Blog

Notes from the lab

Short, honest guides on what your Apple Health data can — and can't — tell you. No hype, no miracle fixes, just how to test things properly.

Sleep & Caffeine

Does Caffeine Really Affect Your Sleep? How to Test It on Your Own Data

Everyone says caffeine wrecks your sleep — but does it wreck yours, and by how much? Here's how to find out with the data already sitting in Apple Health.

Steps & Sleep

Steps and Sleep: Is There a Real Connection? What the Data Actually Shows

"Walk more, sleep better" is repeated everywhere. We break down what a real correlation between daily steps and sleep quality looks like — and how to check your own.

Reading Your Data

Correlation vs. Causation: What Your Health App Numbers Actually Mean

A strong correlation between two Health metrics is not proof that one causes the other. Here's a plain-English guide to reading your own numbers honestly.