Wearables are everywhere now. Watches, rings, and fitness bands sit on millions of wrists, and you may own one yourself. A new study from Stanford Medicine shows what these devices can catch, and what they can miss. The story is a hard one, but it matters for anyone over sixty.
He was seventy-six years old, active, sociable, and fit. By every outward measure, he was healthy. One evening he finished a hard indoor cycling workout, and three minutes later he collapsed.
His wife heard the fall from another room. She is a physician. She found him without a pulse, started CPR, and used his smartwatch to call 911. Paramedics confirmed ventricular fibrillation, a lethal heart rhythm. They worked for nearly forty minutes, including defibrillation shocks, but could not restart his heart. He died in March 2025.
This man studied wearables and longevity himself. He worked with Michael Snyder, a Stanford geneticist. After his death, his wife shared his data with the research team: his smartwatch, his smart ring, and his exercise bike. The bike alone held seven years of records from 530 sessions.
The team found something striking. About five months before he died, many of his health measures changed at once. The change was abrupt, not gradual. The researchers call it a coordinated step-change, and two separate devices captured it.
Here are the five warning signs. First, his heart rate variability fell by half. That measures the variation in time between heartbeats, and low variability is linked to poor sleep, stress, and heart conditions. Second, his resting heart rate climbed, and so did his nighttime rate. His heart was working hard when it should have been resting. Third, his deep sleep declined. Fourth, his six-minute walk distance dropped, which devices infer from step counts, stride length, and pace. Fifth, his gait and breathing rate declined, worsening alongside the others.
No single number told the story. The pattern did.
At the low point, he felt fatigued and saw his primary care doctor, who heard a heart murmur. An echocardiogram in early November 2024 showed advanced structural heart disease, a less common form that affects the heart muscle itself, rather than plaque in the arteries.
He kept exercising hard anyway. On the evening of his death, he did one of his most intense workouts ever, and his heart rate hit one hundred fifty beats per minute, above age-based recommendations. Dr. Snyder said that had the man seen those changes, he might have eased up.
Here is the troubling part. The signals were there, but the system failed to deliver them. Wearable use among American adults grew from about thirty percent in 2020 to over forty percent by 2024. Yet only about twenty percent of users share that data with their doctors. And while eighty-six percent of US physicians have reviewed at least one type of wearable data, only about six percent have built it into routine care. Snyder said we can track health, but we also need something like a check-engine light for your health.
Heart disease is the leading cause of death worldwide. In the United States, someone dies from it every thirty-four seconds, nearly twenty-five hundred people a day.
The Stanford team plans a clinical trial with up to one thousand patients to learn whether others show the same synchronized changes before a major heart event. But keep one thing in mind. This is a single case. It does not prove that wearables can predict sudden cardiac death. The trial is meant to find that out.
So what can you do today? Look at trends rather than single days. One bad night means little. Several measures shifting together, and staying shifted, is a different matter. If your numbers change and stay changed, tell your doctor and share the data. Don’t wait for your next routine visit.
Never ignore fatigue that feels new or unusual. In this case, that fatigue led to the visit that found his heart disease. Ask your doctor what your numbers mean for you, and what level of exercise is right for your heart.
His wife wants the world to learn from what happened. Wearables may someday warn us in time. Until then, pay attention to what yours are already telling you.