Light-Induced Changes of the Circadian Clock of Humans: Increasing Duration is More Effective than Increasing Light Intensity

Dewan, Karuna; Benloucif, Susan; Reid, Kathryn J.; Wolfe, Lisa F.; Zee, Phyllis C.

doi:10.1093/sleep/34.5.593

Cited by 92 publications

(79 citation statements)

References 28 publications

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“…The “dose” of a light exposure is known from basic research studies of humans to be determined by multiple factors (Dewan, Benloucif et al, 2011; Eastman, 2011; Lucas, Peirson et al, 2014). Wavelength is one such factor, but our data suggest that short wavelengths are not crucial for SAD treatment.…”

Section: Discussionmentioning

confidence: 99%

Are short (blue) wavelengths necessary for light treatment of seasonal affective disorder?

Anderson

Hilaire

Auger

et al. 2016

Chronobiology International

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Despite widely published speculation regarding a potential potency advantage of short-wavelength (blue-appearing) light for Seasonal Affective Disorder (SAD) treatment, there have been few systematic studies. Those comparing short-wavelength to broad-wavelength (white) light under actual clinical conditions suggest equivalent effectiveness. This multicenter, parallel-group design trial was undertaken to compare the effects of light therapy on SAD using blue (~465nm) versus blue-free (595–612nm) LED lights. Fifty-six medication-free subjects aged 21–64 years who met DSM-IV-TR criteria for recurrent major depression with winter-type seasonal pattern were enrolled in this blinded study at 5 participating centers between January and March 2012. Thirty-five subjects met criteria for randomization to 30 minutes of either blue (~465nm) or blue-free (595–612nm) daily morning light therapy. Twenty-nine subjects completed the study; three subjects withdrew due to treatment-related adverse events, including migraines, and three withdrew for non-study-related reasons. The primary effectiveness variable was depression score (SIGH-ADS) after six weeks of daily light treatment. Secondary effectiveness variables included Quality of Life and suicidality ratings. Using an intent-to-treat analysis, mean depression scores were different at baseline for the blue group (29±5 vs. 26±5, p=0.05 blue vs. blue-free, respectively), and initial score was used as a covariate. Baseline scores were not significantly different between treatment groups among those who completed the study, and no significant differences in depression scores were observed after 6 weeks (mean ± s.d. scores at 6 weeks: 5.6±6.1 vs. 4.5±5.3, p=0.74, blue vs. blue-free, respectively). In addition, the proportion of subjects who met remission criteria, defined as a depression score ≤8, was not significantly different between the two groups (p=0.41); among the 29 subjects who completed the study, 76% of subjects experienced remission by the end of the trial, which coincided with the beginning of spring. Quality of Life and suicidality ratings were also significantly improved from pre- to post-treatment, with no significant difference between treatments. No subject experienced worsening or non-improved symptoms over the 6-week trial. The main finding of this study is that subjects treated with blue light did not improve more than subjects treated with blue-free light; both showed substantial improvement on multiple measures. Failure to find differences may have resulted from methodological constraints, including a small sample size. Recruitment began mid-winter during an unusually mild season, and the trial was terminated earlier than planned by the study sponsor due to a failure to detect difference. However, if confirmed in a larger randomized sample, these results suggest that blue wavelengths are not necessary for successful SAD treatment.

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Section: Discussionmentioning

confidence: 99%

Are short (blue) wavelengths necessary for light treatment of seasonal affective disorder?

Anderson

Hilaire

Auger

et al. 2016

Chronobiology International

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“…Previous studies compared different durations of continuous bright light exposures, and showed that longer durations produced larger phase shifts [49, 80, 86]. Previously in our lab, we compared daily bright light (~5000 lux) with durations of 3 or 6 hours along with an abrupt 12-hour shift of sleep/dark for 8 days [49].…”

Section: Discussionmentioning

confidence: 99%

“…The phase shift averaged over the last 4 days was 8.1 hours for the 3-hour duration and 9.4 hours for the 6-hour duration. A second study [86] tested three bright light durations (1, 2, and 3 hours) with different light intensities (2000, 4000, and 8000 lux). Subjects were awakened for a single bright light exposure in the middle of their sleep period before the temperature minimum to produce phase delays.…”

Section: Discussionmentioning

confidence: 99%

Phase advancing human circadian rhythms with morning bright light, afternoon melatonin, and gradually shifted sleep: can we reduce morning bright-light duration?

Crowley

Eastman

2015

Sleep Medicine

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OBJECTIVE Efficient treatments to phase advance human circadian rhythms are needed to attenuate circadian misalignment and the associated negative health outcomes that accompany early morning shift work, early school start times, jet lag, and delayed sleep phase disorder. This study compared three morning bright light exposure patterns from a single light box (to mimic home treatment) in combination with afternoon melatonin. METHODS Fifty adults (27 males) aged 25.9±5.1 years participated. Sleep/dark was advanced 1 hour/day for 3 treatment days. Participants took 0.5 mg melatonin 5 hours before baseline bedtime on treatment day 1, and an hour earlier each treatment day. They were exposed to one of three bright light (~5000 lux) patterns upon waking each morning: four 30-minute exposures separated by 30 minutes of room light (2 h group); four 15-minute exposures separated by 45 minutes of room light (1 h group), and one 30-minute exposure (0.5 h group). Dim light melatonin onsets (DLMOs) before and after treatment determined the phase advance. RESULTS Compared to the 2 h group (phase shift=2.4±0.8 h), smaller phase advance shifts were seen in the 1 h (1.7±0.7 h) and 0.5 h (1.8±0.8 h) groups. The 2-hour pattern produced the largest phase advance; however, the single 30-minute bright light exposure was as effective as 1 hour of bright light spread over 3.25 h, and produced 75% of the phase shift observed with 2 hours of bright light. CONCLUSIONS A 30-minute morning bright light exposure with afternoon melatonin is an efficient treatment to phase advance human circadian rhythms.

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“…11,12 The intensity, duration of exposure, and wavelength of light also influence the degree to which the circadian clock will phase shift. [11][12][13][14][15][16] The response for melatonin is opposite to light, with melatonin before the T min resulting in a phase advance and melatonin after the T min resulting in a phase delay. 17,18 The largest phase advances are achieved with low doses (3 mg) of melatonin about 4 hours before habitual dim light melatonin onset, or 6 hours before habitual sleep onset.…”

Section: Introductionmentioning

confidence: 99%

Jet Lag and Shift Work Disorder

Reid

Abbott

2015

Sleep Medicine Clinics

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Light-Induced Changes of the Circadian Clock of Humans: Increasing Duration is More Effective than Increasing Light Intensity

Abstract: Results from the present study suggest that for phototherapy of circadian rhythm sleep disorders in humans, a longer period of moderate intensity light may be more effective than a shorter exposure period of high intensity light.

Cited by 92 publications

References 28 publications

Are short (blue) wavelengths necessary for light treatment of seasonal affective disorder?

Are short (blue) wavelengths necessary for light treatment of seasonal affective disorder?

Phase advancing human circadian rhythms with morning bright light, afternoon melatonin, and gradually shifted sleep: can we reduce morning bright-light duration?

Jet Lag and Shift Work Disorder

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