"The Sleep Mask" Connection

The Sleep Mask Advantage

Could there be a mind-eye connection doing it's job?

Environmental stimulus, especially noise and light, is thought to disrupt sleep in people. We recently came across a study aimed to determine the physiological and psychological effects of ICU noise and light, and of earplugs and eye masks, used in these conditions in healthy subjects.

Subjects had poorer perceived sleep quality, more light sleep, longer rapid eye movement (REM) latency, less REM sleep when exposed to simulated ICU noise and light.

Earplugs and eye masks promote sleep and hormone balance in healthy subjects exposed to simulated noise and light, making their promotion in patients reasonable.

Sleep disruption is common in people and has been characterized by several studies using polysomnography (PSG). Adverse consequences of sleep disruption include impaired immune function, decreased inspiratory muscle endurance and a possible association with delirium and severe morbidity.

"Melatonin therapy has been shown to be effective in the resetting of sleep-wake cycles, the entrainment of circadian rhythms and the treatment of chronic insomnia." 

Despite many claims that the use of noise reduction and lighting practice in home environments may improve the patient's sleep quality, there have been few objective studies to evaluate the effects of these interventions. Most research in this area has focused purely on noise reduction and not explored the combined effects of noise and light factors on physiological and psychological outcomes, including sleep architecture, perceived sleep quality and hormone secretion (melatonin and cortisol). No studies have yet clearly evaluated the effects of earplugs and eye masks on sleep however the one conducted on ICU patients seem promising.

It was hypothesized that patients' sleep is disrupted by the noise and light in the ICU, accompanied by impaired nocturnal melatonin secretion and elevated cortisol secretion. Earplugs and eye masks worn during exposure to a simulated ICU environment may improve sleep and protect nocturnal melatonin and cortisol secretion. To test this hypothesis, an experimental study was conducted in a sleep laboratory.

The results of the study support the notion that sleep and hormones are both disturbed with exposure to simulated noise and light in healthy subjects. Use of earplugs and eye masks improve subjective sleep quality noticeably.

Our results confirm that subjects not only have poorer perceived sleep quality, but also suffer from sleep disruption, measured as more light sleep, longer REM latency and less REM sleep, with exposure to simulated ICU noise and light levels. 

The ICU environment technically is not conducive to sleep. Survey studies showed that ICU patients considered excessive noise and bright lights noxious and disruptive. Our colleagues found that noise, light and patient care activities accounted for less than 30% of nocturnal arousals and awakenings. It was also reported that noise accounted for less than 15% of arousals and awakenings in mechanical ventilation patients. Therefore, noise has proved to be an important sleep-disruptive factor and has negative physiological and psychological effects on patients, although it may not be responsible for the majority of the sleep fragmentation.

Recent emphasis has been on noise reduction and encouraging the dimming of lights overnight in ICU settings, but control of noise is not always possible and lights are always present in critical care for patient observations and patient care activities. Therefore, we hypothesized that use of earplugs and eye masks may have benefits in some ICU patients with regards to sleep disturbances.

Previous studies showed that some ICU patients were unwilling to use the earplugs and/or eye masks because they found the interventions uncomfortable. Some patients commented that there was a feeling of heat, tightness, sore ears, claustrophobia and still being able to hear when using earplugs. The reasons for this may include improper insertion, individual variability in sensitivity or anatomy of the ears, unsuitable type of earplugs and eye masks and the anxious state of patients. Future studies should consider the sleep intervention according to patients' tolerability and explore other methods when patients can not tolerate the devices. 

"Light disturbances may be 'blocked' by other means and exclusion of blue light by patients wearing glasses that filter out this light wavelength or nocturnal lighting sources without blue light may be alternatives with regard to minimizing adverse effects on the nocturnal melatonin surge."

Melatonin is the key circadian regulatory hormone in humans. Cortisol is an important stress hormone. Melatonin secretion normally increases at night and decreases in the early morning hours. In contrast, cortisol secretion falls. Both are biological markers of the circadian rhythm. Melatonin therapy has been shown to be effective in the resetting of sleep-wake cycles, the entrainment of circadian rhythms and the treatment of chronic insomnia.

The melatonin secretion pattern has been related to the sleep disturbances observed in the ICU. Recently there has been some evidence that exogenous melatonin is effective in improving sleep in ICU patients.

Sleep intervention should be extended to a coordinated exogenous melatonin therapy with bright light. One of our colleagues suggested that lighting could be coupled with shielding of patient's eyes to allow for a sufficiently lit environment so ICU staff could carry out necessary nighttime activities and minimize retinal stimulation for the patients. Most previous studies evaluated the effects of earplugs, and recently two studies indicated that earplugs and eye masks were a relatively cheap way to improve sleep quality in critically ill patients. In fact, our study found that subjects disliked light as much as noise and eye masks are better than earplugs in terms of the subject's tolerability.

In addition, our finding of significantly higher cortisol levels when exposure to ICU noise and light agreed with previous results that acute noise stress invokes the stress response and high levels of stress hormones.

Conclusion:

Our results found that use of earplugs and eye masks in subjects not only improves subjective sleep quality, but also increases the amount of REM sleep and nocturnal melatonin levels in a simulated ICU environment.

Our study provides a reasonable basis for promoting the use of earplugs and eye masks for healthier sleeping. Sleep is a basic human need, sleep disruption may contribute to patient morbidity and degenerate quality of life. Therefore, we recommend the routine use of earplugs and eye masks in even though some patients may be undergoing ongoing disease processes. Future studies should be designed to determine if the use of earplugs and eye masks will improve the sleep quality and ultimately benefit the clinical outcome of critically ill patients. 

Key Web Sources

• Sleep study (https://pmc.ncbi.nlm.nih.gov/articles/PMC2887188/?utm_source=chatgpt.com)