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Reply to Bracke et al. Comment on “Prayag et al. Light Modulation of Human Clocks, Wake, and Sleep. Clocks&Sleep 2019, 1, 193–208”

Prayag, A. S. and Munch, M. and Aeschbach, D. and Chellappa, S. L. and Gronfier, C. (2021) Reply to Bracke et al. Comment on “Prayag et al. Light Modulation of Human Clocks, Wake, and Sleep. Clocks&Sleep 2019, 1, 193–208”. Clocks & Sleep, 3 (3), pp. 398-402. Multidisciplinary Digital Publishing Institute (MDPI). doi: 10.3390/clockssleep3030026. ISSN 2624-5175.

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Official URL: https://doi.org/10.3390/clockssleep3030026


We thank Bracke and colleagues [1] for their commentary on our recent article ‘Light Modulation of Human Clocks, Wake, and Sleep’ by Prayag et al. (2019a) [1]. This gives us an opportunity to expand on our reported findings and interpretations and also to remind readers that mathematical models are aimed at simplifying complex biological mechanisms, and hence should be used parsimoniously and never be considered as absolute truths. We also underscore that results should always be interpreted cautiously, taking into account the experimental conditions the data were collected, and the non-visual responses investigated. We appreciate Bracke and colleagues’ [1] concern that our findings may be inappropriately interpreted by the non-specialist, in particular, Figures 4 and 5 of our review paper [2]. They raise two important points: (1) “ . . . Figure 5 could be misinterpreted by this audience as if monochromatic light sources need less melanopic-weighed irradiation than white light sources for the same response”, and (2) “ . . . since the data for the monochromatic light sources are for pharmacologically dilated pupils, with normal pupil constriction (as for the white light irradiance response curves in Zeitzer et al., 2000) a much higher melanopic irradiance will be required for the same monochromatic response”. In our review paper [2], Figure 4 is the illuminance-response curve for melatonin suppression (in response to 6.5 h polychromatic white light exposures) that we redrew from Zeitzer and colleagues (2000) to extend the illuminance axis. Figure 5 is the melanopic illuminance-response curve we modelled in one of our recent articles [3], derived from data obtained in response to 1.5 h of monochromatic light exposures [4]. In the interest of clarity, we would like to provide some elements of context and then address these aspects point- by-point.

Item URL in elib:https://elib.dlr.de/144063/
Document Type:Article
Title:Reply to Bracke et al. Comment on “Prayag et al. Light Modulation of Human Clocks, Wake, and Sleep. Clocks&Sleep 2019, 1, 193–208”
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Aeschbach, D.daniel.aeschbach (at) dlr.deUNSPECIFIED
Date:5 July 2021
Journal or Publication Title:Clocks & Sleep
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In ISI Web of Science:Yes
DOI :10.3390/clockssleep3030026
Page Range:pp. 398-402
Publisher:Multidisciplinary Digital Publishing Institute (MDPI)
Keywords:light, circadian rhythm, sleep, performance
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:Air Transportation and Impact
DLR - Research area:Aeronautics
DLR - Program:L AI - Air Transportation and Impact
DLR - Research theme (Project):L - Human Factors
Location: Köln-Porz
Institutes and Institutions:Institute of Aerospace Medicine > Sleep and Human Factors Research
Deposited By: Sender, Alina
Deposited On:21 Sep 2021 14:31
Last Modified:21 Sep 2021 14:31

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