Human circadian phase in 12:12 h, 200:<8 lux and 1000:<8 lux light-dark cycles, without scheduled sleep or activity

doi:10.1016/S0304-3940(02)00574-8

Neuroscience Letters

Volume 329, Issue 1, 23 August 2002, Pages 41-44

https://doi.org/10.1016/S0304-3940(02)00574-8 Get rights and content

Abstract

The light levels required to maintain human circadian phase in the absence of other strong time cues are not defined. We investigated circadian phase in two groups of men, living in partial temporal isolation, exposed to 12 h:12 h light:dark cycles of: (A) 200:<8 lux, broad spectrum white light for 14 days; and (B) 1000:<8lux for 14 days. The rhythm variables measured were urinary 6-sulphatoxymelatonin, rectal temperature, activity and rest (actigraphy and sleep logs). In 200:<8 lux four/six individuals showed phase delays. Exposure to 1000:<8 lux appeared to maintain synchronisation of rest-activity to 24 h, but with a significant overall phase advance of 0.81 h in temperature. These observations suggest that domestic intensity light does not maintain phase without scheduled sleep/activity, possibly due to indirect effects on behaviour influencing light exposure.

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Acknowledgements

This study was supported by DERA, Farnborough, Hants, UK.

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Human circadian phase in 12:12 h, 200:<8 lux and 1000:<8 lux light-dark cycles, without scheduled sleep or activity

Abstract

Section snippets

Acknowledgements

Neurosci. Lett.

Physiol. Behav.

Radioimmunoassay for 6-sulphatoxymelatonin in urine using an iodinated tracer

Ann. Clin. Biochem.

Sensitivity of the human circadian pacemaker to moderately bright light

J. Biol. Rhythms

Dose-response relationships for resetting the human circadian clock by light

Nature

The effect of light on the human circadian pacemaker

Bright light resets the human circadian pacemaker independent of the timing of the sleep-wake cycle

Science

Phase advance after one or three simulated dawns in humans

Chronobiol. Int.