Daytime light predicts your sleep timing better than evening light

Daytime light predicts your sleep timing better than evening light

A new circadian modeling paper and four seasons of student data point at the daytime end, and autumn is the thinnest part of the evidence.

Sindre Aune

An Arctic coastal town under low daylight, long shadows across the snow, with no identifiable people, device or interior in frame, for the piece on daytime light and sleep timing

Photo Torkil Torgard / Unsplash

As the days shorten, the light you get by day tracks your sleep timing more closely than the light you get after dusk.

Across more than 500 students in Seattle followed over four seasons, each extra hour of daytime light went with a clock about 30 minutes earlier, while each extra hour of light after dusk went with one only 15 minutes later. It is a snapshot across a population, not an experiment.

Get outside within the first hour of being awake, before the desk.
Take the daylight leg of the commute over the subway platform.
If your morning is dark, a light box is the substitute, used on the same schedule.

A lever, not a cure. And this is ordinary seasonal drift: sleep trouble that does not track the seasons, or a mood that comes with it, is a clinician's question.