How Reliable Are Smartwatches and Wearable Devices for Tracking Sleep?

Activity trackers have become a staple on millions of wrists, quietly collecting data on everything from heart rate to daily steps. One of their most intriguing functions is sleep tracking — the promise of understanding how well (or poorly) you rest each night. But just how reliable are wearables like the Apple Watch, Fitbit, or Oura Ring when it comes to sleep?

What Sleep Trackers Actually Measure

While sleep occurs in the brain, wearables measure signals from the body — movement, heart rate, and breathing — to estimate what’s happening during the night.¹ Using sensors like accelerometers and photoplethysmography (PPG) (those tiny green lights that detect blood flow), wearables estimate sleep stages such as light, deep, and REM sleep.¹

However, these devices don’t measure brain waves — the gold standard for identifying sleep stages. That requires polysomnography (PSG), an in-lab sleep study with sensors that record eye movements, muscle tone, brain activity, and more. Compared to that, wearables are convenient but less precise.

How Accurate Are They?

Research over the past few years shows that commercial sleep trackers are surprisingly reliable at detecting when you’re asleep versus awake. A 2024 review found that many consumer wearables performed as well as, or even better than, actigraphy — a medically used wrist device that estimates sleep.²

Still, most wearables tend to overestimate total sleep time, as they can mistake lying still (while awake) for sleeping.² Studies have also shown they’re less accurate at identifying specific sleep stages, such as REM or deep sleep.² For everyday insights, though, they do a decent job of tracking overall sleep duration and patterns.²

The Apple Watch and Sleep Apnea Detection

The Apple Watch Series 9 and Ultra 2 take things a step further. These models can measure breathing disturbances during sleep — subtle variations in respiratory patterns that may signal sleep apnea, a common but often undiagnosed disorder where breathing repeatedly stops during sleep.

If your Apple Watch detects irregular breathing patterns associated with moderate to severe sleep apnea, it can send a notification prompting you to seek medical advice. While it doesn’t diagnose sleep apnea (that still requires a professional sleep study), this feature could be life-changing for early detection.

When to See a Doctor

Wearables can’t replace medical evaluation — especially if you experience loud snoring, choking or gasping during sleep, or constant fatigue during the day. These may be signs of obstructive sleep apnea (OSA) or another sleep disorder. Devices like the Apple Watch or Fitbit can raise awareness, but a formal sleep study remains the definitive diagnostic tool.

The Bottom Line

Consumer wearables have come a long way. They’re accurate enough to help you understand your sleep habits, track trends, and spot changes over time. Just remember to view the data as a guide — not gospel.

If your tracker (or your partner) suggests you might have breathing disturbances or poor sleep quality, talk to your doctor. You may benefit from a home sleep study, which can confirm a diagnosis and help you get the treatment you need for better sleep and overall health.

How Sove CPAP Clinic Can Help

Founded in 2008, Sove CPAP Clinic has grown to become a leading provider of respiratory and sleep services and products in Australia, with over 60 clinics nationwide. Our comprehensive clinical team includes Respiratory & Sleep Specialists, Sleep Technologists, and CPAP Consultants, ensuring that you receive comprehensive and personalised care. All medical procedures, including sleep studies and lung function testing, are bulk billed to all Australians, with minimal wait time.

If you would like to speak to a Respiratory & Sleep Physician, book a bulk-billed sleep study, or seek advice for your sleep apnea, you can reach us at 1300 76 29 39 or info@thecpapclinic.com.au.

ALWAYS FOLLOW THE DIRECTIONS FOR USE. CPAP is used for Obstructive Sleep Apnea treatment. When considering whether a sleep study or CPAP is right for you, speak to your doctor. Medicare criteria and T&Cs apply.

References

1. Miller, Dean. “How Do Sleep Trackers Work, and Are They Worth It? A Sleep Scientist Breaks It Down.” 23 June 2025, The Conversation, https://theconversation.com/how-do-sleep-trackers-work-and-are-they-worth-it-a-sleep-scientist-breaks-it-down-258304. Accessed 8 Oct. 2025.

2. “New Research Evaluates Accuracy of Sleep Trackers.” Sleep Foundation, 9 Feb. 2024, www.sleepfoundation.org/sleep-news/new-research-evaluates-accuracy-of-sleep-trackers#references-245484.