Pulse Age

Nine habits and vitals, averaged over 6 months, each against a reference: a fit person of your age and sex.

VO2 max

From runs in the last 90 days, else Fitbit’s daily estimate at half weight. Reference: your age’s 75th percentile.

Resting heart rate

Fitbit’s daily value from Google. Reference 60 bpm.

Steps

Reference and cap: 10,000 a day under 60, 8,000 from 60.

Sleep hours

Reference 7.5 hours; 7 to 8 scores the same.

Sleep consistency

Reference 86.3.

Light and moderate zones

Google’s daily time in its Light and Moderate zones. Reference 150 minutes a week.

Vigorous and peak zones

Google’s daily time in its Vigorous and Peak zones. Reference 75 minutes a week.

Strength activity

Reference 40 minutes a week.

Lean body mass

Fat-free mass for your height. Needs weight, body fat and height.

Each input maps to a change in mortality risk from a published study. The changes are added, shrunk by 25% for overlap, scaled up when inputs are missing, and turned into years on the rule that mortality risk doubles about every 8 years. A resting heart rate of 70 bpm, all else at reference, adds about 0.75 years.

Pace of Aging repeats this for your last 30 days: 1 + (30-day years − 6-month years) ÷ 5.

Younger than your age

Your inputs beat the reference on balance.

Older than your age

They fall short. The reference is fit, so many people start here.

Pace below 1.0x

Your last 30 days look younger than your 6 months.

Pace above 1.0x

They look older. Pace runs from −1.0x to 3.0x.

On a day Google has no time in zones, Pulse counts them from your heart rate instead. Pulse Age needs 5 of the 9 inputs, is Provisional until 20 days have data, stays within 15 years of your age and updates weekly. Pace of Aging is provisional until your data spans 6 months. Both rest on population studies, not a clinical test of your body.

The full specification, with formulas, constants and worked examples, is healthspan.md on GitHub. The code is tested against those examples.

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2. Zhang D, Shen X, Qi X. Resting heart rate and all-cause and cardiovascular mortality in the general population: a meta-analysis. CMAJ 2016;188(3):E53-63
3. Paluch AE, et al. Daily steps and all-cause mortality: a meta-analysis of 15 international cohorts. Lancet Public Health 2022;7(3):e219-28
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5. Windred DP, et al. Sleep regularity is a stronger predictor of mortality risk than sleep duration. Sleep 2024;47(1):zsad253
6. Ekelund U, et al. Dose-response associations between accelerometry measured physical activity and all cause mortality. BMJ 2019;366:l4570
7. Lee DH, et al. Long-term leisure-time physical activity intensity and all-cause and cause-specific mortality. Circulation 2022;146(7):523-34
8. Momma H, et al. Muscle-strengthening activities are associated with lower risk and mortality in major non-communicable diseases. Br J Sports Med 2022;56(13):755-63
9. Sedlmeier AM, et al. Relation of body fat mass and fat-free mass to total mortality. Am J Clin Nutr 2021;113(3):639-46
10. Finch CE, Pike MC, Witten M. Slow mortality rate accelerations during aging in some animals approximate that of humans. Science 1990;249(4971):902-5
11. Kaminsky LA, Arena R, Myers J. Reference standards for cardiorespiratory fitness (FRIEND). Mayo Clin Proc 2015;90(11):1515-23
12. Bull FC, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med 2020;54(24):1451-62
13. noop: the open-source analytics engine Pulse's recovery, strain and sleep scoring is ported from