I’m riding a recumbent bicycle while wearing my smartwatch, hoping that tracking my fitness and health metrics will inspire me to exercise more.
The smartwatch is no longer just for texting, music and the time (how old school) but instead has become an integral part of some people’s health routines. So, can it detect heart problems, such as irregular heart rhythms or even heart attacks? What about its use in measuring oxygen levels or blood glucose? And can it help with sleep?
More than a quarter of the US population wore a smartwatch or other connected device used for health and fitness tacking in 2023, according to Insider Intelligence/eMarketer. By 2026, it projects that more than 100 million Americans will be using a smart wearable device.
Dr. Leana Wen: A smartwatch is a type of wearable technology device that resembles a wristwatch. Many are Bluetooth-enabled and can connect the watch to a smartphone. That allows the user to access some of the phone’s capabilities, like receiving text messages, listening to music or even responding to phone calls and emails.
A lot of smartwatches also allow tracking of fitness and health data. One function I like a lot is tracking steps. Studies have shown that setting daily step goals can reduce the risk of heart disease and early death.
One study published in March, for instance, found that in people who are sedentary most of the day, taking 9,000 to 10,000 steps per day lowered their risk of developing cardiovascular disease by 21% and their chance of premature death by 39%. Another study, published last year, found that even as few as 4,000 steps a day can reduce the risk of early death.
Wearing a smartwatch helps to keep track of how many steps have been taken throughout the day. It can remind people of their goals and can be a way to motivate people to take more steps.
Wen: What a lot of active people do is to track heart rate during exercise to keep the heart rate in a certain range. Many endurance athletes like runners, cyclists and triathletes train the majority of their time in what’s called zone two, or the endurance zone. This is where the heart rate is under 70% to 75% of your maximal heart rate. You feel like you are working but not so hard that you can’t sustain the exercise.
A smartwatch with a heart rate monitor can help athletes monitor their heart rates so that they can stay within the zones that they are targeting. More advanced smartwatches have more fitness functions, such as tracking pace, distance and running cadence, and some can even detect the type of sport being performed for people transitioning between different disciplines. Some have GPS data and can provide the wearer with directions.
Wen: Smartwatches are not approved to diagnose heart attacks. If you have chest pain and your smartwatch says your heart rate and electrocardiogram are normal, that does not mean you are fine. You should seek immediate medical care.
It’s important to remember that smartwatches do not replace medical-grade monitoring equipment. People who are told by their doctors that they need a specific heart monitoring device should heed that advice.
Wen: There are many smartwatches that purport to detect an irregular heart rhythm called atrial fibrillation. This heart rhythm can increase the risk of stroke if left untreated and is important to diagnose.
The Apple Watch, Fitbit Sense and Samsung Galaxy are among the handful of smartwatches that have received clearance from the US Food and Drug Administration for their function to detect irregular heart rhythms in a subset of adults who do not have a history of atrial fibrillation.
If someone who did not previously have heart abnormalities receives such a notification, they should contact their primary care provider and ask about next steps, which may include an in-office EKG and continuous medical-grade monitoring.
Again, I want to point out that you should also listen to your body. If you feel heart palpitations, shortness of breath, chest pain, lightheadedness or other strange sensations, you should contact your physician, even if your smartwatch says your heart rate and rhythm are normal.
Wen: The accuracy of smartwatches in measuring oxygen levels is variable. My opinion is that if you are someone who needs to measure oxygen levels because you have underlying lung problems, for instance, you should use dedicated equipment for this purpose. A pulse oximeter is inexpensive and easily portable. They are generally reliable, though recent studies suggest that they are less so in people with dark skin.
When it comes to blood glucose, the FDA issued a strong warning this year advising consumers not to “buy or use smartwatches or smart rings that claim to measure blood glucose levels.” These devices may give inaccurate measurements of blood glucose levels.
People with diabetes who need accurate measurements to dose their medicines may end up giving themselves too little or too much medicine if their blood glucose measurements are inaccurate. This could be dangerous. They should continue to use the measurement devices as prescribed by their clinicians, knowing that smartwatches are not yet able to duplicate the accuracy of these medical-grade equipment.
Wen: Possibly. Many smartwatches track sleep and can tell you how long you’ve slept and how much time you spent in each sleep stage.
I personally find this information helpful. I have always had problems sleeping and so am constantly experimenting with different things, like meditation before bed, reading a book and sleeping in different positions. I like the data my smartwatch gives me regarding sleep quality and duration. I can try to correlate this with the changes I’m making in my sleep environment to see what changes work and what don’t.
I also like the feature on my smartwatch that tracks heart rate variation during sleep. This is a measure of the variation in time between each heartbeat. Everyone’s baseline heart rate variation is different. By knowing your own baseline, you can track changes over time.
I’ve found, for instance, that when I don’t sleep well or have had recent heavy training blocks, my heart rate variation goes down — a sign of more stress and less recovery. I can then work to prioritize additional sleep time or adjust my training based on these data.
My main takeaway regarding smartwatches is that they benefit people who like data. That’s me, and I like my smartwatch because it gives me data that can help inform and motivate. There are also people who may find all the data unhelpful or even stressful. The key is to do what works for you. Smartwatches are a tool that could help you with your health and fitness goals; they should not add more pressure and stress to your life.
Wen: There are some people who may benefit from taking a break from data tracking. Exercise should be fun and enjoyable, and if all the data adds to pressure and stress, it’s worth leaving the smartwatch at home a few times to see if it makes the activity more enjoyable. In addition, it’s always important to listen to your body.
