Sleep measurement tools W2 L2

Introduction to Sleep Measurement Tools

• Session overview on various devices claiming to measure sleep.

• Important concepts:

  • Differences between polysomnography and other sleep measurement tools.

  • Advantages and limitations of different sleep measurement tools.

  • Populations or conditions where each tool may be beneficial.

  • Approaches to interpret the accuracy of personal sleep monitors.

Common Sleep Parameters from Polysomnography (PSG)

• PSG provides detailed data about sleep stages and timings:

  • Awake vs. Asleep: Identifies state in 30-second intervals.

  • Time in Bed: Duration from lights off to lights on.

  • Sleep Onset: First instance of falling asleep.

  • Sleep Latency: Time between lights off and sleep onset.

  • Sleep Offset: Time individuals wake up (which may vary from lights on).

  • REM Onset Time: Time at which first REM period occurs.

  • Wake After Sleep Onset (WASO): Periods of wakefulness after initially falling asleep.

  • Sleep Efficiency: Calculated as Total Sleep Time / Time in Bed, factoring in both sleep latency and WASO.

Sleep Parameters from Personal Sleep Monitors

• Personal sleep monitors offer a less detailed view compared to PSG:

  • Common metrics:

    • Time in Bed: Total duration they spend in bed.

    • Total Sleep Time: Period spent asleep.

    • Sleep Onset Latency: Time taken to fall asleep.

    • Wake After Sleep Onset: Instances of wakefulness after falling asleep.

    • Sleep Efficiency: Based on total sleep time versus time in bed.

    • Additional metrics may include awakening counts or stages of sleep (light, deep, REM).

Validating Personal Sleep Monitors

• Many devices lack validation leading to questionable accuracy:

  • Tips for evaluating devices:

    • Check for clinical or scientific advisory information on their website.

    • Look for links to published validation research.

• Understanding validation study metrics:

  • Sensitivity: Correct identification of sleep (e.g., 96.4% in example).

  • Specificity: Correct identification of wake (e.g., 66.6% in example).

  • Accuracy: Overall correct identification of sleep and wake combined (e.g., 92.7% in example).

Actigraphy

• Non-invasive sleep monitoring method used historically for research and clinical settings.

• Composition and functionality:

  • Uses a triaxial accelerometer to measure movement.

  • Movement indicates wakefulness; lack of movement indicates sleep.

  • Limitations include misclassification of awake time as sleep if a person remains still.

• Benefits and applications:

  • Useful in insomnia, circadian rhythm disorders, measuring sleep in large populations, and capturing data over long periods.

  • Not effective for diagnosing sleep apnea.

Accuracy of Actigraphy vs. PSG

• Actigraphy often overestimates total sleep time and sleep efficiency.

• Summary from a meta-analysis:

  • Overestimates total sleep time by about 18 minutes.

  • Underestimates sleep latency and WASO.

  • Sensitivity is generally high (around 95%), but specificity tends to be less than 50%.

Advantages and Disadvantages of Actigraphy

• Advantages:

  • Unobtrusive; can be worn like a watch.

  • Records data over multiple nights at home, offering realistic sleep patterns.

  • Cost-effective compared to PSG.

• Disadvantages:

  • Less effective in measuring sleep latency or daytime naps.

  • Requires multiple nights of data to enhance accuracy.

  • Cannot determine sleep stages.

Personal Sleep Monitors

• Factors influencing consumer adoption:

  • Increased aesthetic appeal compared to clinical devices.

  • Offer feedback, goal-setting features, and data synchronization with smartphones.

• Categories of sleep trackers:

  • Wearables: Watches, rings, headbands.

  • Nearables: Devices on or under mattresses, or pillows.

  • Arables: Devices near the bed or phone apps.

• Validation study results indicate wearables perform well in detecting sleep compared to PSG and actigraphy.

Sleep Diaries

• Subjective assessment tool for sleep patterns, effective when paired with actigraphy.

• Details captured typically include:

  • Duration of sleep, perceived quality, time taken to fall asleep.

  • Completed ideally in the morning.

• Advantages of sleep diaries:

  • Insight into individual perception of sleep, low cost, and simplicity.

• Limitations:

  • Susceptible to bias; unable to measure sleep stages; burdensome for some users.

Summary

• Alternatives to PSG for sleep measurement via actigraphy and personal sleep trackers.

• Some personal sleep monitors validated, showing acceptable measures of sleep detection but limitations in sleep stage differentiation.

• Sleep diaries enhance monitoring accuracy and capture subjective sleep quality.

• Monitoring tools need sensitivity, specificity, accuracy assessments, and validation studies to ensure reliability.