What is a vitality score?
It is one number meant to summarise how your body is doing right now. Useful, but only if you know what is under it and what it cannot tell you. Here is the honest version.
Evidence-based · Sources cited · Updated July 2026
A vitality score is a composite wellness number, usually built from resting heart rate and heart-rate variability, that you track over time. It is a general wellness metric, not a medical test. It cannot diagnose anything. Its whole value is the trend against your own baseline, not the number itself, and not a comparison with anyone else.
What is actually under the number
Nearly every vitality score is built from the same small set of cardiovascular and autonomic signals. Resting heart rate is the simplest. Heart-rate variability, the tiny variation in time between beats, is the interesting one: it reflects how your autonomic nervous system is balancing stress and recovery.[1] Some scores add breathing rate. The app then scales those inputs into a single figure, which is where the standardisation ends.
How those signals get measured varies. A chest strap or wearable reads them directly; a phone camera infers your pulse from tiny colour changes in your face, a technique that has been validated against ECG to within about one beat per minute in good conditions.[2] The measurement method matters less than whether you take it the same way each time.
Why there is no universal good score
Every product scales its score differently, so a 78 in one app and a 78 in another are not the same measurement and are not comparable. There is no agreed clinical definition of a vitality score. That sounds like a weakness, and it is, but it also points at the correct way to use one: as a personal baseline. Your score last Tuesday is the only meaningful comparison for your score today.
How to read it without fooling yourself
Single readings are noisy. Heart-rate variability in particular swings with sleep, alcohol, illness, caffeine, stress, and where you are in your cycle, so one bad morning means very little.[1] The signal lives in the multi-week direction. If the number is drifting down across weeks while your sleep and training are unchanged, that is worth paying attention to. A single low day is mostly weather.
What it cannot do
This is the part most apps skip. A vitality score does not diagnose, screen for, or rule out any disease. It is a general wellness tool, and products in that category stay out of medical-device territory precisely by not making diagnostic claims.[3] It is not a substitute for blood work, and it is not a substitute for a doctor. If something feels wrong, the score is not the thing that will tell you what it is. It can, however, give you an objective trend to bring to the conversation.
See where you actually stand
leto runs the 30-second scan on your phone and turns it into a vitality score you can track.
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Sources
- [1] Shaffer & Ginsberg, an overview of heart rate variability metrics and norms. Frontiers in Public Health. PMC5624990
- [2] Clinical validation of rPPG-enabled contactless pulse rate monitoring software in cardiovascular disease patients. Bioengineering, 2026. mdpi.com
- [3] General Wellness: Policy for Low Risk Devices. US Food and Drug Administration. fda.gov
This article is educational and is not medical advice. A vitality score is a general wellness metric and does not diagnose, treat, or prevent any disease.