Wearable metric
Sleep efficiency
SE
The fraction of time in bed actually spent asleep — the single most actionable wearable sleep metric.
What it measures
Total sleep time divided by total time in bed, expressed as a percentage. Captures both sleep latency (time to fall asleep) and wake-after-sleep-onset. Validated against polysomnography in modern wearables (Oura, Whoop, Apple Watch) with reasonable but imperfect accuracy.
Reference context
2 guideline sources
Younger adults typically achieve 88–92% efficiency. Efficiency declines slightly with age — 80–85% in healthy older adults is normal. Wearable measurements tend to overestimate sleep efficiency compared with polysomnography by 5–10%.
Population context — consult guideline targets below
Mechanism
Why moving this marker matters
Low sleep efficiency reflects fragmented or insufficient sleep, both of which independently associate with impaired glucose tolerance, cardiovascular risk, mood disturbance, and cognitive performance.
Guideline targets
What major guidelines recommend
AASM (healthy adults)
≥85%
AASM (insomnia threshold)
<85% consistently with subjective complaint warrants evaluation
How to measure
The test, where to get it, when to repeat
Method
Computed automatically by sleep-tracking wearables overnight. Manual estimate possible with a sleep diary.
Where
Free with any sleep-tracking wearable.
Typical cost
Free with device.
Fasting
Not required
When to test
AASM 2015
Track over weekly rolling averages; identify patterns rather than fixating on single nights.
How to track
Devices and apps that measure this
These consumer wearables and connected devices report this metric. Healicus is not connected to your device — your data lives in the maker's app and never reaches us.
Oura Ring
INTLFinger-worn ring tracking HRV, resting heart rate, and sleep stages with overnight nasal-temperature trend.
Visit Oura Ring
WHOOP
INTLSubscription wrist band focused on recovery, strain, and sleep — high-resolution HRV trending.
Visit WHOOP
Garmin
INTLSports-watch range with on-watch VO2-max estimate, HRV status, and lab-validated heart-rate tracking.
Visit Garmin
Withings
INTLConnected health-device catalogue — CE-marked blood-pressure cuffs, sleep mats, and body-composition scales.
Visit Withings
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Context
Reading the numbers
Younger adults typically achieve 88–92% efficiency. Efficiency declines slightly with age — 80–85% in healthy older adults is normal. Wearable measurements tend to overestimate sleep efficiency compared with polysomnography by 5–10%.
Caveats
Wearable algorithms are most accurate for total sleep time and least accurate for sleep stages. Use efficiency and total sleep time as the actionable metrics; treat stage breakdowns with skepticism.
See also
Related markers
Take to your physician
Worth discussing
- If sleep efficiency is consistently <80% with daytime symptoms, whether sleep apnea workup is warranted.
- Whether CBT-i would be appropriate if efficiency is low due to insomnia rather than sleep apnea.
- How to interpret stage breakdowns from your wearable in context of overall sleep quality.
Sources
Cited literature
Edited by Carl Pöhl, MD · Healicus editorial
Last reviewed May 2026
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