Bright light has recently been shown to have phase-shifting effects on human circadian rhythms. In this study we applied this effect to 20 patients with delayed sleep phase syndrome (DSPS) who were unable to fall asleep at conventional clock times and had a problem staying alert in the morning. In a controlled treatment study, we found that 2 h of bright light exposure in the morning together with light restriction in the evening successfully phase advanced circadian rhythms of core body temperature and multiple sleep latencies in these patients. This finding corroborates the importance of light for entraining human circadian rhythms.
"Since Czeisler and others  demonstrated a resetting effect of bright light, it has been well documented that bright light before nocturnal sleep significantly delays the core temperature (T c ) rhythm, independent of the timing of the sleep–wake cycle [Boivin and Czeisler 1998; Dijk and others 1991; Drennan and others 1989] and that bright morning light can reset the human circadian rhythm [Clodore and others 1990; Dijk and others 1989; Foret and others 1993; Kondo and others 2007; Rosenthal and others 1990; Scheuermaier and others 2010]. Regarding the effect of bright morning light on phase shifts of the circadian rhythm, Scheuermaier and others  reported that light has a phase-dependent effect on the circadian pacemaker , and modifying habitual light exposure in older individuals could contribute to changes in the timing of circadian rhythms or the phase angle of entrainment. "
[Show abstract][Hide abstract] ABSTRACT: This study tested the hypotheses that 2-h exposure to morning bright
light after waking may avoid a delay in nadir time for individuals who experience
delayed nadir time after waking and may improve the morning rise in core temperature
(Tc) due to residual effects of morning bright light on body temperature
regulation. Eight young men were exposed to 110, 1000, and 4000 lx light for 2 h
after waking at 7:00 AM. After 2-h exposure to a given illuminance, illuminance was
controlled at 1000 lx until 12:00 PM. Rectal temperature (Tre) was measured as a
proxy for Tc continuously from 12:00 AM on the prior night to 12:00 PM on the
day of the experiment. To estimate body heat balance, skin temperatures and values
for regional dry heat loss at seven sites were continuously measured from 8:00 AM
to 12:00 PM, together with measurement of oxygen consumption and finger skin
blood flow rate (SkBF) from 8:00 AM to 12:00 PM at 1-h intervals. Results indicated
delays of a few minutes in nadir time with 1000 and 4000 lx, as opposed to a
120-min delay with 110 lx. In addition, Tre increased after 2-h exposure to 4000 lx
light, probably due to the significantly (P < 0.01) lower mean skin temperature,
SkBF, and dry heat loss compared to the other lighting conditions. Light exposure
over 1000 lx may thus avoid substantial delays in nadir time, and light exposure
over 4000 lx could restore Tc rhythm in a prompt manner due to residual effects of
morning bright light on body temperature regulation.
"Light therapy (LT) has also been successfully applied to the treatment of sleep disorders [17-20], as well as circadian phase sleep disorders associated with jet lag [21,22] and shift work [23,24]. More recently, LT has shown promise as an intervention for obsessive-compulsive symptoms , behavioral disturbances and functioning in dementia and Alzheimer’s disease [26,27], primary and secondary features of Parkinson’s disease , attention deficit hyperactivity disorder , seasonal variations in eating disturbances associated with bulimia nervosa [30,31], and some symptoms of chronic anorexia . "
[Show abstract][Hide abstract] ABSTRACT: Despite the emergence of numerous clinical and non-clinical applications of bright light therapy (LT) in recent decades, the prevalence and severity of LT side effects have not yet been fully explicated. A few adverse LT effects-headache, eye strain, irritability, and nausea-have been consistently reported among depressed individuals and other psychiatric cohorts, but there exists little published evidence regarding LT side effects in non-clinical populations, who often undergo LT treatment of considerably briefer duration. Accordingly, in the present study we examined, in a randomized sample of healthy young adults, the acute side effects of exposure to a single 30-minute session of bright white light (10,000 lux) versus dim red light (< 500 lux). Across a broad range of potential side effects, repeated-measures analyses of variance revealed no significant group-by-time (Pre, Post) interactions. In other words, bright light exposure was not associated with a significantly higher incidence of any reported side effect than was the placebo control condition. Nevertheless, small but statistically significant increases in both eye strain and blurred vision were observed among both the LT and control groups. Overall, these results suggest that the relatively common occurrence of adverse side effects observed in the extant LT literature may not fully extend to non-clinical populations, especially for healthy young adults undergoing LT for a brief duration.
PLoS ONE 09/2013; 8(9):e75893. DOI:10.1371/journal.pone.0075893 · 3.23 Impact Factor
"Finally, desynchronous conditions may occur when circadian rhythms are misaligned due to imposed alterations in light–dark cycles and sleep–wake times. pharmacological administration of melatonin (Dahlitz et al., 1991; Herxheimer and Petrie, 2002; Lockley et al., 2000; Sack et al., 1991), light therapy (Boulos et al., 2002; Eastman, 1990; Eastman et al., 1995; Lack et al., 2005; Rosenthal et al., 1990; Samel and Wegmann, 1997), and promotion of lifestyles that allow for individual preferred sleep–wake times. In the following sections, these established circadian sleep disorders are used as templates for interpreting the most common sleep problems in children with autism. "
[Show abstract][Hide abstract] ABSTRACT: A growing body of research has identified significant sleep problems in children with autism. Disturbed sleep-wake patterns and abnormal hormone profiles in children with autism suggest an underlying impairment of the circadian timing system. Reviewing normal and dysfunctional relationships between sleep and circadian rhythms will enable comparisons to sleep problems in children with autism, prompt a reexamination of existing literature and offer suggestions for future inquiry. In addition, sleep and circadian rhythms continue to change over the course of development even in typical, healthy humans. Therefore, exploring the dynamic relationship between circadian rhythms and sleep throughout development provides valuable insight into those sleep problems associated with autism. Ultimately, a better understanding of sleep and circadian rhythms in children with autism may help guide appropriate treatment strategies and minimize the negative impact of these disturbances on both the children and their families.
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