Smartwatches for Health Monitoring

If you don’t have a smartwatch, chances are you’ve seen them on many others. People use smartwatches for emails, texts, phone calls, weather checks, and more. And many people use them to track their fitness – counting their steps and their heart rate as they go through their days and exercise routines. However, did you know that smartwatches can also track important health metrics that can help you manage your health and warn you about potential medical issues? How reliable are smartwatches for health monitoring? Should you use a smartwatch to monitor your health?

How reliable are smartwatches for health monitoring?

Can you rely on smartwatches to monitor your health? Or to tell you when you need to see a doctor? Studies show mixed outcomes regarding the reliability of smartwatches for health monitoring.

A Stanford Medicine study shows reliable smartwatch measurements.

In a study conducted by Stanford Medicine, researchers found that health “data from smartwatches can flag early signs of some health conditions and predict the results of simple blood tests”. The study, published in 2021, found that a smartwatch can signal physiological changes, such as a change in red blood cell count, as well as early signs of dehydration, anemia, and illness.

Importantly, in the past, doctors could only identify these types of changes through clinical tests, some of which are invasive.

When researchers compared data from the smartwatches with traditional health data, they found direct correlations in the findings between the two data sources. For instance, changes in heart rate identified by the smartwatches often predicted changes in red blood cell count and hemoglobin (the molecule that carries oxygen).

Furthermore, they found that changes in heart rate could predict changes in blood oxygenation. However, they noted that the smartwatch data could not accurately predict specific values such as exact red blood cell count. Nonetheless, they found that smartwatches could flag early signs that something is wrong, such as a low red blood cell count, which can be a sign of anemia.

Interestingly, the researchers also found that smartwatches gave more consistent heart-rate readouts than those taken at a doctor’s office.

But a Thomas Jefferson University Hospital showed limited accuracy.

Do smartwatches need FDA approval or clearance?

This is a bit confusing, but important to understand. So, hang in there while reading this section.

The Food and Drug Administration tells us which foods, drugs and medical devices are safe. It’s easy to assume the FDA rigorously tests anything they label as FDA cleared or FDA approved. However, that is not always the case.

Before feeling confident in an FDA-cleared smartwatch, it’s important to understand how the FDA evaluates smartwatches used for health monitoring.

“FDA approved” means the agency has determined that the “benefits of the product outweigh the known risks for the intended use.” FDA approval is usually required for products that can benefit patient health but also have a significant risk of harm. This includes medications and Class III medical devices (implanted devices, life-sustaining devices, or those that could cause significant harm.)

What’s the approval process for Class II devices?

Smartwatches for health monitoring are considered lower-risk, placing them in Class II, for which the FDA only provides “clearance” not “approval”.

To receive FDA clearance of a Class II medical device, the manufacturer must demonstrate a “substantial equivalence to another legally U.S. marketed device. Substantial equivalence means that the new device is as safe and effective as the predicate.” (A predicate is a product previously given FDA approval or clearance.) Meaning, to get FDA clearance, companies only have to prove their device is as safe and effective as other previously approved or cleared devices.

There are many smartwatches on the market that claim you can use them to monitor your health. However, many of the products are designed to measure fitness criteria and are not considered medical devices. Therefore, before you start relying on a smartwatch to monitor your health, talk to your doctor.

Diabetics can keep track of blood glucose levels. 

Many companies make continuous glucose monitoring systems that monitor glucose levels 24/7. In general, doctors consider continuous glucose monitors an accurate measure of glucose levels. And several companies now have devices that allow you to see your glucose data on your smartwatch.  Here are 2 examples:

Dexcom makes a continuous glucose monitoring system that allows patients to monitor their glucose levels using their App on your Apple or Android watch (or with a smartphone). You insert a tiny wire (using their tool) and then connect a small, reusable transmitter to the sensor wire.

The transmitter, secured to your body, sends real-time readings wirelessly to your watch (or phone).

Additionally, the K’Watch Glucose is a continuous glucose monitor watch device worn on your wrist. The underside of their watch holds their disposable K’apsul which has micro-points and biosensors that measure glucose painlessly through the skin. A hypoallergenic adhesive patch, which you replace every 7 days, holds the K’apsul in place.

It’s worth noting there are other glucose monitoring systems available that integrate with smartphones and/or smartwatches. Talk to your doctor about the best option for you.

Monitor your cardiovascular health.

Many smartwatches have features that can help you monitor your cardiovascular health. However, realize most of the available options are not FDA-cleared devices. Certainly, if you experience any concerning symptoms, contact your doctor.

Measure blood oxygen levels.

There are many smartwatches (and fitness trackers) available that measure blood oxygen levels (pulse oximetry). However, a smartwatch can only measure a peripheral oxygen saturation (SpO2), which is not as accurate as results of a blood sample test of arterial oxygen saturation (SaO2).

Furthermore, conventional medical pulse oximeters, used on fingertips, measure light passing through the finger to determine blood oxygen levels. But for smartwatches, which of course people wear on their wrists, the sensors determine oxygen level by measuring the light reflected, instead of the light passing through the body, which may not be as accurate a reading.

Importantly, realize these sensors are not as accurate as medical devices.

Monitor your heart rate.

Some smartwatches can check for unusually high or low heart rates, which could be signs of a serious underlying condition. Although these are not medical devices, they could help you identify situations that warrant further evaluation by a doctor.

Get ECG readings.

Some smartwatches, in conjunction with an electrocardiogram (ECG) app, allows you to capture an ECG reading. This is particularly helpful if you experience symptoms such as rapid or skipped heartbeat, or if you receive a smartwatch notification of an irregular rhythm. Make sure you read your smartwatches’ instructions carefully to make sure you get a proper reading.

Monitor for irregular heart rhythms.

Some smartwatches can check for signs of irregular rhythms that may suggest atrial fibrillation (AFib). Note that to properly detect the signs of AFib, your smartwatch needs an electrocardiogram (ECG) function. Catching signs of AFib early can help you get treatments that can minimize the risk of harm.

Importantly, this feature won’t detect all instances of AFib, but may catch something that warrants further evaluation. Additionally, the smartwatch companies generally recommended this feature for those 22+ years old with no AFib history.

A success story.

A dear friend of mine recently discovered she had AFib from the notifications on her smartwatch. After the watch alerted her that she was having irregular rhythms, she went to urgent care, who directed her to an emergency room. Her AFib was soon confirmed by doctors. Since she is only 35 years old, it’s possible her diagnosis and treatment may have been delayed if her smartwatch had not alerted her to this potentially serious condition early.

Not only did the watch detect her AFib, but the cardiologist told her she could keep track of any irregular heartbeats on her watch instead of the usual halter monitor.

Monitor blood pressure.

Some smartwatches can monitor your blood pressure, after you calibrate it using a traditional blood pressure measuring cuff.

Detect weak heart pump

When people have a weak heart pump (called low ejection fraction) a smaller percentage of blood is pushed out of the body with each beat. Unfortunately, this condition, which is linked with worsening heart failure, often has no signs or symptoms (although people may experience shortness of breath or blood pooling in the legs).

Interestingly, in May, 2022, Mayo Clinic announced exciting findings. When researchers applied artificial intelligence to ECG data from Apple Watches, they were able to identify who could have a weak heart pump. Although this technology is not widely available right now, it could have widespread use in the future.

Detect potential sleep apnea.

Although there is currently no smartwatch that specifically warns you that you have sleep apnea, smartwatches can identify periods of restless sleep. This notification, combined with blood oxygen sensor (SpO2) readings, can help you detect potential sleep apnea.

Monitor Parkinson’s Disease symptoms.

Apple Watch created a new system called the Motor Fluctuations Monitor for Parkinson Disease (MM4PD) that uses the watch’s accelerometer and gyroscope data to continuously track changes in resting tremor and dyskinesia for Parkinson’s Disease patients.

Research shows the watch MM4PD findings match the symptoms found during doctor’s evaluations. Additionally, MM4PD captured symptom changes in response to treatment that matched doctors’ expected changes in 94% of the study participants.

Additionally, in June 2022, the FDA granted clearance to the Rune Labs Kinematics System, to remotely track tremor and dyskinesias in persons with Parkinson’s disease, using sensors contained within the Apple Watch. FDA clearance means this new tool is safe for daily use, with acceptable correlations to clinically based measures. However, research is needed to prove that these digital signals correlate to clinical outcomes.

Looking for a smartwatch to monitor your health?

There are so many options on the market, you might find it overwhelming. For information on available features of some popular brands, visit their websites:

• Apple Watch 
• Samsung Galaxy Watch 3 
• Fitbit smartwatch
• Withings smartwatch

What’s on the horizon for smartwatches for health monitoring?

The use of smartwatches to monitor health is just getting started. As technology improves, we’ll see more and more applications for detecting diseases earlier and monitoring key health metrics.

Michael Snyder, Stanford Medicine’s chair of genetics thinks this field is just at the beginning. Dr. Snyder states that “devices are becoming much more sensitive and with many more capabilities.

As the technology continues to advance, people will be better equipped to understand what’s going on with their own health in real time, just through their wearable devices.”

Rockley Photonics new technology may change the landscape of smartwatches for health monitoring.

Rockley Photonics makes sensors for wearables and Apple is its biggest customer although it does work with other consumer electronics companies and two medtech companies. They report their products can track blood pressure, body temperature, blood glucose, blood alcohol and blood oxygen levels.

According to a March 2021 Rockley press release, their “clinic-on-the-wrist” technology is significantly more accurate than LED sensors commonly used in smartwatches today. Furthermore, their technology allows for continuous monitoring of key vitals with “laboratory precision diagnostics”. It’s unknown when Apple watches and other smartwatches will include this technology.

You still need a doctor!

Yes, smartwatches can measure your heart rate, temperature, oxygen levels, sweat, glucose levels, and more. But the jury is still out on the accuracy of data provided.

Importantly, these measurements are generally not adequate for a proper diagnosis. However, the Stanford researchers note that these smartwatches are helpful for assessing overall health, and for monitoring recovery after surgery.

I recommend you talk to your doctor before relying on any smartwatch to monitor your health. Better safe than sorry!

Learn more…

Read these blog posts to learn more about managing health conditions:

• 10 Tips to Communicate Better with Doctors.
• What is the Best Time of Day for Medical Care?
• 10 Tips for a Better Medical Appointment.
• How Can You Get the Best Healthcare? Actively Participate!
• 6 Tips to Better Manage Your Care.
• Understanding Medical Information Is Harder Than Most Realize.
• Why Take Detailed Notes at Doctor Appointments?

NOTE: I updated this post on 3-1-23.