Most people hate taking their blood pressure. I have my blood pressure cuff sitting right there on my desk. Yet I haven’t used it in a month. Not a good look for someone who wrote a 20-page guide on blood pressure.
But if a watch did it for me? I can do that!
Apple just released their study on the new blood pressure feature. Here’s what you need to know about whether it might work for you and what to do if you get an alert.
For all you data nerds, there’s a deeper dive into Apple’s study at the end of the article.
On This Page:
An Alert Will Almost Always Mean You Have High Blood Pressure
Apple prioritized making sure the people they alerted had hypertension. Because of this, most people who get an alert actually have high blood pressure.
What to Do If You Get an Alert
If you get an alert, you should make an appointment with your primary care doctor. You can start to protect yourself while you wait for your appointment. Our page on the 3 Most Important Ways You Can Lower Your Blood Pressure is a good place to start.
Possible Hypertension Alert?
(Hypertension = High Blood Pressure)
You Probably Have Hypertension
You Might Still Have Hypertension
You May Still Have Hypertension If You Don't Get an Alert
Because the Apple Watch focuses on only alerting people with hypertension, it doesn’t alert a lot of people. Overall, their study shows that the watch will alert 4 out of 10 people with hypertension.
For All Ages & Body Types
10 People with Hypertension
4 Will Get an Alert
6 Won't Get an Alert
But the watch performs worse for certain groups:
- If you’re younger than 60: Only 3 out of 10 people with hypertension will be alerted
- If your BMI is less than 30 (meaning you’re not obese): Only 3 out of 10 people with hypertension will be alerted
- If you’re both young and not obese: You’d likely have even lower detection rates, though the study doesn’t provide specific data for people with multiple risk factors
Younger than 60
10 People with Hypertension
3 Will Get
an Alert
7 Won't Get
an Alert
BMI Less than 30
10 People with Hypertension
3 Will Get
an Alert
7 Won't Get
an Alert
This is particularly concerning because young people have the most to gain from early hypertension detection:
- Young people don’t think they should worry about hypertension
- But 1 in 4 people aged 18 to 44 have hypertension
- While clinical guidelines for younger people are still being developed, we know addressing hypertension early prevents problems like heart attacks and strokes decades later
This means you shouldn’t throw away your blood pressure monitor yet. Personally, if I got an Apple Watch I would pretend like it doesn’t check my blood pressure. This way I’d still make an effort to measure my blood pressure.
The Bottom Line
The new blood pressure feature on the Apple Watch may let you know you have hypertension, especially if you’re older than 60 or overweight. But many people with hypertension won’t be alerted – particularly those who would benefit most from early detection.
The best way to take care of yourself is to keep checking your blood pressure with a cuff. All of which is to say I’ll be begrudgingly dusting off my blood pressure cuff tonight.
For the Data Heads Out There
How the Blood Pressure Monitoring Feature Works
The Apple Watch uses photoplethysmography (PPG), the same light-based technology as pulse oximeters that measure oxygen levels. A machine learning algorithm analyzes these readings over 30 days, then sends an alert if results consistently stay above a threshold.
The Study Lost More Black/African American Participants and People with Darker Skin Tones
More Black/African American participants and those with darker skin tones weren’t analyzed in the final results. The rates of people who didn’t complete the study were: 29.5% of Black participants, 32.1% of participants with darkest skin tones, 10.6% of Asian participants, and 13.1% of White participants. (add infographic)
These uneven completion rates matter because we don’t know why certain groups were less likely to finish the study. If people who had problems with the watch stopped using it, then the results would show better performance than reality. But the results wouldn’t change if they left for an unrelated reason like moving.
Wide Confidence Intervals
The uneven completion rates seem potentially important when combined with the lower performance and wide confidence intervals for Asian participants. While the wide uncertainty range means we can’t be statistically certain there’s a difference, the best estimate still shows lower detection performance. Apple attributes this to Asian participants being younger (mean age 43 vs 50.9) and having lower BMI (mean 27.7 vs 30.9). However, Apple adjusted their analysis for age and BMI. This creates a contradiction – if age and BMI explain the difference, why does it persist after adjusting for those factors?
Other notable findings:
- People younger than 60 had lower sensitivity (around 0.7) meaning hypertension wasn’t detected as well
- People with BMI less than 30 showed similar poor performance (around 0.7)
- Participants with the darkest skin tones (Fitzpatrick V/VI) showed performance similar to other groups
- Large confidence intervals for Asian and Hispanic participants suggest small sample sizes limit reliable conclusions
What This Means
Apple’s results show encouraging signs that they may have addressed some concerns about PPG device accuracy for darker skin tones. However, broader questions remain about this technology’s performance across different populations, given the uneven study completion rates and large confidence intervals for Asian and Hispanic participants.
More independent research is needed to validate these findings and understand the factors that influence accuracy across diverse users. These findings come from Apple’s own study, and independent validation will help clarify how well these results translate to real-world use.
The watch’s poor performance for younger adults is concerning from a public health perspective. Apple’s technology seems to work best for people who are already more likely to monitor their blood pressure regularly, while missing those who would benefit most from early detection. This doesn’t detract from those who will be helped by the feature. But, it does highlight a tension between consumer device design and public health needs.
