Key Takeaways

Sleep trackers are significantly inaccurate for measuring sleep stages — even the best device, the Whoop, misclassifies deep sleep nearly one in three times.
For people who are already anxious about sleep, tracking creates a new way to fail every morning, a phenomenon with an actual clinical name: orthosomnia.
How you feel when you wake up and throughout the day is more important than any number your tracker produces — and that's what functional testing actually helps you improve.

If you're not sleeping well and you're wearing a tracker, you need to hear this.

Many people assume tracking their sleep is a smart move. More data, more clarity. I used to think so too — I've been wearing a Whoop for about a year now. But for most of my clients who are struggling with sleep, I actually don't recommend it. And I want to explain exactly why.

The first issue is accuracy. Trackers are simply not as reliable as people think, especially when it comes to sleep stages.

The gold standard for measuring sleep is polysomnography — that's the test used in a clinical sleep study. A study from 2025 tested six popular devices against that standard. Every single one of them misclassified waking time, deep sleep, and REM as light sleep. The best device overall was the Apple Watch, and it only reached moderate accuracy. Deep sleep was the worst category across the board. The Whoop was most accurate at about 70%, the Apple Watch came in at 51%, and Fitbit fell under 50%. That means even the best device still gets deep sleep wrong nearly one in three times.

I've run into this myself. When I first got my Whoop, it showed my HRV in the thirties — which isn't good. I was concerned, so I ordered a chest strap to compare. Sure enough, my actual HRV was in the fifties to sixties. The Whoop was off by a significant margin. The trends it shows me over time? Those I trust. The absolute values? Not so much.

Total sleep time tends to be more accurate than sleep stage tracking, though my personal experience with the Whoop hasn't always matched that either. Heart rate variability is where Oura and Whoop do better — Oura has roughly a 6% error rate for HRV, Whoop around 8%.

Now here's the bigger issue, and it's not about accuracy.

If you're already anxious about your sleep — and most of my clients are — tracking can actively make things worse. There's actually a clinical name for this: orthosomnia. It's the obsession with achieving a perfect sleep score on a tracker. Your score becomes another thing to monitor, another metric to fail, another source of dread when you open your eyes in the morning.

My client Andrew had been struggling with sleep since he was 14 years old. By the time we worked together, he was in his late twenties — roughly half his life spent not sleeping well. He was spending all day thinking about sleep, and his cortisol was visibly spiking at night on his lab results. For someone in that state, tracking would have poured fuel on the fire. Another client, Brad, figured this out on his own — he stopped wearing his Oura ring before we even started working together because he noticed it was making him more anxious.

On the other hand, I have a current client who wears her Oura ring and has been able to see her sleep score improve month over month as we work through her protocol. Even before her full lab results came back, small changes — more protein with meals, more steps during the day — showed up in her data. That kept her motivated. That's tracking used well: seeing progress, not diagnosing a problem.

So the answer isn't the same for everyone. If you can look at your tracker the way you'd look at a weather app — useful context, not a verdict — then it can be a genuine tool. If you find yourself in bed dreading tomorrow's score before you've even fallen asleep, it's hurting you.

The deeper problem with trackers is what they can't do. A tracker can tell you that you didn't get enough deep sleep. It cannot tell you why. It doesn't know whether you have a gut pathogen producing toxins that spike your cortisol at 3am. It doesn't know whether your sex hormones are tanking in the second half of the night. It can't see the heavy metals in your system or the neurotransmitter imbalances that are keeping your nervous system in a state of hyperarousal. That's the gap.

My client Paul came to me after six weeks of barely sleeping at all. He was miserable, isolated, couldn't function. Two months into working together, he texted me: "I slept nine hours." By six months in, he was back at the gym and finding new opportunities at work. He did eventually buy an Apple Watch — not because he needed to track his sleep, but because he wanted one. Now he looks at the sleep data as confirmation after the fact. He knows he slept well before he ever looks at the screen.

That is the goal. To wake up and feel it — not to have a device tell you how you should feel.

FAQ

Q: Are sleep trackers accurate?

A: Not for sleep stages. A 2025 study testing six popular devices against clinical polysomnography found that every device misclassified waking time, deep sleep, and REM as light sleep. The best performers were the Whoop (about 70% accurate for deep sleep) and Apple Watch (51%). Total sleep time and HRV trends tend to be more reliable than sleep stage data.

Q: What is orthosomnia?

A: Orthosomnia is the clinical term for anxiety caused by obsessing over sleep tracker scores. It turns your tracker into another source of stress — a bad score first thing in the morning can set the tone for your entire day and make the anxiety that's already disrupting your sleep even worse.

Q: Should I wear a sleep tracker if I have insomnia?

A: It depends on whether you can treat the data as neutral information or whether it triggers anxiety. If you're already anxious about sleep and spending your days fixated on it, tracking will almost certainly make things worse. If you can detach from the score and use it to spot trends over time, it can be a useful motivational tool — especially as you start making progress.

Q: Why isn't my sleep tracker telling me why I can't sleep?

A: Because trackers measure outputs, not causes. They can show you that you're not getting deep sleep — they can't tell you that a gut pathogen is spiking your cortisol at 3am, or that your progesterone is tanking in the second half of the night, or that your GABA levels are too low for your nervous system to downshift. Those are root causes, and finding them requires functional lab testing, not wearable sensors.

Ready to Find Your Root Cause?

If you want to understand what's actually driving your sleep issues — not just measure them — that's exactly what the Complete Sleep Solution program investigates. The program includes four functional lab panels (the Hormone Zoomer, Gut Zoomer, Neurotransmitter Test, and Total Tox Burden) that identify the specific imbalances keeping you awake, so you're not guessing.

→ Learn how the Complete Sleep Solution program works

About Martha Lewis

Martha Lewis is a certified Functional Diagnostic Nutrition practitioner and founder of The Sleep Detective™. Since 2019, she has helped 300+ clients identify the root causes of their insomnia using functional lab testing — including gut analysis, hormone panels, neurotransmitter testing, and toxin screening. She discovered her own root causes (hormone imbalances, heavy metals, and a parasite) after years of trying conventional sleep solutions, and now uses the same investigative approach with her clients.

Learn more about Martha →