Hello,
Sleep tracking devices have become a $20B industry. Most of what they measure is real; not all of what they report is useful. Here's the practical breakdown for someone managing PCOS.
What All the Major Devices Measure Well
- Total sleep duration: accurate within ~10-15 minutes
- Heart rate variability (HRV): meaningful trend data over weeks
- Resting heart rate: reliable
- Movement during the night: a proxy for fragmentation
What They Measure Less Well
- Sleep stages (REM / deep / light): consumer devices estimate from heart rate + movement, not actual EEG. The categories are roughly right; the specific minute counts are not.
- "Sleep score" / "readiness score": vendor-specific composite scores; useful for trends, not as absolute numbers
- Stress detection: usually inferred from HRV; directionally correct, not diagnostic
What Matters for PCOS Specifically
Three metrics are worth watching:
1. NIGHT WAKES (or movement-based fragmentation) As covered in the sleep-quality note: this is the leading indicator for next-day PCOS flares.
2. HRV TREND (not single-day numbers) A persistent HRV decline over 2-3 weeks often correlates with high-stress periods, building inflammation, or pre-illness state. PCOS bodies are more sensitive to this than the general population.
3. RESTING HEART RATE TREND Persistent elevation usually means underrecovery, brewing illness, or — for PCOS — a stressful luteal phase pushing baseline up.
What Is Theater
- "Sleep stage optimization" recommendations
- Daily "score" gamification
- "Body battery" / "energy points" — entertaining, not actionable
- Push notifications when you didn't sleep enough — usually increases anxiety, doesn't change behavior
Device Choice
Differences between the major devices are smaller than marketing suggests. The best device is the one you'll actually wear nightly. For PCOS, ring-form (Oura) is often more comfortable than wrist-form for sleep, but wrist devices give you the activity side too.
What Your Data Will Show
If you're using a device, the Sleep Tracker (#5) in the PCOS Wellness OS has fields for device-reported quality + your own "how I felt" 1-10 score. The two together — over 30 days — surface whether the device matches your subjective experience.
If they diverge, trust your body. The device is a useful instrument, not the ground truth.