The honest read
Sleep trackers: useful, until they are not
What a wearable can genuinely tell you, what it guesses at, and the point where tracking starts costing sleep.
4 minSource: Narrated
What they measure well, and less well
Movement and heart rate they measure genuinely well, so time in bed, restlessness and rough sleep length are fairly trustworthy.
Sleep stages are an estimate. Wrist sensors infer deep and REM sleep indirectly, and against lab equipment the staging is often wrong. A bad deep sleep score is not a diagnosis of anything.
The trap with a name
Sleep researchers coined the term orthosomnia for people whose sleep got worse because their tracker told them it was bad. The anxiety about the score becomes its own sleep problem.
A fair test: if checking the score in the morning changes your mood, take a two-week break from it. How you feel by mid-morning is data the tracker cannot beat.
Used lightly, a tracker is good at one thing above all: showing whether the changes you are making are moving your nights in the right direction over weeks, not judging any single night.
Sleep is where memory consolidates and mood resets. It compounds further than almost anything else here.
General information, not medical advice. Narrated never diagnoses.
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