Lifestyle & Environment
Caffeine, light, temperature, alcohol, screens — framed mechanistically.
Caffeine's half-life is longer than you think
Caffeine's effects last much longer than its perceived 'kick.' One controlled study found that even a 6pm dose for a 10pm bedtime measurably disrupted sleep.
Why alcohol wrecks the second half of your night
Alcohol does sedate. It also suppresses deep sleep, fragments the second half of the night, and produces a rebound that wakes you in the early morning. Even moderate amounts before bed measurably affect sleep quality.
The bedroom temperature that helps you fall asleep
A cool bedroom doesn't just feel pleasant. It helps your body do the natural cooling that sleep depends on. The optimal range is colder than most people keep it.
Morning light is the most underrated sleep tool
Sunlight in the first hour after waking sets your circadian rhythm for the entire day. The effect is large, well-established, and almost completely missed by people who work indoors.
Exercise and sleep: timing matters more than intensity
Regular physical activity is one of the best non-pharmaceutical sleep aids — but the type and timing matter more than the intensity. A walk in the late afternoon often beats a hard workout late at night.