CardioSleep — How It Works

CardioSleep in one minute: a short record of each night's sleep, and a schedule that is recalculated from it once a week.

Where it starts

There is no account and no sign-in. On first launch the app explains the approach in a few screens and asks for one thing: a wake time that can be held every day, weekends included. That time becomes the fixed anchor of the program. The bedtime is what moves around it.

If allowed, the app reads existing sleep records from Apple Health to save typing them in. It only reads — CardioSleep does not write to Health.

The five tabs

Diary

• One entry per night, designed to be filled in over breakfast rather than studied over.
• An entry covers when you went to bed, when you got up, roughly how long you were awake in between, a 1–5 quality rating and an optional note.
• From those four numbers the app derives sleep efficiency — the proportion of time in bed that was actually spent asleep.
• The top of the tab carries the running average for the week, which is what the weekly recalculation is based on.

Window

• This is the core of the program: the sleep window, the period the schedule sets aside for being in bed.
• The tab shows the window currently in force, the fixed wake time it is anchored to, and the dates it applies to.
• Recalculate Window re-derives the schedule from the week's diary. A week that was mostly spent asleep supports a slightly wider window; a week with a lot of waking time in bed supports a slightly narrower one. The intent is to concentrate sleep before letting the window widen again — which is the part of the method that generally feels counter-intuitive at first.
• Only the bedtime moves. The fixed wake time stays put, because holding it constant is the point of the exercise.
• Until a first window has been created there is nothing to recalculate, so the tab opens on an empty state with a single button.

Learn

• A course released a week at a time rather than all at once, so there is one week's material to read instead of six.
• Each week is a short set of modules covering the reasoning behind the program and what to expect from it.
• Modules are marked complete as they are read, and the tab shows progress through the current week.

Sounds

• A small set of ambient sounds, each with its own play control and a shared volume setting.
• These are deliberately plain, and the app says so on the screen. They are a background layer for reading the week's modules, not something to rely on to fall asleep.

Settings

• The current program week and the fixed wake time, so the anchor can be changed if circumstances change.
• The Apple Health connection, showing what is read and offering a way to disconnect it.
• The version number, and the same statement the app carries everywhere else about what it is not.

What CardioSleep does not do

Stated plainly, because it matters more here than anywhere else we build.

• It is not a medical device, and it does not diagnose or treat anything. It is a schedule and a set of reading, presented in plain language. It does not replace a clinician, and it is not a treatment for a sleep disorder.
• It does not monitor you. If Apple Health is connected, the only thing the app reads is your existing sleep records. Nothing is measured in the background, and no sensor is left running.
• It collects nothing about you. No account, no analytics, no advertising, no tracking, no crash telemetry. Your diary stays on your iPhone, and deleting the app deletes it.

Privacy

The approach is set out in the privacy policy for CardioSleep and will be confirmed against the finished app before release. Our company-wide Privacy Policy covers it as well. Every app we publish works the same way: no accounts, no analytics, nothing sent anywhere.

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