For many people living with complex chronic illness, one of the hardest parts is the unpredictability. You can start the day feeling ok, only to take a turn for the worse later in the day that you didn’t see coming.

That’s part of why we built Visible’s Morning Stability score. It brings together your biometrics and recent symptom patterns to indicate when your body may be under more strain than usual. This can help you plan your day with more confidence.

Today, we’re sharing a new peer-reviewed study on the inputs to the Morning Stability score: heart rate, heart rate variability (HRV), and symptom changes in people living with complex chronic illness. Thanks to Visible members, it is the largest study of its kind to date on complex chronic illness.

What the researchers did

The researchers looked at data from 4,244 Visible users who gave consent to participate in the study. In total, the researchers analyzed more than 530,000 matched morning and evening check-ins.

These are the daily check-ins Visible users will already know:

1. the 60-second morning check-in that uses your smartphone camera or Visible band to measure heart rate and HRV
2. the evening symptom check-in, where you log things like crashes, fatigue and brain fog

The researchers then explored at whether morning biometrics, alongside recent symptom patterns, could help predict worse symptoms later that day.

The study was led by researchers at New York University and the Icahn School of Medicine at Mount Sinai, in collaboration with Visible and teams at Yale University, the University of Oxford, and PolyBio Research Foundation. It was published in npj Digital Medicine.

What they found

The key finding was that certain changes in morning biometrics, such as heart rate and HRV, were linked with increased symptoms later that day.

As lead researcher Annie Aitken, PhD, of NYU, said:

“Morning biometrics appear to provide an early signal of symptom worsening later in the day. For people living with these conditions, that kind of information could support more informed pacing and activity decisions, helping people reduce the risk of overexertion and symptom escalation.”

In particular, the researchers found:

• When morning heart rate was higher and morning HRV was lower, people were more likely to report crashes, fatigue and brain fog later that day.
• How people felt the day before was already a strong clue to how they would feel later, but adding morning biometrics improved those predictions.
• Personalization mattered. The models worked best when they were based on each person’s usual baseline, rather than a one-size-fits-all approach.
• Day-to-day variation mattered too. People whose heart rate and HRV changed more over a rolling seven-day period were more likely to experience worsening symptoms.

What makes this study different

A lot of HRV research happens in lab settings using specialist equipment. This study was different in a few important ways.

• It looked at what happens in real life, using smartphones people already own.
• Instead of comparing people living with complex chronic illness to healthy controls, it looked at changes within each person over time.
• It focused on things that matter directly to people living with these conditions: crashes, fatigue and brain fog.
• It is the largest study of its kind to date, using data from 4,244 people and more than 530,000 matched check-ins.

Study co-author Professor David Putrino of Mount Sinai said:

“This is the first time we’ve been able to show, in the largest study of its kind to date, that simple morning biometric- and symptom-tracking hold predictive value for the day-to-day outcomes that people with complex chronic illnesses care about most, including crashes.”

What this does (and doesn't) tell us

As with any study, it’s important to be clear about what this one does and doesn’t show.

This study shows that a single 60-second biometric reading can identify meaningful physiological patterns in complex chronic conditions. But it does not mean a single measurement can tell you exactly when a crash is coming, or explain everything on its own. Recent symptoms remain a key part of the picture, and morning biometrics are most helpful when combined with this information.

At Visible, we're excited about the potential of truly 24/7 biometrics. Our wearable collects data continuously and passively throughout the day and night, giving us far more signal to work with and opening up future opportunities to better understand these conditions. In doing so, we will continue to build the evidence base for conditions that have been under-researched for far too long.

What this means for you

Your morning check-in matters, and it becomes more useful the more consistently you do it.

This study found that patterns over several days, not just a single reading, were important in understanding how symptoms changed. Each check-in helps build a clearer picture of what’s normal for you.

If you’ve been skipping your morning check-in, this is a good reason to come back to it.

This research exists because of you

This study was only possible because of the Visible community. It drew on data from 4,244 Visible users who chose to contribute their data to research through the app.

On its own, one person’s data can only tell us so much. But together, it adds up to something much more powerful: a stronger evidence base for conditions that have long been overlooked and underserved.

To everyone who took part, thank you. You’re not just tracking your own health; you’re helping move progress forward for everyone.

What's next

This study is one more step towards making invisible illness more visible.

The next step is to build on these findings. The researchers note that future studies could improve prediction further by bringing in continuous monitoring, sleep data, and activity data. They also need to test whether acting on these early signals, for example, by adjusting pacing, leads to better outcomes over time.

The full study is available to read here.

Onwards,

Harry

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