What My Bio Age tracks
Updated
My Bio Age reads the Apple Health categories you allow and does its calculations on your iPhone. This page lists every metric it uses, with one line on what each one is and a link to its own guide. For how the weekly Index is put together, see Methods & Sources.
Weekly MyBioAge Index™
The headline estimate and its trend. Both are calculated on your iPhone from complete weeks, never from the current, unfinished one.
- MyBioAge Index™: A weekly wellness estimate of biological age, built from complete Monday–Sunday weeks (up to 24) and shown with a confidence label. It reads Limited when VO₂max, HRV or Sleep + SRI data is thin. You’ll see it on the dashboard, on Apple Watch and in the Monday digest.
- Pace of Aging: The trend of your weekly Index over 4, 12 and 24 weeks, shown as a multiplier per year. It describes the model’s trend, not how fast your cells are ageing.
Index inputs
The Index draws on 12 core inputs, plus two optional blood pressure inputs when readings exist. Most come straight from Apple Health; Recovery and Training Load are calculated by the app. Not everyone will have every input, and missing data is never treated as a zero.
- VO₂max: Apple Watch’s cardio fitness estimate from outdoor walks, runs and hikes. Each week it is compared with age- and sex-specific reference data, and it is one of three critical Index inputs.
- Heart rate variability (SDNN): The variation between heartbeats, summarised as a daily median. It also feeds Recovery, Training Load, Stress Resilience and Circadian Alignment, and is left out in Pacemaker Mode.
- Resting heart rate: Apple’s estimate of your lowest heart rate at rest. It also feeds Recovery, Stress Resilience and Circadian Alignment, and is corrected on days with a logged sauna or ice-bath session.
- Walking heart rate average: Your average heart rate while walking: an everyday fitness signal, compared with reference data each week.
- Sleep duration: Recorded asleep time per night (9 pm to 9 pm), with overlapping sources merged. It also feeds Recovery, Stress Resilience and the sleep-timing scores.
- Sleep Regularity Index (SRI): How closely your sleep and wake times match from one day to the next, scored 0–100 over the last 14 nights. A critical Index input alongside sleep duration.
- Active energy: Calories burned through activity, totalled daily without double counting. It is also the source for Training Load.
- Respiratory rate: Breaths per minute overnight, as a nightly median. An Index input best read as context, with its own trend chart.
- Sleeping wrist temperature: The recorded sleeping wrist temperature, on supported watches. The Index compares it with earlier nights; Training Load uses its variation as a temperature-stability signal.
- Blood oxygen (SpO₂): The overnight median and the share of readings below 95%. An Index input best read as context, and part of Training Load’s oxygen signal. It is not a medical measurement.
- Recovery (Recovery Capacity): A daily 0–100 score from heart-rate recovery, resting heart rate, HRV and sleep: Ready from 70, Moderate from 40. Its weekly average is an Index input.
- Training Load: Your last 7 days of active energy compared with the last 28, shown as a ratio across five zones from Under-training to Overreaching. Its weekly average is an Index input.
- Blood pressure (optional): Systolic and diastolic readings from a separate monitor, read through Apple Health. They count as two optional Index inputs when readings exist; My Bio Age never measures blood pressure itself.
Daily scores
Two daily wellness views with their own calculations. Neither is an input to the weekly Index.
- Stress Resilience: A daily 0–100 view of HRV, resting heart rate, sleep and activity: High from 70, Moderate from 40. It is not a measure of how stressed you feel.
- Circadian Alignment: A daily 0–100 view of sleep timing, weekday and weekend shifts, heart-signal timing and activity timing over up to 30 days: Aligned from 75, Moderate from 50.
Recovery and body signals
Signals that shape other scores rather than standing alone, plus optional measurements from other devices.
- Heart-rate recovery: How far your heart rate drops in the first minute after exercise. Recovery needs a reading from the last 14 days, and this signal reaches the Index through Recovery.
- Cooldown recovery estimates (optional, coming in 1.0.23): An on-device estimate from exercise followed by a logged Cooldown workout, in versions with this setting. It is used only on days without an Apple Health reading and is never written to Health.
- Body composition: Weight, body fat and lean mass from a scale or other source. Optional context: with lean and total mass, the Index adjusts how strongly its heart-rate inputs count, and the AI Coach can refer to these readings.
Laboratory (coming in 1.0.23)
A blood-based estimate in versions with Laboratory results, kept apart from everything above.
- Laboratory PhenoAge: An age estimate from nine blood markers on an eligible, reviewed report. It is shown beside the Index and never blended into it.
Practical guides
Habits that connect these metrics, with what your data can and cannot show about them.
What these numbers can and cannot tell you
What you see depends on your devices, permissions and recorded history, so not everyone will have every metric. The MyBioAge Index™ and the daily scores are wellness estimates for following your own trends. They are not a diagnosis or a laboratory test of biological age. Talk to a qualified healthcare professional about symptoms, results that worry you, or any decision about medication or treatment.
General wellness information, not medical advice.
See your own health metrics in one place
Download My Bio Age free on the App Store to explore the readings available in your Apple Health history. The app is completely free, with no subscription or in-app purchases. Your scores and optional AI Coach run entirely on iPhone, so your health data stays private.
