviors for patients, their families, and the community to follow beyond hospitalization.
Name: David R. Hillman, MBBS.
Contribution: This author is responsible for all aspects of the manuscript’s preparation.
This manuscript was handled by: Toby Weingarten, MD.
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