Cited by 81Circadian rhythm and melatoninSleep and Work-Related FatigueSleep and Wakefulness Research

Daytime melatonin and light independently affect human alertness and body temperature

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Lok, Renske, van Koningsveld, Minke J., Gordijn, Marijke C. M., Beersma, Domien G. M., Hut, Roelof A.·2019·Journal of Pineal Research

Abstract

Light significantly improves alertness during the night (Cajochen, Sleep Med Rev , 11, 2007 and 453; Ruger et al., AJP Regul Integr Comp Physiol , 290, 2005 and R1413), but results are less conclusive at daytime (Lok et al., J Biol Rhythms , 33, 2018 and 589). Melatonin and core body temperature levels at those times of day may contribute to differences in alerting effects of light. In this experiment, the combined effect of daytime exogenous melatonin administration and light intensity on alertness, body temperature, and skin temperature was studied. The goal was to assess whether (a) alerting effects of light are melatonin dependent, (b) soporific effects of melatonin are mediated via the thermoregulatory system, and (c) light can improve alertness after melatonin‐induced sleepiness during daytime. 10 subjects (5 females, 5 males) received melatonin (5 mg) in dim (10 lux) and, on a separate occasion, in bright polychromatic white light (2000 lux). In addition, they received placebo both under dim and bright light conditions. Subjects participated in all four conditions in a balanced order, yielding a balanced within‐subject design, lasting from noon to 04:00 pm . Alertness and performance were assessed half hourly, while body temperature and skin temperature were measured continuously. Saliva samples to detect melatonin concentrations were collected half hourly. Melatonin administration increased melatonin concentrations in all subjects. Subjective sleepiness and distal skin temperature increased after melatonin ingestion. Bright light exposure after melatonin administration did not change subjective alertness scores, but body temperature and proximal skin temperature increased, while distal skin temperature decreased. Light exposure did not significantly affect these parameters in the placebo condition. These results indicate that (a) exogenous melatonin administration during daytime increases subjective sleepiness, confirming a role for melatonin in sleepiness regulation, (b) bright light exposure after melatonin ingestion significantly affected thermoregulatory parameters without altering subjective sleepiness, therefore temperature changes seem nonessential for melatonin‐induced sleepiness, (c) subjective sleepiness was increased by melatonin ingestion, but bright light administration was not able to improve melatonin‐induced sleepiness feelings nor performance. Other (physiological) factors may therefore contribute to differences in alerting effects of light during daytime and nighttime.

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  • This alerting effect-exposure timing dependence has further been reported in the context of absent alerting responses during daytime light exposures, suggesting a relationship to circadian features, such as the melatonin level.

    “This alerting effect‐exposure timing dependence has further been reported in the context of absent alerting responses during daytime light exposures, suggesting a relationship to circadian features, such as the melatonin level 70.”

    From The inner clock-Blue light sets the human rhythm (2019) · cites this paper as [70]

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  1. [53]Dinges DF, Powell JW. Microcomputer analyses of performance on a sustained operations. Behav Res Methods, Instruments Comput. 1985; 17(6): 652‐ 655.

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Authors
Lok, R., van Koningsveld, M. J., Gordijn, M. C. M., Beersma, D. G. M., & Hut, R. A.
Affiliations
  • University of Groningen (NL)
  • Chronobiology Unit, Groningen Institute for Evolutionary Life Sciences University of Groningen Groningen The Netherlands
Corresponding author
Lok, Renske
Venue
Journal of Pineal Research
Publisher
Wiley
Published
2019-05-09
Volume
67
Issue
1
Pages
e12583-e12583
ISSN
  • 0742-3098 (ISSN-L)
  • 1600-079X
OpenAlex
W2943364943
Cited by
81
References
84
Citations by year
2026: 6 · 2025: 5 · 2024: 7 · 2023: 15 · 2022: 22 · 2021: 17 · 2020: 6 · 2019: 3
FWCI
6.63
Type
journal article
Language
en
Open access
Locations
  • Journal of Pineal Research (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • University of Groningen research database (University of Groningen / Centre for Information Technology) (submittedVersion, cc-by)
Funders
Rijksuniversiteit Groningen (01110939)
Topics
  • Life Sciences › Neuroscience › Endocrine and Autonomic Systems › Circadian rhythm and melatonin
  • Social Sciences › Psychology › Experimental and Cognitive Psychology › Sleep and Work-Related Fatigue
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Sleep and Wakefulness Research
Keywords
melatonin, bright light exposure, alertness, daytime sleepiness, core body temperature, skin temperature, thermoregulation, circadian rhythm
MeSH terms
Adult, Body Temperature, Body Temperature Regulation, Circadian Rhythm, Female, Humans, Light, Male, Melatonin

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