The department of
Caffeine
Caffeine affects sleep timing, depth, and quality in ways worth understanding. Explore half-life, sensitivity, timing, and how much is too much with science and honest reviews.
Pieces
6
Caffeine
August 2026 · 9 min
Apple Event Predictions, and the AirPods Sensor Nobody Is Betting On
Apple put a heart-rate sensor in AirPods Pro 3. That is true, it is on the spec sheet, Apple quotes 256 readings per second from the optical module, and it is the most misleading line in this year's…
By Laura Pendleton · Read →
Caffeine
August 2026 · 9 min
The Garmin Fenix 9 and the Nine-Minute Number That Made Me Stop Trusting My Sleep Score
Nine minutes. That is the entire gap my Fenix 8 found between my worst caffeine nights and my cleanest ones across 92 logged nights this spring, and it is the number I could not stop thinking about…
By Marcus Webb · Read →
Sleep
August 2026 · 7 min
The Anti-Smartwatch Smartwatch Review: Six Weeks With a $25 Casio Instead of a Sleep Tracker
Six weeks ago I put my sleep tracker in a drawer and wore a $25 Casio instead. This is therefore a strange smartwatch review, because the watch at the center of it isn't smart: the Casio A158WA tells…
By Diane Norwood · Read →
Sleep
August 2026 · 9 min
What Four Fitness Trackers Told Me About My 2 p.m. Coffee: 100 Nights, One Number, and 17 Minutes
Seventeen minutes. That is the number this piece is built on: the median difference in how long it took me to fall asleep on nights when I'd had caffeine after 2 p.m.
By James Hartley · Read →
Sleep
August 2026 · 6 min
What Fitness Tracker Wearables Can Actually See When You Drink Coffee at Four in the Afternoon
I drank a double espresso at 4:15 on a Tuesday afternoon — about 130 mg of caffeine, roughly a small diner coffee — and then went to bed at 11:20 with a band on my wrist. I knew it was a bad idea.
By Daniel Whitfield · Read →
Sleep
August 2026 · 6 min
Smartwatch Deals and the 2pm Rule: Five Watches, One Evening Coffee, Six Weeks of Data
Every September the wearables go on the front page, and a certain kind of buyer — me, for about six years — starts justifying the upgrade with sleep. The pitch writes itself.
By Samuel Briggs · Read →
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