From Sleep Laboratories to Smart Rings: A History of Sleep Technology

Sleep technology has moved from measuring brain signals in laboratories to tracking multiple body signals with small consumer devices, and is now exploring ways to monitor sleep without contact. The shift has made sleep data easier to collect, but it has not made every estimate equally reliable: consumer wearables can be useful for broad patterns, while they do not replace a clinical sleep study.^[1][2][3]

This history follows three linked changes: researchers learned to identify sleep states, clinical tests added breathing measurements and standardized scoring, and consumer devices made tracking more convenient. The final step, contactless radar, could reduce the burden of wearing a device, though its clinical role remains unproven in the evidence available here.

The laboratory foundation: making sleep measurable

Polysomnography (PSG) is a sleep study that records several physiological signals together. Its roots lie in electrical brain recording: Caton recorded electrical activity from animal brains in 1875, and Berger reported human electroencephalography (EEG) in 1929. In 1937, Loomis described EEG features of non-rapid-eye-movement sleep and classified it into five stages, establishing that sleep could be studied through measurable patterns rather than treated as one uniform state.^[4]

The addition of eye-movement recording helped researchers distinguish rapid-eye-movement (REM) sleep from other sleep states. Researchers studied eye movements in 1951; Aserinsky and Kleitman described REM sleep in 1953, and Dement and Kleitman reported repeating NREM–REM cycles and a staging system in 1957. PSG developed from EEG and other electrophysiological recordings, first as a research method and later in clinical practice.^[5][6]

Standardization made those observations more comparable. In 1968, Rechtschaffen and Kales published a manual establishing sleep-stage terminology, techniques, and scoring rules. Meanwhile, respiratory inductance plethysmography (RIP), which measures breathing-related movement, was introduced in the 1960s. These developments widened sleep measurement from brain and eye activity to breathing, helping PSG become a principal diagnostic method for sleep-related breathing disorders by the 1980s.^[7][8][9]

The overall change was not simply more sensors: combining and standardizing signals made it possible to describe sleep in a consistent way and connect sleep-stage observations with respiratory problems. Later professional guidance continued to incorporate RIP, including an update in the American Academy of Sleep Medicine’s 2012 manual.^[15]

Consumer tracking: convenience, more signals, mixed reactions

Consumer tracking shifted the goal from a detailed overnight clinical assessment to collecting sleep-related data at home over time. Watch-like actigraphy devices in the 1990s used accelerometers to record movement over days or weeks. They inferred that stillness meant sleep and movement meant wakefulness, so quiet wakefulness could be misclassified as sleep.^[16]

Fitness bands and smartwatches extended that approach. Many combine movement sensors with optical photoplethysmography (PPG), which uses changes in blood flow to estimate heart rate. Depending on the device, apps may present sleep duration, stages, or scores; some newer smartwatches also offer proxy ECG or blood-oxygen measurements. Smart rings move multisensor tracking from wrist to finger: Oura is described as combining nighttime movement with pulse rate, heart-rate variability, respiratory rate, and body temperature.^[17][18][19]

The change in consumer attitudes is best described as interest accompanied by uncertainty, rather than a simple embrace of ever more data. A 2026 Norwegian survey of 1,002 adults found that 46% had used a sleep app, most commonly on a smartwatch. Among users, about 48% said they learned something about their sleep, 43% found apps useful, and 15% said their sleep improved. At the same time, 18% felt more worried about sleep and 14% felt something was wrong with their sleep; users with insomnia reported more negative effects. These were self-reported, cross-sectional findings, so they do not show that tracking caused either benefit or worry.^[20]

More signals do not automatically mean more accurate results. The available account says consumer devices estimate sleep duration and stages, but stage estimates are less dependable than sleep-versus-wake estimates. Consumer trackers should therefore be understood as tools for observing personal patterns, not substitutes for clinical PSG.^[21][22]

What may come next: contactless radar

Contactless radar sensors are designed to monitor a sleeper from beside the bed, without a wearable. The described system emits electromagnetic pulses and detects body movement, using those signals to estimate breathing rate and broad sleep patterns. A study protocol planned to assess measures such as sleep onset, waking time, sleep midpoint, and total sleep duration; the evidence supplied does not establish direct measurement of heart-related motion by that system.^[23]

The potential advantage is lower nightly effort: once installed, a bedside sensor may collect data without requiring the user to put on a device or manually start each recording, and could support longer-term collection. But the evidence is still limited. The source reports that Sleepscoremax and Somnofy had been validated against PSG without providing accuracy figures or detailed agreement results. The adolescent study described is a feasibility protocol comparing radar with actigraphy and sleep diaries, not a PSG validation study. Questions about reliability, how consumer estimates are calculated, and bedroom privacy also remain.^[24]

Conclusion: easier tracking, not yet a replacement for diagnosis

The history of sleep technology is a progression from laboratory recordings that made sleep stages visible, to standardized clinical tests that included breathing, to convenient wearables that estimate sleep from multiple signals. Smart rings are one expression of that consumer shift. Contactless radar may extend it by removing the need to wear a sensor, but its future value depends on demonstrating reliable performance and earning user trust. For now, convenience and clinical certainty remain distinct goals: consumer devices can help people follow patterns, while diagnosis still calls for appropriate clinical assessment.^{[25][26][27][28][29]}