Blocking nocturnal blue light for insomnia: A randomized controlled trial
Introduction
Insomnia symptoms, including difficulty falling or staying asleep, frequently awakening, feeling that sleep is unrefreshing or not sound, or having daytime consequences like feelings of sleepiness, irritability, or trouble concentrating, described in the International Classification of Sleep Disorders-3rd Edition (Sateia, 2014), occur in as much as 33–50% of adults (Schutte-Rodin et al., 2008). While the etiology of insomnia is multifactorial and involves cognitive, behavioral, and physiological factors (Roth, 2007), clinicians and researchers are becoming increasingly aware of how nocturnal light exposure contributes to poor sleep (Czeisler, 2013). In humans, the circadian system enables a consolidated nocturnal sleep phase which coincides with ambient darkness and increased circulating levels of the pineal hormone melatonin (Turek and Gillette, 2004). Melatonin acts as the hormonal signal for the onset of the biological night and has been conceptualized as the factor which “opens the sleep gate” (Cajochen et al., 2003). Environmental light can phase delay rhythms of melatonin and alertness when presented during nighttime hours (Cajochen et al., 2014). A delay in melatonin onset, therefore, may be expected to be a factor contributing to subsequent delays in sleep initiation mechanisms. This may play a role in the development of sleep complaints.
Evening light exposure from normal ambient room lighting (Gooley et al., 2011), eBooks (Chang et al., 2015), and light-emitting diode (LED)-backlit computer screens (Cajochen et al., 2011) causes reductions and delays in melatonin secretion. Light exposure from these sources during the hours preceding habitual bedtime can also decrease subjective and objective sleepiness (Cajochen et al., 2011, Chang et al., 2015), prolong sleep onset latency (SOL) (Chang et al., 2015), and decrease rapid eye movement (REM) sleep (Chang et al., 2015) and slow wave sleep (SWS) (Munch et al., 2006). Light also has acute alerting effects, independent of the circadian system, which can interfere with sleep initiation and maintenance (Cajochen, 2007). The circadian photoreceptor system shows peak sensitivity to ∼450–480 nm light within the blue portion of the spectrum (Brainard et al., 2001, Thapan et al., 2001), which accounts for the high efficacy of blue light to suppress melatonin and increase alertness (Cajochen et al., 2005). Most modern computer, TV, smartphone, and tablet screens, as well as an increasing number of domestic light bulbs, are lit by LEDs which have a peak wavelength in the blue range of ∼460 nm (Cajochen et al., 2011).
The ramifications for these observations are widespread and important since 90% of responders in a representative survey of American adults reported using some type of light-emitting electronic device within the hour before bedtime (Gradisar et al., 2013). Considering the near ubiquity of personal light-emitting devices, huge portions of the population are voluntarily engaging in avoidable behaviors that may worsen their sleep and are associated with insomnia (Fossum et al., 2014). However, patients can be resistant to instructions made by clinicians to limit the use of these devices in the evening for purposes of improving sleep (Phelps, 2008). The development of methods to reduce the adverse effects of evening ambient light exposure, while still allowing for the maintained use of light-emitting devices, could have high impact in shaping clinical practice paradigms for improving sleep in individuals with insomnia.
By selectively filtering out blue-wavelength light in the hours preceding bedtime, the impact of light on the circadian system may be ameliorated. This can be accomplished by wearing amber-tinted, blue-blocking (BB) lenses. Indeed, prior work has demonstrated that BB lenses can prevent light-induced melatonin suppression (Kayumov et al., 2005, Sasseville et al., 2006), and there is some evidence of a therapeutic benefit of these lenses for sleep in a variety of pathological states (Burkhart and Phelps, 2009, Fargason et al., 2013, Henriksen et al., 2014, Phelps, 2008). To our knowledge, no study to date has utilized a randomized crossover design to assess the impact of BB lenses on subjective and objective sleep quality and duration in individuals with an insomnia diagnosis. We aimed to test the hypothesis that amber lenses worn for 2 h before bedtime will improve sleep quality and duration, compared to clear lenses, in individuals with insomnia symptoms.
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Participants
A total of 15 men and women, age 18–65 y were recruited and enrolled. Participants were recruited from the New York City area. None of the participants were patients of study investigators. The primary inclusion criterion was reporting chronic insomnia symptoms for >3 mo. Insomnia identification in study participants was achieved via a validated symptom questionnaire, the Insomnia Symptoms Questionnaire (ISQ) (Okun et al., 2009), which is guided by established diagnostic criteria. The ISQ is a
Results
A total of 15 participants were enrolled and randomized to intervention phases (Fig. 1). Eight participants were randomized to clear lenses followed by amber lenses, and 7 participants were randomized to amber lenses followed by clear lenses (Fig. 1). One participant in the amber lenses-first condition declined to complete the second intervention phase, leaving 14 participants who completed both phases and were analyzed for primary and secondary outcomes. Of the completers, 57% were female, and
Discussion
We report here that wearing BB amber lenses for the 2 h preceding bedtime for one week resulted in significant improvements in sleep, compared to clear lenses, in individuals with insomnia symptoms. Specifically, scores on the PIRS (total and subscales) were reduced in the amber vs. clear lenses condition, indicating a reduction in insomnia severity. Subjective measures of sleep duration and quality, as well as actigraphy-derived sleep duration, were also significantly improved by wearing amber
Funding
This research was funded by a Focused-Project Award (144-FP-16; AS) from the American Sleep Medicine Foundation, a foundation of the American Academy of Sleep Medicine. This publication was also supported in part by the National Center for Advancing Translational Sciences, National Institutes of Health, through Grant Number UL1TR001873.
Conflicts of interest
None.
Author contributions
AS designed the study, analyzed and interpreted data, and wrote the manuscript. EWK conducted the study, analyzed data, and contributed to writing the manuscript. MPSO was involved in data interpretation and manuscript preparation. AJW provided medical supervision for the study, assisted with data interpretation, and manuscript preparation.
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