Do you obsessively check the health app on your phone? It’s very seductive, seeing the number of calories it thinks you’ve burnt, or a graph of the variation in your heart rate.
But aside from a rather solipsistic interest in all aspects of yourself, is there any evidence that using these apps can improve your health?
Let’s look at three of the most-studied health app measurements: your heart rate (usually measured using a smart watch), the number of steps you get in a day, and how long you sleep each night.
Resting heart rate
People with lower resting heart rate tend to live longer. They’re at lower risk of all sorts of health conditions, including heart disease, heart failure, and even cancer. Compared to someone with a resting heart rate of 50 beats per minute, someone with 90bpm has about twice the risk of an early death.
None of that’s in dispute, scientifically: so should I be happy that I’m sitting here writing this, according to my smart watch, with a resting heart rate of 51bpm?
Not necessarily. It’s not clear whether your heart rate is a cause or an effect of health problems. Could people’s poor health cause their resting heart rate to rise? Certainly. Could drugs that lower people’s heart rate improve their health? Maybe. It probably goes both ways at the same time.
More importantly though, the relation between heart rate and health isn’t that strong. Going from 50 to 90bpm doubles the death risk – but that’s a huge increase in bpm. Big changes within one person are worth flagging with a doctor, but the sorts of day-to-day changes your health app points out are probably nothing to worry about.
Still, one of the main things people do in an attempt to lower their heart rate is more exercise, and that seems like a good idea for all sorts of reasons. Which brings us to:
Ten thousand steps
I’m a simple man who believes in the “calories in, calories out” theory of weight gain and weight loss: if you burn more calories, or put fewer in in the first place, you’ll lose weight. Losing weight improves all sorts of health outcomes. So encouraging people to do a bit more exercise with a goal like “10,000 steps a day” sounds like a good idea, at first blush.
But is there any reason to go with the specific 10,000 number? It differs a lot by age, occupation, and country, but a healthy adult will apparently walk somewhere between 4,000 and 18,000 steps in a day. Ten thousand is pretty arbitrary and isn’t some magic threshold, above which you’ll get health benefits.
But, according to one of the most recent large-scale studies published in March this year, regularly walking more than 8,000 steps a day was linked to lower risk of a variety of health problems such as cardiovascular disease (not to mention early death).
But of course, just like heart rate, it could be the other way around: poor health could cause you to walk less. So that’s why randomised trials, where people are encouraged to walk more and measure it with a pedometer or app, are useful. And in general, they show that adding steps is linked to better health outcomes, including (as I’d have predicted) weight loss.
But they don’t support the 10,000 number specifically. One states that: “working towards any goal that represents an increase over baseline values is likely to be much more important [than] the exact target number”.
So don’t beat yourself up if you don’t make your 10,000 steps every day. But it’s probably a good idea to do a few thousand more steps than usual if you can. And if you find walking boring – what, you’ve never heard of podcasts?
Eight hours of Sleep
Podcasts, of course, are also a favourite sleep-aid tool. Some people swear by the idea of having voices droning on in their ears to help them drift off at night (others, like me, find this very weird indeed). You’ll even find a “sleep timer” as an option in most podcast apps.
This is all in the service of our big societal quest to Get More Sleep: according to some ultra-popular, bestselling books, nearly all our ills can be pinned on the fact we fail to get our eight hours.
And you know what? In this case the actual number isn’t far off. A meta-review published in 2020 looked at 11 previous systematic reviews of studies of sleep and all sorts of health (and mental health) outcomes, and concluded that “a sleep duration of seven or eight hours per day is the one most favourably associated with health”.
The relation between sleep and health is an upside-down U-shape: up to about seven or eight hours is related to better and better health; but more than that could be an indicator that you aren’t doing so well. And bear in mind, as in both of the cases discussed above, that much of this is correlational research: there’s less evidence on what would happen if we intervened to make people sleep longer.
One thing the meta-reviewers noticed was that in 96 per cent of previous studies, sleep was assessed subjectively: people reported how much sleep they were getting without it being measured using any kind of instrument. That introduces biases, because people tend to overestimate how much sleep they really get (newer studies, done in the smart watch age, will be more reliable). It might actually be that a bit less than eight hours is a perfectly healthy amount.
And there’s a final point: everyone’s different. Sleep research has still yet to get a handle on those lucky people who need less sleep than the rest of us, and what makes them different.
So overall, eight hours is broadly what the average person should be aiming for – but remember you aren’t necessarily the average person.
The worried well
Doctors sometimes talk about the “worried well”. These are people who are pretty much perfectly healthy, but who are still very concerned about their health: that, for example, they aren’t eating right, or aren’t getting enough sleep.
The downside of health apps is that they encourage the worried well to worry more. Anything that allows us to analyse our heart rate in minute detail, or which sets an arbitrary goal like 10,000 steps or eight hours sleep, is catnip to those of us who are looking for things to be concerned about.
So as long as you see the bigger picture – many of the things your health app is monitoring are likely to lead to minor, marginal improvements if anything, and won’t be life-changing – a health app is a great thing to have. But if it’s causing you stress, the best advice is to just delete it. In that case you’ll instantly feel the benefits.