Are Apple Watches Really That Helpful and Accurate?

If your parent wears an Apple Watch, you've probably wondered: is it actually picking up anything useful, or is it just an expensive step counter?

The short answer: it's more useful than most people realise, but it's not a replacement for their doctor.

What the watch actually tracks

Every few seconds, the Apple Watch reads your parent's heart rate using the same light-based technology that hospitals use, just miniaturised onto a wrist. It also tracks blood oxygen levels, sleep patterns, daily movement, and — since 2018 — it can detect hard falls and automatically call emergency services if the wearer doesn't respond within 60 seconds.

So how accurate is it?

The biggest study — published in the New England Journal of Medicine with over 419,000 participants — found that when the Apple Watch flagged an irregular heartbeat, it was right 84% of the time [1]. For people aged 65 and older, more than a third of those flagged turned out to have a real heart rhythm problem called atrial fibrillation. That's significant, because undiagnosed AF is one of the leading preventable causes of stroke.

A head-to-head comparison of five smartwatches found the Apple Watch was the most accurate for detecting heart rhythm issues and was the device that people preferred wearing [2]. A large review covering over 1.2 million people found consumer wearables detected AF with 94% accuracy [3].

For falls, the picture is solid but not perfect — about 82% sensitivity, meaning it catches most falls but not all of them [3]. Real-world stories back this up: in 2025, a 77-year-old woman's Apple Watch detected her fall during a heart attack and called 911 when she couldn't respond. Her family later noted that their other smartwatches would have only sent a text message — they wouldn't have called for help.

Where it falls short

No device is perfect, and it's important to be honest about that.

Sleep tracking is useful for spotting general patterns — like whether your parent is sleeping much more or less than usual — but it's not accurate enough to diagnose sleep disorders [4]. Blood oxygen readings are generally reliable, but they require the wearer to keep their wrist still, which isn't always practical [5]. And the watch can generate false alarms — one study found that about 17-25% of heart rhythm readings come back as "inconclusive" [2].

The Apple Watch also isn't great at measuring blood pressure or energy expenditure. A 2026 analysis found it missed a significant number of hypertension cases. It's a wellness tool, not a diagnostic device.

Why this matters for families

The real value isn't in any single reading. It's in the trend.

A gradual increase in resting heart rate over two weeks. Sleep becoming fragmented. Daily step count dropping. These are the subtle shifts that a weekly phone call will never catch — but a watch worn every day will.

This is exactly what Harmoni is built around. We take the data your parent's Apple Watch is already collecting and look for meaningful patterns — not just single numbers, but changes from their normal. Caregivers can also input vitals manually using their own medical-grade equipment — things like blood pressure cuffs or pulse oximeters — giving Harmoni an even more complete picture. When something shifts, their care circle gets a gentle heads-up. Not an alarm for every blip. Just the moments that matter.

Your parent doesn't need to press any buttons or learn anything new. They just wear the watch they already have.

References

1. Perez MV, et al. New England Journal of Medicine. 2019;381(20):1909–1917.

2. Mannhart D, et al. JACC Clinical Electrophysiology. 2023;9(2):232–242.

3. Singh B, et al. JMIR mHealth and uHealth. 2024;12:e56972.

4. Lee T, et al. JMIR mHealth and uHealth. 2023;11:e50983.

5. Lambe R, et al. npj Digital Medicine. 2026;9(1):63.

This article is for informational purposes only and does not constitute medical advice. Please consult your healthcare provider with any health concerns.