Guides
What the studies say about light, sleep timing and the gear that claims to help. Sources linked in every article.
- Best Light Color for Sleep: Red, Amber or Warm White Bulbs
The best light color for sleep is dim red or amber. Your body clock is most sensitive to blue light near 480 nm, and brightness matters as much as color.
- Caffeine Half-Life: How Long It Lasts and When to Stop
Caffeine half-life is 3 to 6 hours for most adults but can top 10 hours. What slows it, mg per drink, and when to stop caffeine before bed.
- Blue Light Filter App: 2 Circadian Apps Worth Installing
A blue light filter app should turn your screen fully red and dim it, not just warm it. Two circadian apps worth installing: Tap Zap and Circadian.
- Blackout Curtains for Better Sleep: Do They Actually Help?
Blackout curtains for better sleep: what light at night does to sleep and blood sugar, how dark is dark enough (under 1 lux), and cheap fixes for light gaps.
- Do Blue Light Glasses Work? Eye Strain vs Sleep Evidence
Do blue light glasses work? Not for eye strain, a 17-trial Cochrane review found. Dark amber lenses worn before bed have small, mixed sleep benefits.
- Do Sunrise Alarm Clocks Work? The Dawn Simulator Evidence
Do sunrise alarm clocks work? Dawn simulator trials show less morning grogginess and help for winter depression, but they don't replace a 10,000 lux light box.
- Does red light therapy work? The evidence by use, graded
Does red light therapy work? Graded evidence for skin, hair loss, pain, muscle recovery, sleep and fat loss, with trial sizes, doses and FDA status.
- FDA cleared red light therapy devices: how to check one
FDA cleared red light therapy devices explained: cleared vs approved vs registered, how to search the 510(k) database, and verified K-numbers for popular masks.
- Lux Levels: How Much Light You Need, Day and Night
Lux levels for sunlight, offices and homes, plus expert targets: 250 melanopic lux by day, 10 in the evening, 1 at night. How to measure your own.
- Sleep schedule: how to fix yours with a 7-day plan
How to fix your sleep schedule: anchor one wake time, move it 15 to 30 minutes a day with morning light, and skip weekend sleep-ins. Includes a 7-day plan.
- How to reset your circadian rhythm: a 5-step light plan
How to reset your circadian rhythm: fix your wake time, get morning light, dim evenings. Expect about 1 hour of shift a day, and know when to see a doctor.
- Light Therapy Lamp for Seasonal Affective Disorder: How to Use It
How to use a light therapy lamp for seasonal affective disorder: 10,000 lux for 30 minutes, early morning, angled down. Side effects and who should skip it.
- Jet lag: how to get over it faster with light timing
How to get over jet lag: when to seek and avoid bright light after flying east or west, how to shift before you fly, and what melatonin trials show.
- Morning Sunlight: Why It Works and How Long You Need
Morning sunlight moves your body clock earlier. How many lux you get outdoors vs indoors, how long to stay out, and what to do on dark winter mornings.
- Red light therapy for sleep: does it work? Panels vs bulbs
Red light therapy for sleep rests on one 20-person red light trial. Swapping white evening light for dim red or amber has better support. How to set it up.
- Risks of red light therapy: eyes, burns, drugs, overdosing
Risks of red light therapy, from eye damage and skin burns to photosensitizing drugs and overdosing, with who should skip it and how to use a panel safely.
- Shift work sleep: light, naps and caffeine for night shifts
Shift work sleep tips from the research: bright light early in the night shift, dark glasses home, a blackout bedroom, anchor sleep, naps and caffeine timing.
- Time-Restricted Eating and Circadian Rhythm: The Trials
Time-restricted eating, graded against the trials: early windows helped insulin, but TRE has not beaten plain calorie cutting for weight loss.
- What is a chronotype? Science, a free quiz and the animal myth
A chronotype is your body clock's timing, measured as free-day mid-sleep. How a real chronotype test works, what genes and age do, and why animal types fail.