What is it about?

We know that light has the potential to make us more alert and to determine whether we are early or late sleepers, but is this something we should worry about in ordinary everyday life? If you are not in a particular at risk group, don't work shifts or suffer jet-lag does the light that you experience determine whether you feel sleepy during the day and what time you go to bed? We use a new wearable sensor to monitor personal light exposure for 59 healthy adults and show that light exposure does indeed predict daytime alertness and timing of sleep.

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Why is it important?

Many people suffer sleepiness during the day and difficulty waking in the morning. Our data show that these problems are less acute in people who experience high light levels in the morning and through the day. Getting more daytime light is achievable for many people.


I hope this article makes people think about their own light exposure. We are used to being told that light at night is bad but honestly who is giving up screen use in the evening? Not me! Its more realistic to build higher morning and daytime light exposure into daily routines, and our data show that in ordinary everyday life this is associated with being more alert in the day and earlier bedtimes.

Robert Lucas
University of Manchester

Read the Original

This page is a summary of: Associations between light exposure and sleep timing and sleepiness while awake in a sample of UK adults in everyday life, Proceedings of the National Academy of Sciences, October 2023, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2301608120.
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