ORIGINAL RESEARCH article
Front. Physiol.
Sec. Chronobiology
The effects of total sleep deprivation on the circadian rhythms and psychophysiological factors in military cadets; a comparison between wakefulness in light and darkness
Provisionally accepted
Kateřina Skálová1,2
Jan Maleček3
David Kolář2Kateřina Červená2
Jana Koprivova2,4James Tufano3
Dan Omcirk3Jan Padecký3Tomas Vetrovsky3
Zdenka Bendová1,2,4*- 1Faculty of Science, Charles University, Prague, Czechia
- 2Narodni ustav dusevniho zdravi, Klecany, Czechia
- 3Univerzita Karlova Fakulta telesne vychovy a sportu, Prague, Czechia
- 4Univerzita Karlova 3 lekarska fakulta, Prague, Czechia
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Objectives Both sleep deprivation (SD) and light at night have negative effects on human health and performance. The aim of our work was to compare the intermediate effects of total SD under two lighting conditions: full indoor lighting and darkness mimicking natural nocturnal wakefulness. Methods We examined melatonin levels during SD nights, locomotor activity and peripheral temperature rhythms, cognitive performance, mood, hunger, glycaemia and food preference after SD and recovery sleep. Statistical evaluation included ANOVA with FDR correction and confidence intervals Results SD transiently altered peripheral temperature rhythm and post-SD activity, with faster resynchronisation after SD in darkness. Subjective sleepiness increased after SD, with light at night alleviating morning sleepiness. Positive affect decreased after SD but normalised after recovery sleep in both groups. Negative affect worsened in the morning after SD in darkness. Cognitive performance declined after SD, but this effect was higher after SD in darkness. Preprandial glycaemia was higher after recovery sleep following SD in darkness, and sweet taste preference was significantly higher after SD in darkness. Conclusions Light exposure during SD may lead to lower subjective sleepiness and better cognitive performance the next morning compared to SD in darkness. However, light during SD also causes more pronounced and persistent disruptions to circadian rhythms of temperature and activity. This underscores the trade-off between the short-term benefits of nocturnal light exposure and its potential long-term impacts on circadian health.
Keywords: Circadian clock, Cognition, Light at night, Melatonin, Sleep Deprivation, taste preference
Received: 25 Oct 2025; Accepted: 17 Dec 2025.
Copyright: © 2025 Skálová, Maleček, Kolář, Červená, Koprivova, Tufano, Omcirk, Padecký, Vetrovsky and Bendová. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Zdenka Bendová
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