lack of quality sleep is a major problem for all patients , especially those who are critically ill , and so ways of avoiding disruption by sudden or even sustained noise may well have a role in the modern critical care unit . in the previous issue of critical care , van rompaey and colleagues   argue that earplug use not only produces better reported sleep but also decreases delirium . reduced sleep quantity and quality have significant implications for critically ill patients   and are made worse by environmental factors , including patient care activities , noise , and light interruptions . mean levels of peak noise are comparable to those of a busy office and account for 15% to 20% of patient arousals or awakenings . other factors such as medication exposure and the acute illness itself are also important ; for example , endotoxin disrupts sleep patterns in animal models   and in patients with sepsis . to make matters worse , sleep deprivation itself may impair immune function by reducing natural killer and cellular immune responses in humans , promoting bacterial invasion , and reducing the response to immunization . delirium may well indicate organ dysfunction of the brain and is often an early indicator of a more general deterioration . patients who develop delirium have increased critical care and hospital length of stay , mortality , and longer - term cognitive impairment . development of hyperactive delirium complicates critical care therapy , causing , for example , intolerance of continuous positive airway pressure or non - invasive ventilation or increased doses of sedation or related medication to control behavior , which in turn accumulate . hypoactive delirium may not be identified or may be misdiagnosed , leading to delays in correction of delirium risk factors and hence increasing delirium duration . the environment of the intensive care unit is frequently ignored as a key factor in patient well - being . staff members may not recognize the significant disruption caused by care activities , noise at night , and disrupted day / night light patterns . for many years , architects or hospital planners have neglected appropriate sound insulation or the inclusion of sources of natural light to reinforce the day / night cycle . as a result for many critical care environments , it may be important to accept that , in some circumstances , environmental change will take years to effect and will be expensive . therefore , simple and low - cost patient interventions , such as the use of earplugs , may be a pragmatic solution for many . this study illustrates some of the difficulties of conducting this type of study on relatively large numbers of patients in critical care . it shows the importance of reducing ambient noise and reinforces the worldwide need for a consistent focus on critical care unit design and staff behavior . firstly , single - center studies , such as this one , present problems for determining the effectiveness of the application of any therapy to a less cooperative environment in the future . for example , patient acceptance of earplugs was 79% , which is much higher than the 10% reported in another sleep study . we know that many of the patients are surgical and have similar therapeutic intervention scoring system and sequential organ failure assessment scores and simplified acute physiology score , but we do not know how the patient groups differed in terms of type or effectiveness of analgesia . despite the similar scores , we know that 22% ( treatment ) versus 26% ( control ) were emergency surgical patients . could this have impacted on differing modes of analgesia or incidence of sepsis or medicine exposure ? we also see the variable impact of critical care design : only 60% were exposed to visible daylight ( a potential problem for many similar interventions in critical care units ) . it is hard to determine whether these differences in light levels and patterns were important [ 12 - 14 ] . the assessment of sleep is also difficult in critically ill patients , particularly in delirium - positive patients , and an invalidated subjective score was used . noise is only one of the many modifiable risk factors for delirium , and the fact that the most significant difference was in the patients with mild confusion may explain the reported benefits of improved sleep . despite these issues , 136 patients were included and randomly assigned ( with 46 refusals ) , suggesting that this therapy could be widely applied with an improvement in hazard ratio of 0.47 for delirium . in normal life , no one would argue that ongoing loud conversations , combined with sudden and inappropriate changes in light level , extremes of temperature , or the sound of car alarms outside , were conducive to nocturnal sleep , even in healthy individuals . this is an important study showing that a simple intervention to combat noise may have an important role in delirium risk reduction .
quality sleep is a problem for the critically ill who are cared for in an environment where interventions night and day are common , staff members are constantly present in relatively high numbers , and treatment is accompanied by a range of changing warning tones and alarms and lights . 
 these critical care units are generally designed without a focus on patient comfort , sleep , and rest and often lack access to appropriate natural daylight . to add to this problem , critical illness , particularly sepsis , disrupts circadian rhythms and sleep patterns , and disruption of circadian rhythms , in turn , impairs immunity and contributes to delirium . in a randomized controlled trial in the previous issue of critical care , van rompaey and 
 colleagues have intervened to reduce noise , which is a key factor in this disruption , by having patients use earplugs at night . 
 delirium was assessed by using the neecham ( neelon and champagne ) confusion scale , and sleep perception was assessed by patients ' responses to a set of five questions . 
 after the first night , patients reported a better sleep perception and the occurrence of delirium was reduced ( hazard ratio of 0.47 for the development of delirium ) or was delayed . 
 the study did not quantify adequacy of pain control in post - surgical patients and used patient reporting to assess sleep . 
 whether patients were receiving respiratory or other organ support was not reported . 
 the potential benefit of earplugs is an important practical finding that could be implemented in most intensive care units .