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Evidence watch

Trends: what's new, what's hyped, what's proven

Sleep is full of trends — new supplements, new wearables, new protocols. We track them and tell you honestly which have real evidence behind them. which are just well-marketed. Popular is not the same as proven.

Comparison grid rating five sleep trackers from one to five on comfort, battery, sleep-stage accuracy, app quality and cost to own. Oura Ring 5,5,4,5,2. Whoop 4,4,4,4,1. Apple Watch 3,2,3,4,5. Garmin 3,5,3,3,5. Fitbit 4,4,3,3,3. Longer bar is better, including cheaper to own.
How the popular trackers stack up. A relative guide across comfort, battery, stage accuracy, app and cost to own. Longer bar is better. Not lab data.
Six sleep tracker metrics decoded: HRV in milliseconds, higher is better; resting heart rate, lower is better; breathing rate, stable around 12 to 20 per minute; skin temperature, watch the trend; sleep stages, estimates not lab-grade; readiness or recovery, a composite of recovery and strain.
What the numbers actually mean. Trackers estimate, they do not measure a lab study. Watch weekly trends in these six metrics, not any single night.

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