Apple's watch got cleared for what WHOOP got a warning letter for. The difference is the paperwork, and the design.

The FDA cleared Apple's hypertension notifications last night, three days after the company announced them. The feature runs passively on the watch's optical heart sensor, looks for patterns consistent with chronic high blood pressure over thirty-day windows, and sends a notification telling the wearer to log readings with a cuff for a week and share them with a clinician. It is not for people under 22, during pregnancy, or already diagnosed. Apple expects it to notify more than a million people with undiagnosed hypertension in its first year. Two months ago the FDA sent WHOOP a warning letter over a blood-pressure feature. Both companies measure the same signal. The regulatory outcomes could not be more different.

What was cleared, and what wasn't. Apple did not get clearance to tell you your blood pressure. It got clearance for a screening flag that points you to a cuff. The numbers matter: in Apple's testing the feature flagged well under half of people with hypertension — more of those with severe disease — while rarely flagging people with normal pressure. A missed case is the price of avoiding false alarms. WHOOP, by the FDA's account, showed a daily estimated number on a color-coded gauge. One design says "go get measured." The other said "here is your measurement." Clearance, note, is a lower bar than approval; it means substantially equivalent to a device already on the market, not proven to improve outcomes.

Ben’s take

This is a regulatory moat, and it is wide. Apple has spent a decade and a lot of money clearing features one at a time — irregular rhythm, sleep apnea, a hearing-aid mode, now this. A startup cannot. The WHOOP letter in July and the Apple clearance in September are the same policy read from two sides, and together they say the wearable business will consolidate around whoever can afford the paperwork. For consumers that is mostly good. For the dozens of smaller bands, it is a deadline.

Loree’s take

Four in ten hypertensives flagged means six in ten not flagged. The danger of a feature like this is the person who reads "no notification" as "normal." The feature is honest about that limit; the people wearing it will not all read the fine print. A drugstore cuff, used properly, is still the device that diagnoses high blood pressure. The watch's best use is to nag you toward it.

Why it matters to a recovering optimizer. Here is a wearable feature that does the right thing with a number: it refuses to be the number. It points you to the cheap, boring, validated instrument and the person who can interpret it. That is the correct relationship between a gadget and a diagnosis, and it took the FDA two letters to draw it.