Hey Drs,
Is there any validity to the idea that sleeping earlier (ex: 9pm to 5am) relatively speaking is any healthier than sleeping later (ex: 2 am to 10 am) if the amount of time sleeping is equal?
Short answer: We don’t really know.
Long answer: The effect of sleep timing is hard to tease out, as many different things contribute to an individual’s sleep schedule that also could influence health trajectory. For example, people who go to bed later tend to consume more alcohol than those who go to bed earlier. There are many other similar correlations here…
Based on existing data, I tend to think it doesn’t really matter all else being equal. People have different sleep phase preferences, some earlier and some later. I think the biggest contributors here would be consistency of a particular sleep phase, e.g. getting into and out of bed at similar times, and duration of high quality sleep.
For a good review of the topic:
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