Understanding Shen AI health markers

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Shen AI measures more than 30 physiological parameters and health insights. Some, like heart rate or blood pressure, are familiar to most people. Others - such as heart rate variability, parasympathetic activity, or vascular age - may be less obvious.

This guide explains what each type of measurement represents, why it's useful, and how Shen AI estimates it. For detailed formulas, reference ranges, and scientific sources, see the metrics documentation.

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Heart Rate

Heart rate measures how many times the heart beats each minute. It's one of the most commonly used indicators of cardiovascular activity and can change throughout the day depending on exercise, stress, sleep, illness, or emotional state.

For many applications, heart rate is the foundation for tracking trends over time or providing users with immediate feedback about their current physiological state.

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Heart Rate Variability (HRV)

While heart rate tells you how fast the heart is beating, HRV tells you how much the time between heartbeats changes.

A healthy heart doesn't beat with perfectly regular timing. Small variations between heartbeats are normal and reflect how the autonomic nervous system responds to stress, recovery, sleep, exercise, and everyday life.

Because of this, HRV is widely used in wellness, fitness, and preventive health applications to help monitor recovery, resilience, and overall cardiovascular health.

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Stress Index

The Stress Index reflects physiological stress, not emotional stress. It is calculated from heart rate variability and estimates how hard the body's cardiovascular regulatory system is working.

For example, physical exertion, illness, poor sleep, or psychological stress can all influence the Stress Index. It should always be interpreted alongside other measurements rather than as a standalone indicator.

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Parasympathetic Activity

The autonomic nervous system has two main branches: one that prepares the body for action and another that supports rest and recovery.

Parasympathetic Activity estimates how active the "rest and recover" part of the nervous system is by analyzing heart rate variability.

This measurement can provide additional context when evaluating recovery, relaxation, and overall autonomic balance, especially when used together with HRV and the Stress Index.

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Blood Pressure

Blood pressure measures the force of blood against the walls of the arteries as the heart pumps blood around the body. It's one of the most widely used indicators of cardiovascular health and is commonly monitored to identify changes over time.

Unlike a traditional cuff, Shen AI estimates blood pressure from the facial pulse waveform using computer vision and machine learning models trained on clinically validated datasets. For many digital health applications, this provides a convenient way to monitor blood pressure trends without requiring dedicated hardware.

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Cardiac Workload

Heart rate alone doesn't tell the whole story. For example, two people may have the same heart rate but very different blood pressure. In that case, their hearts are working under different levels of strain.

Cardiac Workload combines heart rate and systolic blood pressure to estimate how hard the heart is working. It can provide additional insight into cardiovascular demand during daily monitoring.

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Body Mass Index (BMI)

Rather than calculating BMI from manually entered height and weight, Shen AI uses computer vision models trained to identify facial characteristics that correlate with body mass index.

This provides an estimate rather than a direct calculation, making it useful for wellness, screening, and engagement scenarios where traditional measurements may not be available.

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Wellness Score

Users may not know what to make of ten different health measurements at once. The Wellness Score brings them together into a single, easy-to-understand indicator of overall wellbeing.

Instead of replacing the individual metrics, it helps users see the bigger picture and track changes over time. If the score changes, they can always look deeper to understand which measurements contributed to it.

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Vascular Age

While your chronological age is fixed, your vascular age reflects the condition of your cardiovascular system. Healthy lifestyle habits may help keep your vascular age lower than your actual age, while factors such as high blood pressure, smoking, or poor diet can have the opposite effect.

Shen AI estimates Vascular Age using physiological measurements collected during the scan together with established clinical models. It's designed to support preventive health and long-term monitoring.

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Cardiovascular Disease Risk

This estimates your overall likelihood of experiencing a first major cardiovascular event within the next 10 years.

Rather than predicting one specific condition, it combines multiple cardiovascular risk factors into a single percentage that represents your overall cardiovascular risk.

To help provide more context, Shen AI also estimates the risk of several specific cardiovascular conditions, including:

- Coronary heart disease
- Stroke
- Heart failure
- Peripheral vascular disease

These estimates are derived from the overall cardiovascular disease risk using established clinical prediction models.

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Hard and Fatal Events Risk

While the previous score estimates the overall risk of cardiovascular disease, Hard and Fatal Events Risk focuses specifically on the most serious cardiovascular outcomes.

It estimates the likelihood of fatal cardiovascular events over the next 10 years, including:

- Coronary death
- Fatal stroke
- Total cardiovascular mortality

These estimates are based on established cardiovascular risk models and are intended to support preventive health monitoring rather than diagnosis.

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Cardiovascular Risk Score

Unlike the previous two measurements, this isn't expressed as a percentage.

Instead, it uses a point-based scoring system developed from the Framingham Heart Study to show how different risk factors contribute to your overall cardiovascular risk.

The score takes into account factors such as:

- age,
- blood pressure,
- smoking status,
- diabetes,
- cholesterol.

This can help explain why one person has a higher or lower cardiovascular risk than another and which factors contribute most to the overall result.

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Hypertension Risk

A blood pressure measurement tells you what's happening right now. Hypertension Risk estimates the likelihood of developing high blood pressure in the coming years by combining current measurements with additional risk factors such as age, BMI, smoking status, and family history. It's designed to support early prevention.

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Diabetes Risk

Type 2 diabetes often develops gradually, long before symptoms appear.

Shen AI supports two established diabetes risk models:

- Framingham Diabetes Risk Score, which estimates the long-term risk of developing type 2 diabetes using clinical risk factors.
- FINDRISC (Finnish Diabetes Risk Score), a widely used screening questionnaire that estimates diabetes risk without laboratory tests.

Together, these models help identify people who may benefit from lifestyle changes or further medical evaluation.

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Fatty Liver Disease Risk

Many people with metabolic dysfunction-associated fatty liver disease (MASLD) don't know they have it.

Instead of relying on liver imaging, Shen AI estimates the risk using body composition measurements that are strongly associated with fatty liver disease, particularly the Body Roundness Index (BRI) and Waist-to-Height Ratio (WHtR).

The goal is to identify users who may benefit from further assessment or preventive lifestyle changes.

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Body composition and metabolic health

Shen AI also estimates several measurements that help describe body composition and metabolic health.

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Waist-to-Height Ratio (WHtR)

WHtR compares waist size with height to estimate abdominal fat. Research suggests it is often a better indicator of cardiometabolic risk than BMI because it focuses on where body fat is distributed rather than how much someone weighs.

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Body Fat Percentage

Body Fat Percentage estimates how much of the body is made up of fat tissue rather than muscle, bone, or other tissues. It provides more detail than body weight alone and is commonly used to assess overall fitness and obesity-related health risk.

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Body Roundness Index (BRI)

BRI estimates abdominal fat distribution using body shape rather than body weight alone. It is often used to assess the risk of obesity-related conditions such as cardiovascular disease and type 2 diabetes.

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A Body Shape Index (ABSI)

ABSI is another measure of abdominal obesity. Unlike BMI, it places greater emphasis on waist circumference, making it useful for identifying health risks associated with excess abdominal fat.

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Conicity Index

The Conicity Index estimates how much body fat is concentrated around the abdomen. Higher values are associated with increased risk of metabolic disorders, hypertension, and cardiovascular disease.

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Basal Metabolic Rate (BMR)

BMR estimates how many calories the body uses each day just to maintain essential functions such as breathing, circulation, and cell repair while at rest.

It provides a useful starting point for nutrition and weight management applications.

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Total Daily Energy Expenditure (TDEE)

TDEE estimates the total number of calories a person burns during a typical day, including both resting metabolism and physical activity.

Together with BMR, it can help users better understand their daily energy needs.

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Want to dive deeper?

This guide provides a simple introduction to Shen AI's measurements, but there's much more to explore.

The Shen AI Health Metrics Reference Guide includes detailed information for every available metric, including:

- units and reference ranges,
- estimation methodology,
- interpretation guidance,
- scientific references,
- validation studies,
supporting clinical literature.

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If you're evaluating Shen AI for clinical, regulatory, or procurement purposes, we also recommend reading the Clinical evidence and validation section of this onboarding series.

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