Personal sleep evidence from Apple Watch
Find what actually changes your sleep.
BodySignal turns your existing Apple Watch history into one personal comparison, then helps you test one separate question for 14 days.
One focused path
History first. Experiment second.
Analyze your Watch history
BodySignal privately reads sleep timing, heart rate during sleep, and nightly HRV from Apple Health.
See one repeated pattern
Later nights are compared with your own typical timing using up to 180 valid nights.
Understand the evidence
You see the group sizes, primary difference, one supporting signal, evidence grade, and limitations.
Test one new question
For 14 assigned days, compare a 2 PM caffeine cutoff with your usual routine.
Receive an honest result
The answer can be positive, negative, null, inconclusive, or not ready because the data was incomplete.
The free value moment
One comparison you can understand immediately.
Later vs. typical nights
Your own sleep timing defines the two groups. BodySignal does not compare you with a generic population target.
Sleeping heart rate first
The primary comparison uses median heart rate during sleep. Sleep duration or HRV may appear as one supporting detail.
Evidence with limitations
BodySignal shows how many nights supported the finding and states clearly that association is not proof of cause.
The first experiment
Does avoiding caffeine after 2 PM improve my sleep?
14 assigned days
Seven cutoff days and seven usual-routine days are created before you begin.
One answer each day
Record whether you followed the assignment, did not follow, had no caffeine, or need to skip the day.
No forced caffeine
Usual-routine days never instruct you to consume caffeine. Follow your normal routine.
Transparent result
See what changed, what remained uncertain, how many nights counted, and what the evidence supports.
Private by design.
Health values, historical findings, experiment answers, and results stay on your iPhone unless you explicitly choose to share an export.
Paid access
Pay for a personal answer, not a dashboard.
One Sleep Experiment
A one-time purchase to run the caffeine experiment once and receive the full result.
BodySignal Founding Annual
Run the current experiment and receive future BodySignal experiments while subscribed as they are released.
Localized price and billing details are shown by the App Store before purchase. Future experiments are not promised on a fixed schedule.
FAQ
Common questions.
How much history do I need?
BodySignal needs at least 30 valid sleep nights and at least 10 nights in each timing group before it shows the historical comparison. It may need more calendar time when Watch data is incomplete.
What if no pattern is ready?
BodySignal shows exactly how many valid nights were found, checks new nights automatically, and does not manufacture a score or finding.
Does the caffeine experiment explain my past pattern?
No. The historical sleep-timing association and the future caffeine experiment are separate questions.
What Apple Watch do I need?
You need Apple Watch sleep tracking with heart-rate data available in Apple Health. HRV is used when available. Data completeness varies by Watch model, settings, wear, and sync.
Is BodySignal medical advice?
No. BodySignal is a wellness product for personal pattern discovery. It does not diagnose, treat, prevent, or screen for any medical condition.
Does BodySignal upload my Health data?
The current app analyzes Health data on your iPhone. Health values and experiment answers are not sent to an analytics server.
Stop copying routines. Test what works for you.
BodySignal is preparing a small paid TestFlight validation cohort.
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