Body Insights calculates Pace of Aging with research on daily steps and death rates. It compares your recent steps with a target for your age. Then the Gompertz model turns the study results into a pace reading. This is a research-based model result, not a test of your biological age or a forecast of your life span. Trends shows the current marker and six months of history.
What does Pace of Aging mean?
Researchers have linked daily step counts with deaths from any cause. Body Insights compares your recent average with a target for your age. It then shows the research result on a pace scale. The middle line marks your age-based target. The marker moves from slower to faster pace across that line.
The measure brings population research into a personal trend. It cannot show that a change in your steps caused a change in your biological aging.
What data does the card use?
The card uses daily step totals from Apple Health (HealthKit) and your age to choose its reference. Sleep, heart rate variability, blood tests, DNA, and other age scores do not feed this calculation.
| Part of the card | What it uses | What you see |
|---|---|---|
| Current pace reading | Recent step average, your age-based target, and study results on steps and death rates | Current pace marker |
| Recent step pattern | Daily step totals from the same period | Step pattern behind the marker |
| Monthly history | Daily totals grouped by calendar month for six months | Monthly pace dots on the same scale |
The reference reflects research showing that the link between steps and death rates differs by age. The current reading uses the latest 30 full days. Today is left out because its count is still growing. The card needs 10 recorded days in this period to show a reading. Each month needs seven recorded days to add a history dot.
Apple Watch and other sources can save step totals to Apple Health. Body Insights reads the Health data you allow it to access. It uses those steps in a calculation based on mortality research and an age-related model.
How should you read the scale and history?
The marker shows your current pace. The vertical line marks the reference for your age. The strip moves from slower to faster pace. The marker shows where your recent steps fall on the research scale. The dots below it show each month's average on the same scale. Older dots are fainter; newer dots are darker.
The trail helps you see how the modeled pace has changed across months as your step pattern changes. It is not a biological-age test repeated each month. A blank marker means the app needs more recorded step days or your age to select a reference.
If your plan does not include Pace of Aging, Trends shows a locked preview instead of your personal result.
How does published research inform the calculation?
The calculation starts with published research. A 2020 JAMA study by Saint-Maurice and colleagues tracked daily steps and deaths from any cause among US adults. Body Insights uses its results in the calculation. Read the JAMA study.
The card links to a 2022 meta-analysis by Paluch and colleagues. It combined 15 groups from several countries. It found a link between more steps and fewer deaths. The link differed by age and leveled off at higher step counts. Body Insights uses these findings to set its age-based reference. Read the study in The Lancet Public Health.
Pang and Hanley describe how a death-rate difference can become an age comparison with the Gompertz model. This model describes how death rates rise with age. Body Insights uses it to show the step research as a pace of aging. The method assumes that the relative difference in death rates stays similar across ages. It also assumes that death rates follow a Gompertz pattern. Read their paper in the American Journal of Epidemiology.
Together, these studies, the age-based reference, and the Gompertz method form the science behind the card. The studies track groups of people. They support the link between step counts and death rates, but they do not test the Body Insights score itself. The card does not measure cell aging, predict your life span, or prove that a change in steps changed your biological aging.
For a comparison of other Watch apps with a named aging-pace or related age result, see the best Pace of Aging apps for Apple Watch.
Explore your research-based pace
See how mortality research and the Gompertz model inform your Pace of Aging, then follow six months of history.
See Pace of Aging