The advanced guest often arrives with their own sleep sensor, and will judge the room by what the screen tells them on waking.

Why it matters

A ring, a watch or a sensor slipped under the mattress: these devices have become commonplace. They give a figure every morning. That figure is useful if it is read for what it is, and misleading if it is read as a medical test.

A hotel that talks about sleep must therefore know two things: what bedding changes, and what the sensor can really measure.

What science establishes

A sensor detects sleep well, wakefulness poorly. Seven consumer devices were compared with polysomnography, the reference laboratory test, in 34 young, healthy adults. All recognise sleep in at least 93 % of cases. They recognise wakefulness in only 18 to 54 % of cases, and their sleep stages are inconsistent. They perform less well on restless nights. Chinoy et al., 2021. Established, young adults.

The same bias is found under the mattress. Over more than 400 nights and 183 participants with an average age of 45, a sensor placed under the mattress classifies 83 % of the time correctly, with a sensitivity of 95 % for sleep and a specificity of 37 % for wakefulness. It overestimates sleep time by 48 minutes on average. Manners et al., 2025. Established.

Stages remain approximate. In patients at a sleep laboratory, the best rings distinguish sleep from wakefulness with about 85 % accuracy, but classify the four stages (wake, light, deep, REM) correctly only about one time in two. Herberger et al., 2025. Established, patient population.

In older adults, only duration holds. In a home-based study of 74 older adults, 20 of them living with dementia, and 752 nights, most measures agree poorly between devices and with polysomnography. Sleep duration is the only one that carries over from one device to another. It often takes up to seven nights for a measure to become reliable. Ravindran et al., 2026. Established for duration, in a small sample.

What is emerging

The figure can become a source of worry. Clinicians have described patients seeking help for disorders they attributed to themselves based on their sensor, and pursuing perfect sleep to the point of sleeping badly. They named this picture orthosomnia. Baron et al., 2017. Emerging, case series.

The sensor says little about perceived sleep. A systematic review finds that measures from wrist-worn devices explain only 2.5 to 16.2 % of reported sleep quality, with weaker agreement in older adults and people with insomnia. Srivali et al., 2026. Emerging, low to moderate certainty.

Bedding matters, with caution. A review of 24 controlled trials concludes that a medium-firm mattress, or one the sleeper can adjust, promotes comfort, reported sleep quality and spinal alignment. Firmness is often judged subjectively, which limits comparisons. Radwan et al., 2015. Emerging.

What we refuse to say

We do not say that a mattress cures back problems. We say that firmness and support influence reported comfort.

We do not say that a night at the hotel increases deep sleep. Consumer sensors do not measure stages precisely enough to claim it.

We never present a sensor's score as a diagnosis. A consumer device does not replace a medical examination.

What a hotel can do

Why hotel bedding disappoints. The same mattress and the same pillow for every body, every age and every sleeping position. The advanced guest feels it from the first night.

Minimum baseline (around 150 to 400 € per room). A pillow menu, with two or three firmnesses and heights; a mattress topper to adjust firmness without changing the mattress; breathable linen, cotton percale or linen; two duvet weights depending on the season.

Optimised baseline. At renewal, a medium-firm or adjustable mattress. And, for guests who wish, the loan of a sleep sensor from the IO8 stack: catalogue price 750 € per device, made available at 50 € per night against a card pre-authorisation, paid off in fifteen nights at catalogue price, fewer than ten at the volume rate. The device is used with the guest's own app and account. The data remain theirs.

The target. Bedding the guest adjusts themselves, and a sensor they read with the right reservations. The amounts are indicative and to be confirmed by quote.

What the Living Lab measures

Measurement planned. The Living Lab, near Lisbon, is being equipped in waves. Over the same nights, we will compare two types of consumer sensor, a ring and an under-mattress sensor, to show where they agree and where they diverge.

We will set these nights against the room environment: temperature, noise, light and CO2. The readings will be dated and published here.

Sources

• Chinoy ED et al. Performance of seven consumer sleep-tracking devices compared with polysomnography. Sleep, 2021. doi:10.1093/sleep/zsaa291
• Manners J et al. Performance evaluation of an under-mattress sleep sensor versus polysomnography in > 400 nights with healthy and unhealthy sleep. J Sleep Res, 2025. doi:10.1111/jsr.14480
• Herberger S et al. Performance of wearable finger ring trackers for diagnostic sleep measurement in the clinical context. Sci Rep, 2025. doi:10.1038/s41598-025-93774-z
• Ravindran KKG et al. Are different consumer sleep technologies measuring the same essential aspects of sleep? Sleep, 2026. doi:10.1093/sleep/zsag231
• Baron KG et al. Orthosomnia: are some patients taking the quantified self too far? J Clin Sleep Med, 2017. doi:10.5664/jcsm.6472
• Srivali N, Cheungpasitporn W. Concordance of wearable device sleep metrics with patient-reported sleep quality: a systematic review. Sleep Med, 2026. doi:10.1016/j.sleep.2026.108941
• Radwan A et al. Effect of different mattress designs on promoting sleep quality, pain reduction, and spinal alignment in adults with or without back pain; systematic review of controlled trials. Sleep Health, 2015. doi:10.1016/j.sleh.2015.08.001

Also from the founder

Question 24 · A biological age: what is it actually worth?

The longevity audit for venues  ·  The Research Journal

IO8 Living Lab, near Lisbon. Measured, never promised.

← Previous articleSeries 1Next article →