Evidence: Some

A few trials or consistent observational studies. Likely true, size of effect uncertain. How we rate evidence.

Body scan and cognitive shuffleTwo in-bed techniques for a tense body or a busy mind. Relaxation has decent evidence; the cognitive shuffle has very little.
- Evidence: Some
- Low effort
- Free
- Works: 1–2 weeks
Building sleep pressureBe properly tired at bedtime. Stay awake long enough, move during the day, don't go to bed too early, and keep naps and caffeine from draining the pressure.
- Evidence: Some
- Low effort
- Free
- Works: tonight
ChronotypeYour chronotype is how early or late your body clock runs. It's partly genetic and changes with age, but light can move it by an hour or two.
- Evidence: Some
- Low effort
- Free
- Works: 1–3 weeks
Consistent wake timeGet up at the same time every day, weekends included. It anchors your body clock and makes falling asleep easier.
- Evidence: Some
- Medium effort
- Free
- Works: 1–2 weeks
Darkness and eye masksMake the bedroom as dark as you can, with blackout curtains or an eye mask. Experts recommend under 1 lux at the eye while you sleep.
- Evidence: Some
- Low effort
- Low cost
- Works: tonight
Exercise timingRegular exercise helps sleep a little. Evening exercise is fine for most people; just finish hard sessions more than an hour before bed.
- Evidence: Some
- Medium effort
- Free
- Works: a few weeks
Hot shower or bathA warm bath or shower 1–2 hours before bed, at about 40–42.5 °C (104–108.5 °F), can help you fall asleep faster.
- Evidence: Some
- Low effort
- Free
- Works: tonight
How accurate are wearables?Sleep trackers are good at telling sleep from wake and at total sleep time. They are weaker at spotting time awake and at sleep stages.
- Evidence: Some
- Low effort
- Free
- Works: today
HRV, resting heart rate and temperatureWhat your overnight HRV, resting heart rate and skin temperature mean, what moves them, and why to compare them only with your own baseline.
- Evidence: Some
- Low effort
- Free
- Works: 1–3 weeks
Jet lagJet lag is your body clock running on home time after you fly. Timed light, a shifted sleep schedule and, where allowed, melatonin can cut it short.
- Evidence: Some
- Medium effort
- Low cost
- Works: 2–7 days
MelatoninMelatonin is better at shifting your body clock than at knocking you out. For sleep onset it saves about 7 minutes on average. Low doses work; labels are often wrong.
- Evidence: Some
- Low effort
- Low cost
- Works: 1–3 days for timing shifts
Morning lightGet outside in daylight soon after you wake up. It sets your body clock earlier, so you get sleepy at a sensible time.
- Evidence: Some
- Low effort
- Free
- Works: 1–2 weeks
NapsA short nap of 10 to 20 minutes in the early afternoon can boost alertness without hurting your night. Long or late naps cost you deep sleep and make it harder to fall asleep.
- Evidence: Some
- Low effort
- Free
- Works: today
Noise and earplugsNight-time noise disturbs sleep even when you don't fully wake. Block it at the source or wear earplugs; the evidence for white noise is very weak.
- Evidence: Some
- Low effort
- Low cost
- Works: tonight
Room temperatureKeep the bedroom between about 18 and 25 °C (64–77 °F), and use bedding to fine-tune. Heat harms sleep more clearly than mild cool.
- Evidence: Some
- Low effort
- Low cost
- Works: tonight
Screens and blue lightThe light from your phone matters less than you've heard. What you do on it, and how late it keeps you up, matters more. Dim the room, and put the phone down when you're sleepy.
- Evidence: Some
- Medium effort
- Free
- Works: tonight
Sleep positionsFor most people, any comfortable position is fine. Position matters if you snore, have reflux at night, or are more than 28 weeks pregnant.
- Evidence: Some
- Low effort
- Free
- Works: tonight
Social jet lagSocial jet lag is the gap between when you sleep on workdays and on days off. Shrink it by keeping your wake time steady and getting morning light.
- Evidence: Some
- Medium effort
- Free
- Works: 1–2 weeks
Waking at 3 a.m.Brief wake-ups are normal. What to do when you can't get back to sleep, and when it's a sign of insomnia.
- Evidence: Some
- Low effort
- Free
- Works: 1–2 weeks
What sleep scores measureWhat goes into the sleep and readiness scores from Oura, WHOOP, Apple Watch and Garmin, according to each company's own documentation.
- Evidence: Some
- Low effort
- Free
- Works: today
Which habits change which metricA table of common sleep habits against the numbers your wearable shows, with the direction of each effect, how sure the research is, and where nobody has looked.
- Evidence: Some
- Low effort
- Free
- Works: tonight to 2 weeks