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Sleep, hospital environment, inpatients, sleep deprivation, sound, light This paper reviews studies of exogenous (i.e. non-pharmacological) strategies for improving the nighttime sleep of patients in hospitals. The significance of sleep disruption in hospitals has been addressed in other papers, as have the negative consequences for patient outcomes [1–6]. The authors identified all research papers on sleep improvement studies in hospitals, as well as studies that sought to make correlations between existing conditions and sleep outcomes, evaluated the evidence to support the efficacy of those interventions and provide recommendations for quality improvement initiatives. Sleep is vital for maintaining health and healing, and is essential for a quality hospital experience. Growth hormones, responsible for physical repair and renewal, are primarily secreted during sleep [7, 8]. Sleep deprivation has serious impacts including decreased pain tolerance, increased immunosuppression, delayed healing, confusion, disorientation and delusions [7], higher blood pressure [9] and higher heart rate [10]. Longer term impacts include decreased performance on activities of daily living [4, 5], lower physical functioning after release from the hospital [11, 12], higher overall mortality 1-year post discharge [7] and incidence of delirium [13, 14]. Because of these varied negative impacts, hospitals have tried different improvement practices to enhance the quality of patient sleep in their facilities. A brief description of sleep helps explain how it can be disrupted or promoted. During sleep we are no longer conscious of our environment, yet the brain continues to receive sensory information monitoring the environment for threats, filtering out and ignoring what it can and only attending to potentially threatening stimuli [15]. This subconscious vigilance is important for protecting us from danger, but makes sleep fragile in high sensory environments like the patient room. The arousal threshold is highest during the most restorative phase of sleep, slow wave sleep, which is decreased in critically ill patients [3, 16, 17], suggesting that patients spend more time at night with a lower arousal threshold. Given that sleep is non-responsiveness to sensory stimuli from the environment, sleep can be supported through three basic mechanisms: reducing the stimuli themselves; interrupting the transmission of sensory stimuli from the environment to the receiver; or reducing the brain's attention to the stimuli. We call the first group ‘Environmental’ because it entails changing the environment to eliminate or minimize stimuli. The next category we call ‘Intermediate’ because it operates as a barrier between the environment and the internal conditions through simple devices (earplugs, eye masks) that dampen the reception of environmental stimuli by the internal system. The final category we call ‘Internal’ because these strategies change the internal receptiveness to sleep, and include relaxation strategies such as aromatherapy, massage, and daytime exposure to light to entrain the circadian rhythm. If sleep is a state of disconnection with the environment, then how can hospitals support and encourage sleep? What quality improvement practices have been demonstrated to work and should be replicated? This review discusses the research in each mode of application (environmental, intermediate and internal) and then the programs that used multiple modalities to improve sleep. Regarding the sources of sleep disruptions, this review specifically focuses on sleep disruptions caused by environmental factors and does not explore sleep disruptions caused by pain, nor arousals caused by sleep-disordered breathing and ventilators. MethodsWe searched Medline, CINAHL, PsycINFO and Web of Science databases for articles published in peer-reviewed journals or conference proceedings, between 1970 and 2015 in English using combinations of three sets (intervention, outcome, setting) of keywords, listed in Table 1. The resulting set of articles, were filtered to include only those studying adult hospitalized patients in medical/surgical or intensive care inpatient units, and excluding populations with specific psychological conditions such as dementia because of their unique sleep architecture. Next, we performed a quality screening to identify articles reporting randomized controlled trials, quasi-randomized trials, before-and-after studies, cohort and observational studies that looked at the predictive power of hospital conditions on sleep. Table 1 Search terms and results for each database
Study selectionThe initial search retrieved 13 113 articles from four databases for which we excluded 12 330 articles based on a review of the titles. A review of the abstracts for the remaining 783 articles resulted in 277 articles that warranted closer examination, and of these only 40 met all our criteria. Two papers published subsequently were discovered through hand searching. Fig. 1 shows the process of inclusion/exclusion. Literature review flow diagram. Data extractionEach article was reviewed by both authors, and key information about the variables, setting, population and findings was abstracted into tables. Additionally, articles were labeled by the modality of intervention (environmental, internal, intermediate, and multi-modal) and the way in which sleep was measured (polysomnography, self-report, observation, actigraphy). These details are captured in Tables 2–5; the specific strategies used by each are listed in Table 6. Table 2 Summary of environmental references
Table 3 Summary of intermediate references
Table 4 Summary of internal references
Table 5 Summary of multi-modal references
Table 6 Detailed strategies employed by experimental studies
ResultsGeneral features and quality assessmentThese studies vary significantly in research designs, methods, independent variables, measurement techniques, patient population and reported outcomes creating a challenge for synthesizing the data and drawing general conclusions. There were 27 experimental studies where the researchers made a change to the environment, care process or offered patients a sleep aid (earplugs, eye masks) and documented subsequent impacts on sleep. The other 15 articles described observational studies where researchers looked for correlations between existing conditions and sleep. Most of the studies evaluated the impact of intervention bundles making it difficult to assess the effectiveness of individual measures. Patient population also was variable across the selected studies with 8 studies on cardiovascular patients, 4 medical surgical patients, 15 ICU patients, 5 medical surgical patients, 3 internal medicine patients, 4 critical care patients and 3 postoperative patients. Geriatric, neuro and respiratory populations were among those studied. Only eight studies measured sleep using polysomnography, a technique that records biophysiological changes and provides the most accurate and detailed information about sleep. Actigraphy, which measures lack of movement as a surrogate for sleep, was used in four studies. Thirty-four studies used a self-report survey tool such as the Pittsburgh Sleep Quality Index, Richards Campbell Sleep Questionnaire and Verran-Snyder-Halpern Sleep Scale to measure quality and quantity of sleep. In eight studies, a trained observer recorded sleep status. Many studies employed more than one sleep measurement methodology. There was great variance in the sleep outcomes reported. The most common was overall sleep quality and total sleep duration. Other outcomes reported were sleep onset latency (time it takes to fall asleep), sleep efficiency (percentage of time in bed that is spent asleep), number of awakenings, number of arousals, daytime sleepiness, sleep depth and perceived disturbance of sleep. We only noted the impact on sleep, not capturing other outcomes such as sedative use or patient satisfaction. Environmental strategies for minimizing stimuliThis category includes strategies to minimize the external stimuli (noise, light, temperature, aroma, nursing care activities) that wake patients during the night. See Table 2 for a summary of each article. NoiseNoise is frequently cited as a major contributor to sleep disruption in hospitals. The studies of noise and sleep tend to have high quality objective data for sleep [18–21] and environmental sound levels [18–23]. Several studies found a correlation between number of sound peaks and number of arousals [18–20]. One study found that 20% of the arousals or awakenings from sleep could be attributed to sound peaks [18] and another found environmental noise explained 11.5% of the arousals and 17% of awakenings [19]. Research has found that the average noise level in hospitals is also important. In one hospital a significant dose response relationship between the self-reported sleep disturbances score and the mean noise levels was found, whereas the maximum noise level was not an indicator of sleep disturbances [22]. Patients find noise highly disruptive [21] and report feeling tired in the morning in noisier hospitals [23]. LayoutTwo studies were found that evaluated the impact of hospital unit layout on sleep. One found no statistical difference in sleep in two ward layouts [24]. A second study found people slept better in private rooms compared with sleeping in an open ward [18]. Association with noise, light and sleepTwo observational studies evaluated impact of noise and light conditions in hospitals on sleep. In one study environmental conditions were significantly correlated with sleep quality; environmental noise was the most frequently reported sleep disturbing factor, although lighting conditions had a stronger negative effect on sleep quality [25]. While not significant, another study's findings trended in the same direction [26]. Noise, light and nursing care combined interventionsAn observational study evaluating multiple environmental factors found that noise and nursing activities were significantly correlated with poor sleep quality [27]. Four multipronged improvement programs combining strategies to reduce nighttime disruptions from noise, light and nursing activities were evaluated. Two studies documented significant improvements in sleep quality and confirmed noise reductions [28, 29]. A third study confirmed significant reduction in noise, light and staff-patient interactions at night and found significant improvements in mean sleep efficiency index, daytime sleepiness and time asleep at night [30]. The final study showed a significant improvement in falling asleep more quickly after implementation, but found no impact on overall sleep quality [31]. Quiet time programsHospitals have tried designating ‘quiet times’ (typically from 2 to 4 p.m.) when lights are dimmed and staff and visitors are asked to minimize sounds. Two studies reported a positive impact on patient's likelihood of being asleep during a quiet time versus a control group but found no impact on sleep quality [32, 33]. Patients reported valuing quiet time in another study despite failing to find a significant impact on sleep [34]. Nursing careNighttime nursing activities are recognized as a major contributor to sleep disruption in hospitals [6, 16, 18, 35–39]. Several multifactorial studies included nursing care [28–30]. Only one study found this to be the sole factor, and reported that nighttime care activities were negatively correlated with sleep quality, but none impacted sleep quantity [40]. Ambient temperatureIn the only article that studied the impact of temperature, sleep apnea researchers exposed 40 patients to different nighttime temperatures over three nights and found increased total sleep time and greater sleep efficiency on nights with the lowest temperature [41]. Summary of environment strategiesNoise and light have both been shown to be related to poor quality sleep in hospitals [25]. A direct relationship between noise in hospitals and sleep has been observed in several studies [20, 22, 23]. Hospitals have been able to reduce noise and light levels through interventions such as quiet times [32, 33]. Reducing disruptions due to nursing care activities have been included in successful multifactorial solutions [28–30], but rarely as a singular intervention [40]. Intermediate solutions for blocking external stimuliEarplugs and eye masks offer an easy and affordable solution for improving sleep by blocking out noise and light. Five studies evaluating the impact of earplugs and eye masks in isolation were reviewed [42–46]. In one study patients with earplugs reported significant improvements in sleep depth, ease of falling asleep, satisfaction, amount, movement during sleep, and waking in the night [42]. A second study reported a significant decline in sleep quality in the control group, while the group with earplug and eye masks maintained a constant sleep quality [43]. Two other studies reported positive impacts on patient sleep quality, but provided no statistical analysis [45, 46] and another failed to find any significant impact on sleep [44]. Internal strategies for promoting sleepThere were 12 studies which used strategies for creating internal conditions to encourage sleep (see Table 4) including techniques to calm the mind through relaxation, music, aromatherapy, as well as strategies intended to support internal circadian rhythms in patients. RelaxationRelaxation through massage or guided imagery has not been proven to be effective in promoting sleep. A clinically meaningful (>1 h), but not statistically significant, impact on total patient sleep time was measured for a back massage program [47]. Another study that evaluated relaxation and guided imagery at bedtime found no significant difference in self-reported sleep depth or fragmentation between the intervention and control groups [48]. MusicThree studies found a significant positive impact of music on self-reported sleep quality [49–51]. Patients who were exposed to music with a nature video had better sleep quality than the group who only had a rest [49]. Another study measured significant improvement in sleep quality in an experimental group who listened to 45 min of ‘sedating’ music [50]. The final study compared patients sleeping with earphones with and without calming music and found the music to improve sleep quality and quantity [51]. AromaStudies have demonstrated a positive impact of aromatherapy [52, 53]. Measures of quality of sleep, such as sleep index, duration and sleep disturbance were significantly improved in one study [52]. Another study reported that sleep quality remained constant in the experimental group while declining for controls [53]. A third multifactorial study included prevention of noxious odors through closing toilet room doors as an intervention and found no improvement in sleep disturbance [28]. While the quantity of these studies are limited, the findings suggest aromatherapy may be beneficial for promoting sleep. Daytime lightDaylight plays an important role in sleep regulation. It suppresses melatonin increasing alertness and entraining the circadian rhythm to support better sleep at night. We categorize daytime light exposure as an internal strategy because it impacts sleep as a result of a change in internal conditions. Light at night acts as an external stimulant so those studies were grouped with environmental strategies. Elderly patients exposed to bright daytime light for a week slept longer and awoke later [54]. Delirium patients treated with a combination of morning light and antipsychotic drugs slept longer than those with just the drugs [55]. The use of bright light in the early evening was also found to be effective in increasing total sleep time and reducing awakenings for elderly patients [56]. Two studies were found that focused on the full course of lighting throughout the day as opposed to limited treatment episodes [57, 58]. In one study patients who slept near the window experienced significantly higher light levels during morning and early afternoon and reported significantly better subjective sleep quality than those sleeping far from the window [57]. An interventional study found that patients in rooms with simulated daylight fell asleep faster and slept longer with the impact of the effect increasing over their length of stay [58]. In general these studies confirm the positive impact of bright light exposure increasing total sleep time by between 27 min [54] and over an hour more [55]. Summary of internal strategiesThere is strong evidence about the positive impact of music on sleep [49–51] and good foundational evidence of the potential for daytime light exposure to increase the duration of sleep [54, 55, 58]. The evidence for massage, relaxation and aromatherapy is not strong at this point, but these strategies may warrant further investigation. Multiple modality strategiesSome of the sleep promotion studies used a combination of environmental, intermediate and internal strategies [59–64]. These were evenly split between observational [59–61] and interventional [62–64] research methods. Two observational studies [59, 60] evaluated patient survey data on disruptive environmental and psychological factors to determine the correlations with sleep quality and satisfaction. One found that while noise and light were highly disruptive they were not significantly associated with sleep [60]. The other study found noise, unfamiliar bed, pain and anxiety to each be correlated with sleep effectiveness [59]. The third observational study documented use/presence of a defined list of sleep promotion and relaxation aids and found no correlation with self-reported sleep disturbance [61]. Three separate studies of sleep-promoting quality improvement programs (combinations of nursing, light and quiet times) failed to find any significant impact on self-reported sleep quality [62–64] despite the findings in one of the studies of a significant decrease in noise and reported disruptions caused by medication administration [64]. While it is likely that a successful sleep improvement program will need to address both internal and external factors, there were no studies found presenting strong evidence of the efficacy of such an intervention. ConclusionStudies with multifactorial interventions to improve sleep are difficult to conduct and interpret. The majority of the experimental research reviewed for this paper employed a combination of strategies to improve sleep for hospitalized patients making it a challenge to isolate the effect of individual strategies. Looking across the research we are able to conclude that hospitals can make quality improvements to support better sleep. The constant level of noise and the number of peak noise events in hospitals is responsible for some of the sleep disruptions, it is modifiable through quiet time protocols and use of single patient rooms, and when reduced leads to more sleep for patients. Although nursing care activities are responsible for sleep disruption, efforts at limiting nurse activity have not been demonstrated to improve sleep conditions. Offering patients earplugs and eye masks is an easy and affordable solution that may help, but changing the sound and light environment is more effective. Positive solutions such as calming music in the evening has been shown to be effective, as well as bright light exposure during the day. While the research results are uneven and hard to consolidate due to the multitude of independent variables and sleep outcome metrics, overall these studies point to the potential for making meaningful improvements in the quality of patient sleep. ImplicationsThe disruption of sleep in hospitals results from a number of factors intrinsic to the patient, the external environment and the care process. Altogether the intrinsic and extrinsic factors included in these studies only explained about a quarter of the variance in sleep quality [18, 60] leaving the cause of most of the awakenings/arousals from sleep unexplained. Even with this uncertainty, this literature review demonstrates that we can make progress; conditions in hospitals can be improved such that patients get a better, even if not perfect, night of sleep. It is also clear that any successful solution will be multifactorial and require involvement of many stakeholders from architects, suppliers, nurses, environmental services, laboratory, clinicians and leadership. Limitations of this reviewA major challenge in summarizing this body of literature has been the diversity of independent and dependent variables making it impossible to compare impacts. A narrower focus could have allowed for more in-depth comparison of the results, but we found it important to include the full range of non-pharmacological approaches. At the same time by limiting our focus to studies conducted in hospitals we have excluded a large body of research on sleep that has taken place with healthy subjects in sleep labs. It is important to recognize that patient subgroups may have sleep challenges related to their health conditions or the specific hospital department [65] and therefore not all solutions will have the same impact across patient types or with healthy subjects. Research needsTo adequately capture the true impact of multifactorial sleep improvement projects, larger sample sizes will be needed. Additionally, other factors should be considered in the mix. Limited work has been done on the impact of somatosensory stimuli on sleep disruption such as medical devices [8], comfort in bed [66], and skin temperature [67]. The most impactful research at this point may be to quantify the financial costs of these interventions and the impact on a widely recognized metric such as patient satisfaction. Healthcare leaders are likely to pay far more attention to improving sleep conditions if they know it is an affordable way to improve the patient experience. AcknowledgmentsThe authors would like to thank the research team at the SimTigrate Design Lab especially Lisa Lim, who helped us in early conceptualization of the project. FundingThis work was supported by Hill-Rom. References4 , , et al. . Sleep quality in residents of assisted living facilities: effect on quality of life, functional status, and depression . ;:–.5 , , et al. . Stroke patients’ functions in personal activities of daily living in relation to sleep and socio-demographic and clinical variables in the acute phase after first-time stroke and at six months of follow-up . ;:–.18 , , et al. . Contribution of the intensive care unit environment to sleep disruption in mechanically ventilated patients and healthy subjects .Am J Respir Crit Care Med ;:–.19 , , et al. . Abnormal sleep/wake cycles and the effect of environmental noise on sleep disruption in the intensive care unit .Am J Respir Crit Care Med ;:–.29 , , et al. . 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