Posted by Dr Sophie Bostock - Sleep Expert on 21st Feb 2022
Should I Buy a Smart Watch to Track My Sleep? The Pros and Cons of Sleep Trackers
I have a love-hate relationship with wearable sleep trackers. I absolutely love that technology is being used to shine a light on sleep; a crucial behaviour which so many of us have neglected in the past. I’m less of a fan of hyped up claims that wearables alone can transform your sleep patterns.
Before you buy a sleep tracker, here are a few things to consider when deciding whether it will be the right choice for you..
1.‘If you can’t measure it, you can’t improve it’
Peter Drucker is the business guru credited with the philosophy that to improve something, you need to be able to measure it. Since we’re not conscious during sleep, using a tracking device gives us visibility of sleep quality metrics such as total sleep time, time to fall asleep (or sleep latency), the number of wakings and total time awake during the night.
Traditionally these metrics have been measured during sleep therapy using a paper sleep diary, based on your memory in the morning. I would still argue that your perception of you sleep, based on how you feel, is the most important measure of sleep, but there is no doubt that tech gives us some more objective measures to monitor over time in a quick and effortless way. You can see at a glance the times that you fell asleep and woke up, which gives a helpful steer about whether you’re sticking to a routine – consistency is key for good sleep.
Some wearables combine multiple different measures, including sleep quality and heart rate variability into a bespoke sleep or recovery score, which is designed to nudge you to pay more attention to self-care on days when your internal batteries are running low. For people who often push themselves too hard, and rely on caffeine and sugar to keep them going, a reminder to allow more time for recovery could be a positive step.
2. You can become a scientist of yourself
A potential benefit of tracking sleep is to improve your knowledge of the factors which influence your sleep patterns. The wearable will only be as helpful as the data you include on things like alcohol, smoking, caffeine or having a bath before bed, but if you input data about your behaviours and compare this with sleep metrics over time, you could have a powerful tool for recognising the triggers which help and hinder your own sleep.
For example, you might decide to cut out caffeine after midday for two weeks, and see what difference this makes to your sleep metrics. Seeing a difference in your own data can be much more motivating than simple reading general sleep advice based on other populations.
3. Keep sleep and recovery top of mind in the long term
If you buy a sleep-specific watch, wristband or ring, you’ll be wearing a constant reminder, day and night, that you have invested in improving your sleep and wellbeing. Most wearables are accompanied with an app with optional notifications and reminders designed to help keep you on track. These prompts may encourage you to repeat the behaviours which favour good sleep patterns, such as starting to wind down at night, or staying active during the day. For example, one study using the Oura ring found that for those initially receiving 1-2-1 coaching, the device helped users to maintain sleep and activity improvements over 12 months (Browne et al 2021). Lifestyle changes were stronger for those receiving coaching advice than using the tracker alone.
Top 3 reasons to avoid a wearable sleep tracker
1.What does the data really tell us? Accuracy and interpretation
The gold standard for assessing stages of sleep is called polysomnography, which relies on many (poly) measures to measure how much time we spend asleep and in different sleep stages. This includes measurements of electrical energy taken from the scalp using an EEG, or electroencephalogram.
Trackers which are fitted to your wrist, finger or even stuck under the mattress may use a combination of movement, body temperature, breathing rate, heart rate and heart rate variability to guesstimate what is happening in the brain. Wearables which rely on movement tend to overestimate sleep time (Danzig et al 2020). Devices which are fitted to the mattress are likely to be less accurate than wearables (Ellender et al 2021). Newer multi-sensor wearable devices are pretty good at estimating how much time we spend asleep, with accuracy over 90%, but sleep staging is a less exact science with the latest studies showing 50-65% accuracy for individual sleep stages for the Oura ring (Zambotti et al 2019) and 60-70% for the WHOOP band (Miller et al 2020).
There is still a real question about how useful knowing your sleep stages really is. We don’t have a specific recipe for the ideal night of sleep. You sleep cycles will depend on how you spent your day, and how well you slept the night before. So for example, after a broken night’s sleep you will probably have more deep sleep the following night to compensate. Your sleep need is unique to you, so while the ‘coaching’ advice from the wearable apps is designed to sound personalised, it is still based on standardised algorithms for the average person of your age and sex. It can be a helpful tool, but I’d still err on the side of how you feel being the best measure of sleep quality.
2.Orthosomnia: an unhealthy obsession with the perfect night’s sleep
I’ve had several clients contact me because they were concerned about the sleep data from their tracking device. One entrepreneur, let’s call him Bob, adopted all sorts of rigid behaviours about sleep, believing if he didn’t have the ‘perfect’ sleep routine, his sleep would suffer. He would check his feedback from the wearable every morning, and sometimes even in the middle of the night.
Orthosomnia is the term given to an unhealthy, and unhelpful obsession with driving improvements in sleep tracking data (Glazer Baron et al 2017). This can drive anxiety about sleep, which can increase levels of arousal and make sleep worse. It might also lead people to spend longer in bed, which can be a counterproductive behaviour for insomnia.
Bob would complain of poor concentration and fatigue on the days that his tracker told him he’d had little deep sleep. However, as discussed above, most trackers are imperfect at measuring sleep stages. Research has shown that if you give someone false poor feedback about their sleep – such as telling them that they have slept for less time than they have – they will perform poorly at tests of alertness (Gavriloff et al 2018). This could mean that inaccurate feedback from a tracker actually makes people feel worse during the day.
My advice for my Bob was to put his sleep tracker away in a drawer for 3 weeks and revert to going to bed when he felt sleepy, and waking up at the same time each day. I reminded him that waking up in the middle of the night is a normal part of sleep, and to just make himself comfortable and go
3. False security: feeling as though you’re taking action
It’s a nice idea to think that spending money on a sleep ‘solution’ will solve the problem. The thing is, the interventions with the best evidence for treating insomnia are cognitive and behavioural in nature. In other words, it usually requires questioning unhelpful thoughts and changing lifestyle habits. A tracker can help track your progress if you’re adapting healthier sleep habits!
Buying a tracker without changing your habits is a bit like buying a weighing scale and expecting to lose weight… you still have to do the work.
If you do decide to buy a sleep tracker…
If you do decide to buy a tracker, there are many different options to consider, as well as simply the cost. Do you want your device to be able to measure different types of physical activity during the day, for example, or have a GPS function to track your running or cycling? Will you be happy wearing a ring day and night, or would you prefer a wristband? What’s the battery life? Do you need it to be waterproof?
Some companies are now offering monthly subscriptions where the device is free, but you pay every month. Wearable technology changes fast. Subscriptions are likely to become expensive over time but it might mean you always have access to the most up-to-date model. You could potentially try something for a few months to get your sleep on track, and then return it. Look for a warranty and ideally a money back guarantee.
I would recommend checking to see whether the company has published research validating their sleep tracking approach. Validated devices are likely to be more expensive, but will be more reliable.
If you’re not sure whether a tracker is for you, try keeping a pen and paper sleep diary for a week. It’s free, and it is likely to help you develop more consistency over your sleep habits, which is a great place to start when trying to improve your sleep.
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