Sleep Better

Lesson 11: Tracking your sleep with wearables

Goal: use a smartwatch or ring to learn about your sleep, without letting the numbers keep you awake.

Watches and rings from Garmin, Apple, Fitbit, Oura, Samsung, Whoop and others estimate your sleep from movement, heart rate, heart rate variability (HRV) and sometimes skin temperature and blood oxygen. Used well, they’re a great way to see patterns you’d never notice otherwise.

Garmin is a good place to start

Garmin watches are a favourite here: the battery lasts days rather than hours, so you actually wear it overnight, and Garmin Connect brings together the numbers that matter for sleep in one place:

• Sleep score and sleep stages (light, deep, REM and awake), with a short written summary each morning.
• HRV status: a rolling view of your heart rate variability overnight. A drop below your normal range often goes with poor sleep, illness, stress, alcohol or hard training.
• Resting heart rate: a rise of several beats above your usual is a useful early warning sign of the same things.
• Body Battery: an energy score that shows how much sleep recharged you.

Other brands show similar information under different names. The best device is the one you’ll wear every night.

What they’re good at, and what they’re not

A 2020 study compared seven consumer trackers with polysomnography (the full lab sleep test). In line with other research, the devices were reasonably good at telling sleep from wake and estimating total sleep time, but much less consistent at sleep stages. Most trackers also miss some short awakenings, so they tend to overestimate how much you slept.

So:

• Trust trends over weeks, not single nights.
• Trust total sleep, timing and resting heart rate/HRV more than the exact minutes of deep or REM.
• Use the data to test changes: did cutting the afternoon coffee or the evening wine change your total sleep, HRV or resting heart rate over a fortnight?

Alcohol is one of the clearest things a tracker shows: many people see their overnight heart rate rise and HRV drop after even a couple of drinks.

Don’t let it make you anxious

In 2017 sleep researchers described patients who had become so focused on perfecting their tracker’s sleep scores that the worry itself was keeping them awake. They called it orthosomnia. Signs you’re heading that way:

• you check your score before you’ve even noticed how you feel
• a “poor” score ruins your mood for the day
• you go to bed earlier and earlier, or spend longer in bed, chasing a number

How to keep it healthy:

• Check in once a week, not every morning. Look at averages and trends.
• Notice how you feel first, then look at the data.
• Never check it in the night.
• If it’s making things worse, take it off for a couple of weeks. Your sleep doesn’t need a witness.

Going further: coaching with your data

If you’d like help turning wearable data into habits, VP Human Performance Collective, founded by Dervla Loughnane on the Gold Coast, runs a 7-week coaching program built on behavioural neuroscience and powered by wearable data. Participants get a wearable to keep, weekly one-to-one coaching, and protocols covering sleep, light exposure, stress and recovery, with sleep architecture (light, deep and REM sleep) tracked before and after. Full disclosure: Refactor helped build the program’s technology.

Understanding HRV

• Heart rate variability: harnessing your own personal superpower (Inna Khazan, TEDx): what HRV is and how slow breathing can train it
• What HRV reveals about your nervous system (Andy Galpin, short)
• Understanding heart rate variability and its performance potential (WHOOP Podcast, with Kristen Holmes and Emily Capodilupo)

Exercise 11

If you have a tracker, open the last 4 weeks of data and write down your average sleep time, average resting heart rate and average HRV. Those are your baselines. Pick one change from Lessons 4 to 7, run it for two weeks, then compare.

Sources

• Chinoy et al. (2020), Performance of seven consumer sleep-tracking devices compared with polysomnography, Sleep
• Baron et al. (2017), Orthosomnia: are some patients taking the quantified self too far?, Journal of Clinical Sleep Medicine
• VP Human Performance Collective, Human Performance Quantified

This course is general information, not medical advice. If you have ongoing sleep problems, loud snoring with pauses or gasping, or sleepiness that affects driving or work, see your doctor. In Australia, if you are struggling or feel unsafe, call Lifeline on 13 11 14.