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. 2019 May 11;21(6):e13482. doi: 10.2196/13482

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©Zhongxing Zhang, Christian Cajochen, Ramin Khatami. Originally published in the Journal of Medical Internet Research (http://www.jmir.org), 11.05.2019.

This is an open-access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work, first published in the Journal of Medical Internet Research, is properly cited. The complete bibliographic information, a link to the original publication on http://www.jmir.org/, as well as this copyright and license information must be included.

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The sleep schedules and sleep durations on work and free days in the 3 subgroups with zero naps, short naps (≤30 minutes), and long naps (>30 minutes). The error bars are standard deviation. The group of zero naps has longer nocturnal sleep duration on both work (P<.001) and free days (P<.001) than the other two groups, and the group of short naps has longer nocturnal sleep on both work (P<.001) and free days (P<.001) than the long naps group. However, people taking longer daytime naps have significantly longer total sleep durations across the 24-hour day on both work (P<.001) and free days (P<.001) than the other two groups.