Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2023 Sep 2;13(1):14458.
doi: 10.1038/s41598-023-41742-w.

Moving time zones in a flash with light therapy during sleep

Renske Lok  1 , Marisol Duran  2 , Jamie M Zeitzer  3   4
Affiliations

Moving time zones in a flash with light therapy during sleep

Renske Lok et al. Sci Rep. .

Abstract

In humans, exposure to continuous light is typically used to change the timing of the circadian clock. This study examines the efficiency of a sequence of light flashes ("flash therapy") applied during sleep to shift the clock. Healthy participants (n = 10) took part in two 36-h laboratory stays, receiving a placebo (goggles, no light) during one visit and the intervention (goggles, 2-ms flashes broad-spectrum light for 60 min, delivered every 15 s, starting 30 min after habitual sleep onset) during the other. Circadian phase shift was assessed with changes in salivary dim light melatonin onset (DLMO). Sleep, measured with polysomnography, was analyzed to assess changes in sleep architecture and spectral power. After 1 h of flashes, DLMO showed a substantial delay (1.13 ± 1.27 h) compared to placebo (12 ± 20 min). Two individuals exhibited very large shifts of 6.4 and 3.1 h. There were no substantive differences in sleep architecture, but some evidence for greater instability in sleep. 1 h of flash therapy during sleep evokes large changes in circadian timing, up to 6 h, and does so with only minimal, if any, impact on sleep. Flash therapy may offer a practical option to delay the circadian clock in shift workers and jet travelers.

PubMed Disclaimer

Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Circadian phase shift (Δϕ). Depicted is the absolute change in melatonin secretion timing (A) and the changes relative to baseline melatonin assessment (B). A more negative value indicates a greater phase delay. Black dots and red circles indicate individual data points. The phase change presented after placebo, the initially calculated phase change, and the phase change corrected for stimulus timing are shown (A).
Figure 2
Figure 2
Polysomnography recorded during 1-h of intervention. Presented are the duration spent in each sleep stage during flashes and the same hour during placebo exposure (A–E), as well as the number of transitions from deep (N3) to light (N2/N1) sleep (F) and sleep (REM, N1, N2, N3) to wake transitions (G). Placebo (grey) and flash exposure (yellow-black striped) are plotted along with individual data (black dots), the mean (white dots), and the median (black line).
Figure 3
Figure 3
Polysomnographic sleep was recorded during the 6.5 h after the 1-h intervention. Shown is the time spent in each sleep stage following flashes (yellow-black stripe) or placebo (grey) (A–E), as well as the number of transitions from deep (N3) to light (N2/N1) sleep (F) and any stage of sleep (REM, N1, N2, N3) to wake (G). Individual data (black dots), mean (white dot), and median (black line) are also presented.
Figure 4
Figure 4
Average probability scoring during flash or placebo therapy. Presented are the average probabilities for wake in 15-s epochs scored as wake (A), N1 sleep in 15-s epochs scored as N1 (B), N2 sleep in 15-s epochs scored as N2 (C), N3 sleep in 15-s epochs scored as N3 (D), and rapid eye movement (REM) sleep in 15-s epochs scored as REM (E). Placebo (grey) and flash exposure (yellow-black striped) are depicted as individual data (black dots), mean (white dots), and median (black line).
Figure 5
Figure 5
Probability scoring after flash or placebo therapy. Presented are the probabilities for wakefulness (p(W)) (A), N1 sleep (p(N1)) (B), N2 sleep (p(N2)) (C), N3 sleep (p(N3)) (D), and rapid eye movement sleep (p(REM)) (E) Placebo and flash exposure are depicted in grey and yellow-black striped respectively. Individual data are presented in black, the mean of all data points is indicated in white, and the median is presented as a black line (B, C).
Figure 6
Figure 6
In-laboratory experimental design. Example clock times are given for an individual with HSOn of midnight and HSOff of 8:00; all experimental times were operationalized relative to an individual’s HSOn. An initial and final constant routine (light grey) is used to establish the position of the circadian clock before and after the experimental stimulus (yellow striped) delivered during sleep. Saliva samples (red circles) are collected every half hour.
Figure 7
Figure 7
Example of circadian phase delay. Salivary melatonin during baseline (black) and the next day following the stimulus during sleep (red) are indicated.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

References

    1. Moore RY, Reppert SM, Klein DC. Suprachiasmatic Nucleus: The Mind’s Clock. New York: Oxford University Press; 1991.
    1. Stephan FK, Zucker I. Circadian rhythms in drinking behavior and locomotor activity of rats are eliminated by hypothalamic lesions. Proc. Natl. Acad. Sci. 1972;69(6):1583–1586. - PMC - PubMed
    1. Gooley JJ, Lu J, Fischer D, Saper CB. A broad role for melanopsin in nonvisual photoreception. J. Neurosci. 2003;23(18):7093–7106. - PMC - PubMed
    1. Hattar S, Liao HW, Takao M, Berson DM, Yau KW. Melanopsin-containing retinal ganglion cells: Architecture, projections, and intrinsic photosensitivity. Science. 2002;295(5557):1065–1070. - PMC - PubMed
    1. Czeisler CA, Duffy JF, Shanahan TL, Brown EN, Mitchell JF, Rimmer DW, et al. Stability, precision, and near-24-hour period of the human circadian pacemaker. Science. 1999;284(5423):2177–2181. - PubMed

Publication types