[jvans]

fitbits and similar are fine for measuring awake vs asleep but really terrible at breaking up the stages

[sheefrex]

They're not as accurate as polysomnography but there is some correlation which should allow these measurements to serve as a useful proxy over 100-180 days. See this review for example:

"The findings of this systematic literature review indicate that the devices with higher relative agreement and sensitivities to multistate sleep (ie, Fitbit Charge 4 and WHOOP) seem appropriate for deriving suitable estimates of sleep parameters. However, analyses regarding the multistate categorization of sleep indicate that all devices can benefit from further improvement in the assessment of specific sleep stages."

Source: https://mhealth.jmir.org/2024/1/e52192/PDF

[taeric]

I've been curious about this. They all are reporting it, nowadays. I'm assuming they have reason to think they are getting better at it?

[pintxo]

I have reason to believe product management wants not to be left behind by the competitors, independent of the quality of their implementation.

[jvans]

metrics sell, even when they're not that accurate, and even when people know that.

[dyauspitr]

Well at the end of the day the underlying metrics are still just heart rate and movement which can only tell you so much.