Sleep by Numbers: Pros and Cons of Wearable Devices for Measuring Sleep

By Professor Shona Halson

Key Takeaways

• Wearables are useful for spotting long-term sleep trends, but their accuracy in measuring sleep stages is slightly limited.

• Behaviour change is their biggest potential, as they can increase awareness and encourage healthier routines.

• Over-reliance on data can backfire, with anxiety about ‘perfect sleep’ sometimes leading to worse outcomes.

• Use wearables as a guide, not a diagnosis, and focus on trends rather than nightly scores.

• Sleep, nutrition, and hydration remain the most powerful and evidence-backed recovery tools.

Introduction

Sleep is a cornerstone of recovery, performance, and overall wellbeing. In recent years, wearable devices have become increasingly popular tools for monitoring sleep, giving both everyday individuals and athletes insights into sleep duration, quality, and overnight physiology (including heart rate, heart rate variability, and body temperature). Typically, available as smartwatches or rings, these devices rely on technologies such as accelerometry (movement tracking), heart rate monitoring, and skin temperature sensors to estimate sleep patterns.

While they offer unique advantages, it’s important to understand their limitations so users can make the most of the data without becoming overly reliant on it.

The Benefits of Wearable Sleep Devices

One of the greatest strengths of wearable sleep technology is accessibility and convenience. These devices allow for continuous, non-invasive monitoring of sleep across long periods in real-world settings — something that would be impossible with traditional sleep lab studies.

Key benefits include:

• Long-term tracking: Helps identify patterns and lifestyle factors (such as caffeine, stress, late meals, or exercise) that may be influencing sleep.

• Behaviour change potential: Many people report greater awareness of sleep habits, prompting positive changes like sticking to consistent bedtimes and prioritising earlier nights.

• Support for expert feedback: Having objective data can be useful when consulting with sleep specialists, coaches, or health professionals about ongoing concerns.

• This combination of awareness and accountability can be particularly valuable for athletes, where quality sleep underpins recovery and performance.

The Limitations of Wearable Sleep Devices

Despite their popularity, wearable sleep devices come with important limitations:

• Accuracy of sleep stages: While reliable for measuring total sleep duration and efficiency, most devices struggle with precise detection of sleep stages (REM vs non-REM). Software updates are improving this, but variation between brands remains high.

• Over-interpretation of data: Users may focus too much on nightly fluctuations, when the real value lies in tracking broader trends.

• Orthosomnia: Anxiety about achieving ‘perfect’ sleep scores can increase stress, paradoxically making sleep worse.

• Data privacy concerns: Wearables collect vast amounts of personal health information. Users should be aware of how this data is stored, shared, and interpreted.

The Recovery Pyramid

To put the usefulness of wearables in context, the importance of sleep can be viewed alongside other recovery strategies. Research suggests that not all recovery methods carry the same weight in terms of evidence or impact.

The Recovery Pyramid (illustrated below) organises recovery methods into three tiers:

• Strongest evidence (highest priority): Sleep, rest, mental recovery, nutrition, and hydration form the foundation of effective recovery.

• Moderate evidence (moderate priority): Active recovery, stretching, massage, foam rolling, compression, and hydrotherapy may provide benefits but should be secondary to the basics.

• Minimal evidence (lowest priority): Tools such as massage guns, cryotherapy chambers, or vibration therapy show promise but require further research before being considered reliable recovery strategies.

• This perspective reinforces that while wearables can provide insights, the most important recovery strategies remain simple and science-backed — sleep, nutrition, and hydration.

Conclusion

Wearable devices can help raise awareness of sleep behaviours and drive positive changes. For athletes, combining wearable insights with recovery nutrition, good hydration, and sound sleep hygiene can be a powerful tool.

Still, wearables should be viewed as guides, not diagnostic tools. Their value lies in tracking trends over time, not chasing nightly perfection. By blending objective data with self-awareness and expert input, individuals can make smarter choices to support both sleep and performance.

References

• Baron, K. G., Abbott, S., Jao, N., Manalo, N., & Mullen, R. (2017). Orthosomnia: Are some patients with insomnia “too worried to sleep”? Journal of Clinical Sleep Medicine, 13(02), 351–357. https://doi.org/10.5664/jcsm.6462

• Halson, S. L. (2014). Sleep in elite athletes and nutritional interventions to enhance sleep. Sports Medicine, 44(Suppl 1), 13–23. https://doi.org/10.1007/s40279-014-0147-0

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