WELLNESS: Should you track your sleep? The pros, cons and realities of sleep trackers

Sleep is one of the most unusual health behaviours because you cannot observe yourself doing it. You can watch your weight and the food you buy and make sure your step count is high enough (sometimes cramming in a few steps around the block after work).

Yet, sleep remains unknowable because you are, well, asleep while doing it. Sleep trackers allow you to pull back this veil and see what is going on when your eyes are closed.

There are some reasonable goals you can get out of tracking your sleep. First and foremost is seeing what is really going against what you assume is happening.

You might think your sleep is sufficient and stable, and the data shows you go to bed at fluctuating hours and for smaller totals than is sensible. Being able to see without assumption is its own kind of power.

It also can help with spotting some trends. Maybe you have a fragmented night after a slightly too boozy dinner party, or see your bedtime tends to be very late over the weekend.

Noticing these patterns is the first step towards changing some behaviours for the better. They may even have some clues in the data of something more significant going on, such as very fragmented sleep being a good reason to suspect one might need to see the doctor.

A few people, typically those with Discovery, will also want to track their sleep for the benefits their insurance gives them. Perhaps I am too nervous about the creep of monitoring from companies into our privacy to think this is a very compelling reason.

But now we should pause and ask how useful these devices are; and their usefulness will in most part depend on their accuracy. Let’s begin with how they work.

Depending on the device, there are a range of different ways they can track sleep. Typically, they are based in actigraphy: a method of tracking sleep through accelerometers that detect movement (and stillness). More complex ones can integrate other modes of data, such as heart rate and its variability, blood oxygen levels, temperature, skin galvanic response, light and sound in algorithms that turn the data into sleep staging.

Large reviews have looked at most commercially available devices, and found they are indeed good at detecting sleep; yet are inconsistent in their sleep staging accuracy. They perform as well as medical actigraphy, but are not diagnostic (yet) and formal sleep studies are needed for complex sleep disorders.

Knowing these limitations is part of being able to unpack the data they give you. And I cannot stress this enough: limitations. The only strong opposition I believe there is to sleep trackers is a very unusual phenomenon which I have seen unfolding, creeping into my work as a sleep-focused doctor. It is called orthosomnia.

Orthosomnia is an obsession with obtaining perfect sleep. The once curious now turn their interest in sleep to an internal competition.

Slowly a good night becomes mediocre; much like the gifted child performing at school – 95% becomes a mockery of the potential 100%. Small disturbances in sleep, which are entirely normal and unavoidable, become reasons for catastrophes.

And this is fertile ground for developing insomnia. As we become more preoccupied with our sleep, we begin monitoring ourselves and developing the very mechanisms that establish insomnia marked by high effort to sleep. Anyone who has tried to will themselves to sleep will know how impossible it is.

Overall, there is some decent benefit to tracking your sleep; if you can hold the data lightly, not worry about the results and know its limitations.

If you are curious and want to keep an eye on it; by all means. Yet, if you know you are someone prone to self-pressuring and health anxiety, it might not be the best idea.

It is something we can nudge and give space to grow – but sleep remains outside of voluntary control. And no number of smartwatches or amount of willpower can change that. DM

Dr David Backwell is a medical doctor working in sleep medicine, based in Cape Town.