Abstract
Sleep debt is becoming a better acknowledged cause of physiological stress and neurobehavioral deficits with major public-health concerns. We investigated whether exposure to blue light during daytime could be an efficient countermeasure to limit sleep restriction’s impact on relevant behavioral (stress, sleepiness, sustained attention, and memory performance) and physiological (saliva cortisol, testosterone, and alpha-amylase) markers. Our semi-ecological, crossover, randomized design included 17 young men that underwent two sleep-restricted nights (3 h each) followed or not by blue light exposure (30-min-long sessions at 100 lux repeated four times throughout the day). Behavioral and physiological measurements were performed in the lab but outside these periods the participants kept following their usual routine. After sleep restriction, morning cortisol and testosterone, and afternoon alpha-amylase levels decreased. In parallel, subjective ratings of stress and sleepiness increased while performance on the sustained attention and memory tasks deteriorated. In contrast, after periods of blue light exposure, all these parameters were largely restored to baseline levels, despite an identical sleep restriction procedure, although this restorative effect was reduced for the memory task. Our findings suggest that even short exposure to blue light could trigger persistent beneficial effects throughout the day and could be potentially efficient in real-life settings.
Highlights
Reduced sleep [e.g., total sleep time (TST) less than 6 h per 24-h] has been reported in 20–30% of working adults (Léger et al, 2011; Ryu et al, 2011)
Our study design was performed in a semi-ecological protocol with 30 min of blue light repeatedly administered across the daytime period
Subjects slept in the “sleep restriction” session for 6 h 57 min ± 54 min on average with a bedtime of 23 h 46 min ± 29 min, a get-up time of 7 h 53 min ± 23 min and a sleep efficiency of 90.1 ± 2.5%; and in the “sleep restriction + blue light” session slept for 7 h 11 min ± 69 min with a bedtime of 23 h 24 min ± 48 min, a get-up time of 7 h 55 min ± 32 min and sleep efficiency of 8.8 ± 3.1%
Summary
Reduced sleep [e.g., total sleep time (TST) less than 6 h per 24-h] has been reported in 20–30% of working adults (Léger et al, 2011; Ryu et al, 2011). Sleep restriction impacts behavioral performance, which has been extensively studied through simple cognitive tasks assessing individuals’ ability to respond to unpredictable stimuli or more complex paradigms involving memory or executive control (Banks and Dinges, 2007; Banks et al, 2010). Our study design was performed in a semi-ecological protocol (behavioral and physiological measurements were performed in the laboratory but outside these periods the participants kept following their usual routine outside the laboratory) with 30 min of blue light repeatedly administered across the daytime period This semi-ecological paradigm was designed to be as close as possible to what sleep-deprived adults experience on a daily basis and to warrant the transfer of our results to reallife settings
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