In one sentence
A rolling 28-night figure that scores your sleep as a habit, with regularity carrying the most weight, duration next, and sleep stages none.
Why it is built this way
Each component's weight follows the strength of the evidence linking it to health outcomes and the size of the effect. Regularity, 35 percent: the Sleep Regularity Index over 28 nights, the sleep measure that predicted mortality best in the largest objective cohort to date (Windred 2024), and the one most within your control. Duration, 30 percent: hours asleep against an age-banded range, the only component with Mendelian-randomization support for a hard outcome (Daghlas 2019); long sleep is not penalized, because its association with harm is most likely the other way round, and it raises a prompt to talk to your doctor instead. Continuity, 15 percent: efficiency, time to fall asleep and time awake in equal parts, scored against age-banded laboratory norms (Boulos 2019) only after the device's known bias has been applied, or else against your own baseline. Circadian alignment, 10 percent: how your timing sits against your own chronotype, scored only when there is something to align to (a completed chronotype questionnaire first, your habitual timing second) and left out when there is not. Restoration, 10 percent: your own morning sleep satisfaction (60 percent of it) and daytime alertness (40 percent), from validated questions, because subjective sleep correlates poorly with measured sleep and is exactly for that reason not redundant (Buysse 2014). Sleep stages, 0 percent: displayed as a low-confidence estimate, excluded from the score, because no device measures them well and no trial has set a target.
What you see
The index with its band: Optimal 85 to 100, Good 70 to 84, Fair 55 to 69, Needs attention 40 to 54, and below 40 a suggestion to talk to your doctor. Beside it, the coverage, the share of the weight that was actually measured, with the name of what is missing: an 84 with the restoration questions answered is not the same as an 84 without them, and the display says so. Optimal needs at least 90 percent coverage; you cannot reach it by not answering. And a confidence, which rises as your device's provenance improves.
What moves it
Slowly, by design: it is 28 nights. Regularity, most. A continuous regularity multiplier reaches full strength only when low regularity persists across two consecutive 28-night windows, so one disrupted month, a newborn, a holiday, a bereavement, is treated as an episode, not a verdict; an earlier version capped the index at 50 below a fixed regularity threshold, and the external reviewer's objection to that cliff is why the multiplier replaced it. Then duration; then continuity; then your own morning answers.
How Vitality Tracker uses it
The flagship sleep number, available once 14 usable nights exist, computed in the app. A missing component is never silently replaced by the others; the index is computed over what exists and the coverage says so. Nights from a device other than your usual one do not enter until that device has nights of its own, and a device whose firmware changes without a discoverable version drops to the own-baseline tier. At launch the calibrated tier holds Oura's validated generation; as of October 2026 no polysomnography validation of staging has been published for Oura Ring 4 or 5, so both sit on the own-baseline tier, and the list grows as validations are published. The last seven days of sleep, not the index, feed the Vitality Score's lifestyle area.
What it is not
Not a medical device and not diagnostic: it cannot rule out sleep apnea and cannot replace a sleep study. It has not been validated against health outcomes, because no sleep score has. It does not say how you will perform today; Capacity is the closer reading for that, and it is a different question.
How far to trust the number
Calculated from measured, estimated and self-reported inputs, with the coverage and the confidence shown beside it every time. Trust the band and the direction over months; a point or two of movement within a band is noise.
Sources
- Vitality Tracker Sleep Scoring Methodology, open specification v2.0.1, public edition (8 October 2026). doi:10.5281/zenodo.23223863
- Windred DP, et al. Sleep regularity is a stronger predictor of mortality risk than sleep duration. Sleep 2024;47:zsad253. doi:10.1093/sleep/zsad253
- Daghlas I, et al. Sleep duration and myocardial infarction. J Am Coll Cardiol 2019;74:1304–14. doi:10.1016/j.jacc.2019.07.022
- Boulos MI, et al. Normal polysomnography parameters in healthy adults. Lancet Respir Med 2019;7:533–43. doi:10.1016/S2213-2600(19)30057-830057-8>)
- Buysse DJ. Sleep health: can we define it? Does it matter? Sleep 2014;37:9–17. doi:10.5665/sleep.3298.