News broke yesterday that Aetna will become the first health insurer to subsidize Apple Watches. Remarkably, they’re doing so not only for their 50,000 employees, but also for people on the individual market (“Obamacare”) and for employer-sponsored health plans.

We think this will become a trend. Just as your cell company subsidizes your iPhone, health insurers will subsidize your Apple Watch.

The reason is that the ROI makes sense: unlike step counts, heart rate data can serve as not only as a source of digital biomarkers to detect disease, but a platform for lifestyle interventions to prevent it entirely. Below we present some very preliminary data based on Cardiogram for Apple Watch.

Continuous Digital Biomarkers are associated with the most expensive health conditions

At Cardiogram, we’ve been collaborating with groups like UCSF’s Health eHeart study to translate raw heart rate data into continuous digital biomarkers. Just like blood tests today measure biomarkers like cholesterol, over time, raw sensor data from wearables will be used to derive digital biomarkers that can predict risk.

Let’s take diabetes, one of the most expensive conditions for the working age population, and atrial fibrillation, one of the most costly conditions in the Medicare Advantage population. What happens when stratify a population by a digital biomarker like resting heart rate? The top and bottom 10% of resting heart rate show more than double the risk of diabetes and atrial fibrillation:

Resting heart rate is highly correlated with conditions like diabetes and atrial fibrillation. Preliminary research data.

Of course, this is preliminary research—I’m not suggesting anybody go out and modify medical practice right now. And the atrial fibrillation result, in particular, likely includes rate/rhythm control drug interactions that must be teased out. But research studies running today (from us and other groups) are starting to bear fruit, and I think you’ll start to see a high-quality, peer-reviewed evidence base start to emerge in 2017.

The Apple Watch’s heart rate sensor allows continuous digital biomarkers to be shown to the end user. Screenshots: Cardiogram for Apple Watch.

Beyond association: can behavior change actually drive outcomes?

A condition like atrial fibrillation is 90% behavioral. Yoga, for example, reduces your risk of a recurrence by 24%. Stress increases it by 32%. Moderate exercise can half your risk, but extreme exercise such as triathlons has been shown to increase your risk by 30%.

Many conditions like atrial fibrillation are 90% behavioral. Source: John D. Day, StopAfib.org Patient Conference.

In our data set, people in the highest decile of Apple Watch exercise are 23% less likely to have atrial fibrillation, 25% less likely to have sleep apnea, and 61% less likely to have diabetes. Again, this is a preliminary research result, and we need to tease apart correlation and causation. But there are active research projects planning randomized control trials on exactly this type of question. As that evidence base emerges, that creates an opportunity both to drive engagement and to reduce healthcare costs by preventing hospitalizations, heart attacks, strokes, and more.

Patient Protections

Part of the announcement yesterday was that Aetna would build apps for the Apple Watch. People often worry about sharing data with their health insurer. What if you have a pre-existing condition?

The good news is that the Patient Protection and Affordable Care Act protects you in several ways. First, insurers have to cover you during open enrollment (“guaranteed issue”)—they cannot drop you or deny coverage for pre-existing conditions. Second, they can only set your monthly premium based on your age, location, and whether you smoke (“rating factor limitations”)—so they can’t charge a diabetic more than a non-diabetic. In fact, under the PPACA, insurers actually receive a small subsidy if their population turns out to have more people with chronic conditions than average.

What insurers can do is rebate up to 30% of your monthly premium for participating in a program to keep you healthy. That 30% is where the “budget” for Apple Watches comes from.

What next?

Digital Health is still in its infancy, and it will take sustained work over a period of years to turn its potential into reality. We need well-run studies to build a peer-reviewed evidence base that patients and doctors can trust. And we likewise need to characterize the accuracy of all devices on the market: Apple Watch, Android Wear, Fitbit, Garmin, Xiaomi, and more. But Aetna’s move here is a huge step forward. If you’re helping to build that evidence base, you will soon have 50,000 more potential participants with new Apple Watches.