7 guides
Sleep
How much sleep adults need, what the stages are, and how far a sleep tracker can be trusted.
Tests and markers
How Accurate Are Sleep Trackers at Measuring Your Sleep Stages?
The summary screen reports a stage-by-stage breakdown with the confidence of a lab printout. The sensor producing it has never recorded a brainwave, which changes what the number is actually worth.
Limited evidence18 Sept 2026
How Many Hours of Sleep Do You Actually Need?
The line everyone repeats is 'eight hours.' The number actually published is a range that shifts by decade of life, and the harder question isn't which target to hit — it's what a night below it really costs you.
Strong evidence18 Sept 2026
REM Sleep vs. Deep Sleep: What's the Real Difference?
Both stages get called 'the important one' by different corners of the internet, as if a night had to pick a winner. What each stage actually is — and which one's absence is the real red flag — is a sharper question than ranking them.
Strong evidence18 Sept 2026
Conditions and symptoms
How Do You Reset Your Sleep Schedule After Working Night Shifts?
Chronobiology says light timing can shift your body clock to match a graveyard schedule. Most permanent night workers never fully get there, and the reason has little to do with discipline.
Moderate evidence18 Sept 2026
Why Do You Keep Waking Up at 3 AM and Can't Fall Back Asleep?
The wake-up gets blamed on a hormone spike, a digestive clock, or a sleep stage gone wrong — explanations more specific than anything a major health authority actually publishes about insomnia.
Moderate evidence18 Sept 2026
Explainers
Does Blue Light From Your Phone Actually Ruin Your Sleep?
The mechanism connecting light to melatonin is one of the best-established findings in sleep biology. Whether an ordinary evening of phone use delivers enough of it to be the reason you're still awake is a narrower, murkier question.
Limited evidence18 Sept 2026
How Long Does Caffeine Actually Keep You Awake Before Bed?
The common advice — stop caffeine by early afternoon — is built on one average adult's clearance rate. Whether that fits your own bedtime depends on a number that varies enormously between people.
Moderate evidence18 Sept 2026