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Effects of artificial dawn on subjective ratings of sleep inertia and dim light melatonin onset

Taylor & Francis
Chronobiology International
Authors:
  • SleepCogni, Sheffield, United Kingdom

Abstract and Figures

The timing of work and social requirements has a negative impact on performance and well-being of a significant proportion of the population in our modern society due to a phenomenon known as social jetlag. During workdays, in the early morning, late chronotypes, in particular, suffer from a combination of a nonoptimal circadian phase and sleep deprivation. Sleep inertia, a transient period of lowered arousal after awakening, therefore, becomes more severe. In the present home study, the authors tested whether the use of an alarm clock with artificial dawn could reduce complaints of sleep inertia in people having difficulties in waking up early. The authors also examined whether these improvements were accompanied by a shift in the melatonin rhythm. Two studies were performed: Study 1: three conditions (0, 50, and 250 lux) and Study 2: two conditions (0 lux and self-selected dawn-light intensity). Each condition lasted 2 weeks. In both studies, the use of the artificial dawn resulted in a significant reduction of sleep inertia complaints. However, no significant shift in the onset of melatonin was observed after 2 weeks of using the artificial dawn of 250 lux or 50 lux compared to the control condition. A multilevel analysis revealed that only the presence of the artificial dawn, rather than shift in the dim light melatonin onset or timing of sleep offset, is related to the observed reduction of sleep inertia complaints. Mechanisms other than shift of circadian rhythms are needed to explain the positive results on sleep inertia of waking up with a dawn signal.
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... As a result, much research has been dedicated to investigating potential countermeasures, including consuming caffeine before naps [26,27] or immediately upon waking [28] and face washing [29]. In addition, a number of environmental interventions at different time-points (i.e., waking during the day and at night) have been explored, including manipulating lighting [29][30][31][32][33] and sound [34][35][36] and measuring the relationship with body temperature [37,38]. ...
... With respect to lighting-based solutions for sleep inertia, Giménez et al. [31] found that an alarm clock with dawn simulation significantly reduced complaints of sleep inertia, though the mechanism for how this occurred was unclear. Exposure to polychromatic short-wavelength-enriched light immediately after waking from slow-wave sleep at night was shown to potentially improve subjective alertness, mood, and vigilant attention [32]. ...
... To the best of our knowledge, the current study is the first to measure the impact of a multimodal bedroom-based dawn simulation alarm-where ambient temperature, light, and sound gradually increase over a period of time prior to an individual's scheduled wake-up time-on symptoms of sleep inertia. It has been previously demonstrated that sunrise simulation alarm clocks [31], red light exposure [30], changing sound [34,36], and manipulations to skin temperature [47] individually can have some impact on certain symptoms of sleep inertia. The current study sought to combine these various environmental elements into one intervention and measure the collective impact on sleep inertia. ...
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Previous work has demonstrated the modest impact of environmental interventions that manipulate lighting, sound, or temperature on sleep inertia symptoms. The current study sought to expand on previous work and measure the impact of a multimodal intervention that collectively manipulated light, sound, and ambient temperature on sleep inertia. Participants slept in the lab for four nights and were awoken each morning by either a traditional alarm clock or the multimodal intervention. Feelings of sleep inertia were measured each morning through Psychomotor Vigilance Test (PVT) assessments and ratings of sleepiness and mood at five time-points. While there was little overall impact of the intervention, the participant’s chronotype and the length of the lighting exposure on intervention mornings both influenced sleep inertia symptoms. Moderate evening types who received a shorter lighting exposure (≤15 min) demonstrated more lapses relative to the control condition, whereas intermediate types exhibited a better response speed and fewer lapses. Conversely, moderate evening types who experienced a longer light exposure (>15 min) during the intervention exhibited fewer false alarms over time. The results suggest that the length of the environmental intervention may play a role in mitigating feelings of sleep inertia, particularly for groups who might exhibit stronger feelings of sleep inertia, including evening types.
... For example, Dong and Zhang [4] reported a significant difference in daylight for one of the four investigated beds due to different window distances and solid blocking walls, leading to a different -but unknown -difference in daylight exposure before awakening. Both Giménez et al. [5] and Brubaker et al. [6] mentioned that the participants in their field study were free to use the provided dawn simulator, but it was not reported if this was monitored and if data were corrected. ...
... In particular, the results showed that there are multiple days that people do not sleep at home, which may cause disruptions in a (stable) sleep routine that is supported by lighting. Other studies [e.g., 5,6] have reported the number of days that a dawn simulator was used (circa 11 out of 14 days) but have not reported sleep-wake patterns stability and if people slept at home. ...
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... In fact, although light is a more powerful zeitgeber, social cues may influence exposure to bright light as well as affect the sleep-wake cycle (Elmore et al., 1994), though these effects may be mediated by chronotype (Korczak et al., 2008). Just as sleep routines are affected by travel across time zones, the difference between biological and social time (including time of work obligations and daylight savings time (Kohyama, 2011)) can lead to "social jetlag" (Kramer and Merrow, 2013;Wittmann et al., 2006) and studies have reported effects of social jetlag on melatonin (for example, in night shift workers (Vieira et al., 2021) and people with discordant sleep on work and free days (Geerdink et al., 2016;Gimenez et al., 2010)).Therefore, like other non-photic zeitgebers (e.g., exercise, food) (Schulz and Steimer, 2009), the effects of social interactions should be monitored. ...
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... Moreover, early morning exposure to light was found to decrease the secretion of melatonin (e.g., [2]) and increase cortisol levels (e.g., [6,7]), thus mitigating morning drowsiness. Similarly, artificial dawn awakenings in healthy persons can result in enhancing wakefulness, which reduces sleep inertia complaints (e.g., [8][9][10]). Hilditch et al. [11] also indicated that light can be utilized as a countermeasure to sleepiness. ...
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... 42 However, sleepiness is often accompanied by diminished attention and increased reaction times leading to reduced vigilance and impaired performance during SI. 43,44 Therefore, SI countermeasures, such as a single exposure to 30-min artificial dawn signal (50 lux) prior to the alarm sounded, 45 should be used to reduce the subjective sleepiness in the general population who may need to perform tasks upon waking. Specifically, they may put on light 30 minutes prior to getting up by using a digital timing light. ...
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